Free & impinging jets
Supersonic jets
Free and impinging supersonic jets, from VTOL and launch pads to cooling and cold spray, and how shocks, expansions and vortices interact in them.
Supersonic free and impinging jets play an important role in many applications, such as vertical short take-off and landing, jet blast deflectors, turbine blade cooling, lunar landing modules, space launch vehicle systems, electronics cooling and cold spray coating. Their complexity comes from the simultaneous presence of multiple shocks, expansion waves and their interactions with large-scale vortical structures in the shear layers.
The flow characteristics of underexpanded impinging jets are mainly governed by the nozzle pressure ratio (NPR), the ratio of stagnation pressure to ambient pressure (\(P_\infty\)); the nozzle temperature ratio (NTR), the ratio of stagnation temperature to ambient temperature (\(T_\infty\)); the nozzle-to-wall distance (\(h\)); and the jet Mach number (\(Ma\)). The HAVA Lab carries out subsonic and supersonic jet simulations to analyse the expansion behaviour of turbulent jets under varying NPR and NTR.
Shocks, expansion waves and shear-layer vortices of a supersonic jet impinging on a wall.
Spatial variation of (a) the density gradient (kg/m⁴), (b) temperature (K), (c) Mach number and (d) turbulence kinetic energy (m²/s²) for the impinging-jet case.
Velocity field and centreline profile of a free jet at NPR 4.03 compared with the experiment of Henderson (2005).
Comparison of the velocity profiles for a free expansion jet with a nozzle pressure ratio of 4.03: (a) velocity magnitude (m/s) from the present work, (b) the experiment of Henderson (2005), and (c) the streamwise velocity along the centreline.
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