Adaptive software for high-fidelity simulations of multi-phase turbulent reacting flows

This project focuses on the development, validation and documentation of a next-generation fully parallelised computa-tional fluid dynamics (CFD) code called HAMISH based on adaptive mesh refinement (AMR) which will enable high-fidelity Direct Numerical Simulations (DNS) of advanced turbulent reacting flows such as flame-wall interaction, localised ignition, and droplet combustion including atomisation processes. Such simulations cannot be achieved at present without limiting simplifications due to their prohibitive computational cost. AMR for large-scale highly-parallel simulations of compressible turbulent reacting flows is a significant new functionality which will offer major benefits in terms of computational economy for problems involving thin fluid-mechanical structures, e.g. resolution of both the flame and the boundary layer in flame-wall interaction, droplet surfaces in atomisation in spray combustion, shock waves in localised forced ignition, etc. Such structures have either been ignored or simplified severely in previous work due to the prohibitive computational cost of fixed global meshes, thus limiting the usefulness of the simulations. Hence AMR will offer a step-change in capability for the computational analysis of turbulent reacting flows, and will provide data with the degree of detailed physical information which is not currently available from simulations using existing CFD codes. The proposed software will be validated with respect to the results obtained from the well-proven uniform-mesh DNS code SENGA2, which has already been ported to ARCHER and is currently widely used by members of the UK Consortium on Turbulent Reacting Flows (UKCTRF). The newly developed code, HAMISH, will not only be ported to ARCHER, but also be prepared for architectures supporting accelerators thanks to OpenMP 4.5, which will support OpenACC, targeting a POWER8 cluster. As a part of this project, a detailed user guide will be produced at each new release of the code. This user guide will be made available on a website for public download along with the open-source version of the code and the associated documentation on code validation and user tutorials.

(i)Development of fundamental understanding and modelling of turbulent reacting flows: The design-cycle of modern combustors and fire-safe engineering structures depends heavily on the predictive capability of advanced CFD calculations. The adaptive mesh refinement (AMR) based CFD software developed during the course of this project will make it possible to carry out advanced turbulent reacting flow simulations (e.g. FWI, ignition with shock wave formation, and spray combustion with atomisation etc.), which were hitherto either impossible or extremely expensive to conduct. Furthermore, the newly developed CFD software HAMISH will not only utilise the current High Performance Computing (HPC) facilities but also will be made compatible for the next generation UK National computer, including hybrid MPI+OpenMP & MPI+OpenACC for GPUs, and other accelerators. The DNS simulations, to be carried out based on HAMISH, will yield important fundamental physical insights, which in turn can be used for the development of high-fidelity models for turbulent reacting flows. This exercise will offer maxi-mum benefit for manufacturers of new generation Internal Combustion (IC) engines and gas turbines, who are engaged in developing new low-pollution and high efficiency engines. In the UK, Renuda, Rolls-Royce and Siemens are involved in the Impact Advisory Panel (IAP) of UK Consortium on Turbulent Reacting Flows (UKCTRF) who will be interested in the outcome of this work, though the benefits are not limited to the UK as important findings will be disseminated through leading peer-reviewed journals (Journal of Computational Physics, Computers and Fluids, Combustion and Flame, Combustion Theory and Modelling, Physics of Fluids etc.) and international conference (Parallel CFD, PARENG, International Combustion Symposium, European Combustion Meeting, SIAM Numerical Combustion Conference etc.) publications.

(ii) Engagement with industry: In order to maximise the impact of the project, the PI, CIs and RAs will work actively to publicise the results by attending reputed international conferences and important UK combustion meetings organised by the British Combustion Institute and Institute of Physics and UKCTRF. The outcomes of the project will be widely disseminated to the members of UKCTRF and industrial IAP members by utilising the UKCTRF meetings and hosting a website linked with UKCTRF website.The website will be maintained during the course of this project to promote and disseminate the newly developed code HAMISH. On the website, links will be provided for easy access to the source code, information regarding code validation, user manual and tutorials for potential users. This website will be particularly important for commercial CFD companies who will have cutting-edge information on the subject, and can implement the models in industrial CFD codes.

(iii) Manpower development: The proposed project is based on the collaboration between three different turbulent reacting flow research groups in the UK, which will ensure an extensive knowledge exchange. This project will not only broaden the expertise of the investigators but also be highly valuable for the RAs for their academic and career development. The RAs will receive extensive training on a variety of topics such as advanced CFD techniques (e.g. AMR), thermo-fluid mechanics, turbulence, and combustion physics. They will also learn advanced techniques for for high performance computing, which will improve their analytical and mathematical skills. This project lays substantial emphasis on on the development of both technical and transferable skills of the RAs, which, in turn, increases the chances of their employability. As a result of this, this project has high impacts in terms of developing highly skilled UK based workforce and this benefit will be felt in 3-5 years' time-scale.