The Aeroelasticity research team is led by Dr Sina Stapelfeldt.
Aeroelastic phenomena are responsible for a significant number of aircraft engine distress events. They account for a large proportion of engine development costs and severely restrict the design and operating space, imposing limitations on efficiency and performance. Despite their importance, some of these phenomena are poorly understood because the underlying intricate fluid dynamics are further complicated by deforming structures.
The group’s research uses computational fluid dynamics (CFD) to predict and improve our understanding of a range of aeroelastic phenomena in aircraft engines, ranging from flutter and forced response to compressor stall and surge. This involves the development of advanced computational methods and the application of these to uncover underlying physical mechanisms.
Application of the Lattice Boltzmann Method to turbomachinery flows
Researcher: Sam Mitchell
The Lattice Boltzmann Method (LBM) is an emerging CFD method based on the solution of the Boltzmann equation. It is effective for the high-fidelity modelling of transient flows around complex geometries. This project seeks to explore its applicability to turbomachinery flows that may require a high degree of fidelity. Firstly, an established LBM solver, OpenLB, is used to model the dynamic stall behaviour of a compressor blade at incompressible Mach numbers. Secondly, the extensions to the standard LBM necessary for modelling compressible flows are investigated.
Flutter in core compressors
Researcher: Harry Hill
Flutter is a self-excited aeroelastic instability which can cause high blade vibration amplitudes and damage components. In core compressors, flutter stability is influenced by a number of factors, including operating point and vibration mode shape. This project researches the influence of plunge and twist component in the fundamental mode shapes and steady blade loading on compressor stability.
High order discretisation schemes for edge-based flow solvers
Researcher: Vinko Jezercic
Numerical schemes of high-order accuracy are a promising avenue for improving the performance of modern CFD codes. The aim of this project is to implement a high-order scheme into the in-house Aeroelasticity code AU3D, which will result in reduced simulation time with the current error level, as well as more accurate simulation results without prohibitive costs. Particularly, simulations of cases involving acoustic wave propagation and advanced turbulence modelling procedures like LES will be possible, due to the reduced resolution requirement with the high-order solver.
Lattice Boltzmann Methods for High Reynolds flows
Researcher: Zhishang Xu
Xu’s research develops an adaptive mesh refinement solver for the lattice Boltzmann method (LBM). LBM has advantages in running efficiently on massively parallel architectures and simulating complex geometries or moving boundaries. Grid refinement is essential to reduce the computational cost of high Reynolds number simulations.
Low engine order excitations in turbines
Researcher: Alex Trafford
One of the pressing issues facing the airline industry is the need for cleaner aero engine emissions, of which the reduction of NOx and particulates form a key component. One future technology that is being developed to combat this is ‘lean-burn’ combustion, which due to its abundance of air and lower temperatures leads to less unburnt hydrocarbons in the emission stream and a reduction in NOx. A big concern for the implementation of this technology is the increased likelihood of multiple burner failure. This results in large total temperature distortions at irregular intervals around the annulus, which after propagating downstream, lead to Low Engine Order (LEO) forced vibration in the turbine. This phenomena tends to excite damaging modes of vibration at typical engine operating speeds, and leads to high and low cycle fatigue failures hindering the reliability and reducing the effective life of the engine. This project aims to understand the effect of combustor outlet distortions on low engine order forcing in the high, intermediate and low pressure turbine stages, as well as its interaction with other typical forcing drivers and turbine relevant flow phenomena. With this understanding, aero engine designers will be able to protect against the damaging effects of vibrations whilst continuing the push toward creating cleaner skies.
Outlet guide vane buffeting
Researcher: Jonah Harris
Under certain off-design conditions outlet guide vanes (OGVs) within the low pressure system of modern turbofan engines can experience buffeting. This project aims to use CFD to examine the causes of this unsteadiness, predict the affected operating points and develop design recommendations for mitigation. Recent work has recreated known buffeting operating points with good frequency matches and confirmed that OGV buffet is driven by a quasi-2D transonic buffet phenomenon.
Outlet guide vane forced response
Researcher: Jacob Merson
Novel aero-engine architectures comprise short slim-line aggressive intake designs and reduced axial distance between components. Fan sub-system operability in these designs could be limited by forced response of the OGVs, especially at off-design conditions. OGV forced response requires specialised analysis techniques because the aerodynamics are very complex due to non-axisymmetric designs and interaction with downstream elements. The aim of this PhD project is to improve prediction methods and physical understanding of forcing mechanisms on such non-axisymmetric assemblies.
Pre and post stall modelling of axial compression systems
Researcher: Jose Moreno
Jose's research focus on aerodynamic modelling of core multi-stage compressors in pre stall and post stall operation. His work covers a wide range of machines from single stage compressor rigs to very complex high speed flows in three-shaft engine compression systems. He is experienced in working with high performance computing systems to gather, extract and process large amounts of data from his expensive calculations. His research seeks to gain relevant knowledge to explain and improve compression systems reliability and stability.
Towards the application of Boltzmann methods for computational fluid dynamics in turbomachinery environments
Researcher: Sam Mitchell
Boltzmann methods form an emerging group of computational fluid dynamics (CFD) methods based on the numerical solution of the Boltzmann transport equation. A well-known example is the Lattice Boltzmann Method (LBM). Standard LBM is highly effective for solving unsteady, turbulent flows over complex geometries, but is limited to the incompressible regime. Sam’s work is focused on the modifications to standard LBM required for it to be applicable to the compressible flows often encountered in turbomachinery.
Post-doctoral Research Projects
Fan forced response
Researcher: Dr Prathiban Sureshkumar
This project investigates the effects of inlet distortions, as generated by operation in cross-wind, angle-of-attack or ground vortex ingestion, on the forced response of fan blades. In particular, it looks at the effects of unsteady distortions and variations in ambient conditions.