Help with understanding the results of CFD simulations

[mateuszn05]

Hi, for 2 months i m doing the project of RC car with massive standing on Aerodynamics that i m testing in CFD, i may have wrong question for that forum but maybye someone will help me there. However i have the results of simulation that amazed me. My car that is about 70cm long and without any spoilers and undertray the car is generating a lift force about 16N. Car with undertray but still with no spoilers have a vertical vorce about 0.004 N with a return upward. The same model but with spoilers generate more LIFT FORCE (about 0.1) that making me crazy because in simulation where i tested only the spoilers the results was a downforce about 5.4 N. So there is some mistake or mistakes that i definitely doing but i dont have any idea what may be wrong with it. I added screens of simulation results without any devices in car (aIRSHARD _ BEZ AEROPACKU.PNG), only with undertray (AFTER.PNG), with full aerodynamics (NOLIDEEEE,JPG) may that results may tell someone more than me. Thanks for help, regards

Matt

[karol.suchon]

Hello Mateusz,

With the current settings, you will be not able to get reasonable results. The air volume around the car is too small, probably the mesh also will be rather not the best one. In that situation, the forces generated by the fluid could be far from the real ones and be more or less random.

Here you have some information about the outside volume and BC. I will also set the floor BC as velocity in the Y direction. In reality, the car is driving on the road, not on the road 🙂

Aerodynamics simulation require also very fine mesh and a proper turbulence model.

Here you have more information.

After the meshing, you will get a lot of elements, so if that is possible, please cut the model in half and apply symmetry BC.

BR 

Karol