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## continuous magnetic separation model

Posted 2011年2月1日 GMT-0500下午2:57 Chemical Reaction Engineering, Results & Visualization Version 3.5a 8 Replies

I am modeling a continuous magnetic separator. As it can be seen from the model attached, I have five magnetizable wires that get magnetized by the magnetic field boundary conditions applied to the boundaries of the surrounding domain.

I have applied a square wave function for the magnetic field boundary condition to simulate magnet on-off situation. The Nernst Planck equation calculates the concentration profiles for particles moving under the influence of convection, diffusion and magnetic force (represented here as voltage).

I solve for magnetic field first. Save the results and then follow it with solving the nernst planck and navier stokes equation simultaneously (since I have expressed viscosity as a function of concentration).

I had a couple of strange results and was hoping for your help on it.

1. The square function applied resulted in not a smooth square magnetic field function but rather a sinusoidal increasing and decreasing magnetic field, followed by zero field for a period

Is the boundary conditions inputted wrong?

2. After solving the navier stokes/nernst planck equations, magnetic field was observed again as a function of time. It now showed a constant magnetic field and not the square function that was inputted (or the sinusoidal function that was observed).

Why does this happen?

3. Magnetic field of the wires should attract the particles while the flow pushes it through the outlet. Given that the on-off magnetic field was applied, it is natural to expect a greater concentration of particles exiting boundary 15 compared to 14. However, boundary integration yields the almost same concentration/flux for the two boundaries.

Why is that so?

Any help on this will be appreciated.

-Asha

I have applied a square wave function for the magnetic field boundary condition to simulate magnet on-off situation. The Nernst Planck equation calculates the concentration profiles for particles moving under the influence of convection, diffusion and magnetic force (represented here as voltage).

I solve for magnetic field first. Save the results and then follow it with solving the nernst planck and navier stokes equation simultaneously (since I have expressed viscosity as a function of concentration).

I had a couple of strange results and was hoping for your help on it.

1. The square function applied resulted in not a smooth square magnetic field function but rather a sinusoidal increasing and decreasing magnetic field, followed by zero field for a period

Is the boundary conditions inputted wrong?

2. After solving the navier stokes/nernst planck equations, magnetic field was observed again as a function of time. It now showed a constant magnetic field and not the square function that was inputted (or the sinusoidal function that was observed).

Why does this happen?

3. Magnetic field of the wires should attract the particles while the flow pushes it through the outlet. Given that the on-off magnetic field was applied, it is natural to expect a greater concentration of particles exiting boundary 15 compared to 14. However, boundary integration yields the almost same concentration/flux for the two boundaries.

Why is that so?

Any help on this will be appreciated.

-Asha

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8 Replies Last Post 2013年4月8日 GMT-0400上午1:27