Simplified 2D Sediment Modeling with HEC-RAS ("Capacity Only" and "Concentration Only" Modes)
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- เผยแพร่เมื่อ 20 ก.ย. 2023
- HEC has added some simplified, "fixed bed," sediment transport options to the 2D Sediment model. Stanford Gibson gave this presentation to the Corps' River Engineering Working Group about how the tools developed, what they do, and how they have been applied.
2D Sediment Background and Motivation 0:05
Conceptual Model of Morphological Analysis: 3:22
Story of Tool Development (Iao Project): 5:47
Overview of Capacity/Concentration Only Tool: 15:30
Application of Capacity Only (Arkansas): 16:18
Application of Concentration Only (Eagle Ck): 23:55 - กีฬา
Happy to see such insightful content !!
Sediment modeling has been cost prohibitive on all my project. This may be the first tool i can actually use on a day to day basis for designing structures here in Texas.
Hello Stanford,
I hope this message finds you well. I wanted to commend you on the superb content and engaging work you've been producing.
I have a question regarding the "Concentration Only" Mode. Currently, I am in the process of calibrating experiments conducted by GUTA at LEGI LAB Grenoble, France, using HEC-RAS 2D. The setup involves different settings of incoming loads (below capacity) categorized as LOW, MED, and HIGH, with a flume width of 0.35m.
I've encountered a few challenges:
1. Firstly, I am working with a particle density of 1192 kg/m³. Utilizing "User Defined Grain Classes," I inputted SG = 1.192 and BD = 655.6 kg/m³ with a porosity of 45%. I also adjusted the classes' diameters as required. My question is, does this approach work effectively?
2. Secondly, when inputting the upstream inflow boundary condition, whether using the Rating Curve or Time Series, I entered a value of 2 tonnes/day, which translates to 0.078 kg/m/s. However, the Results Map for "Total Load Transport Capacity" is indicating a significantly lower value of about 0.003 kg/m/s. Which Results Map should I refer to for the sediment rate or flux? I find it peculiar that the induced value is not reflected accurately in the model. Any insights on this discrepancy would be greatly appreciated.
3. Thirdly , is there a way to separate the sediment boundary condition from the flow boundary location? In the lab flume, the inflow is controlled by a hopper/funnel, positioned precisely. Is there a workaround for this?
Your expertise and guidance on these matters would be invaluable. Thank you for your time and assistance.
4. Lastly, I'm interested in understanding how to utilize the Non-Erodible Method in Adaptation Parameters. Could you please provide guidance on its implementation?
If you reach out to me on LinkedIn or ResearchGate I can look at your model and see if there is a bug in the boundary
Hi Standford, very nice video. I have the following query, how would a mudflow impact a river confluence, would the flow increase at the rate of the mixing flow or would the solids be deposited as a function of the carrying capacity and the flow increase would only be due to the contributing liquid flow. Thanks!
Hi Stanford, great insightful video! At the Iao sediment study, why does the flow velocity (and capacity) decrease abruptly upstream of your profile line by approx. 12 ft/s? Thanks!
So there is a concrete apron there, at about a 30% slope. So its an ultra-high velocity zone even at high flows. Probably should have shown a picture of that, because it does give it a very distinctive velocity signature.
Hi Stanford, thanks for sharing this. If I assume concentration only, the sediment still can deposit along the way downstream?
The model can "lose" or "gain" sediment out of or into suspension, but it does not change the bed or bed gradation, so there is no feedback. If capacity exceeds supply it will pick up sediment and if capacity drops downstream it will decrease the concentration, but it does not actually deposit or erode (e.g. update the geometry or starting gradation)
I was tryig to define the boundary condition for non erodible beds such that bigger rocks that couldn't be moved or the banks as walls, because the HECRAS is assuming the same sediment curve for whole domain? How can I solve this? any relevant videos regarding this?
Sorry, I don't totally understand. If you are using the sediment model, you can define "gradation" polygons as "non-erodible" - which is usually how I deal with it. www.hec.usace.army.mil/confluence/rasdocs/h2sd/ras2dsed/latest/sediment-data/initial-conditions-bed-materials-and-transport-parameters#id-.InitialConditions,BedMaterials,andTransportParametersv6.3-BedGradations
Dr. Gibson - Thank you for all the work! Is the R source code available for the Transport/Capacity equations? Rather than re-invent the wheel, I would like to convert portions of the code to python to help determine capacity using SRH-2D (HDF5) output.
Hello Jeffrey, our code is still in Fortran (for another 1-3 years)
@@stanfordgibson I work for a State DOT and developed a program to compute the transport capacity per unit width using SRH-2D Output. I used the Brownlie and MPM equations as a start.
My goal is to make this simple for Consultants in my State as there is never budget for stream restoration projects. That said, for gravel bed rivers, can the D50 be used to estimate the average transport capacity? Or is this an under estimation?