Calibration and Commissioning of a Mach 5 Ludwieg Tube at the University of Arizona

Abstract

Calibration, commissioning, and design features of a new Mach 5 Ludwieg Tube(LT5) at the University of Arizona are discussed. In addition, a tunnel shake-down has been completed and is examined. Diaphragm characterization for operation of LT5 has been completed and is reviewed. An experimental investigation into the Mach-number uniformity and free-stream noise levels using a Pitot rake at a range of unit Reynolds numbers (Re′) at multiple spanwise and streamwise positions has been performed. The wind tunnel has been shown to have a Mach number of 4.82 with variance less than 0.8% (and less than 0.5% at most streamwise positions). Throughout the experimental collection, streamwise positions of Pitot sensors range from -601.2 mm upstream of the nozzle exit plane to 256.3 mm downstream of the nozzle exit plane. Spanwise positions of Pitot sensors range from centerline to within 7.62 mm (0.3 in) of the tunnel wall. Mach number and free-stream noise profiles have been determined in both streamwise and spanwise directions. Calculating the thickness of the boundary-layer as the location where M is 99% of the free-stream value (δ99), a central core flow region has been determined at three locations. Within this central core, the average free-stream noise level (based on Pitot measurements) is shown to be less than 1.2% at an intermediate Reynolds number with some regions locally dropping below 1.0%. Additionally, as Re′ is increased, the free-stream noise level consistently decreases. Further, within both the boundary-layer and central core flow region, spectral content of the free stream has been characterized to estimate the power spectral density (PSD).