Simulation results and validation measurements of a viscous coupling are presented. The analyzed Visco^® clutch of MAHLE Behr is used to control the speed of the cooling fan of heavy duty trucks. It consists of a driven primary disc and a secondary housing with an engine cooling fan mounted on it. Highly viscous oil is pumped into small channels between these parts. Therefore, the fan speed depends on the amount of oil and its distribution within the clutch.

The objective of the simulation is to reproduce the dynamic behavior of the coupling with respect to time dependent cooling requirements of the engine. Furthermore, local effects within the work chamber can be studied in detail.

Challenges for the simulation arise from underresolved multiphase flow, high rotation rates, the small dimension of the microchannels and the non Newtonian behavior of the working fluid. The presentation gives insight into the modeling approach needed to cover the relevant physics reliably. Results of the dynamic phase distribution, flow field and pressure distribution are shown and compared to measurements.