Fluids

Fluids

Drag coefficient calculation

    • mstricks
      Subscriber


      This is a fuselage and i want calculate drag coefficient of this body I have done all the procedures but my drag coefficient is coming negative. 


      I request to please guide me what parameters i need to set


      to calculate drag coefficient.


      Thanks

    • paguado
      Ansys Employee

      Have you checked the drag force? Is it negative or positive? The drag coefficient is obtained from this force and may take the sign. You can also use 1/2*rho*S*U_inf^2 to non-dimensionalize the drag Force and take the net value to calculate the Cd. It would be good to know if this absolute value is the same as the one you observe when you plot the Cd

    • DrAmine
      Ansys Employee

      Check the direction vector along which drag force and the coefficients are calculated. The vector for drag will be the direction of the flow (for lift will be perpendicular for that direction). paguado wrote what you can else try! 

    • mstricks
      Subscriber

      Have you checked the drag force? Is it negative or positive? The drag coefficient is obtained from this force and may take the sign. You can also use 1/2*rho*S*U_inf^2 to non-dimensionalize the drag Force and take the net value to calculate the Cd. It would be good to know if this absolute value is the same as the one you observe when you plot the Cd


      thanks sir I understand what you are saying


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