So far for my problem I have been successful in getting the Umax and the inflow\outflow flux. I am using Solving PDEs in Python - <br> The FEniCS Tutorial Volume I as a framework to solve the problem. My last step is to obtain the drag and lift values, and as of now printing them in this way seen be…

Those forms are integrals, which you can compute using DOLFIN’s assemble() function. Something like print(f"drag: {assemble(D)}")

Thank you for your assistance, however I am getting an error using this function. It reads the following … Traceback (most recent call last): File "main.py", line 154, in <module> print(f"drag: {assemble(D)}") File "/usr/lib/petsc/lib/python3/dist-packages/dolfin/fem/assembling.py", line 202, in as…

I am not using the test or trial to compute the values. I have a reference to the code I am based my solution off of in the original post, but I am unable to pinpoint the issue if I can get assistance that would be wonderful. I am posting my MWE now below, thank you! # Function Space V = VectorFunc…

I figured out the issue, it was due to not defining the force correctly, I changed it to be the code below and it worked. Thank you for the assistance! I = Identity(u_.geometric_dimension()) force = dot(-p_*I + 2.0*nu*sym(grad(u_)), n)

Hello Ria I am using Solving PDEs in Python - The FEniCS Tutorial Volume I as a framework to solve the problem as well. I am trying to obtain the drag and lift values but as you have done, but I end up with the following errors : name ‘fe’ is not defined, when running ds = fe.ds(subdomain_da…

I figured them out as follows : ds = ds(subdomain_data=bc) And I changed n by j in my for loop. But why are you using ds(4)? I get zero values for drag and lift when ds(4), However, different values when ds()

Hi there, Solution to problem 2): You need to define n = FacetNormal(mesh) This should solve your problem and also give you non-zero values for drag and lift when you use ds(4). Keep j in your for loop so there are no conflicting variable names. Ben

I defined it. but i am still getting zero values. Would you please share your entire code.

The ds(4) is indicating that the integral should be over the subdomain labeled “4”. The integer labels are arbitrary, but the cylinder is marked as “4” in cylinder().mark(bc, 4). But if you just use ds() I think it will integrate over all boundaries. So the boundaries are handled slightly differe…

Would you please check the following steps if I did correctly : class cylinder(SubDomain): def inside(self, x, on_boundary): return x[0]>=0.15 and x[0]<=0.25 and x[1]>=0.15 and x[1]<=0.25 and on_boundary bc = MeshFunction(“size_t”, mesh, mesh.topology().dim() - 1, cylinder=4 ) and then delet…

How to Get Drag and Lift Coefficients for Flow Around a Cylinder

mathematics

nate June 30, 2021, 4:06pm 4

Make sure you’re computing the lift and drag of the solution function. Not a trial or test function. It’s difficult to debug without a MWE.

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How to Get Drag and Lift Coefficients for Flow Around a Cylinder

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