how to calculate the drag force of a sphere in axisymmetry

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how to calculate the drag force of a sphere in axisymmetry

Nora
Hi
I have a rather basic simulation that I would like to preform that can be compared to reference values.
What I want to do is to simulate the drag force of a sphere in axisymmetry setup.
I have manage build the model and run the simulation and the velocity plot looks reasonable.
My question is how I should define the correct equation for drag force in the Boundary Integration box (for axisymmetry)?
My thanks for help in advance!
BR





 
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Re: how to calculate the drag force of a sphere in axisymmetry

Precise Simulation
Administrator
Similar to the flow around a cylinder benchmark example

https://www.featool.com/doc/fluid_dynamics_04_flow_around_cylinder1

you would need to derive and integrate the (axisymmetric) expression for the Total-stress tensor in the z-direction, which should be something like

  fz = r*(nz*p+miu*(-nr*(wr+uz)-2*nz*wz))
  cd = 2*fz/(rho*umean^2*diam) 

That said, the solution in the attached image does not look converged as fluctuates a lot between grid cells. Depending on the flow regime you might need to increase the mesh density, use artificial (numerical) stabilization, and/or a turbulence model.
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Re: how to calculate the drag force of a sphere in axisymmetry

Nora
Thank you for your replay. I will consider you comments and redo the simulation.