Modelling of fluid-mechanical arc instability in pure-mercury HID lamps

Abstract

A fully unsteady compressible 2D flow model is used to reproduce observed fluid-mechanical arc instability in a horizontally-running pure-mercury HID lamp. The model represents a 2D lamp cross-section normal to the arc, and assumes an infinitely long lamp. Departure from the steady condition is driven by oscillating lamp current. Sound-wave propagation and induced flows result from full coupling between the current, energy balance, ideal-gas law and conservation of mass and momentum, on two separate relevant time scales. Observed acoustically generated arc instability is reproduced with the model.