Congratulations, excellent contribution! We can also consider a constraint on the size of the element of the last layer, to provide a smooth transition between the elements of the layer and the surrounding mesh. It is common to choose the average size of the surrounding mesh elements. For a 2D mesh with triangular elements, let's imagine that the area of the last element of the layer has to be approximately the area of the triangular element of the mesh just around the layer, so: Area of last layer element: A = (x1+x2)*y_last, where y_last = y*G^(N-1). Area of surrounding mesh element: A = (x1+x2)*h/2 Therefore: h=2*y*G^(N-1)=2*y*(G^N)/G (for square elements h = y*G^(N-1)). Substituting G^N into equation (13), and rearranging: G = (δ-y)/(δ - h/2) and, N = 1 + log(0.5*h/y)/log(G), in previous equation note that h/2 < δ. We round off the number of layers and recalculate the growth rate: G = (0.5*h/y)^(1/(N-1))
I was revisiting this video and I have just realized that we don't actually need to use root-finding algorithm such as Newton-Raphson to solve equation (13) shown at 28:40. We can rearrange that equation and then apply logarithm to both sides, ending with: N = Ln (CG-C+1) / Ln (G). With C = delta_99 / y_H Common values for G are 1.1 or 1.2 (which is in the range you presented in the slides), so the solution is straight forward. Btw I have already implemented this new equation to my Excel sheet.
Amazing video, I love your channel! As a high school student finding videos on fluid dynamics which are understandable is so hard, but this was perfect
Another problem with large volume transitions is that these volumes appear in the system matrix. Large volume transitions can result in much stiffer system matrices yielding poor iterative performance, and sometimes solver divergence.
This video helped me to understand meshing better and concept of inflation layer covered in this video was what I was searching on youtube. Looking forward to learn more about CFD and fluid dynamics with your help.
Great video, very very useful. I recently completed my Master's Degree in Aeronautical Engineering and my thesis was a CFD simulation of flow around thick airfoil. I was misunderstanding the process of mesh generation and now a lot seems more clear to me. Really great work, I hope you continue posting more and more videos and my answer to your question on whether you should continue videos on mesh generation - definitely !
Amazing Lecture, most useful for an engineering student like myself. It would be much appreciated if further meshing methodolgy videos could be uploaded. Thank you once again and keep up the excellent content.
Great summary of the topic. I'd be interested in any suggestions for meshing with a stalled wing arise. I've read some allusions to meshes being to fine. In practice reducing element size in the x direction led to stall not being apparent from the simulation. I understand that no turbulence model properly predicts stall but any advice would be good. It seems like a nebulous topic like the inflation layers.
Some points I wanted to highlight: 1. If total thickness of your prismatic layers is greater then delta_99 then sudden cell volume increase shouldn't make any significant effect on friction coefficient, as friction is mostly generated in boundary layer. 2. In internal flows boundary layer usually spreads across the whole cross-section of a channel. So following your recommendations, meshes for internal flows should consist only of prism layers...
Yes to both. For 2) you normally have to have a few unstructured cells near the middle of the pipe to finish the mesh off (have a look for butterfly meshes, these are pretty popular for pipes)
... technically when the flow is fully developed the boundary layer fills the entire pipe. However, for meshing the inflation layers normally a good choice is 10% of the pipe diameter
Amazing! Your videos are helping me build a strong foundation in CFD as a beginner. I have sent you a LinkedIn request. I would like to discuss and clear few doubts regarding Masters in CFD. So if you are okay with it please accept my request 🙃🙂 Thank you Dr. Aidan. Really appreciate the efforts!
I don't really use LinkedIn, so best to post your questions as precisely as possible in the comments or just send me an email (fluidmechanics101@gmail.com)
In case of the upstream flow condensation in a vertical duct, the inflation layer should cover both condensate film and boundary layer on the film surface? What would be the correct approach? Here I am talking not about the stable upstream flow where one would have stable falling film, but rather the case, where the flow velocity increases that much, that condensate begins to accumulate inside the pipe and liquid would be present across whole cross-section. Any comment would be useful. Thank you & great job with video lectures!
It sounds like you might need a pretty fine mesh resolution across your entire geometry, as you need accurate gradient calculation everywhere (you don't have a uniform freestream, which is usually assumed for boundary layer flow over a flat plate). For your case it sounds like a fully structured mesh in ICEM CFD or a hexcore mesh would be a good idea 👍
Very informative video Dr Aidan. I have doubt, if my cfd analysis involve blade with hub and shroud, do i still need to put the prism layer on the hub and shroud?
Hello Dr. Aidan, Thanks a lot for all your videos, which my colleagues and I find extremely useful! Thank you for all the time and effort you are investing in it, for the high-quality material you are producing and the clear explanations!! I have two questions regarding the topic of inflation layers: 1. When you say in pipe flow it is common practice to size the prism layers to cover 20% of the diameter, is this the height of the actual prism layer on the inner pipe wall? (which would give 40% of the diameter of the pipe covered by inflation layers if we take the layer on the opposite side, along the diameter) Or is it 20% in total, which means 10% on each "side" (10% of the diameter is the actual thickness of the prism layer) 2. In the Inflation Layer Calculator on your website (and also in the course video), I am a bit confused about the term "maximum growth ratio" : if I understand correctly, that value of G is actually calculated from the equation $ \delta_{99} = y_H \frac{1-G^N}{1-G} $. This is the value that allows the total height of the prism layers to match exactly the estimated boundary layer thickness $\delta_{99}$, with a given number of layers N chosen by the user. If I take for G a value higher than the calculated value, then my boundary layer will SURELY be contained within the inflation layers (which was actually the objective). I know it will make the mesh unnecessarily large, but I'm just saying that the objective is still fulfilled. On the other side, if I take for G a value smaller than the calculated one, the condition is not fulfilled anymore. The prism layers will not contain the entire boundary layer. So, according to my understanding, if the objective is that the inflation layers contains the entire boundary layer, shouldn't the value we are calculating actually be called "Minimum Growth Ratio" ? Thanks a lot in advance, I really highly appreciate your work and your videos.
For anyone who might have the same questions, here is the reply I received from Dr. Aidan: Hi Theo 1) It's been a long time since I wrote this video, but I'm guessing 20% means 10% on each wall. 2) I think the implication is that if you adopt a higher growth ratio than the calculated value then there would be fewer layers between the wall and the edge of the boundary layer. This would give poor accuracy. For example, if you took an extreme case and went with a growth ratio of 5, you might only have 2 or 3 layers between the wall and the boundary layer thickness. This would give a really inaccurate answer, so you should reduce G and add more layers. Kind regards Aidan
Thanks, but i have a few question. In this article, they used a unstructured mesh with large volume transition. I wonder why they do that, can we have a exception ? And how to handle if we make elements near the wall very very small, it will make quality bad (with prism layers) ? This is article "Investigation of ribs disturbed entrance effect of heat transfer and pressure drop in pin-fin array"
It's hard to know why without reading the paper. If they didn't state a specific reason, they probably didn't think about it at all and just made a mesh that they thought was ok ....
@@fluidmechanics101 they didn't state a specific reason :( maybe they just look at the value which they need to find. So if that value is fine, they will think mesh is fine
Thank you so much for the wonderful video. You are a great teacher. I have one question reagrding the calculation of growth ratio. Since the growth ratio G is above 1, shouldn't the formula in (6) be yH*(G^N-1)/(G-1)?
You mentioned that for RANS, we want to avoid a large volume transition as it can lead to an error in the local gradients. Isn't the error dependent on the size of the cells, rather than on the growth rate? E.g. could you not have really small cells with a large growth rate, and still have small gradient error as long as the cells continue to remain small enough?
Hi, I’m a beginner for ANSYS fluent user. Now I’m simulating a natural convection by creating an air enclosure for a complex system. A minimum gap in my system is about 0.6 mm (between solid mating part). what method should I use to create the inflation layer?
It probably depends on the meshing software you are using 🙂 the real question is: are you sure you need to mesh the gap? Is it important? 0.6mm is quite a narrow gap ...
@@fluidmechanics101 I use the fluent meshing. If it’s possible, I will eliminate them, but I don’t know how to do this, please suggest me. One more question, I create an air enclosure and what is the boundary conditions I should apply to 6 faces of air enclosure. thank you in advance
Yes, if your gaps aren't of interest you should really try and close them up. 0.6mm gaps will be very difficult for Fluent meshing and probably give you bad cell quality. The best thing to do is probably go back to your CAD and try and close them up. It will save you a lot of trouble in the long run!
Great video! My case study is tubular heat exchanger. Where can I find the equations for internal flow in order to calculate the boundary layer thickness (δ99)?
I hope this message finds you well sir🙏 Sir, A rectangular duct 640 mm length, 20 mm height and 100 mm depth in which air is flow inside the duct with cross section ( 100 * 20 mm^2), with range of Reynolds numbe is 4000 to 20000, so please suggest me a formula to calculate boundary layer height Delta 99.
Hi Aidan, you mentioned that dU/dY is more for RANS and hence a wall normal resolution is necessary and if we were to perform LES simulations dU/dX comes into play and resolution of cells also needs to be done along the wall. Is it a characteristic of the analysis type itself that gives rise to these gradients or does a combined dU/dY and dU/dX variation exist in flows in nature?
An easy way to think about this is to think about turbulent eddies. In LES and reality, there are very small eddies close to the wall, which we need to resolve. These have gradients in the x, y and z directions which we need to resolve. In RANS we don't resolve these eddies so we only need to resolve the gradients in the mean flow variables in the y direction
Hello sir, I have a doubt......... as you mentioned at th-cam.com/video/1gSHN99I7L4/w-d-xo.html that we generally for a given inflation layer height, would like to have a smaller growth ratio and more layers, will that not make the cell aspect ration to become excessively high, also please correct me if I'm wrong, generally high aspect ration cells are not desirable right?
Yes, the aspect ratios will be higher and this can sometimes make the equations more difficult to solve (technically the matrices are stiffer). However, if you are in a boundary layer, the variation in the flow variables along the wall is much smaller than normal to the wall, and the CFD solver can usually handle it. If the aspect ratio gets too high (say larger than 5000) then it is worth reducing the cell size along the wall as well, to reduce the aspect ratio, rather than making the inflation layers thicker
From previous videos about y+ I get that both y+ = ~1 and y+ = ~30 are both viable choices. But then why would anyone want y+ = ~1? That's way more cells, way longer calculation time! Why one should aim for y+ = ~1 instead of y+ = ~30?
Great question! The logarithmic velocity profile that is used in the wall functions was derived from horizontal flow over a flat plate. So if your flow is similar to horizontal flow over a flat plate (say flow in a pipe, duct, or over a long surface without separation or heat transfer) then the logarithmic profile is likely to be a good approximation to the real flow that you are trying to simulate. This is implicitly what you are doing when you set y+ ~ 30. However, if your flow is different to these conditions (perhaps you have separation, strong buoyancy or an impinging jet) then the real flow is very different to what the logarithmic profile assumes. Hence, if you have y+~30 the CFD code will use the logarithmic profile and you will get the wrong answer!! (But you may never notice this). So the alternative is to make y+ ~ 1, so there is no model or assumption, since your are calculating the entire boundary layer using the CFD code. This is far more expensive but you are more likely to get the right answer. TLDR: y+ ~1 is more accurate, so use this if you can afford it and you are able to generate a mesh that solves. Use y+ ~ 30 if you have no other option 👍
@@fluidmechanics101 Thank you very much. I also watched your video on Transition SST, and there is requirement for y+~1 there. So I see it is also model dependent. That notice about heat transfer. If wall is adiabatic, but flow if very supersonic hence heated, should I consider that heat transfer exists? And aim fo y+~1?
When I use the Standard k-e model and I tried to keep the first layer y+~30, that gives me a large first cell height. Do I still need 10 prism layers even if I can just use 2 to cover the boundary layer?
What is your Reynolds number and what type of flow are you trying to simulate? It sounds like you won't get the resolution you need for an accurate solution with only 2 inflation layers. Have you tried aiming for y+ ~ 1 with k omega SST instead?
@@fluidmechanics101 Thanks for your reply Aidan. I am trying to simulate a free surface LBE flow in air in a closed channel. The Re is around 60000. Based on my understanding of your video on prism layers, the prism layers need to cover the thickness of the boundary layer. So if 2 layers are enough why need 10? I tried aiming for y+~1 using sst k-w but that the first layer height is very small and I will need a large number of cells otherwise the quality of the mesh is not good. I always have this question in generating mesh for sst k-w model. That is the cell number is too large and it takes so long to run the simulation.
Hi Ran, the key to remember is that the variation of the field variables across cells in the CFD mesh is linear (at best). So in a boundary layer, where the flow variables vary steeply, you need more than 2 cells to capture the shape of the profile. You can see this if you plot a line normal to the wall through the boundary layer, the profile will be piecewise linear. The best thing I can recommend for you is to do a thorough mesh sensitivity study. You will almost definitely find that 2 inflation layers is not enough to get the wall shear stress and heat transfer coefficient correct. Yes, having y+ ~ 1 will need a lot of cells and the simulation will be slow to run, but sometimes you just have to live with this in order to get an accurate answer 🙂
Yes it will correct the wall shear stress and heat transfer coefficient on the face of the cell in contact with the wall. However if you think of the other face of the cell in contact with the wall, because the cell is 'too fat' the shear stress and heat transfer across this face will be incorrect because the cell is too large to capture the physical gradient across the cell with a linear profile. (Remember that all gradients in CFD are linear but real gradients can be much steeper, which is why we need small cells in regions of high gradient). Does this help? I know this is quite complex and isn't really explained properly anywhere, so apologies if I am still a bit confusing
Beautiful video! Begginer in Ansys Fluent. I am trying to model a surf fin and get lift and drag coefficients. What model and y+ do you think it would be more accurate? I was aiming for y+ --> 1 and k-e but I am not so sure... Thank you in advance
I want to know if CFD is a good career opportunity in future looking 20+ years. Please guide me for my career. I am equally interested in CFD as well as FEA but not able to decide which to choose. Please help.
CFD and FEA will be stable careers for the foreseeable future. The reason for this is our energy systems, transport and industry rely on water, air, stainless steel and we need CFD and FEA to work out how these things will operate and fail. As industries they will always be niche, because they are only needed in special circumstances where hand calculations aren't capable. This is partly why they won't really be replaced by AI or machine learning because they are used as bespoke calculation tools and can't really be automated (as the art is how they are setup, not how they are solved). So as a career choice, if you want something consistent, they are a good choice. However, if you want the next best industry / popular thing, then a career in software development is probably a better choice. How to choose between CFD and FEA? Which one do you prefer? 🙂
The way to think of structured meshes is that the 'inflation layers' extend all the way through the block. The same ideas apply that you want to keep the boundary layer within the first block off the wall 👍
@@fluidmechanics101 Thank you for your reply. I am im CFD business for few years now. I find some basic topics are not clearly explained and even many professionals struggle to understand them. You are filling that gap in inspiring way. I'm not sure if I understand correctly your answer so let me paraphrase. What you trying to say is structured mesh doesn't need inflation layer because it already has desired shape/structure. But in order to capture BL (w/o use of wall func.) you need the same mesh resolution as described in the video. Is that right?
Damn... Just started working on quite big project with approx. 150 layers on the airfoil profile. I think I will find this talk EXTREMELY USEFUL ;) thanks for well done job. Regards
Great job. Thanks for the video. I have my own excel file to calculate y+ and I guess I'll add these formulas to help me estimate my first guess for the inflation mesh =)
I'm really fascinated with all of your videos. Big thanks! By the way, a topic "How should we do a mesh refinement study" would be very useful. In many research papers, authors do comparision base on the number of cells but not the meshing parameters
Great video! I would like to let you know that there is another channel called "ANSYS TUTORIAL | ANSYS COURSE | SIMULATION " that has uploaded this video. The name of the video is "Ansys | Inflation Layers Prism Layers In CFD".
Thank you for a nice explanation. Finally, I got a better understanding on defining a Y+. But, how to estimate Y+ for a complex geometry where flow accelerates/decelerates and defining dimension varies?
Just use your best guess. What is a representative length? How fast is the flow (roughly)? The important thing is to get the order of magnitude, not the actual value
For a rans calculation with refinement regions, does the same suggestion apply with regards to the cell volume transition? More specifically, the transition area should be placed in an area with low gradients? Also if a case has a high cell volume translation after the inflation layers, but the inflation layers span well beyond the boundary layer, is the concern lower because of the relatively low gradients? Thanks for the education!
@@fluidmechanics101 fantastic. I am really looking forward to more videos on meshing, the more CFD I do the more I realize the importance of meshing. Topics I have been asked a lot about and find interesting involve moving mesh and AMR. for AMR maybe you could talk about the different data structures and time marching techniques associated (global vs local), along with pros, cons, etc..
Thank you for making this video it clarify a lot of things for me. I have one question, to define the boundary layer thickness, we have to calculate Re and L, for a simple case of a flat plate, L is the length of the plate, and for pipe, its a hydraulic diameter. But in engineering application, the geometry is quite complex, if we take an example of formula 1 or engine cooling jacket, What value of L we should consider/ calculate?
The length of the car would probably be a good guess 👍 Remember that this is all to create a good initial mesh. After you have run your initial simulation it is worth looking at the mesh and checking to see if it is any good. (I.e check y+ and the velocity profiles close to the wall to see if the boundary layer is contained within the inflation layers)
Great video, so much to learn here. I have a question regarding the variation of y+ for mesh refinement studies though. How much do you advise the variation of y+ in different cases? for eg: for a case where I am targeting y+30, shall I take 30, 40 and 50? it would be a great help if you can clarify this. Thanks!
I think that covering an order of magnitude with your changes in y+ is a good idea. So y+ = 0.1, 0.2, 0.5 and 1.0 would be a good idea, or y+ = 30, 50, 100, 300. If you make the values too close together, then it can be difficult to see the changes in the solution. For example, y+ = 30, 35, 40, 45 probably wouldnt be as useful as 30, 50, 100 and 300. If you then find that the changes are large, you could refine you search afterwards. For example, if you tried 30, 50, 100 and 300, and the results change a lot, then you could add extra data points and try 35, 40, 45 and 55 afterwards. This is likely to be case dependent, so try it out and see what you find!
Hey, what do you think about mesh quality of the first layers of the inflation? I have performed some cases using inflation for an external flow simulation and the first layers of inflation (wedge element, similar to a pizza slice) get a low quality value. Despite of that, the flow behavior near to the ground is totally better than only using tetras. Thanks for this valuable information. Thumbs up!
Yes, the first layer often has bad quality because the cells are so thin. Usually most CFD codes are happy if the aspect ratio is less than 2000. For quality, it is worth zooming in and looking at the cells close to the wall. If the mesh lines are roughly perpendicular to the wall, then the cell quality should be fine. The difficulties tend to occur when the mesh lines close to the wall are skewed AND the aspect ratio is high. Good luck with your simulations! Don't get too put off my low quality, your simulation may still run successfully .... Give it a try!
Thank you, many of my doubts got cleared with this video. I have a doubt regarding determining y+ for natural convection problem. i searched internet but couldn't find any reliable source. Can you help me how to determine y+ in case of natural convection.
You can make a reasonable engineering estimate based on judgement for the velocity. i.e maybe 1 m/s for moderate temperature or 5 m/s for really hot temperatures (say 500C). Then run a quick CFD calc with a coarse mesh, see what you get and update your mesh. A first cell height of 0.1mm seems to work pretty well in most cases, as the flow velocities aren't that high in natural convection compared to forced convection
how about flow in a pipe when it comes to number of layers because at somewhere it s gonna fully developed but entrance region its developing so that will effect the size of the cell in x direction?
I have seen most of your videos and they are really very very helpful for CFD problem solving . So thank you very much for posting your videos . We would be more happy if you also post some videos on errors in CFD solvers and some more videos on the CFX or fluent software as well as how to solve errors which will not be straight forward at all . Hope to see them soon , thank you 🙏
Hello sir, thank you for the video. For guessing the number of inflation layer and its geometric growth rate, can we just make a layer height column in spreadsheet, next its total height up to each column number, and next its error% relative to delta_99? Then, simply try different growth rate values and pick whichever combination of N and G gives the smallest positive error% (a negative error% means the inflation layer doesn't capture the boundary layer). My initial thought is that this eliminates the hassle of using root finding methods or using arithmetic and logarithmic manipulation.
I think this is a historical question. Historically engineers would refer to block structured meshes as 'structured meshes' as a shorthand, because you could identify a particular cell in the block with an I,j,k index notation. In this sense the mesh is 'structured' by its blocks. A more modern interpretation would be that regions of a mesh with a regular 'structure' such as inflation layers could be referred to as 'structured' while the tetrahedral or polyhedral volume fill doesn't have a particular structure to it and can be referred to as 'unstructured'. Hence the mesh itself is a hybrid. Overall I think it is up to you. As long as the viewer/reader/reviewer understands how you made your mesh and where the cells are etc. you can describe it however you want. It is just semantics at the end of the day 😊
Hello, does anyone know a 3D grid generator that can provide prism layers using only hexahedrals and tetrahedrals while avoiding polyhedrals? SnappyHexMesh would be ideal but unfortunately produces polyhedra which our solver cannot handle. Thanks!
Yes. You can do this in ANSA or Fluent Meshing (formerly Tgrid). I assume that the reason for doing this is you want to use CFX and CFX can't handle polyhedral cells that are sometimes created in the buffer layer between the inflation layers and the hexcore?
@@fluidmechanics101 Awesome! Thanks for such a quick response. You're right about the solver not being able to handle polyhedral cells but I am using the hypersonics code, US3D. What would be ideal is hexahedrals on the surface with either a tetrahedral or hex core. Looks like ANSA produces tetrahedra on the surface while Fluent Meshing can do hexs on the surface. Can Fluent Meshing really do that without any polyhedral? Would be great and something on the level of GridPro.
I'm pretty sure ANSA can do hexes on the surface (if you are really careful when you make the mesh). As for fluent meshing, I am pretty sure it is possible but I am not sure of the exact TUI commands to do it
How to set the total thickness of prism layers for a fully developed internal flow? We can set the value to the boundary layer thickness for external flow. When you try to do the same for a fully developed internal flow, set the total thickness to pipe radius and this doesn't make sense.
![[CFD] Aspect Ratio Warnings in CFD](http://i.ytimg.com/vi/oa3sxesYsKc/mqdefault.jpg)
![[CFD] Aspect Ratio Warnings in CFD](/img/tr.png)
![[CFD] How Fine should my CFD mesh be?](/img/n.gif)
Congratulations, excellent contribution!
We can also consider a constraint on the size of the element of the last layer, to provide a smooth transition between the elements of the layer and the surrounding mesh.
It is common to choose the average size of the surrounding mesh elements. For a 2D mesh with triangular elements, let's imagine that the area of the last element of the layer has to be approximately the area of the triangular element of the mesh just around the layer, so:
Area of last layer element: A = (x1+x2)*y_last, where y_last = y*G^(N-1).
Area of surrounding mesh element: A = (x1+x2)*h/2
Therefore:
h=2*y*G^(N-1)=2*y*(G^N)/G (for square elements h = y*G^(N-1)).
Substituting G^N into equation (13), and rearranging:
G = (δ-y)/(δ - h/2)
and,
N = 1 + log(0.5*h/y)/log(G), in previous equation note that h/2 < δ.
We round off the number of layers and recalculate the growth rate:
G = (0.5*h/y)^(1/(N-1))
This is awesome. I'm going to pin the comment for everyone to see
I was revisiting this video and I have just realized that we don't actually need to use root-finding algorithm such as Newton-Raphson to solve equation (13) shown at 28:40.
We can rearrange that equation and then apply logarithm to both sides, ending with:
N = Ln (CG-C+1) / Ln (G).
With C = delta_99 / y_H
Common values for G are 1.1 or 1.2 (which is in the range you presented in the slides), so the solution is straight forward.
Btw I have already implemented this new equation to my Excel sheet.
Well spotted! I spent ages trying to rearrange it into a closed form solution 😄 I have pinned your comment so everyone else can see as well
If you write a book I will be the first to buy a copy!
i really need this to complete my undergraduate project. thank you so much.
Really enjoyed that, super interesting - as per normal! And yes, would love to see more on meshing
Amazing video, I love your channel! As a high school student finding videos on fluid dynamics which are understandable is so hard, but this was perfect
Another problem with large volume transitions is that these volumes appear in the system matrix. Large volume transitions can result in much stiffer system matrices yielding poor iterative performance, and sometimes solver divergence.
I've pinned your comment, as this is another great point that was missed out 👍
This video helped me to understand meshing better and concept of inflation layer covered in this video was what I was searching on youtube. Looking forward to learn more about CFD and fluid dynamics with your help.
This is groundbreaking to me, I´m learning so much from you!
I'm really looking forward on a video about Enhanced Wall Treatment in Fluent. Keep up the great work!
there is one already uploaded on his channel!
Super interesting material, excellent explanation. Many thanks.
It is very useful for me, and I really hope you can give more talks like this.
Great video, very very useful. I recently completed my Master's Degree in Aeronautical Engineering and my thesis was a CFD simulation of flow around thick airfoil. I was misunderstanding the process of mesh generation and now a lot seems more clear to me. Really great work, I hope you continue posting more and more videos and my answer to your question on whether you should continue videos on mesh generation - definitely !
Amazing Lecture, most useful for an engineering student like myself. It would be much appreciated if further meshing methodolgy videos could be uploaded. Thank you once again and keep up the excellent content.
Wonderful video. Captured every detail.
Great summary of the topic. I'd be interested in any suggestions for meshing with a stalled wing arise. I've read some allusions to meshes being to fine. In practice reducing element size in the x direction led to stall not being apparent from the simulation. I understand that no turbulence model properly predicts stall but any advice would be good. It seems like a nebulous topic like the inflation layers.
This is a really good talk
Outstanding Video! thank you for making these!
I really loved the talk, Thank you very much.
Some points I wanted to highlight:
1. If total thickness of your prismatic layers is greater then delta_99 then sudden cell volume increase shouldn't make any significant effect on friction coefficient, as friction is mostly generated in boundary layer.
2. In internal flows boundary layer usually spreads across the whole cross-section of a channel. So following your recommendations, meshes for internal flows should consist only of prism layers...
Yes to both. For 2) you normally have to have a few unstructured cells near the middle of the pipe to finish the mesh off (have a look for butterfly meshes, these are pretty popular for pipes)
Thanks for the informative video
It is quite useful!
appreciate your work.
thank you very much for your generosity in sharing this knowledge.
Thanks sir for great explanations and issues
Does anyone know where can I find empirical values of Boundary Thickness Layer for a fully developed turbulent pipe flow? Thanks!
... technically when the flow is fully developed the boundary layer fills the entire pipe. However, for meshing the inflation layers normally a good choice is 10% of the pipe diameter
Great video, thanks! This knowledge I needed :)
... I really appreciate ur work u have all my thanks 🙏🙏🙏🙏
Amazing!
Your videos are helping me build a strong foundation in CFD as a beginner.
I have sent you a LinkedIn request. I would like to discuss and clear few doubts regarding Masters in CFD.
So if you are okay with it please accept my request 🙃🙂
Thank you Dr. Aidan.
Really appreciate the efforts!
I don't really use LinkedIn, so best to post your questions as precisely as possible in the comments or just send me an email (fluidmechanics101@gmail.com)
@@fluidmechanics101 Thank you Dr. Aidan
Hello mr. Hardik Sharda
Your comments were really helpful for me to achieve proper results in cfd
Thank you so much for helping me
In case of the upstream flow condensation in a vertical duct, the inflation layer should cover both condensate film and boundary layer on the film surface? What would be the correct approach? Here I am talking not about the stable upstream flow where one would have stable falling film, but rather the case, where the flow velocity increases that much, that condensate begins to accumulate inside the pipe and liquid would be present across whole cross-section. Any comment would be useful. Thank you & great job with video lectures!
It sounds like you might need a pretty fine mesh resolution across your entire geometry, as you need accurate gradient calculation everywhere (you don't have a uniform freestream, which is usually assumed for boundary layer flow over a flat plate). For your case it sounds like a fully structured mesh in ICEM CFD or a hexcore mesh would be a good idea 👍
Very informative video Dr Aidan. I have doubt, if my cfd analysis involve blade with hub and shroud, do i still need to put the prism layer on the hub and shroud?
Yes, if you want to calculate the total drag (and hence pressure loss) correctly
@@fluidmechanics101 thanks for the reply Dr Aidan
Hello Dr. Aidan,
Thanks a lot for all your videos, which my colleagues and I find extremely useful! Thank you for all the time and effort you are investing in it, for the high-quality material you are producing and the clear explanations!!
I have two questions regarding the topic of inflation layers:
1. When you say in pipe flow it is common practice to size the prism layers to cover 20% of the diameter, is this the height of the actual prism layer on the inner pipe wall? (which would give 40% of the diameter of the pipe covered by inflation layers if we take the layer on the opposite side, along the diameter) Or is it 20% in total, which means 10% on each "side" (10% of the diameter is the actual thickness of the prism layer)
2. In the Inflation Layer Calculator on your website (and also in the course video), I am a bit confused about the term "maximum growth ratio" : if I understand correctly, that value of G is actually calculated from the equation $ \delta_{99} = y_H \frac{1-G^N}{1-G} $. This is the value that allows the total height of the prism layers to match exactly the estimated boundary layer thickness $\delta_{99}$, with a given number of layers N chosen by the user. If I take for G a value higher than the calculated value, then my boundary layer will SURELY be contained within the inflation layers (which was actually the objective). I know it will make the mesh unnecessarily large, but I'm just saying that the objective is still fulfilled. On the other side, if I take for G a value smaller than the calculated one, the condition is not fulfilled anymore. The prism layers will not contain the entire boundary layer.
So, according to my understanding, if the objective is that the inflation layers contains the entire boundary layer, shouldn't the value we are calculating actually be called "Minimum Growth Ratio" ?
Thanks a lot in advance, I really highly appreciate your work and your videos.
For anyone who might have the same questions, here is the reply I received from Dr. Aidan:
Hi Theo
1) It's been a long time since I wrote this video, but I'm guessing 20% means 10% on each wall.
2) I think the implication is that if you adopt a higher growth ratio than the calculated value then there would be fewer layers between the wall and the edge of the boundary layer. This would give poor accuracy.
For example, if you took an extreme case and went with a growth ratio of 5, you might only have 2 or 3 layers between the wall and the boundary layer thickness. This would give a really inaccurate answer, so you should reduce G and add more layers.
Kind regards
Aidan
Thanks, but i have a few question. In this article, they used a unstructured mesh with large volume transition. I wonder why they do that, can we have a exception ? And how to handle if we make elements near the wall very very small, it will make quality bad (with prism layers) ?
This is article "Investigation of ribs disturbed entrance effect of heat transfer and pressure
drop in pin-fin array"
It's hard to know why without reading the paper. If they didn't state a specific reason, they probably didn't think about it at all and just made a mesh that they thought was ok ....
@@fluidmechanics101 they didn't state a specific reason :( maybe they just look at the value which they need to find. So if that value is fine, they will think mesh is fine
Yep, I think you are probably 100% correct there 👍
Thank you so much for the wonderful video. You are a great teacher. I have one question reagrding the calculation of growth ratio. Since the growth ratio G is above 1, shouldn't the formula in (6) be yH*(G^N-1)/(G-1)?
Yep, that would also work
You mentioned that for RANS, we want to avoid a large volume transition as it can lead to an error in the local gradients. Isn't the error dependent on the size of the cells, rather than on the growth rate? E.g. could you not have really small cells with a large growth rate, and still have small gradient error as long as the cells continue to remain small enough?
thanks, Dr. Aydan so please can you explain that in Ansys fluent program
Amazing Job!
Hi, I’m a beginner for ANSYS fluent user. Now I’m simulating a natural convection by creating an air enclosure for a complex system. A minimum gap in my system is about 0.6 mm (between solid mating part). what method should I use to create the inflation layer?
It probably depends on the meshing software you are using 🙂 the real question is: are you sure you need to mesh the gap? Is it important? 0.6mm is quite a narrow gap ...
@@fluidmechanics101 I use the fluent meshing. If it’s possible, I will eliminate them, but I don’t know how to do this, please suggest me. One more question, I create an air enclosure and what is the boundary conditions I should apply to 6 faces of air enclosure. thank you in advance
Yes, if your gaps aren't of interest you should really try and close them up. 0.6mm gaps will be very difficult for Fluent meshing and probably give you bad cell quality. The best thing to do is probably go back to your CAD and try and close them up. It will save you a lot of trouble in the long run!
Thanks for your effort
Great video! My case study is tubular heat exchanger. Where can I find the equations for internal flow in order to calculate the boundary layer thickness (δ99)?
The BL fills the pipe in an internal flow. Use 20% of the pipe diameter instead as a reasonable estimate
@@fluidmechanics101Thank you for your reply! Do you have a reference that expresses this correlation?
Amazing Content!
Thank you so much sir!
Can you please make a video on region refinement 🙏
I hope this message finds you well sir🙏
Sir, A rectangular duct 640 mm length, 20 mm height and 100 mm depth in which air is flow inside the duct with cross section ( 100 * 20 mm^2), with range of Reynolds numbe is 4000 to 20000, so please suggest me a formula to calculate boundary layer height Delta 99.
Hi Aidan, you mentioned that dU/dY is more for RANS and hence a wall normal resolution is necessary and if we were to perform LES simulations dU/dX comes into play and resolution of cells also needs to be done along the wall. Is it a characteristic of the analysis type itself that gives rise to these gradients or does a combined dU/dY and dU/dX variation exist in flows in nature?
An easy way to think about this is to think about turbulent eddies. In LES and reality, there are very small eddies close to the wall, which we need to resolve. These have gradients in the x, y and z directions which we need to resolve. In RANS we don't resolve these eddies so we only need to resolve the gradients in the mean flow variables in the y direction
Thanks for clearing that up!👍
Hello sir, I have a doubt......... as you mentioned at th-cam.com/video/1gSHN99I7L4/w-d-xo.html that we generally for a given inflation layer height, would like to have a smaller growth ratio and more layers, will that not make the cell aspect ration to become excessively high, also please correct me if I'm wrong, generally high aspect ration cells are not desirable right?
Yes, the aspect ratios will be higher and this can sometimes make the equations more difficult to solve (technically the matrices are stiffer). However, if you are in a boundary layer, the variation in the flow variables along the wall is much smaller than normal to the wall, and the CFD solver can usually handle it. If the aspect ratio gets too high (say larger than 5000) then it is worth reducing the cell size along the wall as well, to reduce the aspect ratio, rather than making the inflation layers thicker
Hi
Just a quick question. If my inflation layer height is higher than my boundary layer then is that a very bad practice?
That's fine for accuracy. You might just have a few extra cells in your mesh. (More cells = slower solver)
@@fluidmechanics101 Great, thanks a lot for your response. Btw, big fan !!!
What exactly is the mathematical relationship between y+ and YH?
Y+ = y u_tau rho / mu, where u_tau = sqrt (wall shear stress / rho)
@@fluidmechanics101 Thank you for your reply :) the y in the y+ eqn you stated above is YP as opposed to YH right?
Yes! It is yp, not yH
@@fluidmechanics101 so yH is 2x yP?
Yes! YH = 2 yp
From previous videos about y+ I get that both y+ = ~1 and y+ = ~30 are both viable choices.
But then why would anyone want y+ = ~1? That's way more cells, way longer calculation time! Why one should aim for y+ = ~1 instead of y+ = ~30?
Great question! The logarithmic velocity profile that is used in the wall functions was derived from horizontal flow over a flat plate. So if your flow is similar to horizontal flow over a flat plate (say flow in a pipe, duct, or over a long surface without separation or heat transfer) then the logarithmic profile is likely to be a good approximation to the real flow that you are trying to simulate. This is implicitly what you are doing when you set y+ ~ 30. However, if your flow is different to these conditions (perhaps you have separation, strong buoyancy or an impinging jet) then the real flow is very different to what the logarithmic profile assumes. Hence, if you have y+~30 the CFD code will use the logarithmic profile and you will get the wrong answer!! (But you may never notice this). So the alternative is to make y+ ~ 1, so there is no model or assumption, since your are calculating the entire boundary layer using the CFD code. This is far more expensive but you are more likely to get the right answer. TLDR: y+ ~1 is more accurate, so use this if you can afford it and you are able to generate a mesh that solves. Use y+ ~ 30 if you have no other option 👍
@@fluidmechanics101 Thank you very much. I also watched your video on Transition SST, and there is requirement for y+~1 there. So I see it is also model dependent.
That notice about heat transfer. If wall is adiabatic, but flow if very supersonic hence heated, should I consider that heat transfer exists? And aim fo y+~1?
(if in doubt aim for y+ ~ 1, then we don't have to think too much about the resolution normal to the wall 😂)
When I use the Standard k-e model and I tried to keep the first layer y+~30, that gives me a large first cell height. Do I still need 10 prism layers even if I can just use 2 to cover the boundary layer?
What is your Reynolds number and what type of flow are you trying to simulate? It sounds like you won't get the resolution you need for an accurate solution with only 2 inflation layers. Have you tried aiming for y+ ~ 1 with k omega SST instead?
@@fluidmechanics101 Thanks for your reply Aidan. I am trying to simulate a free surface LBE flow in air in a closed channel. The Re is around 60000. Based on my understanding of your video on prism layers, the prism layers need to cover the thickness of the boundary layer. So if 2 layers are enough why need 10? I tried aiming for y+~1 using sst k-w but that the first layer height is very small and I will need a large number of cells otherwise the quality of the mesh is not good. I always have this question in generating mesh for sst k-w model. That is the cell number is too large and it takes so long to run the simulation.
Hi Ran, the key to remember is that the variation of the field variables across cells in the CFD mesh is linear (at best). So in a boundary layer, where the flow variables vary steeply, you need more than 2 cells to capture the shape of the profile. You can see this if you plot a line normal to the wall through the boundary layer, the profile will be piecewise linear. The best thing I can recommend for you is to do a thorough mesh sensitivity study. You will almost definitely find that 2 inflation layers is not enough to get the wall shear stress and heat transfer coefficient correct. Yes, having y+ ~ 1 will need a lot of cells and the simulation will be slow to run, but sometimes you just have to live with this in order to get an accurate answer 🙂
@@fluidmechanics101 Thanks again Aidan. For this case, shouldn't the wall function correct the wall shear stress and heat transfer coefficient?
Yes it will correct the wall shear stress and heat transfer coefficient on the face of the cell in contact with the wall. However if you think of the other face of the cell in contact with the wall, because the cell is 'too fat' the shear stress and heat transfer across this face will be incorrect because the cell is too large to capture the physical gradient across the cell with a linear profile. (Remember that all gradients in CFD are linear but real gradients can be much steeper, which is why we need small cells in regions of high gradient). Does this help? I know this is quite complex and isn't really explained properly anywhere, so apologies if I am still a bit confusing
Beautiful video! Begginer in Ansys Fluent.
I am trying to model a surf fin and get lift and drag coefficients. What model and y+ do you think it would be more accurate? I was aiming for y+ --> 1 and k-e but I am not so sure... Thank you in advance
And also, what of your videos do you think its best for understanding y+ in turbulent flow? Thank you!
Yep, a y+ of around 1 is a good place to start. Do you have any experimental data for your aerofoil sections to see how accurate your simulation is?
@@fluidmechanics101 Nop :(. You think k-e is good choice as well?
It's a good start. I would check out k omega SST as well
I want to know if CFD is a good career opportunity in future looking 20+ years. Please guide me for my career. I am equally interested in CFD as well as FEA but not able to decide which to choose. Please help.
CFD and FEA will be stable careers for the foreseeable future. The reason for this is our energy systems, transport and industry rely on water, air, stainless steel and we need CFD and FEA to work out how these things will operate and fail. As industries they will always be niche, because they are only needed in special circumstances where hand calculations aren't capable. This is partly why they won't really be replaced by AI or machine learning because they are used as bespoke calculation tools and can't really be automated (as the art is how they are setup, not how they are solved). So as a career choice, if you want something consistent, they are a good choice. However, if you want the next best industry / popular thing, then a career in software development is probably a better choice. How to choose between CFD and FEA? Which one do you prefer? 🙂
@@fluidmechanics101 Thanks for your reply sir. I would like to go with CFD as a career option and also learn FEA.
Good choice 😎
What about structured meshes? Great video, thanks.
The way to think of structured meshes is that the 'inflation layers' extend all the way through the block. The same ideas apply that you want to keep the boundary layer within the first block off the wall 👍
@@fluidmechanics101 Thank you for your reply. I am im CFD business for few years now. I find some basic topics are not clearly explained and even many professionals struggle to understand them. You are filling that gap in inspiring way.
I'm not sure if I understand correctly your answer so let me paraphrase. What you trying to say is structured mesh doesn't need inflation layer because it already has desired shape/structure. But in order to capture BL (w/o use of wall func.) you need the same mesh resolution as described in the video. Is that right?
Yep that seems right to me 👍
Love you [gay silence].
Wilson Donald Garcia Donna Lee Robert
Thompson Ronald Jones Elizabeth Lee Sandra
Please consider put Star CCM+ on your CFD software list :)
Damn... Just started working on quite big project with approx. 150 layers on the airfoil profile. I think I will find this talk EXTREMELY USEFUL ;) thanks for well done job. Regards
hello Aiden sir
Very nice video
please make the next video on CFD of combustion
Just by the time I started learning CFD you started to add content that i had questions about. Thank you :)
Solid work! Thanks a lot for sharing your knowledge with us! Cheers!
I totally agree with your opinion... There isn't too much information on how to to do a great mesh!!! Unhappilly I've found your content just now
Thank you
Thanks for this interesting and helpful tutorial. I really enjoyed it.
Thank you for the helpful in-depth explanation !❤
Your video was exactly what I needed to learn about inflation layers
Great job. Thanks for the video. I have my own excel file to calculate y+ and I guess I'll add these formulas to help me estimate my first guess for the inflation mesh =)
Awesome!
Absolutely amazing work, thank you!
You are totally wrong man , we should thank you not the inverse , what a great lesson thanks a lot
I'm really fascinated with all of your videos. Big thanks! By the way, a topic "How should we do a mesh refinement study" would be very useful. In many research papers, authors do comparision base on the number of cells but not the meshing parameters
Great video! I would like to let you know that there is another channel called "ANSYS TUTORIAL | ANSYS COURSE | SIMULATION " that has uploaded this video. The name of the video is "Ansys | Inflation Layers Prism Layers In CFD".
Thanks for letting me know. I really appreciate it
Thank you so much sir
Thank you for a nice explanation.
Finally, I got a better understanding on defining a Y+.
But, how to estimate Y+ for a complex geometry where flow accelerates/decelerates and defining dimension varies?
Just use your best guess. What is a representative length? How fast is the flow (roughly)? The important thing is to get the order of magnitude, not the actual value
For a rans calculation with refinement regions, does the same suggestion apply with regards to the cell volume transition? More specifically, the transition area should be placed in an area with low gradients?
Also if a case has a high cell volume translation after the inflation layers, but the inflation layers span well beyond the boundary layer, is the concern lower because of the relatively low gradients?
Thanks for the education!
Yep, that seems sensible. You can get away with a sudden volume transition if you are away from the areas with high gradients that you care about 👍
@@fluidmechanics101 fantastic. I am really looking forward to more videos on meshing, the more CFD I do the more I realize the importance of meshing.
Topics I have been asked a lot about and find interesting involve moving mesh and AMR. for AMR maybe you could talk about the different data structures and time marching techniques associated (global vs local), along with pros, cons, etc..
you are just amazing sir
Thank you! I would say this topic is essential. I looked at my meshes and it was immediately clear they need to be completely remeshed.
Very good information.... Cleared lot of doubts in layer generation...
Thank you for making this video it clarify a lot of things for me. I have one question, to define the boundary layer thickness, we have to calculate Re and L, for a simple case of a flat plate, L is the length of the plate, and for pipe, its a hydraulic diameter. But in engineering application, the geometry is quite complex, if we take an example of formula 1 or engine cooling jacket, What value of L we should consider/ calculate?
The length of the car would probably be a good guess 👍 Remember that this is all to create a good initial mesh. After you have run your initial simulation it is worth looking at the mesh and checking to see if it is any good. (I.e check y+ and the velocity profiles close to the wall to see if the boundary layer is contained within the inflation layers)
Thank you so much...
no matter what topic you go through, I like what you say
Great video, so much to learn here. I have a question regarding the variation of y+ for mesh refinement studies though. How much do you advise the variation of y+ in different cases? for eg: for a case where I am targeting y+30, shall I take 30, 40 and 50? it would be a great help if you can clarify this. Thanks!
I think that covering an order of magnitude with your changes in y+ is a good idea. So y+ = 0.1, 0.2, 0.5 and 1.0 would be a good idea, or y+ = 30, 50, 100, 300. If you make the values too close together, then it can be difficult to see the changes in the solution. For example, y+ = 30, 35, 40, 45 probably wouldnt be as useful as 30, 50, 100 and 300. If you then find that the changes are large, you could refine you search afterwards. For example, if you tried 30, 50, 100 and 300, and the results change a lot, then you could add extra data points and try 35, 40, 45 and 55 afterwards. This is likely to be case dependent, so try it out and see what you find!
@@fluidmechanics101 Thanks a lot for explaining it so clearly.
Very clear ! Without wall function
Very useful!
great one bro
Thank you!
"First LATER height" on "First Layer Height" slide
Thank you 😊
Hey, what do you think about mesh quality of the first layers of the inflation? I have performed some cases using inflation for an external flow simulation and the first layers of inflation (wedge element, similar to a pizza slice) get a low quality value. Despite of that, the flow behavior near to the ground is totally better than only using tetras. Thanks for this valuable information. Thumbs up!
Yes, the first layer often has bad quality because the cells are so thin. Usually most CFD codes are happy if the aspect ratio is less than 2000. For quality, it is worth zooming in and looking at the cells close to the wall. If the mesh lines are roughly perpendicular to the wall, then the cell quality should be fine. The difficulties tend to occur when the mesh lines close to the wall are skewed AND the aspect ratio is high. Good luck with your simulations! Don't get too put off my low quality, your simulation may still run successfully .... Give it a try!
Perfect
Hello really enjoy your CFD talk in your channel. can I ask to discuss a topic about the fundamental of 6-DoF. Thankyouu
Thank you, many of my doubts got cleared with this video. I have a doubt regarding determining y+ for natural convection problem. i searched internet but couldn't find any reliable source. Can you help me how to determine y+ in case of natural convection.
You can make a reasonable engineering estimate based on judgement for the velocity. i.e maybe 1 m/s for moderate temperature or 5 m/s for really hot temperatures (say 500C). Then run a quick CFD calc with a coarse mesh, see what you get and update your mesh. A first cell height of 0.1mm seems to work pretty well in most cases, as the flow velocities aren't that high in natural convection compared to forced convection
@@fluidmechanics101 Thank you
how about flow in a pipe when it comes to number of layers because at somewhere it s gonna fully developed but entrance region its developing so that will effect the size of the cell in x direction?
Yes, you are correct. For pipe flows, layers are normally set to cover around 20% of the diameter (which is based on the fully developed region)
@@fluidmechanics101 well-explained thank you.
I have seen most of your videos and they are really very very helpful for CFD problem solving . So thank you very much for posting your videos . We would be more happy if you also post some videos on errors in CFD solvers and some more videos on the CFX or fluent software as well as how to solve errors which will not be straight forward at all . Hope to see them soon , thank you 🙏
Hello sir, thank you for the video.
For guessing the number of inflation layer and its geometric growth rate, can we just make a layer height column in spreadsheet, next its total height up to each column number, and next its error% relative to delta_99? Then, simply try different growth rate values and pick whichever combination of N and G gives the smallest positive error% (a negative error% means the inflation layer doesn't capture the boundary layer). My initial thought is that this eliminates the hassle of using root finding methods or using arithmetic and logarithmic manipulation.
Would you call a unstructured mesh with inflation layers a hybrid mesh as it's a mix of the two?
I think this is a historical question. Historically engineers would refer to block structured meshes as 'structured meshes' as a shorthand, because you could identify a particular cell in the block with an I,j,k index notation. In this sense the mesh is 'structured' by its blocks.
A more modern interpretation would be that regions of a mesh with a regular 'structure' such as inflation layers could be referred to as 'structured' while the tetrahedral or polyhedral volume fill doesn't have a particular structure to it and can be referred to as 'unstructured'. Hence the mesh itself is a hybrid.
Overall I think it is up to you. As long as the viewer/reader/reviewer understands how you made your mesh and where the cells are etc. you can describe it however you want. It is just semantics at the end of the day 😊
@@fluidmechanics101 Thank you for such a detailed answer so quick! Really helpful!!!
dude, i love you so much, thank you for all of your amazing videos
Hello, does anyone know a 3D grid generator that can provide prism layers using only hexahedrals and tetrahedrals while avoiding polyhedrals? SnappyHexMesh would be ideal but unfortunately produces polyhedra which our solver cannot handle. Thanks!
Yes. You can do this in ANSA or Fluent Meshing (formerly Tgrid). I assume that the reason for doing this is you want to use CFX and CFX can't handle polyhedral cells that are sometimes created in the buffer layer between the inflation layers and the hexcore?
@@fluidmechanics101 Awesome! Thanks for such a quick response. You're right about the solver not being able to handle polyhedral cells but I am using the hypersonics code, US3D. What would be ideal is hexahedrals on the surface with either a tetrahedral or hex core. Looks like ANSA produces tetrahedra on the surface while Fluent Meshing can do hexs on the surface. Can Fluent Meshing really do that without any polyhedral? Would be great and something on the level of GridPro.
I'm pretty sure ANSA can do hexes on the surface (if you are really careful when you make the mesh). As for fluent meshing, I am pretty sure it is possible but I am not sure of the exact TUI commands to do it
How to set the total thickness of prism layers for a fully developed internal flow? We can set the value to the boundary layer thickness for external flow. When you try to do the same for a fully developed internal flow, set the total thickness to pipe radius and this doesn't make sense.
Can I get these ppts
Yes, they are all on my website: www.fluidmechanics101.com
Learnt some valuable info for my dissertation, thanks 👍
Does anyone know the previous video he is mentioning where he covered the y+ understanding?
Thanks,
Dr. Aidan, you are a blessing. Thank you for your contributions.💙
This lecture is great!! thank you very much!!