Discussion Forum

Dear all,
My name is Francesca and I'm working with comsol 5.2a.
I'm new in this forum. I hope that someone can help me.
I'm currently trying to simulate a magnetic helmet consisting of 60 permanent magnets.
I have a tube in which there is blood under the effect of the magnetic field produced by the magnets.
I have to study particles' behaviour under the effect of drag force and magnetic force in the tube.
After computing the stationary study for magnetic field I noted that at the coordinates of the tube the magnetic field shows relevant disorders. If I remove the tube the field disorders disappear. I think there is difference in results because of change in meshing by presence of cylinder, that is very small (diameter 50 micron).
So I proceed in this way:
I create a component 1 in which I study the magnetic field (study 1) produced by 60 magnets without cylinder.
Then I create a component 2 where there is only the cyilinder and I set the following physics:
-creeping flow (spf)
-particle tracing for fluid flow (fpt), in which I set the drag force and the magnetophoretic force, where I import the magnetic field solved in study 1 along the axis of the cylinder (with General Extrusion Coupling operator" which is defined in first component).
In component 2 I study the fluid-Dynamics (study 2 stationary) and I study the particles tracing (study 3 time dependent). When I setup the particle tracing, I can't solve for the magnetic field and fluid-dynamics at the same time. I check off "Values of variables not solved for" (in study 3) and I can choose either study 1 solution or study 2 solution and not both at the same time. I need to use them both at the same time when simulating the trajectory of the particles.
I hope that someone can help me.
Regards
Francesca