Boundary Layer Characteristics At Mach Numbers 2 Through 5 In The Test Section Of The 12 Inch Supersonic Tunnel

As part of a general tunnel calibration program, an investigation was made of the boundary-layer characteristics at Mach numbers 2, 3, 4, and 5 in the test section of the 12-Inch Supersonic Tunnel (D). The boundary-layer measurements were made at one longitudinal station (near the pitch sector center of rotation) on the centerline of both the flexible plate and sidewall. Measurements were also made at vertical locations on the sidewall between the sidewall centerline and the upper flexible plate. The boundary-layer total thickness, displacement thickness, and momentum thickness, are presented at each Mach number over a Reynolds number range corresponding, in general, to tunnel stagnation pressures between 5 and 60 psia. At each Mach number, the variation of displacement thickness on the side wall between the centerline and the upper flexible plate is presented as is a correlation of the flexible plate displacement thickness with experimental data obtained in other wind tunnels. Velocity profiles and test section Mach numbers are presented to indicate variations with Reynolds number.

A test program was conducted to investigate the boundary-layer characteristics of the von Karman Gas Dynamics Facility's 40 x 40 inch continuous, supersonic wind tunnel (Tunnel A). The program was divided into two parts: (1) a survery of the boundary layer at one station at the center of the flexible nozzle plate (curved wall) and (2) a survey at one station at the center of the tunnel sidewall. For the minimum Reynolds number, the boundary-layer displacement thickness is greater on the sidewall than on the flexible nozzle plate at all Mach numbers, whereas at maximum Reynolds numbers the displacement thicknesses are essentially the same. The measured displacement thicknesses on the flexible nozzle plate and sidewall showed good agreement with theory when the turbulent skin friction coefficients were evaluated from Reynolds numbers based on wall density and kinematic viscosity. Theoretical estimates of the displacement thicknesses determined by using Reynolds numbers based on free-stream density and kinematic viscosity were consistently higher than the experimental values.

A compilation has been made of all calibration data obtained since 1958 in the von Karman Gas Dynamics Facility's 12-Inch Supersonic Tunnel (D). Test section flow characteristics are presented for the nominal Mach number range from 1.5 to 5 over the available Reynolds number range. Along the axis of the test section for all contours the maximum variation in Mach number is within =0.01, and the average flow angles in pitch and yaw are less than 0.2 deg. Somewhat larger variations in Mach number and flow angularity are found off-axis. At the higher Mach numbers, significant changes in the average test section Mach number with decreasing Reynolds number are accompanied by corresponding changes in the tunnel boundary layer. (Author).