Sidewall Mach Number Distributions for the NASA Langley Transonic Dynamics Tunnel

The TDT was recalibrated due to the conversion of the heavy gas test medium from R-12 to R-134a. The objectives of the tests were to determine the relationship between the freestream Mach number and the measured test section Mach number, and to quantify any necessary corrections. Other tests included the measurement of pressure distributions along the test-section walls, test-section centerline, at certain tunnel stations via a rake apparatus, and in the tunnel settling chamber. Wall boundary layer, turbulence, and flow angularity measurements were also performed. This paper discusses the determination of sidewall Mach number distributions. SYMBOLS f R flap setting, counts f S flap schedule configuration number M Mach Number P pressure, psf q dynamic pressure, psf T temperature, F X distance downstream from origin of tunnel contraction, ft y s slot width, in. Y lateral dimension from tunnel centerline (positive using right-hand rule), ft Z vertical dimension from tunnel centerline (positive upward), ft a f,R re-entry flap angle (positive when flap surface is divergent from tunnel centerline), deg. D difference operator g ratio of specific heats Subscripts: local value at surface pressure measurement orifice nose forward (upstream) re-entry flaps main aft (downstream) re-entry flaps t stagnation condition tc test chamber (plenum) wall tunnel sidewalls or top and bottom walls # freestream Abbreviations: DAS data acquisition system ESP electronically scanned pressure ID inside diameter OD outside diameter 2 psf pounds per square foot psid pounds per square inch differential TDT Transonic Dynamics Tunnel