We are running simulations of fluid dynamics in a stirring reactor including three impellers. Multiple frames of reference are used: inner zone including three impellers, and outer zone including tank walls and baffles. When we created the interface between the inner and outer zones, walls are automatically generated. We have specify all walls inside the inner zone as moving wall boundaries but the rotational speed is zero. The question is that how do we treat these walls? The second question is we use the torque function to calculate the power consumption using the function torque@default walls in the inner zone, is that correct? We know the interface between the inner and outer zone is artificial, the radius of the interface should not interfere with the torque values, however, we did find that the torque values change as the radius interface varies. There must be something wrong with the model. any suggestion for checking the model or set up?