Computational Modelling Group

Advanced modelling for two-phase reacting flow

Edward Richardson (Investigator)

Engine designers want computer programs to help them invent ways to use less fuel and produce less pollution. This research aims to provide an accurate and practical model for the injection and combustion of liquid fuel blends.

Aerofoil noise

Richard Sandberg (Investigator)

High-performance computing is used to identify noise sources on aerofoils.

Assessment of the performance of novel RANS and hybrid turbulence models on the flow around a cylinder

Manuel Diaz Brito

The turbulent flow around a circular cylinder is a widely studied problem in fluid dynamics. At a certain characteristic Reynolds numbers the development of a turbulent wake occurs simultaneously with separation of the laminar boundary layer. The mechanisms defining this critical flow state are very complex to predict computationally. In this project the suitability of novel non-linear eddy viscosity closures and a hybrid Flow Simulation Methodology formulation to face these massively separated flows is studied. The flow predicting capabilities of the baseline EASM, ?-?-EASM and FSM-?-?-EASM tested are contrasted with the industrial renowned k-?-SST turbulence model. In the visualisation of the results it is evident that the ?-?-EASM has greater flexibility estimating the components of the Reynolds stresses with respect to the baseline EASM and the k-?-SST. Although dome differences are observed, the prediction of the critical flow around a cylinder is not accurately achieved by any of these RANS models, but the FSM-?-?-EASM shows great resemblance with the validation data, demonstrating capabilities of resolving very complex flow phenomena with minimum user input if the computational grid is fine enough. In order to demonstrate even greater advantages of non-linear models it was postulated that the addition of a streamwise impinging vortex hitting the leading edge of the cylinder would make the flow field fully three-dimensional. First attempts were tried in this route but time constraints limited the ultimate scope of the present work.

Body Forces in Particle Suspensions in Turbulence

Gabriel Amine-Eddine (Investigator)

The behaviour of multiphase flows is of primary importance in many engineering applications. In the past, experimental observations have provided many researchers with the ability to understand and probe the phenomena and physical processes occurring in such flows. With advancements in modern day computational power, we now have the ability to gain an even greater wealth of knowledge, from what used to be a physical experiment, is now a virtual simulation.

Amine-Eddine, G.H. (2015) Body forces in particle suspensions in turbulence. University of Southampton, Faculty of Engineering and the Environment, Doctoral Thesis , 283pp.

Development of a novel Navier-Stokes solver (HiPSTAR)

Richard Sandberg (Investigator)

Development of a highly efficient Navier-Stokes solver for HPC.

Diffusion at solute/solvent interfaces

Anatoliy Vorobev (Investigator), Ruilin Xie

We aim to develop the theoretical model that would provide an accurate description for the mixing process of two miscible liquids, and, in particular, would reproduce our experimental optical observations. The model based on the phase-field (Cahn-Hilliard) approach is adopted for the mixture of two miscible liquids. The model takes into account the surface tension effects, the non-Fickian diffusion across the liquid/liquid interface, and hydrodynamic flows that might be generated near the interface by the concentration gradients.

DIPLOS - Dispersion of Localised Releases in a Street Network

Trevor Thomas, Ian Castro (Investigators)

The security threat level from international terrorism, introduced by the UK Security Service, has been classified as either "severe" or "critical" for much of its six-year history, and currently remains as "substantial" (source: MI5 website). Part of the risk posed by terrorist threats involves potential releases of air-borne chemical, biological, radiological or nuclear (CBRN) material into highly populated urbanised areas. Smoke from industrial accidents within or in the vicinity of urban areas also pose risks to health and can cause widespread disruption to businesses, public services and residents. The Buncefield depot fire of 2005 resulted in the evacuation of hundreds of homes and closure of more than 200 schools and public buildings for two days; consequences would have been much more severe if prevailing meteorological conditions had promoted mixing or entrainment of the smoke plume into the urban canopy. In both these scenarios it is crucial to be able to model, quickly and reliably, dispersion from localised sources through an urban street network in the short range, where the threat to human health is greatest. However, this is precisely where current operational models are least reliable because our understanding and ability to model short-range dispersion processes is limited. The contribution that DIPLOS will make is:

1. to fill in the gaps in fundamental knowledge and understanding of key dispersion processes,
2. to enable these processes to be parametrized for use in operational models,
3. to implement them into an operational model, evaluate the improvement and apply the model to a case study in central London

Most of the existing research on urban dispersion has focused on air quality aspects, with sources being extensive and distributed in space. Scientifically, this research is novel in focusing on localized releases within urban areas, and on dispersion processes at short range. Through a combination of fundamental studies using wind tunnel experiments and high resolution supercomputer simulations, extensive data analysis and development of theoretical and numerical models, DIPLOS will contribute to addressing this difficult and important problem from both a scientific research and a practical, operational perspective.

Direct Numerical Simulations of transsonic turbine tip gap flow

Richard Sandberg (Investigator)

Direct Numerical Simulations are conducted of the transsonic flow through the tip gap at real engine conditions.

Eddy-resol?ving Simulation?s for Turbomachi?nery Applicatio?ns

Richard Sandberg (Investigator), Li-Wei Chen

Traditionally, the design of turbomachinery components has been exclusively accomplished with steady CFD, with Reynolds Averaged Navier-Stokes (RANS) models being the predominant choice. With computing power continuously increasing, high-fidelity numerical simulations of turbomachinery components are now becoming a valuable research tool for validating the design process and continued development of design tool.
In the current project, Direct Numerical Simulations (DNS) and other eddy-resolving approaches will be performed of turbomachinery components to establish benchmark data for design tools, and to investigate physical mechanisms that cannot be captured by traditional CFD approaches.

Hybrid RANS/LES methods

Richard Sandberg (Investigator), Markus Weinmann

Novel hybrid RANS/LES methods are developed for more accurate and efficient simulation of flow over complex geometries.

Is fine-scale turbulence universal?

Richard Sandberg (Investigator), Patrick Bechlars

Complementary numerical simulations and experiments of various canonical flows will try to answer the question whether fine-scale turbulence is universal.

Jet noise

Richard Sandberg (Investigator), Neil Sandham

Direct numerical simulations are used to investigate jet noise.

Laminar to Turbulent Transition in Hypersonic Flows

Neil Sandham, Heinrich Luedeke

Understanding of laminar to turbulent transition in hypersonic boundary-layer flows is crucial for re-entry vehicle design and optimization. The boundary-layer state directly affects the temperatures on the vehicle surface and its viscous drag. Therefore transition has to be considered to correctly compensate for drag and to properly design the thermal protection system.
For the proposed study, in order to obtain a clear understanding of the transition process, the configuration is kept as simple as possible by varying only a minimum number of parameters affecting transition on a simple test geometry such as a swept ramp at different sweep angles. To investigate the influence of such sweep angles on the transition process in the hypersonic regime, Direct Numerical Simulations (DNS) of the turbulent flow field are carried out on the Iridis cluster.

Study of global instability in separated flows at high Mach number

Neil Sandham, Zhiwei Hu (Investigators), Kangping Zhang

Flow instability is observed when extending two-dimensional (2D) stable flow into three-dimensional (3D). Development of instability varies along different spanwise length. Thresholds are also discovered for the flow studied to become instable.

Supersonic axisymmetric wakes

Richard Sandberg (Investigator)

Direct numerical simulations are used to shed more light on structure formation and evolution in supersonic wakes.

Towards biologically-inspired active-compliant-wing micro-air-vehicles

Richard Sandberg (Investigator), Sonia Serrano-Galiano

Despite a good knowledge of the physiology of bats and birds, engineering applications with active dynamic wing compliance capability are currently few and far between. Recent advances in development of electroactive materials together with high-fidelity numerical/experimental methods provide a foundation to develop biologically-inspired dynamically-active wings that can achieve "on-demand" aerodynamic performance. However this requires first to develop a thorough understanding of the dynamic coupling between the electro-mechanical structure of the membrane wing and its unsteady aerodynamics. In this collaborative initiative between the University of Southampton and Imperial College London, we are developing an integrated research programme that carries out high-fidelity experiments and computations to achieve a fundamental understanding of the dynamics of aero-electro-mechanical coupling in dynamically-actuated compliant wings. The goal is to utilise our understanding and devise control strategies that use integral actuation schemes to improve aerodynamic performance of membrane wings. The long-term goal of this project is to enable the use of soft robotics technology to build integrally-actuated wings for Micro Air Vehicles (MAV) that mimic the dynamic shape control capabilities of natural flyers.

Transition to turbulence in high-speed boundary layers

Neil Sandham (Investigator), Nicola De Tullio

This work is focused on the numerical simulation of hypersonic transition to turbulence in boundary layers. We use direct numerical simulations of the Navier-Stokes equations to analyse the effects of different flow conditions and external disturbances on the transition process. The main objective is to gain insight into the different aspects of transition to turbulence at high speeds, which can lead to the design of new transition models and transition control techniques for high-speed flows.