Dominique Laurence

The University of Manchester · School of Mechanical, Aerospace and Civil Engineering

As part of a flow accelerated corrosion investigation, the reliability of 4 RANS models, namely a 2-layer k-ε, the k-ω SST, the Elliptic Blending k-ε and the Elliptic Blending Reynolds Stress Model, for mass and heat transfer predictions (Sherwood and Nusselt numbers) is evaluated by reference to a recent experiment (=16-24,000, Pr = 0.707, Sc = 2....

Computations of the flow inside the rotating cage, a widely used testing methodology for flow-accelerated corrosion studies, are presented in this study. The main objectives here are to elucidate the flow behaviour inside the cage geometry that is recommended by the American Society for Testing and Materials (ASTM) and to investigate the effects of...

This study is concerned with the investigation of the suitability of the dual-mesh method for the buoyancy driven flow inside a cylindrical annulus with one internal cylinder. This flow situation can occur, for instance, in gas cooled nuclear reactors and is characterized by complex features, including a buoyant plume and a negatively buoyant wall-...

In this study the rotating cage setup, a simple laboratory methodology extensively used for flow-accelerated corrosion and erosion-corrosion testing, is optimized via CFD simulations for flow-accelerated corrosion testing with liquid lead for lead-cooled nuclear reactors. In the rotating cage, samples manufactured from the material of interest are...

In this work, the dual-mesh hybrid RANS-LES approach was applied for the first time to a natural convection flow, namely a high Rayleigh number differentially heated square cavity flow. This approach involves running an unsteady Reynolds Averaged Navier-Stokes (RANS) simulation and a coarse Large Eddy Simulation (LES) simultaneously using two diffe...

A hybrid RANS/LES model for high Reynolds number wall-bounded flows is presented, in which individual Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES) are computed in parallel on two fully overlapping grids. The instantaneous, fluctuating subgrid-scale stresses are blended with a statistical eddy viscosity model in regions wh...

A short report is given on the 16th ERCOFTAC SIG 15 Workshop on Turbulence Modelling, which was organized at the Jožef Stefan Institute of Ljubljana on 15th and 16th of October 2019. The workshop was focused on turbulent natural convection. The test cases were differentially heated vertical channel flows and differentially heated square cavities.

Nuclear Thermal-hydraulics (NTH) is a key element of Nuclear Power Plant (NPP) design and safety. It is the study of engineering systems where energy from nuclear fuel is transferred by a coolant to a power generation turbine or to the environment, by heat transfer, phase change and flow processes. Computational modelling of NTH is already a vital...

The paper is devoted to the application of the model order reduction to the results of direct numerical simulation of a low momentum laminar jet discharged into a laminar channel crossflow through a circular orifice (Reynolds number Re=3333, jet-to-crossflow velocity ratio is R=1/6, mesh 13 million nodes, (Wu et al., 2017a)). Main attention is paid...

To enable economic hybrid RANS/LES of wall-bounded flows at very high Reynolds numbers, two separate RANS and LES velocity and temperature fields are computed in parallel and are dynamically coupled. Both simulations are performed on proprietary grids, each with an optimal, model-adapted topology: a quasi-homogeneous grid for the LES, and a wall-re...

A hybrid RANS/LES model is presented, in which RANS and LES contributions to the subgrid- scale (SGS) Reynolds stresses are computed on two distinct grids and are seamlessly blended. The instantaneous, fluctuating SGS Reynolds stress field is supported by a statistical RANS eddy viscosity model in regions where the LES grid is considered as coarse....

In the case of conjugate heat transfer, the dissipation rate associated with the temperature variance is discontinuous at the fluid-solid interface. The discontinuity satisfies a compatibility condition involving the fluid-solid thermal diffusivity and conductivity ratios and the relative contribution to the dissipation rate of its wall-normal part...

This paper presents a combined RANS and LES methodology, which automates the dual-mesh hybrid LES/RANS approach and circumvents the need for wall-functions. Unlike RANS, wall-resolved LES is still unaffordable for studying high Reynolds number complex flows in industry and requires much user expertise when turbulence features are unknown a priori....

Results of a direct numerical simulation of a jet in crossflow with passive scalar mixing are presented. The laminar jet issues from a circular exit into the channel crossflow with a low jet-to-crossflow velocity ratio of 1/6. The governing equations are solved by Incompact3d, an open-source code combining the high-order compact scheme and Poisson...

In assessing whether nuclear plant components such as T-Junctions are likely to suffer thermal fatigue problems in service, CFD techniques need to provide accurate predictions for wall temperature fluctuations. Though it has been established that this is within the capabilities of wall-resolved LES, its high computational cost has prevented widespr...

Flows in pipe bends and T-Junctions are of great interest to the nuclear power industry, as turbulent temperature fluctuations in coolant flow can cause high cycle thermal fatigue in pipe walls. However, these flows often feature separation, streamline curvature and Reynolds stress anisotropy; as a result, they are challenging for RANS eddy viscosi...

Turbulent mixing of fluids in a T-Junction can generate oscillating thermal stresses in pipe walls, which may lead to high cycle thermal fatigue. This thermal stripping problem is an important safety issue in nuclear plant thermal-hydraulic systems, since it can lead to unexpected failure of the pipe material. Here, we carry out a large eddy simula...

Direct numerical simulation (DNS) with high-order compact scheme (Incompact3d) is used for simulating a jet in cross flow (JICF) with passive scalar mixing and wall heat transfer. The low momentum laminar circular jet is orthogonal to the walls of a turbulent channel flow generated using recycling technology. Instantaneous and time-averaged profile...

A Direct Numerical Simulation was used to study the buoyancy driven turbulent flow inside a horizontal annular cavity at Rayleigh number, Ra = 1.18x10^9, and cylinders diameters ratio of 4.85. Mean and rms temperature profiles are in good agreement with experiments. Turbulent kinetic energy budgets have been calculated to verify the accuracy of the...

Budgets of turbulent heat fluxes and temperature variance obtained from the Direct Numerical Simulation of an incompressible periodic channel flow with a Reynolds number of 150 (based on friction velocity) and a Prandtl number of 0.71 are presented and analysed for four cases: locally imposed temperature at the wall (constant Dirichlet), locally im...

Adaptive wall-functions are developed for the near-wall elliptic-blending eddy-viscosity model (Billard and Laurence, Int. J. Heat Fluid Flow 33(1), 45–58, 2012). The aim of the new methodology is to make the predictions of this turbulence model less dependent on the spatial resolution in the viscous, buffer and logarithmic layer of the near-wall f...

Thermal fatigue is a major concern in the service-life management of nuclear plant thermal-hydraulics systems. Hybrid LES/RANS techniques have the potential to provide predictions which are computation-ally affordable for studies of this problem in industry, however they require further development and validation. The present work compares various...

The flow past a flat plate at a Reynolds number (ReU0 ) of 750 has been numerically investigated via fine Large Eddy Simulation (LES). Initially, two configurations were tested; plate normal (at 900) and oblique (at 450) to the mean flow direction with a uniform steady inlet. The results have been compared to DNS and experimental data and have been...

The present paper uses the weakly compressible smoothed particle hydrodynamics (SPH) to model numerically the sediment suspension and the shear layer induced by rapid flows resulting in scouring of the sediment with two yield criteria based on the Mohr-Coulomb and Drucker-Prager formulations. To the best of the authors' knowledge this is the first...

The flow over a flat plate at a Reynolds number of 750 is numerically investigated via fine large-eddy simulation (LES), first at normal (90\textdegree) and then at oblique (45\textdegree) incidence flow direction with a uniform steady inlet. The results are in complete agreement with the direct numerical simulation (DNS) and experimental data, the...

Wall boundary conditions in smoothed particle hydrodynamics (SPH) is a key issue to perform accurate simulations. We propose here a new approach based on a renormalising factor for writing all boundary terms. This factor depends on the local shape of a wall and on the position of a particle relative to the wall, which is described by segments (in t...

Coolant flows in the cores of current gas-cooled nuclear reactors consist of ascending vertical flows in a large number of parallel passages. Under post-trip conditions such heated turbulent flows may be significantly modified from the forced convection condition by the action of buoyancy, and the thermal-hydraulic regime is no longer one of pure f...

La stabilité d'un écoulement de sillage derrière une île de forme conique, lorsque la hauteur d'eau est petite devant les échelles horizontales, est étudiée au moyen de la simulation numérique en utilisant le code éléments finis TELEMAC-2D. Cet écoulement est numériquement difficile à appréhender car le fort confinement entre la surface libre et le...

The paper presents refined three-dimensional simulations of the flow and heat transfer in fuel assemblies as found or suggested for liquid metal coolant fast reactors. The wire spacers, helically wound along the pin axis, generate a strong secondary flow pattern in opposition to smooth pins. The eddy viscosity and second moment turbulence models yi...

The paper presents the development and validation of adaptive wall functions that allow local “down-to-the-wall” resolution based on a three-equation plus elliptic-blending eddy-viscosity model. Two wall-treatments are proposed: 1/ the wall function values are applied as boundary conditions (local treatment) or 2/ the wall function profiles are app...

This paper reports the application of a recently developed turbulence modelling scheme known as the C as model. This model was specifically developed to capture the effects of stress-strain misalignment observed in turbulent flows with mean unsteadiness. Earlier work has reported the approach applied within a linear k-ε modelling framework, and so...

Subgrid scale (SGS) models used in Large-Eddy Simulation (LES) have been mainly derived on spectral energy transfer grounds and only represent the mean energy dissipation. A new SGS stress tensor model based on the resolved stresses (in the line of Bardina’s scale similarity model) is shown to better represent backscatter effects and SGS stress ani...

A rod bundle is a key constitutive element of a wide range of nuclear reactor designs. It is composed by a set of long thin rods containing the nuclear fuel and fluid-flow between them and generally parallel to the rods. As experiments in a such densely packed geometries are difficult, thermal-hydraulics simulations are valuable to study heat trans...

With the steady increase in computing power, there have been numerous efforts to numerically quantify turbulence modulation by inertial particles. However, highly resolving the flow around thousands to millions of particles to get an accurate particle/turbulence interaction has been prohibited by the number of grid points required. Thus, physical m...

The flow around a trailing edge is computed with a new hybrid method designed to more clearly separate the effects of total and sub-grid turbulent stress-modelling on the time-averaged and instantaneous velocity fields, and in turn, mean momentum and kinetic energy balances. These two velocity fields independently define Reynolds averaged and sub-g...

Since its original introduction in Durbin (1991), more than 15 different versions of the v2-f model have been proposed, the purpose of most of them being to cure the recognised numerical stiffness associated to the original formulation. Even though comparisons of variants show results do not significantly differ from one another on near-wall cases...

Turbulent flow parallel to fuel rod bundles arranged in a triangular array are computed using LES and hybrid RANS/LES. Inner-channel flow pulsations are captured and the dominant frequency is in agreement with the experiments. The hybrid method shows a lack of accuracy in the near wall region probably due to the formulation of the blending function...

Description of Research Smoothed Particle Hydrodynamics (SPH) is a Lagrangian meshless method dealing with potentially violent simulations such as a wave breaking, or a dam break where Eulerian methods can be difficult to apply. Dealing with wall boundary conditions is one of the most challenging parts of the SPH method and many different approache...

The stability and accuracy of three methods which enforce either a divergence-free velocity field, density invariance, or their combination are tested here through the standard Taylor–Green and spin-down vortex problems. While various approaches to incompressible SPH (ISPH) have been proposed in the past decade, the present paper is restricted to t...

The present paper reports RANS simulations of the flow and heat transfer in a 2-dimensional rib-roughened passage. Rib pitch-to-height ratios of 6, 9, and 12 are examined. The blockage ratio of the transversely-mounted rectangular ribs is 10%, making the case 'very rough'. The Reynolds number, based on the channel bulk velocity and hydraulic diamet...

A coupling methodology between an upstream Reynolds Averaged Navier–Stokes (RANS) simulation and a Large Eddy Simulation (LES) further downstream is presented. The focus of this work is on the RANS-to-LES interface inside an attached turbulent boundary layer, where an unsteady LES content has to be explicitly generated from a steady RANS solution....

The flow around a trailing edge is computed with a new hybrid method designed to split the influences of the averaged and instantaneous velocity fields. The model is first tested on channel flows at different Reynolds numbers and coarse meshes giving good predictions of mean velocities and stresses. On the trailing edge flow the predictions of the...

This paper presents a review of recent applications of Computational Fluid Dynamics on problems dealing with power generation. Various turbulence models are used on different configurations involving heat transfer, ranging from Reynolds Averaged Navier-Stokes Equations (RANSE) with first or second order moment closure to Large Eddy Simulation (LES)...

Dispersion of heavy particles from a point source in high-Reynolds pipe flow was studied using large-eddy simulation, LES. A stochastic Langevin type Lagrangian model developed by Berrouk et al. was used to account for heavy particle transport by the sub-grid scale motion. In both the LES and in an experiment by Arnason, the larger particles disper...

In the smoothed particle hydrodynamics (SPH) discretisation method for the Navier–Stokes equations the most widespread method to solve for pressure and mass conservation is the weakly compressible assumption (WCSPH). This includes hydraulics applications and leads to some drawbacks such as severe artificial pressure fluctuations and a limitation to...

Aerosols deposition in turbulent bend flows is a major concern that is critical to many industrial, environmental and biomedical applications. In this work, a well-resolved LES was performed to compute the deposition efficiency of aerosols in turbulent circular cross-section bend flow of Dean number De = 4,225. The numerical predictions were compar...

The present paper proposes a new uncoupled formulation of the v2-f model that addresses numerical issues usually arising with such models without any loss in prediction accuracy. The model is based on elliptic blending, and unlike its “code-friendly” predecessors, it correctly predicts near-wall asymptotic behaviours without impairing its overall r...

In the present study, the possibility of performing cheap and accurate LES computations using unstructured grids on complex geometries has been examined. The test case considered is a turbulent flow around a thin controlled diffusion airfoil at low speed, with angle of attack of 8° to the incoming free-stream flow. The flow velocity is set to satis...

The flow structure around a generic side mirror of a car is numerically investigated via large eddy simulation (LES) incorporating polyhedral meshes. The aspect ratio defined as height to radius of the cylinder is 3 and the Reynolds number based on cylinder diameter and free stream velocity is 3.2 × 105. The aim of the current paper is not only to...

This paper reports the predictions of three turbulence modelling schemes in the application to the flow around a circular cylinder in a square duct. A URANS scheme known as the Stress-Strain Lag model has been developed in the DESider project, specifically to capture the effects of stress-strain misalignment observed in unsteady mean turbulent flow...

The present paper summarizes the research conducted at the University of Manchester over the course of the Desider project on methods of generation of synthetic turbulence. A random procedure, referred to as the Synthetic Eddy Method (SEM), based on the classical view of turbulence as a superposition of coherent structures was developed and compare...

The present work is concerned with the modelling of ascending turbulent ('mixed convection') flow in a vertical heated pipe. All fluid properties are assumed to be constant and buoyancy is accounted for within the Boussinesq approximation. Four Eddy Viscosity Models (EVMs) are examined against experimental measurements and the direct numerical simu...

An attempt is made to provide a criterion for optimal unstructured meshing for LES from the knowledge of different turbulence lengthscales. In particular, the performance of a grid based on the Taylor microscales for turbulent channel flow, is investigated, with the final view of facilitating an a priori determination of the mesh resolution require...

Organizing Committee: LESCHZINER M.A. (Chairman), KASSINOS S. (Co-chairman and local organiser), BONNET SJ.P., LAURENCE D., MENTER F., RODI W., TOMBOULIDES A., TROPEA C.

The flow structure around wall mounted circular cylinders of finite heights is numerically investigated via large eddy simulation (LES). The cylinder aspect ratios (AR) are 6 and 10 and the Reynolds number (Re) based on cylinder diameter and free stream velocity is 20,000 for both cases. The cantilever cylinder mounted on a flat plate is chosen sin...

The turbulent natural convection of air flow in a confined cavity with two differentially heated side walls is investigated numerically up to Rayleigh number of 1012. The objective of the present work is to study the effect of the inclination angle and the amplitude of the undulation on turbulent heat transfer. The low-Reynolds-number k–ε, k–ω, k–ω...

In order to study wave-structure interactions for coastal applications (wave shoaling in front of the structure and breaking, run-up, overtopping and forces due to wave action), we examine the potential and limitations of two different numerical approaches, namely an extended Boussinesq-type finite difference model and the SPH Lagrangian numerical...

Aiming at the better prediction of inertial particle dispersion in LES of turbulent shear flow, a stochastic diffusion process of the Langevin type is adopted to model the time increments of the fluid velocity seen by inertial particles. This modelling is particularly crucial for dispersion and deposition of inertial particles with small relaxation...

The neglect of the effects of sub-filter scale velocities often remains a source of error in LES predictions of particle dispersion and deposition. Indeed, sub-filter fluctuations should be expected to be more significant for particles with smaller relaxation times compared to the LES-resolved turbulence time scales. In this work, a stochastic diff...

A new Eddy viscosity model is proposed to include stress–strain lag effects in the modelling of unsteady mean flows. A transport equation for the lag parameter, hereby denoted Cas, is derived from a full Reynolds stress model (RSM), to be solved in conjunction with a standard two equation Eddy viscosity model (EVM). The performance of the new k–ε–C...

The generation of inflow data for spatially developing turbulent flows is one of the challenges that must be addressed prior to the application of LES to industrial flows and complex geometries. A new method of generation of synthetic turbulence, suitable for complex geometries and unstructured meshes