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글 편집
글 편집 (이전 에디터)
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To include the air resistance effect in RecurDyn, co-simulation with CFD software may give high-fidelity results but the calculation time would be very long.
Instead of co-simulation, Translational force can be used to represent the simple air resistance force.
You can define the x, y, z directional forces applied to CM (center marker) of a body.
Before you define the expressions for the translational force, you must create the action marker and reference marker that satisfy the following conditions.
- The action marker must be located at the same position as the CM of the body.
- The orientation and the location of the reference marker must be the same as the CM either.
The formula for drag force (air resistance) is as follows:
F=\({1}{2}C_dρAv_2\)
here, C_d=Drag Coefficient, rho=Fluid Density, A=Cross-sectional Area, v=Velocity
In the case of rigid bodies, all coefficients except the velocity will be defined as constants.
And for velocity, you need to use the relative velocity between the fluid and the body.
If the fluid is stationary and the density is constant, the force equation in each direction is as follows.
Fx= -0.5 * |VX|/VX * Cd_x * ρ * A_x * VX * VX
Fy= -0.5 * |VY|/VY * Cd_y * ρ * A_y * VY * VY
Fy= -0.5 * |VZ|/VZ * Cd_z * ρ * A_z * VZ * VZ
In the above formula, |VX|/VX is used to change the direction of the force according to the direction of the velocity.
