Nathan R. Tichenor

Calibration of an Actively Controlled Expansion Hypersonic Wind Tunnel

** In this paper, we report on the status of the Actively Controlled Expansion (ACE) hypersonic wind tunnel facility, which is under development at Texas A&M University. The tunnel was designed to provide continuously variable hypersonic flow conditions over a Mach number range of 5.0 to 8.0. The facility operates in a pressure-vacuum blow-down mode, and the run time is nominally 50 seconds. The nozzle system was designed such that the Mach number can be actively controlled as the tunnel is running. The estimated response time of the flow is on the order of 2.0 milliseconds. The cross-sectional area of the test section is 9.0 inch x 14.0 inch. In this paper, we describe the design, calibration and current status of the facility development.

On the Design and Calibration of an Actively Controlled Expansion Hypersonic Wind Tunnel

*† ‡ § ** The Actively Controlled Expansion (ACE) hypersonic wind tunnel facility was deigned to provide continuously variable hypersonic flow conditions over a Mach number range of 5.0 to 7.0. The facility operates in blow-down mode, and the run time is nominally 50 seconds. The nozzle system was designed such that the Mach number can be actively controlled as the tunnel is running. The estimated response time of the flow is on the order of 5-10 milliseconds. The cross-sectional area of the test section is 9.0 inch x 14.0 inch. In this paper, we describe the design and calibration of this new facility.

Reynolds Stresses in a Hypersonic Boundary Layer with Streamline Curvature-Driven Favorable Pressure Gradients

The role of streamline curvature-driven favorable pressure gradients on modifying the Reynolds stresses in Mach 4.9, high Reynolds number (Reθ = 43,000) boundary layers is examined. Three boundary layers ( ≈ 0, -0.3 and -1.0) are investigated using particle image velocimetry. The expected stabilizing trends in the Reynolds stresses are observed, with the sign reversal in the Reynolds shear stress for the strongest favorable pressure gradient. For the present flows, the increased transverse normal strain-rate and reduced principal strainrate are the primary factors. Reynolds stress quadrant decomposition studies reveals that as the boundary layer negotiate the favorable pressure gradient, the quadrant events are redistributed, such that the relative differences between the quadrant magnitudes decrease. Very little preferential quadrant mode selection is observed for the strongest pressure gradient considered. Overall, the observed processes appear to be driven primarily by largescale mechanisms, and hence, given the simple geometry, the present data provide a suitable test-bed for Reynolds stress transport and large-eddy model development and validation. As an example, a simplified evaluation of the LRR Reynolds stress transport equation demonstrates promise for this class of flow.