Sailing aerodynamics: Sail trim variations
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- เผยแพร่เมื่อ 23 ก.ย. 2024
- Some results from our trim simulations. Forces from XFlow are connected to our VPP to give direct estimates of the difference in boat speed. Some conclusions:
- The mainsail leech controls most of the power.
- More power results in more boat speed in this wind range, despite a higher heeling force and increased heeling moment.
- In-hauling the jib pays off in the simulated conditions, but nearly a similar performance can be achieved with the out-hauled sail by adjusting its leech to be parallel with that of the in-hauled sail, and adding some fullness.
- The performance loss of a furling jib lifted from the deck (#1 in the graphic at the end) is considerable in this light wind case with little heel. With more heel, the loss would be less.
- The highest boat speed #14 was achieved by twisting the main 10° and adding leech return in the same amount, with the base jib. Nearly the same performance results in #13, with base mainsail and shape-optimized jib.
To put the speed differences in perspective, 0,1 knots means roughly 4 boat lengths after 15 min. of sailing. The simulation was run in 14 kn apparent, at an angle of 24°.
Sailing aerodynamics (c) WB-Sails 2021
Is this a mesh free CFD method? I am curious as to the numerical tool you use and if it compares well to wind tunnel tests
Yes, XFlow is a Lattice-Bolzmann besd, so-called meshless FCD code by Dassault Systemes. Wind tunnel tests have their own issues, like simulating the natural wind and scale effects, so there's little comparisons to od when it comes to sailboats. There's plenty of validations for well known industry benchmarks, see for intance www.3ds.com/fileadmin/PRODUCTS-SERVICES/SIMULIA/PRODUCTS/XFlow/pdf/Solution_to_industry_benchmark_problems_with_the_Lattice-Boltzmann_code_XFlow_01.pdf, or google "Xflow validation data" for more.
This is very interesting but difficult to understand, since it was so fast and short (22 seconds!). It would be better if you broke it down some more, explaining each of the sail settings by reference to a diagram in each simulation.
You are so right, Dave. Wish we had more time to document these simulations, but we are a sail loft, not a content producer. However, as we feel it is important to share knowledge, we try to post what we can. Setting up and running a simulation takes several weeks, but the analysis & documentation of the results can take many more.
@@WBSAILS1 Can't you get a student to do it as a masters project? Would be really great.
It's perfectly understandable that our sailmakers have things to do apart from making videos. We can say 'thank you!' and encourage them to do more like this. We can also use the pause button, which TH-cam so thoughtfully provides, if we can't listen/watch/read/assimilate/understand fast enough. Thank you WB Sails!