Discussion Forum

Hello,

I am a graduate student at SU working on a model of the brake disc heat generation in our formula SAE car. I have attempted to create a model of our custom designed brake discs in order to identify the temperature gradient of the disc under brake loading. However upon attempt to compute the solution I am obtaining the following error.

Undefined variable. - Variable: ht.tc1.Qb - Geometry: geom1 - Boundary: 63 Failed to evaluate Jacobian of expression. - Expression: ht.tc1.Qb

Since boundary 63 (and 66) is the pad face that is supposed to be in contact with the disc face, I believe that the error has something to do with the geometric interface of those entities. The variable ht.tc1.Qb is defined in the thermal contact and global equations node.

I have attempted to create a 'contact pair' (in order to mitigate another error in which boundaries 63 and 66 were 'not applicable' for thermal contact) and a few other pair combinations but am obtaining the same/similar errors. I believe there is a relatively easy fix to my problem but being new at Comsol and after reading as many discussions I couldnt derive a solution on my own so I decided to create my own thread. Any help would be greatly appreciated. Thank you for your time and consideration.

Note: for the formulation of the physics I have closely followed the comsol heat generation in a brake disc pdf which can be found on their website here https://www.comsol.com/model/download/468901/models.heat.brake_disc.pdf

I was successful in simulating that, and another geometry (a simple disc) that I built in comsol. However I have not been successful while using the imported CAD geometries.