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Compressible Flows

Supersonic engine intakes

The behaviour of oblique shock waves is important in the design of supersonic engine intakes when the Mach number is greater than 2.

 

Supersonic shock reflection Schlieren

 Credit: Holger Babinsky

This Schlieren visualisation shows the reflection of a supersonic oblique shock wave at M=2.5, where the incident shock wave was generated with an 8° wedge. The resulting interaction of the shock wave with the turbulent boundary layer growing along the plate produces a separation bubble.

 

Supersonic shock reflection p and u

 Credit: Holger Babinsky

The left-hand image shows a plan view of the surface streamlines, produced with oil-flow visualisation, underneath the above supersonic oblique shock reflection, while the right-hand image depicts the surface pressure field (obtained from pressure sensitive paint) superposed on the streamline pattern.


 

Active galactic nuclei as drivers of large-scale outflows

Point explosion in gas sphere

 Credit: Tiago Costa and Debora Sijacki

Simulation of a point explosion in a dense, spherical, self-gravitating cloud with the moving mesh code Arepo (highest density regions are shown in red). Point explosion generates a central cavity and a dense, highly compressed shell of gas which propagates outwards with time in the energy-conserving fashion, as shown in the series of panels. At later times the shell becomes Rayleigh Taylor unstable which leads to the development of the characteristic "mushroom-like" features and eventual mixing of the shell with the surrounding medium. For further details see Costa, Sijacki, Haehnelt, 2014, MNRAS, 444, 2355.