Reply To: ICFD Extremely high and constant drag pressure forces

[arnau994]

 

Hello Reno,

Thank you for your fast response. I am answering your questions below:

1. I am using version mpp d R13, revision R13.1.1-17-ga451ec960f

2. I have run the cylinder example without changing any input data (Re = 100, right?). At 50s, on the icfdragi.dat I get the following forces:
Fpx = -2.622783E-01    Fpy = 9.907471E-02  Fvx = -8.534790E-02   Fvy = 1.326471E-02

Which is: Fx = 0.347N (cD = 3.53) and Fy = 0.112N (cL = 1.14). From the icfdraga.dat i get simillar forces on x and considerably lower on y

This does not correlate with page 10 of the pdf that you have attached. Let me know what do you think, as it might be that I am not looking to the correct data.

3. At 10m/s I already have pressures of 2e6 (very homogeneous). At 56m/s, I have pressures that vary between 3.5e6 and 7.5e5. Pressure distribution however makes sense qualitatively. According to published data, pressures should be between 6e3 and 2e4 

This makes me think that there is some kind of initial pressure on the model, but the only pressure-related input/boundary condition is at the output surface with *ICFD_BOUNDARY_PRESCRIBED_PRE.

4. I have run the model applying a freeslip condition in the body surface. Now I don’t get any viscosity forces in both icfdraga.dat and icfdragi.dat. Pressure forces are simillar between files, and have decreased by 14% aprox in all x, y and z axes compared with non-slip simulation. But still, they remain in the range of 10^4/10^5, when they should be in the range of 10^2/10^3.

I hope this helps. Thank you very much,
Arnau