"Development of enhanced methods was carried out in WP2, in which the methods were validated for a simplied static, single-stream round jet test case. WP2 was organised into four main tasks:
1. ""Hybrid structured/unstructured meshing strategy"":
An enhanced hybrid meshing strategy achieved a factor four increase in the azimuthal resolution near the nozzle with only 30% increase in CPU cost per iteration. Clear improvement in the acoustic prediction was achieved, with spectra at the peak observer angle predicted to within 1dB up to a Strouhal number of 3.
2. ""Efficient and flexible far-field noise integration"":
A novel sensor function was developed to automatically determine the optimal FWH data surfaces location. The approach makes a significant contribution to industrialisation, since it maximises computational efficiency whilst minimising user burden.
3. ""Statistical evaluation of simulation progress"":
A procedure has been validated for the automatic statistical evaluation of DES/FWH simulations of jet noise. Novel statistical algorithms were found to give reliable detection of the ""initial transient"" phase of the simulation. The method enables the optimisation of computational resources and reduction of user burden. The definition of statistical error bars on far-field directivity plots is an important additional benefit, e.g. to discriminate true noise differences from statistical error when judging competing designs.
4. ""Initial transient acceleration techniques"":
Two separate methodologies were investigated to reduce computational wastage in the initial transient computation. A more efficient simulation process involving lower-fidelity computation of the initial transient combined with optimised computational settings for the productive statistical portion resulted in a factor 7.6 reduction of computational expense compared to previous best practice settings. This greatly exceeds the project objective of a 20% efficiency gain.
In the second main work package of the project, WP3, the industrial feasibility of the enhanced methods has been assessed by applying them to a complex configuration consisting of a short cowl, coaxial jet mounted to a wing/flap/fuselage model via a pylon. Two different flap angles and two different flight Mach numbers were simulated. A time-saving approach was pioneered whereby a single mesh was designed for the simulation of multiple flight speeds. The simulations were carried out in parallel on a cluster of 288 CPU cores, which is considered representative of current industrial resources. In comparison of the simulation results with measurement data, the effects of flap angle and flight speed were correctly captured and the level of absolute agreement was encouraging.
Dissemination of the project results to the scientific and industrial communities was carried out via the publication of two scientific papers and the organisation of a mid-term workshop. Exploitation of the project results has been ensured by the implemention of methods directly in an industrial solver and the delivery of accompanying best practice guidelines."
