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-   -   Why my simulation not agree with the wind tunnel experiment (http://www.cfd-online.com/Forums/cfx/86652-why-my-simulation-not-agree-wind-tunnel-experiment.html)

 zhaowei March 29, 2011 07:08

Why my simulation not agree with the wind tunnel experiment

2 Attachment(s)
Hi, all

I have done a simulation of the Harrington-2 helicopter rotor using CFX. The geometry is based on NACA-TN-2318 (can be downloaded from http://naca.larc.nasa.gov/search.jsp...3Dnaca-tn-2318) Page 11 and 21, single lower, tip speed of 262ft/s (rotational speed of 20.96 rad/s). I selected the collective pich angle of 5 deg to do the simulation. I use ICEM to generate the unstructured mesh. The boundary conditions are as follows:

Inflow: opening
Outflow: opening
simulation boundary: wall (free slip)

All interfaces setup between two domains are GGI and fronzen rotor. The fluid is air at 25 degree celsius, 1 atm. The simulation has run for 432 steps still not converge, but the forces and momets has converged, so I stoped it.

In the postprocessing stage, the thrust is 174.17N, and torque is 163.192Nm, then thrust and moment coefficients will be 0.00092 and 0.00022. These two numbers are not agree with the experiment with a relative error of 100%. :eek: I also use OpenFOAM to do the simulation using the same meshes, the result is thrust of 188.60137N, torque of 204.3016Nm, almost the same result. I did not put prism boundary mesh for the rotor mesh at first. Later I put 7 layers of prism mesh at the rotor, but no significant improvement, the result is quite similar. I wonder what might be the problem.

If my description is not enough to figure out the problem, please do not hesitate to ask for more details. Thanks in advance.

 ghorrocks March 30, 2011 19:13

http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

 aer July 9, 2015 09:24

hi Zhaowei

I'm sorry that I asked a question about the old post. I'll be gratefull if you help me.

I have been modeling harrington rotor 2 by CFX, I don't know, How can I calculate thrust and torque in cfd post?

Can you help me?

Thanks alot

 ghorrocks July 9, 2015 18:40

use the force() and torque() CEL expressions.

 aer July 11, 2015 03:36

Hi