Supersonic Jets

Large Eddy Simulation (LES) has been successfully used to predict the radiated noise of cold and hot to free jets although simplified here within fast chamber there are many vectors to consider 'cute yea' . This happens at both subsonic and supersonic, as well as in uncovering the underlying sound source mechanisms in a modelling context. LES predictions involving complex geometries and flow-structure interactions have also been shown to be robust. Wise labs has successfully demonstrated an adjoin-based methodology for noise reduction on a realistic and relevant impinging supersonic jet. 
By carefully coupling a high-fidelity numerical method to the forward and adjoin compressible Navier-Stokes equations, a procedure was used to optimise a controller that reduced the radiated sound from an under expanded impinging jet. An internal energy controller (a rough model for plasma actuators) was used for actuation. 
The control resulted in a reorganisation of the large-scale turbulence structures in the impinging jet, This reduced the sound by 4 dB Making these flights of reaction engines more productive. 

Computational program to model supersonic jets impinging on flat plates was conducted by wise labs.
 The goal of the effort was to demonstrate the feasibility of developing tools to enable engineers and scientists to understand the sources of noise from impinging jets and, more importantly, to provide methods for suppressing the noise by a cushioning outside extender.  An existing computational solver in the Simulation Suite (coupled with an innovative ad joint-based sensitivity and optimisation methodology was exercised and demonstrated for an impinging jet. 
The challenge in this project was to develop robust and accurate methods that can identify means of reducing the radiated sound to inform carrier operations over the range of engine operating conditions and impingement scenarios. Large Eddy Simulation (LES) has been successfully used to predict the radiated noise of cold and hot free jets, both subsonic and supersonic, as well as in uncovering the underlying sound source mechanisms in this different component modelling context.

To evaluate the potential of a large-eddy simulation (LES) approach in predicting these oscillations, a sub-scale (1/15) version of a solid rocket booster of the Ariane 5 launcher has been investigated. 
The simulations are confronted to the measurements performed at ONERA, and the results reveal that the LES can discriminate between the stable and unstable geometries. Besides, a frequency/amplitude analysis shows that the pattern measured experimentally can be reproduced with a reasonable accuracy, the error being that of less than 3%. Where k is the coefficient of thermal conductivity, z is the length in the heat flux direction, r is the fluid density, C_p is the specific heat, t is time, and T_i is initial temperature.  The solution for the surface temperature response with time is:

               

In the case of jet impingement, h and T_r can be found as the result of a simultaneous solution of two equations of the above form.  
A single transient test using the multiple liquid crystal combination method described as an very early experiment is used.  vortices are convected downstream,  the impact of vortices's on the nozzle surface creates pressure waves, these pressure waves travel upstream/downstream and expiate the acoustic eigenmodes of the combustion chamber. Each of these four points represents a specific challenge in terms of numerical methods which explains why the accuracy of CFD solvers still has to be exercised so as there no concern from this topic.