Velocity vector - incidence angle of aero profil - MotionView

Thomas_Bécue
Thomas_Bécue New Altair Community Member
in Community Q&A

Hi,
I'm working on an aero project on MotionView.
I need to return the incidence angle for a lift force calculation.

The incidence angle is the angle between the Chord line of my aerodynamics profil (represented by one of the direction of a marker in my model) and the vector of his relative velocity, Vr.
To calculate Vr, I return the Vx, Vy and Vz velocity amplitudes of my marker linked to my profil body and ad a wind value in the x direction :

Vx_relative = Vx + Vwind
Vy_relative = Vy
Vz_relative = Vz

image.png



Do you know how can i have this velocity vector ?
I didn't manage to give solver variable values to a Vector entity : "Error"

Thanks in advance,
Thomas

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Answers

  • GTT Adam
    GTT Adam
    Altair Employee

    Hi Thomas,

    It seems like this can be solved with some trigonometry.

    1. Create Solver Variables for VX, VZ, and VR.
      1. Let's call them sv_vx, sv_vz, sv_vr.
    2. Set their types to expression, and use the VX and VZ functions to compute the velocity components for sv_vx and sv_vz. If there is a marker on the wing, called MODEL.m_wing, then the expression could be:
      1. ` VX({MODEL.m_wing.idstring},{MODEL.Global_Frame.idstring}) `
    3. For sv_vr, the resultant velocity expression would be:
      1. ` sqrt({MODEL.sv_vx.VARVAL}^2 + {MODEL.sv_vz.VARVAL}^2) `
    4. The angle of the resultant velocity relative to the Chord Line wind would be:
      1. ` A + ATAN({MODEL.sv_vx.VARVAL}/{MODEL.sv_vz.VARVAL} `, where A is the angle between the Chord Line and the Relative Wind vector.

    Measure these new system variables using an Output with the type set to Expression. Here you can reference the new variables to see their time-history through the event.

    I suggest you create a test model with simple values and a predictable output to make sure you have it all figured out before deploying it in your full model.

    Hope this helps!

    Adam Reid

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