Design and Initial Characterization of the UTSI Mach 4 Ludwieg Tube

View Video Presentation: https://doi.org/10.2514/6.2021-0384.vid The University of Tennessee Space Institute has constructed a Mach 4 Ludwieg Tube (M4LT) in the Tennessee Aerothermodynamics Laboratory (TALon). The UTSI TALon M4LT has a two-dimensional, planar nozzle connected to a 24" x 24" x 72" test section that allows for the use of models that bridge the gap between scales used for foundational research to those used in the Test and Evaluation (T&E) community. The facility is designed with substantial optical access for a variety of optical diagnostic techniques such as high-speed schlieren imaging, unsteady pressure-sensitive paint, focused laser differential interferometry, and particle image velocimetry. Furthermore, the tunnel scale permits the development and subsequent transition of diagnostic capabilities from academia to T&E scale facilities. This paper provides details about the design of the tunnel and measurements from the commissioning and facility characterization experiments. The Mach 4 Ludwieg Tube at UTSI has excellent flow uniformity (M = 4.00 ± 0.5% in the first test region) and flow quality (normalized RMS Pitot pressure fluctuations are 0.67 - 1.14% in the first test region). The tunnel is currently operated by rupturing one or more stacked Mylar diaphragms, though near-term upgrades include the installation of a fast-acting valve to enable tunnel operation over a wider range of unit Reynolds numbers from Re = 1.0 - 16.5 million per foot.