Modification of Transonic Blowdown Wind Tunnel to Produce Oscillating Freestream Mach Number

This paper details the design, construction, and evaluation of a modification to Ohio State’s 6” × 22” Transonic Wind Tunnel to enable modulation of the freestream Mach number. The test section Mach number in this blowdown facility is dynamically set by varying the choke area in a harmonic fashion. Disturbances from the modulated throat area propagate upstream to vary the test section Mach number. Flow properties such as wave propagation speed were evaluated using 1D theory, 2D CFD, and experiments in order to understand the fundamental mechanisms of the Mach oscillation process and subsequent performance limitations of the facility. The current configuration of the Mach oscillation feature enables Mach oscillations between 0.4 and 0.6 at a controlled frequency up to 25Hz and a Reynolds number range of 2 – 16 million per foot.