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Lead: Mark Savill
The use of LBM with LES, as considered by Savill's group at Cranfield, is one of several ways in which LBM can be incorporated in an appropriate hierarchy of CFD methods to address multi-scale fluid effects. This is required if we are to move beyond current established multi-objective, multi-disciplinary, and multi-physics design optimisation capabilities to address true multi-scale simulation and optimisation; an objective which has been recognised as one of the current Engineering Grand Challenges identified by EPSRC. The fact that LBM can handle multi-phase flow with phase change opens up the possibility of extending such optimisation to fluid-solidification problems in a more natural manner than has previously prove possible. In particular existing work on aerodynamic icing using coupled Navier-Stokes and Lagrangian water droplet tracking codes, with specialist splashing, wetting, and thin -film heat transfer treatments, may be superseded by use of LBM for both the core and surface flow interactions. This is already the subject of work at Cranfield with recent Airbus/EPSRC CASE PhD & EngD activities continuing via ATI and MSc projects.
Alistair Revell (Manchester University) is separately pursuing the use of LBM in conjunction with Smooth Particle Hydrodynamics as Co-Investigator for an EPSRC X-Med project on Extreme Loading of Marine Energy Devices due to waves, currents, flotsam and mammal impact. This provides an opportunity to compare and contrast these two mesh-less solution methods for impact of rigid and flexible objects with a moving turbine, and thus enable their cross-validation. Such model validation remains crucial to build confidence in handling such challenging and highly complex real-world fluid-structure interactions.
A first WPG workshop was held at UCL on December 17th, 2014, attended by 10 representatives of participating consortium groups with presentations by Cranfield (Prof.Savill & Dr. Timos Kipouros); UCL (Prof. Kai Luo & Dr. Daniel Lycett-Brown; Leeds (Dr. Mark Wilson & Nicholas Delbosc); and attendance of Michael Seaton (Daresbury STFC), Rupert Nash (Edinburgh EPCC), Joe O'Connor (Manchester for Revell). A second WPG discussion group meeting , with inputs from groups at Cambridge (Kipouros), Cranfield (Savill), Huddersfield (Krysztof Kubiak), Leeds (Summers) and Sheffield (Rongshan Qin), was held as a session within the UKCOMES Annual Workshop at UCL on December 17th , 2015; with representatives from Brunel, Daresbury, EPCC, Manchester, NextLimit Dynamics, and UCL also in attendance. These workshops identified the exciting possibilities opening up for topology optimisation and real-time simulation/optimisation, as well as new prospects for deploying LBM for acoustic analyses.
The work of WPG within UKCOMES has also been reported and discussed at successive STFC CCP Steering Panel meetings at Daresbury and Rutherford Appleton Laboratories. A wider collaboration across the work package topics, involving consortium participants as well as co-operating groups outside the UK, has been initiated also with additional Early Access Support from the STFC Hartree Centre for comparative NS and LBM Simulations by separately funded RA and PhD researchers.
Two (international and national) test cases have been established: a baffled micro-reactor configuration for fluid mixing; and a micro-combustor geometry for electrical power generation or thrusters propulsion - URANS, LES and DNS data are already available for these to allow multiscale evaluation against LBM.
Additionally Krysztof Kubiak at Huddersfield University has now extended the Leeds multi-phase LBM research code to design optimisation for super hydrophobic surfaces, while other groups have started using LBM for simpler parametric optimisation applications - in particular non-obtrusive electric field methods for controlling particulate impurities in molten metal casting by Rongshan Quin at Sheffield University.
CPU-based work initiated with the first consortium PDRA (Daniel Lycett-Brown) for cross-comparing the Southampton/UCL LBM code with the Cranfield one in 2D and then 3D for the micro-reactor case, will be completed once a further researcher is in place; before moving onto DL_MESO for the micro-combustor mixing case. This will then allow the extension to combustion LBM to be explored.
Daniel Lycett-Brown has meantime moved to NextLimit Dynamics who promote the commercial LBM code XFlow; joining Professor Savill's former EngD student, Giuseppe Trapani, and being joined by Nicholas Delbosc in 2016. This has opened up the possibility to greatly strengthen our industrial collaboration, with a focus especially towards aeroacoustic/MDO applications and more effective interactive optimisation generally.
A first integration of LBM for micro-fluidic design optimisation within a GPU environment has been achieved at Cranfield; speeding up the process by a factor of more than 50, resulting in a much richer and more detailed design space exploration. Further extension to incorporate a more flexible, level-set geometry representation has now provided even further speed up and allowed very general parameterisation required to move towards fully topological Multi-Disciplinary Optimisation. A next development will involve coupling and sharing of code between the Cambridge/Cranfield and Leeds groups to incorporate on-the-fly visualisation within a fully interactive design optimisation environment.
The experience gained in porting under CUDA has already benefitted GPU porting by Daresbury of the UCL medical flow code HEME_LB for patient-specific computational analysis, and ultimately guided surgical intervention. Similar attention will next be transferred to porting DL_MESO also.