Development of a Supersonic Ludwieg-Tube Facility for Investigating High-Speed Multi-Phase Flows

The capabilities and characteristics of the University of Maryland’s new Mach 4 Ludwieg tube are presented for a pure nitrogen test gas. The wind tunnel is operational at Mach 4 for unit Reynolds numbers spanning ∼2.5×10⁶ m⁻¹ to ∼24×106 m⁻¹ with steady test times ranging from 30 to 40 ms and an average startup time of 15 ms. The pitot rake study indicates a core flow diameter of 160 mm at the nozzle exit that reduces to 140 mm at the tunnel viewing window. An analysis of the pressure fluctuations at various radial locations demonstrates that the plug valve produces no adverse effect on the flow. A particle size characterization study is performed for droplets produced from a 5% volume concentration of Di-Ethyl-Hexyl-Sebacate in methanol, resulting in known conditions for monodisperse DEHS droplet sizes. Initial results show a high-supersonic multi-phase flow in the wind tunnel test section.