Learning Forum

[Danielius Snitkus]

Hello everyone,

I'm facing a problem with my ANSYS FLUENT simulations regarding the calculation of lift coefficients for aircraft elevator and elevator trim tab. Whenever I adjust the dimensions of the trim tab, I notice significant fluctuations in both the trim tab and elevator lift coefficients, the latter which should most definitely not happen.

Despite following methodologies that used to work before, I can't seem to achieve any consistent results. Maybe I'm going about this in a wrong way, I'd love to know how to accurately make lift calculations for every seperate part (stabilizer, elevator, trim tab) and get consistent results for my simulations or how to calculate moments, because I'm trying to find the change of the hinge moment for elevator using trim tabs. If anyone has encountered similar issues or has any insights on this, I'd greatly appreciate your guidance.

Thanks for your help in advance.

These are my calculation results (cl_e and l_e being elevator lift coef. and lift and cl_t and l_t being trim tab lift coef. and lift):

First

cl_e-op -1.9281960608e-02 []
cl_t-op 3.1437584034e-02 []
l_e-op -2.3816207438e+03 [N]
l_t-op 1.4113290342e+02 [N]

Second (smaller trim tab, same elevator size and conditions)

cl_e-op -4.4154678560e-02 []
cl_t-op 1.8855157262e-02 []
l_e-op -6.5873093253e+03 [N]
l_t-op 5.4930372883e+01 [N]

[Essence]

Hello,

How does the mesh look? I mean, what is the y+ value, number of infation layers and the growth rate? What is the minimum orthogonal quality? What is the Mach number? Could you share the screenshots of the mesh and the case setup panels?

[Danielius Snitkus]

These are most of my simulation and mesh settings. Also my lift coefficient aswell as some others are set to average a value over a 100 iterations. When I have trouble converging, I set the Time Scale Factor to 0.1

[Danielius Snitkus]

Minimum Orthogonal Quality is 0.286

[Essence]

Thanks for sharing the screenshots. I see that you have only two inflation layers. I would suggest to have at least 10-15 inlfsation layers as you are dealing in compressible flows. Turn ON the Warped Face Gardient correction and High Order Term Relaxation in Methods panel. If the temperature change is large, use temperature dependent properties in Materials panel. Try using Hybrid or FMG initialization.

[Danielius Snitkus]

 

 

I have tried out all of your suggestions and I believe the tab lift coefficient seems to be consistent now, but I am still getting extremely varying lift coefficients and therefore lift values on my elevator (wing) profile (changing the deflection angle of the tab seems to afect the elevator lift drastically). I also noticed my pressure distribution graphs are good for the tab, but messed up for the elevator. Also the center of pressure values at Y = 0, are correct for tab, but way out side the bounds of the elevator.

TAB

ELEVATOR

 

 

[Essence]

Hello,

If the flow is getting separated, on the wing, please use intermittent transition model or Transition 4-eqn model. Refer the Ansys guide for more information on the mentioned models.