SimScale CAE Forum

MRF simulation settings

Dear Simscale Community,

I am trying to see the effect of rotating propeller on my design model, so I have attached 4 propellers to half of my model and ran simulations. When i compared the results with simulations without propellers, there is significant increase in drag which I cannot understand.

Can any kind soul kindly help me look through my settings? Since I am simulating at 4 degress alpha, would Inlet-Outlet boundary condition be appropriate? If theres any other settings issue please also let me know! Thanks a lot!

Here’s my project: https://www.simscale.com/workbench/?pid=8260458426540833859&mi=spec%3A42f37c60-e2e6-430e-9c85-69d7a63141eb%2Cservice%3ASIMULATION%2Cstrategy%3A36&ps=analysis%2FIncompressible--oneOf%2FboundaryConditions%2F1

Hi @000xwh,

The explanation I can offer is linked to a very turbulent and quicker flow behind your propellers making bigger wing drag. Moreover that flow is a ‘swirl’, hence even the lift forces can be (and are) lower.

About your BC: I suggest you edit your Wall3, as face99@solid should be at least set for ‘Slip’. But it would better to move it to inlet-outlet BC group.

Possibly you can make your mesh smaller (and simulation quicker), refining it around the geometry and making at level 5-6 elsewhere.

If you do not need to set yourself the turbulence etc., you can simplify the BC by just using standard Velocity Inlet and standard Pressure Outlet. All sides but Symmetry can be set to Custom > Zero Gradient (all) as you use AoA 4 or 5 degrees.

Take care,

Retsam