Alistair Revell

• MEng, PhD
• Deputy Head of Department at The University of Manchester

This paper describes a recent development of the Synthetic Eddy Method (SEM) proposed by Jarrin et al. (Int J Heat Fluid Flow 30(3):435–442, 2009) for generation of synthetic turbulence. The present scheme is designed to produce a divergence-free turbulence field that can reproduce almost all possible states of Reynolds stress anisotropy. This impr...

A numerical approach based on the Lattice Boltzmann and Immersed Boundary methods is proposed to tackle the problem of the interaction of moving and/or deformable slender solids with an incompressible fluid flow. The method makes use of a Cartesian uniform lattice that encompasses both the fluid and the solid domains. The deforming/moving elements...

Coherent waving interactions between vegetation and fluid flows are known to emerge under conditions associated with the mixing layer instability. A similar waving motion has also been observed in flow control applications, where passive slender structures are used to augment bluff body wakes. While their existence is well reported, the mechanisms...

Download here: https://authors.elsevier.com/a/1YXQm15eiew8HK Abstract This paper presents a novel wind/solar energy-harvesting device based on the inverted flag concept that combines flexible piezoelectric strips with flexible photovoltaic cells to simultaneously harvest both wind and solar energy. Three inverted flags built using off-theshelf co...

Wind-energy-harvesting generators based on inverted flag architecture are an attractive option to replace batteries in low-power wireless electronic devices and deploy-and-forget distributed sensors. This study examines two important aspects that have been overlooked in previous research: the interaction between an inverted flag and a neighboring s...

In this paper, the process of encapsulating solid particle(s) into liquid droplets in a high-throughput flow-focusing microchannel is investigated numerically. Open source software is used which computes fluid flow in an Eulerian framework and particle dynamics with a Lagrangian approach. Previous studies have demonstrated that if no action is take...

Cardiovascular diseases (CVDs) are the principal cause of morbidity worldwide. According to the World Health Organisation (WHO), around 17.9 million deaths were reported in 2016 due to CVDs, representing 31% of the global death, while this number is expected to reach over 23.6 million by 2030. Arterial disease, stroke, transient ischaemic attack, a...

This paper presents results from a practical assessment of the endurance of an inverted flag energy harvester, tested over multiple days in a wind tunnel to provide first insights into flapping fatigue and failure. The inverted flag is a composite bimorph, composed of PVDF (polyvinylidene difluoride) strips combined with a passive metallic core to...

Objectives: The PartneRships in cOngeniTal hEart disease (PROTEA) project aims to establish a densely phenotyped and genotyped Congenital Heart Disease (CHD) cohort for southern Africa. This will facilitate research into the epidemiology and genetic determinants of CHD in the region. This paper introduces the PROTEA project, characterizes its initi...

Energy harvesting devices based on the inverted flag configuration have recently attracted attention as a viable option to power small electronics and remote wireless sensors from wind excitation. Despite showing high potential, relatively little research has considered how the dynamics and power generation performance of these devices vary with pl...

We present a GPU-based turbulent flow simulation by link-wise artificial compressibility method (LW-ACM). The standard implementations of the lattice Boltzmann method are limited by memory requirements due to the nature of the distribution functions employed. LW-ACM avoids the need to store the density distribution function via the use of a hybrid...

This study focuses on assessing state of art Delayed Detached Eddy Simulation turbulence modelling techniques and their mesh sensitivity of the flow prediction around a simplified truck. Different sub-grid length scales and mesh topologies, including both trimmed (cut-cell) and polyhedral meshes are tested in this work. The difference between simul...

In this paper, we propose a new simplified lattice Boltzmann method (SLBM) for magnetohydrodynamic flows that outperforms the classical one in terms of accuracy, while preserving its advantages. A very recent paper [A. De Rosis, J. Al-Adham, H. Al-Ali and R. Meng, Double-D2Q9 lattice Boltzmann models with extended equilibrium for two-dimensional ma...

Introduction Congenital heart disease (CHD) is the most common birth defect and a significant cause of paediatric morbidity and mortality worldwide. Epidemiological data from Africa are lacking, although this information is of importance in determining the burden of CHD and guiding policy. As a multifactorial disease, the role of genetic factors in...

This paper presents a new approach for mitigating the unphysical delay in the Reynolds-averaged Navier–Stokes (RANS) to large-eddy simulation (LES) transition, often referred to as the gray area, which is a common issue for hybrid RANS–LES turbulence models such as delayed-detached eddy simulation. An existing methodology designed for improving the...

A bstract Lumped (zero-dimensional) technique is a robust and widely used approach to mathematically model and explore bulk behaviour of different physical phenomena in a lower expense. In modelling of cardio/cerebrovascular fluid dynamics, this technique facilitates the assessment of relevant metrics such as flow, pressure, and temperature at diff...

The control of boundary layer separation, to bring about performance enhancements on air/water vehicles, has been a very active research area in recent years. In this paper, the passive separation control of a Naca0012 airfoil via a rigid/flexible flap at Reynolds number Re = 1000 is investigated. The effects of the flap configurations (length, att...

The use of electric propulsion systems is increasing and is operational in more than 300 active spacecraft. The present study uses a 2D axisymmetric model to numerically investigate the electric field within an electrospray thruster by considering different emitter geometries and varying extractor placement relative to the emitter. The electrohydro...

Atrial fibrillation (AF) can alter intra-cardiac flow and cardiac output that subsequently affects aortic flow circulation. These changes may become more significant where they occur concomitantly with ageing. Aortic ageing is accompanied with morphological changes such as dilation, lengthening, and arch unfolding. While the recognition of AF mecha...

This paper aims to develop a novel concept for energy harvesting via flexible inverted flags combining photovoltaic cells with piezoelectric material. Using technology currently available off-the-shelf, we have built dual piezo-solar harvesters made of polyvinylidene fluoride (PVDF) piezoelectric elements combined with mini solar panels of differen...

The coupled interactions between fluidsO’Connor, Joseph and slender structures play a number of critical roles in a broad range of physical processes. In flow control applications, poroelastic coatings consisting of arrays of passive slender structures have been shown to provide beneficial aerodynamic characteristics when applied to bluff bodies.Re...

In recent years, researchers have found that separation control could increase the mean lift, decrease the drag, delay stall, reduce noise and influence the transition to turbulence, which has a significant economic and ecological impact on society, and it has been used extensively in the design of unmanned aerial vehicles (UAVs) and micro aerial v...

In the present paper, we report a systematic investigation of planform geometry and ex-citation level effects on the dynamics and power generation characteristics of polyvinylidene difluo-ride (PVDF)-based cantilevered vibration energy harvesters. Piezoelectric vibration energy harvesters provide a promising energy harvesting solution for widesprea...

Blood flow in the vasculature can be characterised by dimensionless numbers commonly used to define the level of instabilities in the flow, for example the Reynolds number, Re. Haemodynamics play a key role in cardiovascular disease (CVD) progression. Genetic studies have identified mechanosensitive genes with causal roles in CVD. Given that CVD is...

Congenital heart disease (CHD) is the most common birth defect globally and coarctation of the aorta (CoA) is one of the commoner CHD conditions, affecting around 1/1800 live births. CoA is considered a CHD of critical severity. Unfortunately, the prognosis for a child born in a low and lower-middle income country (LLMICs) with CoA is far worse tha...

The Detached Eddy Simulation (DES) turbulence model presented by Spalart et al. (Comments on the Feasibility of LES for Wings, and on a Hybrid RANS/LES Approach, [1]) in the late 90s, was specifically designed to simulate those flow configurations where massive separation was involved.

This paper presents the vector-based discrete element method applied to two-dimensional elastic bodies, including details of formulation, its implementation on graphics processing units (GPUs) for accelerating simulations and validation cases. Simulation of elastic bodies has traditionally been realised through continuum-mechanics based methods suc...

Atrial fibrillation (AF) is the most common type of arrhythmia, which undermines cardiac function. Atrial fibrillation is a multi-facet malady and it may occur as a result of other diseases or it may trigger other problems. One of the main complications of AF is stroke due to the possibility of clot formation inside the atrium. However, the possibi...

This book gathers the proceedings of the Seventh Symposium on Hybrid RANS-LES Methods, which was held on September 17-19 in Berlin, Germany. The different chapters, written by leading experts, reports on the most recent developments in flow physics modelling, and gives a special emphasis to industrially relevant applications of hybrid RANS-LES meth...

This book gathers the proceedings of the Seventh Symposium on Hybrid RANS-LES Methods, which was held on September 17-19 in Berlin, Germany. The different chapters, written by leading experts, reports on the most recent developments in flow physics modelling, and gives a special emphasis to industrially relevant applications of hybrid RANS-LES meth...

This paper presents a novel computational framework for modelling multiscale fracture that can be used to solve engineering problems subject to dynamic loading. The framework simulates, mechanistically, at the mesoscale, the physical processes that lead to brittle fracture. A homogenisation step is used to translate the accumulation of damage from...

Tip masses are used in cantilevered piezoelectric energy harvesters to shift device resonance towards the required frequency for harvesting and to improve the electric power generation. Tip masses are typically in the form of concentrated passive weights. The aim of this study is to assess the inclusion of solar panels as active tip masses on the d...

The incorporation of nature-inspired techniques to control or reduce boundary layer separation, to bring about performance enhancements on air/water vehicles, has been an active research area for many years. In this paper, a baseline NACA0012 airfoil is modified using a short flap on its upper surface at a Reynolds number of Re = 1000. The impact o...

Background Tetralogy of Fallot (ToF) and coarctation of the aorta (CoA) each constitute approximately 7% of congenital heart disease (CHD) births worldwide. Compared to developed countries, developing countries have a disparate level of access to prompt diagnosis and treatment for these diseases. Computational fluid dynamics (CFD) approaches implem...

This paper presents OpenFPCI, a framework for coupling the C++ toolbox OpenFOAM-Extend, a computational fluid dynamics package, with the general purpose finite element package ParaFEM, written in Fortran and used to solve structural mechanics problems. The coupling of these two open source and scalable toolboxes, facilitates the use of high perform...

There have been a number of significant power outages caused by unexpected levels of flow-induced vibration of valves in partially-open operating conditions and as such the understanding of this phenomena is critically important. On-site testing is normally expensive and inherently difficult given typical flow rates but while computational fluid dy...

This article presents an integrated, interactive modelling and simulation tool for aerodynamic design and analysis. The development and coupling of a GPU-accelerated Computational Fluid Dynamics (CFD) library, a 3D scanning library and a virtual-reality-powered video game are presented and the resulting virtual wind tunnel described. Users of the t...

This paper presents results from experiments and simplified numerical simulations on the flow-induced dynamics and power generation of inverted flags that combine flexible piezoelectric strips with photovoltaic cells to simultaneously harvest kinetic wind energy and solar radiant energy. Experiments were conducted in a wind tunnel under controlled...

Introduction Abdominal aortic aneurysm (AAA) is a life-threatening cardio-vascular condition. Current NHS recommendation for surgical interventions to avoid potential rupture is based on the maximum diameter threshold of 5.5 cm. However, in some cases aneurysms smaller than the threshold value have been observed to rupture(1). Over the past years,...

Fluid–structure interaction (FSI) problems involving thin slender bodies are a difficult modelling problem particularly for highly flexible bodies. An accurate, numerically stable approach is presented for fixed bodies as a first stage where weakly compressible smoothed particle hydrodynamics in Eulerian form (EWCSPH) is coupled with the immersed b...

In this paper Eulerian weakly compressible SPH (EWCSPH) is coupled to the Vector-based discrete element model (V-model) to produce a robust mesh-less SPH-V model for fluid-structure interaction (FSI) applications including thin highly flexible bodies. The V-model, originally proposed as a model for granular structures, is extended herein to model n...

Computational modelling of the cardiovascular system offers much promise, but represents a truly interdisciplinary challenge, requiring knowledge of physiology, mechanics of materials, fluid dynamics and biochemistry. This paper aims to provide a summary of the recent advances in cardiovascular structural modelling, including the numerical methods,...

Scale-resolving turbulent flow simulation for urban environments is computationally expensive and not widely used in industrial practice, despite inherent complexities from geometry and high Reynolds number effects. One way to reduce the computational demand of the simulation is to focus a turbulence-resolving solver on the region of interest, and...

This paper presents the methodology of an improved wall function for large eddy simulation (LES). The sub-domain wall function for LES simulates two regions of the flow domain concurrently. The first region covers the entire flow domain and solves LES transport equations, with a coarse grid near the solid walls. The second region is much smaller an...

Purpose Image-based computational fluid dynamics (CFD) is widely used to predict intracranial aneurysm wall shear stress (WSS), particularly with the goal of improving rupture risk assessment. Nevertheless, concern has been expressed over the variability of predicted WSS and inconsistent associations with rupture. Previous challenges, and studies f...

This paper aims to develop a novel concept for energy harvesting via flexible inverted flags combining photovoltaic cells with piezoelectric material. Using technology currently available off-the-shelf, we have built dual piezo-solar harvesters made of polyvinylidene fluoride (PVDF) piezoelectric elements combined with mini solar panels of differen...

An important component of any computational method research project must always be a comprehensive assessment of all new findings to ensure that meaningful and reliable conclusions can be obtained. This was also attempted in previous collaborative EU-funded turbulence modelling research projects such as Haase et al. (2009) and Schwamborn and Strele...

Enhanced computational resources and improvements in synthetic turbulence generation methods have motivated a higher level of activity in embedded (zonal) approaches for turbulence simulation in recent years.

In contrast to the non-zonal, DES-like, hybrid approaches, in which a transition from RANS to LES relies upon a natural instability of separated shear layers in massively separated flows, the zonal RANS-LES (actually, RANS – Wall Modelled LES or RANS-WMLES) hybrids imply the presence of a sharp interface between the flow regions treated by RANS and...

This paper describes a multi-scale fracture framework, for modelling dynamic fracture in polycrystalline materials. The motivation behind developing such an application is to provide a high fidelity tool to model and capture dynamic structural deformations, at the macro scale, undergoing fracture at the micro scale. The application links two highly...

The ability to perform credible CFD simulations at accelerated speeds has opened up the potential for a new use-mode for CFD as a tool in engineering: the application of CFD for first-order parameter-space exploration, analysis, and design communication. When coupled with a suitable real-time rendering and interaction capability for in-situ visuali...

When scale-resolving simulation approaches are employed for the simulation of turbulent flow, computational cost can often be prohibitive. This is particularly true for internal wall-bounded flows, including flows of industrial relevances which may involve both high Reynolds number and geometrical complexity. Modelling the turbulence induced stress...

The Lattice-Boltzmann Method at the University of Manchester (LUMA) project was commissioned to build a collaborative research environment in which researchers of all abilities can study fluid–structure interaction (FSI) problems in engineering applications from aerodynamics to medicine. It is built on the principles of accessibility, simplicity an...

This book reports on the latest developments in computational fluid dynamics and turbulence modeling, with a special emphasis on hybrid RANS-LES methods and their industrial applications. It gathers the proceedings of the Sixth Symposium on Hybrid RANS-LES Methods, held on September 26-28 in Strasbourg, France. The different chapters covers a wealt...

The ability to perform interactive CFD simulations on mobile devices allows the development of portable, affordable simulation tools that can have a significant impact in engineering design as well as teaching and learning. This work extends existing work in the area by developing and implementing a GPU-accelerated, interactive simulation framework...

This presentation describes the characteristics of different CFD models used in video games and in engineering applications. It also states which general techniques used in video games and animation models could be applied to engineering.

The paper reports the computational fluid dynamics (CFD) investigations of the flow induced excitations in a high-pressure integral throttle valve. The effect of the valve openings on the characteristics of the unsteady fluids force on the valve head are studies. 2D CFD models are developed based on high pressure integral throttle valve and normal...

The authors are working towards the development of an open source platform for solving fluid-structure interaction (FSI) problems that is scalable on high performance computing (HPC) systems. Using existing open source software, we have built a prototype application to demonstrate the benefits of high performance computing for this class of problem...

The purpose of this paper is to provide a high level, holistic overview of the work being undertaken in the wind energy industry. It summarises the main techniques used to simulate both aerodynamic and structural issues associated with wind turbines and farms. The motivation behind this paper is to provide new researchers with an outlook of the mod...

The academic literature is a rich source of articles about fluid-structure interaction. A common feature of these publications is that the structure is almost always an elastic solid. The structure is so unimportant that it is often dismissed as a " ghost " structure. One might interpret this as a cultural difference between experts in CFD and expe...

Engineering simulation is essential to modern engineering design, although it is often a computationally demanding activity which can require powerful computer systems to conduct a study. Traditionally the remit of large desktop workstations or off-site computational facilities, potential is now emerging for mobile computation, whereby the unique c...

In contrast to the non-zonal, DES-like, hybrid approaches, in which a transition from RANS to LES relies upon a natural instability of separated shear layers in massively separated flows, the zonal RANS-LES (actually, RANS – Wall Modelled LES or RANS-WMLES) hybrids imply the presence of a sharp interface between the flow regions treated by RANS and...

The fluid-structure interaction mechanisms of a coating composed of flexible flaps immersed in a periodically oscillating channel flow is here studied by means of numerical simulation, employing the Euler-Bernoulli equations to account for the flexibility of the structures. A set of passively actuated flaps have previously been demonstrated to deli...

The passive control of bluff body wakes using a sparse layer of elastic hairy filaments has been investigated via a series of numerical simulations and compared to selected experiments under well-controlled boundary conditions. It has been found that a distribution of filaments spaced half of the dominant three dimensional instability and resonatin...

Previous studies of flexible flaps attached to the aft part of a cylinder have demonstrated a favourable effect on the drag and lift force fluctuation. This observation is thought to be linked to the excitation of travelling waves along the flaps and as a consequence of that, periodic shedding of the von Kármán vortices is altered in phase. A more...

With performance in mind, we propose two general improvements to the popular class of turbulent inlet boundary conditions known as the ?synthetic eddy method?, originally proposed 10 years ago by Jarrin 2006. Our updated version offers improvement in both statistical accuracy and computational efficiency. We first demonstrate that the original appr...

The paper investigates effects of various valve openings on the unsteady fluids forces on the stem of a high-pressure governor valve through a simple simulated CFD (Computational Fluid Mechanics) study. A validated CFD model is developed based on the earlier experimental study on a simple mechanical valve published in the literature. The CFD model...

Complex fluid-structure interactions between elastic filaments, or cilia, immersed in viscous flows are commonplace in nature and bear important roles. Some biological systems have evolved to interpret flow-induced motion into signals for the purpose of feedback response. Given the challenges associated with extracting meaningful experimental data...

Pulmonary hypertension is usually related to obstruction of pulmonary blood flow at the level of the pulmonary arteries (eg, pulmonary embolus), pulmonary arterioles (idiopathic pulmonary hypertension), pulmonary veins (pulmonary venoocclusive disease) or mitral valve (mitral stenosis and regurgitation). Pulmonary hypertension is also observed in h...

Fluid-Structure Interaction (FSI) problems typically involve strong vortices due to dynamic shear layers developing near the interface. Smoothed Particle Hydrodynamics (SPH) is known for its ability to model violent bulk flows but accurate modelling of vorticity and dynamic shear layers requires modifications to the classical SPH scheme. Herein, Eu...

Patient-specific simulations, efficient parametric analyses, and the study of complex processes that are otherwise experimentally intractable are facilitated through the use of Computational Fluid Dynamics (CFD) to study biological flows. This review discusses various CFD methodologies that have been applied across different biological scales, from...

The current criterion for surgical intervention in abdominal aortic aneurysms, based upon a maximal aortic diameter, is considered conservative due to the high mortality rate in case of rupture. The research community is actively investigating the use of computational mechanics tools combined with patient-specific imaging to help identify more accu...

A detailed Computational Fluid Dynamics (CFD) study of transient, turbulent blood flow through a positive displacement left ventricular assist device (LVAD) is performed. Two common models for Non-Newtonian blood flow are compared to the Newtonian model to investigate their impact on predicted levels of shear rate and wall shear stress. Given that...

Laminarization is an important topic in heat transfer and turbulence modeling. Recent studies have demonstrated that several well-known turbulence models failed to provide accurate prediction when applied to mixed convection flows with significant re-laminarization effects. One of those models, a well-validated cubic nonlinear eddy-viscosity model,...

Background and purpose: A variety of approaches exists where numerical methods that underlie numerous assumptions are used in order to predict rupture in intracranial aneurysms. Since many hemodynamic parameters have been derived from these computations but no persistent explanation for rupture has been found, the acceptance of CFD among physician...

The Ahmed car body represents a generic vehicle exhibiting key aspects of the 3D flow arising due to standard automobile designs. It is recognised to be a challenging test case for the turbulence modelling community; combining strong separation with a pair of counter-rotating vortices, which interact to produce a downstream recirculation region. In...

In this paper we present a novel reconstructed- Immersed Boundary Model (r-IBM) developed for SPH with partially immersed surface piercing boundaries. We propose a flow field reconstruction technique which overcomes the limitation of IBMs to CFD methods which use a uniform mesh. It has been shown that MLS techniques can also be used to overcome thi...