[Daniel S.]

Hello,
I’m a student working on an aircraft trim tab project, and I have very little experience with ANSYS. I have run into a problem while doing the ANSYS FLUID elevator and trim tab aerodynamic analysis. I’m attempting to create a trim tab that would provide enough of a moment at the hinge point to stabilize the elevator hinge moment at any given elevator deflection angle. Theoretically, I should be able to achieve this with a relatively small trim tab (such as a 1 mm thick sheet of alloy), but it seems that even at the cruise speed of the aircraft, angle of attack being at 0° (angle of airflow to the wing) and with a relatively small deflection angle the flow at both the elevator and the trim tab gets cut off (a turbulent drag zone is created, blue area in the velocity magnitude picture) and isn’t able to generate enough pressure to create the necessary moment at the hinge. It seems like I’m doing something wrong and that this shouldn’t be happening at these deflection angles.

Is there anything I could try to fix this? I need to be able to create a moment at the trim tab hinge point big enough to null the elevator hinge moment, so that my output m_0 ≈ 0, and achieve this at higher elevator and trim tab angles of deflection so I would know what dimensions and maximum deflection angles I need for my trim tab.

I hope I didn’t make my problem too confusing and explained it well enough. Any help would be greatly appreciated.

I am providing two of my ANSYS FLUENT simulation results.

First result:

Elevator at -20° deflection, trim tab at +20° deflection; 0° AoA, 160 km/h airspeed.
574 solution is converged (500 at Time Scale Factor of 1; 74 at Time Scale Factor of 0.1).
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Output Parameter Value Units
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cl-op 6.4211260463e-01 []
cd-op 5.9087811254e-02 []
cl_t-op -1.4966996697e-02 []
cd_t-op 1.7894364467e-04 []
cm_e-op 4.3395780641e-02 []
cm_t-op -3.2668749899e-04 []
m_e-op 3.7439656010e+03 [N]
m_t-op -1.8984239790e-01 [N]
m_0-op 3.7437757586e+03 [N]
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Second result:

Elevator at +5° deflection, trim tab at -20° deflection; 0° AoA, 160 km/h airspeed.
403 solution is converged (144 at Time Scale Factor of 1).
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Output Parameter Value Units
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cl-op -5.9847706313e-02 []
cd-op 1.3447028534e-02 []
cl_t-op 2.9844562064e-02 []
cd_t-op 8.0936517087e-03 []
cm_e-op 1.0344199814e-02 []
cm_t-op 3.1078055068e-03 []
m_e-op 8.9244455801e+02 [%]
m_t-op 1.8059866124e+00 [%]
m_0-op 8.9425054462e+02 [%]
------------------------------------------------