Parallelisation of CABARET

Phil Ridley
Numerical Algorithms Group Ltd,
Wilkinson House, Jordan Hill Road,

Abstract:

The CABARET (Compact Accurate Boundary Adjusting high REsolution Technique) code may be used to solve the compressible Navier-Stokes equations. The code is based on a low dissipative and low dispersive conservative CABARET method that constitutes a substantial upgrade of the second-order upwind leapfrog scheme. Most notably, the CABARET algorithm has a very local computational stencil that for scalar advection constitutes only one cell in space and time.

The present application of CABARET is for the investigation of aircraft noise, which is currently a very important environmental concern. An important component of aircraft noise is due to airframe/engine installation effects, the reduction of this remains a very challenging problem. In particular, when deployed at a large angle of attack at approach conditions, the wing flaps become a very important noise source. For engine-under-a-wing configurations, flap interaction with the jet can even become a dominant noise component. A crucial element of any noise prediction scheme is the high fidelity Large Eddy simulation (LES) model. For the airframe/engine noise problem, this model needs to accurately capture all important wing-flap, free jet and wing-flap-jet interaction effects.

With the high-resolution CABARET algorithm capable of resolving the fine-flow structures on coarse grids, we have already reduced the problem size needed for acoustic-sensitive modelling. But for high-fidelity LES modelling, we require a computational means capable of handling grid resolutions of the order of, at least, several millions of points. Hence for this dCSE project we will develop a scalable CABARET code enabling use of the full capability of HECToR for investigating grid sensitivity effects on the flow transition to turbulence in the initial part of the jet as well as to study the effect of inflow conditions, e.g., with and without including the nozzle exit geometry in the calculation.

This project was proposed by Dr Sergey Karabasov of the University of Cambridge Engineering Department and was approved for 12 months effort at the December 2008 round. The project began in March 2009 and was completed January 2011 after 10 months full time effort. For jet-flap-interaction, this dCSE will provide a key computational tool that will hopefully help to answer the question ``What is the effect of fine-scale-flow structures on far-field noise in the audible range of frequencies?''