Two-dimensional streaming flows in high-intensity discharge lamps

Abstract

High-intensity discharge (HID) lamps embody a practical application in which acoustically generated streaming flows are used to significantly improve energy efficiency. Streaming in these lamps is examined using finite-element simulations in conjunction with available experimental results on the basis of the assumption that the streaming motion is excited by two-dimensional acoustic standing waves. Neither the magnitude nor the direction of the time-averaged flows is adequately explained by existing theory. Consequently, a modified streaming analysis is proposed in which the fluctuating flow is driven by an oscillating pressure field rather by a moving boundary and convective terms in both the instantaneous and streaming flows are included. Density variations are also shown to be important to the generation of the observed and simulated streaming. This analysis highlights the differences between streaming flows in HID lamps and those described in canonical problems appearing elsewhere in the literature.