  For energy efficiency and material cost reduction it is preferred to drive
high-intensity discharge lamps at frequencies of approximately 300 kHz.
However, operating lamps at these high frequencies bears the risk of
stimulating acoustic resonances inside the arc tube, which can result in low
frequency light flicker and even lamp destruction. The acoustic streaming
effect has been identified as the link between high frequency resonances and
low frequency flicker. A highly coupled 3D multiphysics model has been set up
to calculate the acoustic streaming velocity field inside the arc tube of
high-intensity discharge lamps. It has been found that the velocity field
suffers a phase transition to an asymmetrical state at a critical acoustic
streaming force. The system behaves similar to a ferromagnet near the Curie
point. Furthermore, it is discussed how the model allows to investigate the
light flicker phenomenon. Concerning computer resources the procedure is
considerably less demanding than a direct approach with a transient model.
