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dibyadeep January 12, 2008 20:46

query from a newbie

I am actually trying to solve a problem using fluent, but since I am very new to it, I would appreciate any suggestions that you might give.

A schematic sketch of the problem can be found here:

The problem is a steady state problem, where the particle/2d sphere is suspended freely in the fluid, which is moving at a velocity 'u'. It is required to find the velocity and rotational speed of the particle as a function of its position in the tube. As far as I could understand I found three different ways of solving it.

1)Assume a very long tube, and restrict the particle to a fixed position by assuming a position dependent artificial external force field. Then use a dynamic mesh and start from a static particle and calculate the velocity, angular velocity far away from the entry point

2)Assume a short tube, and the particle fixed wrt to the tube. Use a moving coordinate system, moving with a velocity 'U' equal to that of the particle. Assume the particle angular velocity 'w', and then calculate the force and torque on the particle. Then iterate, varying the 'U' and 'w' of the particle such that both torque and force goes to zero. This would happen since the particle is freely bouyant in the fluid.

3)Assume a short tube, and the particle fixed wrt to the tube. Instead of assuming a fixed velocity/angular velocity for the particle as input, use the condition of no net axial force and torque, to calculate the velocity and angular velocity of the particle.

This last scheme seems particularly attractive to me, but I wanted to know whether it is implement such boundary conditions in fluent. Mathematically I don't see any problems, since the two extra conditions of no net torque/axial force provides two additional conditions for the two unknowns 'U' and 'w', but can this be implemented in fluent?

I would sincerely appreciate any help from you guys.

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