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Hello Everyone,
thanks for all the support or tips you may give on the following problem.
I am trying to couple three different modules, to monitor the displacement of a bubble in a channel in 3D under the effect of an electric field.
I solve the displacement of the bubble through a differential equation in the ODE solver, for which one term is given by the electromagnetic force computed by the electrostatic module at each position of the bubble.
The force computation is done on the domain of the bubble. The bubble boundaries move with the prescribed mesh displacement given by the solution of the ODE solver. I use a ALE moving mesh to move the bubble.
I have verified the single physics/modules together and coupled two by two. The ODE and ALE work fine together with an arbitrary force not given by the electrostatic module. The ODE and electrostatic work well together and now that I am coupling the ALE with the electrostatic module, Comsol does not recognize the Maxwell stress tensor anymore (the variable mod1.es.unTz evaluated on the boundaries of the bubble.
I don't understand why with adding the moving mesh ALE, the simulation just doesn't start anymore and says it fails to evaluate the variable. I attach my model file for clarifications. I hope anybody out there can point some way around this.
Thanks a lot.

Stefano