Rishabh Choudhury

Measurement and simulation of hypersonic fluid-structural interaction on a cantilevered plate in a Mach 6 flow

The fluid-structural interaction of a cantilevered low-carbon steel plate oscillating and deforming plastically under the action of a hypersonic flow at Mach 5.8 was measured and simulated analytically and numerically. Displacement, flow field and surface pressure histories were measured during the fluid-structural interaction. High-speed schlieren video was used to simultaneously measure the displacement of the edge of the plate and the structure of the interacting compressible flow field including the position of shocks, expansions and the boundary layer. Fast response pressure-sensitive paint was used to map the history of pressure distribution on the surface of the plate. The plate was observed to deform plastically and this was accounted for in the FEM simulations. Experimental and numerical results showed partial agreement and suggestions for improving the experiment are discussed.

Thermal-structural modelling of TDLAS system for SCRAMSPACE hypersonic flight test

A thermal-structural analysis of the TDLAS (Tunable Diode Laser Absorption Spectroscopy) system used on the SCRAMSPACE mission was performed to determine the integrity of the in-flight experiment when subjected to descent heat loads. This analysis is essential for the design of optical sensing equipment, which needs to survive the high temperatures generated in hypersonic flight. Firstly, in-flight temperatures reached by critical electro-optical components due to viscous heating were determined. In addition, the structural viability of the sapphire optical window was analysed to ensure it surpassed requirements at flight heating conditions. Lastly, the effect that in-flight heating has on the optical alignment of the system is currently being investigated. It was found that electronic components will operate within recommended temperature bounds. In addition, numerical and experimental analysis verified the flight worthiness and seal integrity of the sapphire window when subjected to the simulated hypersonic flight conditions.

Supersonic Combustion of Hydrogen in Mach 2 Flows Over an Axisymmetric Model

An external axisymmetric model featuring a cavity flame-holder fuelled by hydrogen was adopted for the study of the supersonic combustion in Mach 2 flows. The self-sustained hydrogen flames ignited by a spark gap igniter were detected using two optical techniques: an intensified camera attachment coupled with a high speed camera with a narrow-band-pass filter centred at 310 nm for detection of OH* chemiluminescence; and high-speed schlieren imaging for flow visualization. The spark ignition was identified on the schlieren images which also enabled visualisation of changes in the flow structure associated with the combustion. Local concentrations of the radiating radical OH* were determined using the inverse Abel transformation based on the ICCD images and calibration against a light source of known radiance. The combustion flow was reconstructed numerically using a CFD Solver, Eilmer4 in an axisymmetric configuration coupled with a detailed H2/O2 oxidation chemistry mechanism and a OH* chemiluminescence sub-scheme. The maximum magnitude of the results for the OH* chemiluminescence simulations demonstrated reasonable agreement with measurements.

Subscale hypersonic free flight dynamics of HEXAFLY-INT EFTV + ESM (multibody separation)

This study investigates the separation dynamics of the HEXAFLY-INT hypersonic glider and its attitude control module that is to be released prior to the flight experiment. Both experimental and numerical techniques are utilised. With regard to experiments, dynamically scaled down models with on-board accelerometers and gyroscopes are released into Mach 6 test gas and ‘fly’ unconstrained within the inviscid flow core. Dynamic behaviour was sought to be replicated using 3D printed models with a similar mass distribution. Numerical studies have been conducted using the DLR Tau coupled CFD/RBD solver. Both experimental and numerical trajectories of the module were compared and similar separation trends were observed throughout.

Free Flight Testing in Hypersonic Flows: HEXAFLY-INT EFTV

This study reports the application of free flight testing in a hypersonic wind tunnel for the aerodynamic characterization of a hypersonic vehicle. Sub-scale models of ESA’s HEXAFLY-INT EFTV geometry were released into hypersonic flow and motion was measured through a combination of high-speed video analysis and on-board gyroscopes and accelerometers. These measurements allow aerodynamic coefficients to be determined and give insight into the stability of the design. Models were fabricated using both 3D printing and CNC milling techniques. A light-weight instrumentation system was assembled to measure angular movements (pitch, roll and yaw) and accelerations and transmit the sensor data via a Bluetooth transceiver to an off-board computer for post processing. The University of Southern Queensland’s short-duration hypersonic wind tunnel (TUSQ) was used for testing. It produces a quasi-steady test flow of approximately 200 ms at nominally Mach 6. Results are presented from two separate test campaigns. The first is a comprehensive repeatability study of the free flight technique and the second is the preliminary results of testing a new model design with interchangeable flap angles. The repeatability study showed that the free flight technique is inherently repeatable, despite large variations in model movement between experiments. As expected, lift coefficient showed less scatter than pitching moment coefficient, due to accelerations being measured directly as opposed to angular accelerations which required differentiation of the gyroscope data. Preliminary data from the new hybrid metallic-plastic models showed static stability in all cases. The models themselves proved to be robust, surviving all experiments with minimal damage.