# Some help understandig my simulation results

Hi everyone, all good?

So I am a freshman in college and I am using SimScale to mine reserach projects, right now my goal is: Calculate Lift (in Newtons), Drag (in Newtons) of a flying model.

I setup my simulation based on this tutorial https://www.simscale.com/docs/tutorials/tutorial-compressible-flow-simulation-around-a-wing/ with some minor changes to acommadate the small scale model, I am still working on a better mesh, but thats not the question today.

Thats my force plot:
Note the Y axis the lift and the Z the drag

Question are this the actual sum of total forces on the model? Or a pressure? If its the first case, makes no sense, if its the second how can I obtain the sum of the forces as a result?

My pressure area average of the flying model

I am doing something wrong? Or just misinterpreting the results? If you can reffer me to some tutorial or any kind of learning material I will be grateful
Best regards
Lucas

1 Like

Hi!

To quickly answer your question, the â€śForces and momentsâ€ť plot which you posted above (figure 1) represents the sum of forces onto the model.

To me, the values that you found donâ€™t look too weird. I can see that your model currently has an angle of attack of 0 degrees, so Iâ€™d expect little to no lift (or even negative lift) and a larger value for drag.

Some things worth noting:

• The tutorial that you posted was aiming for velocities > 0.3 Mach (where compressibility effects are not negligible). In your case, the velocities are far less than that, so using an Incompressible approach is not a bad idea.
• Running the simulation for more iterations is advised, as I can see that the forces are still shifting a little bit
• Apart from that tutorial, thereâ€™s also a workshop forum thread, which contains a similar tutorial for a wing (but using an incompressible approach instead). Iâ€™ll link it here in case you find it interesting: Workshop 2 Session 1: Optimization of a wing - Part II
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Hi! First thanks for the help! Made my day

The things is: Thats a 2m wingspan model capable of caring 7kg in the real life, I was expecting at least 70N as lift.

I will redo the simulation adding an 5 degrees angle of attack (BTW I do this by adding a Y velocity component right?) and based on the Workshop link you send, I will also be redoing my mesh, near the edge of the doing I am seing some anormalitties and I guess it is afeecting the results.

Thanks a lot for the help

1 Like

Hi!

That is correct. In fact, there are two ways to account for an angle of attack:

• Defining an angled inlet velocity (like in the tutorials) or,
• Rotating the geometry in your CAD software and importing to SimScale

I personally prefer to use the first option, because I can quickly change the AoA without having to upload a new geometry each time.

Cheers

3 Likes

Hi

The following Workshop 2 Session 1: Optimization of a wing - Part II seems mising. I really loved the tutorial and was following it. Do you have it anywhere else?

Thanks