ABSTRACT Computational fluid dynamics (CFD) modelling was performed to simulate spatial and temporal airborne pathogen concentrations during an observed COVID-19 outbreak in a restaurant in Guangzhou, China. The reported seating configuration, overlap durations, room ventilation, layout, and dimensions were modelled in the CFD simulations to determine relative exposures and probabilities of infection

A high-fidelity, low-Mach computational fluid dynamics simulation tool that includes evaporating droplets and variable-density turbulent flow coupling is well-suited to ascertain transmission probability and supports risk mitigation methods development for airborne infectious diseases such as COVID-19. A multi-physics large-eddy simulation-based paradigm is used to explore droplet and aerosol pathogen

Although weighted compact nonlinear scheme (WCNS) has been successfully applied to the simulation of complex configurations, due to the excessive dissipation, the scheme is still not suitable for many circumstances. In this article, an optimised five-point-stencil WCNS is proposed. On the one hand, by assembling two fourth-order sub-schemes, the background upwind scheme is optimised for low dissipation

ABSTRACT This work presents a computational model for a discontinuous fibre composite manufacturing process. The alignment mechanism of this novel process, called the High Performance Discontinuous Fibre (HiPerDiF) method, involves highly coupled fluid–structure interactions. Fibres with a length on the order of a few millimetres are placed in a water suspension, sprayed between two parallel plates

ABSTRACT This paper addresses the influence of the scheme used in the convective terms of turbulence and transition transport equations on the numerical accuracy of transitional flow simulations. Three transition models are combined with the k − ω Shear Stress Transport turbulence model: the γ − R e θ model, the γ model and the Amplification Factor Transport model. Two airfoils and a 6:1 prolate spheroid

The vorticity confinement (VC) method was applied to tip vortices shed by edges of wings in order to predict induced drag using far-field integration. The optimal VC parameter was determined by its application to tip vortices shed by 3-D stationary and rotating wings. The VC was used with a total variation diminishing (TVD) approach to reduce the needed confinement. The TVD minmod and differentiable

This paper develops a new hybrid finite difference scheme which consists of a nonlinear WENOCU4 scheme to maintain the numerical stability near discontinuities and a fourth-order linear central scheme elsewhere to accurately resolve smooth fluctuations and to speed up the computation. The central scheme is constructed in a robust skew-symmetric form which satisfies energy conservation property. A new

A compact high-order gas-kinetic scheme (GKS) with spectral resolution will be presented and used in the simulation of acoustic and shock waves. Based on high-order gas evolution model, the GKS provides a time accurate solution at a cell interface, from which both time accurate flux function and flow variables can be obtained for updating cell averaged conservative flow variables and gradients. Based

This paper aims to introduce the core features of the Fuzzy Logic (FL) approach in simulations of turbulent Supersonic flows as a cost-effective methodology. Computational Fluid Dynamic (CFD) analysis is conducted to study the effect of Mach number (M e ), nozzle pressure ratio (NPR) and expansion corners (EC) on primary recirculation region length (Xr1). An Open FOAM numerical solver was used for

One of the main issues with naive Smoothed Particle Hydrodynamics (SPH) implementations is the lack of uniform accuracy in the computational domain. If not mastered correctly, this leads to non-physical predictions when dealing with large-domain hydraulic problems or with very fine resolutions. The present article addresses two recommended methodologies to achieve the best numerical accuracy with single-precision

When the tire of aircraft landing gear passes through the contaminated runway, besides the side water spray, the water spray between the multi-wheels will collide and form the pattern similar to the tail of the rooster. This kind of water spray is called the cock tail flow. In this paper, numerical analysis is used to study the formation process of the cock tail flow caused by the main aircraft tires

A mathematical model is developed to study on the influence of magnetic field on the flow of biofluids. This paper describes the laminar, viscous incompressible flow, which is a fully developed flow of a conducting biomagnetic fluid in a rectangular duct with square cross-section, is numerically studied under the influence of magnetic field. Therefore, numerical simulation was carried out by using

The objective of this paper is to check the ability of the high-order OSMP scheme [Daru, V., and C. Tenaud. 2004. “HighOrder One-Step Monotonicity-Preserving Schemes for Unsteady Compressible Flow Calculations.” Journal of Computational Physics 193 (2): 563–594] to accurately compute turbulent compressible flows with a special focus on the effect of the MP constraints on solutions of wall bounded turbulent

A series of challenging fluid flow applications are used to demonstrate the powerful capabilities of the SPH method. The applications are classified according to whether they are industrial, geophysical or biophysical in nature. The versatility and flexibility of SPH allows it to be used to predict wide ranges of flow types with diverse coupled secondary physics and chemistry. The demonstration examples

(2020). High Performance Computing Techniques in CFD. International Journal of Computational Fluid Dynamics: Vol. 34, High Performance Computing in CFD (GHMG). Guest editors: Guillaume Houzeaux and Marta Garcia-Gasulla, pp. 457-457.

Computational fluid dynamics (CFD) computations often require coupling of some values on one computational domain or portion thereof to another. This is the case both for multi-physics couplings, and for the implementation of various features, such as restarting on a different mesh, boundary condition couplings, and others. This usually involves locating points or elements relative to other elements

ABSTRACT The present study performs direct numerical simulations of turbulent channel flows using a spectral method in a large computational domain. Because of applying Fourier discretisation in the spectral method, parallelisation of the method may incur heavy communication overhead, thereby resulting in poor scalability. We design and improve the spectral code by exploring parallel techniques, including

Solidification is an important issue that needs to be addressed when modelling supercooled large droplets (SLD) impacting aircraft surfaces. This work develops a 3D triple-phase smoothed particle hydrodynamics (SPH) solver that can simultaneously simulate SLD impingement and solidification on cold surfaces by solving the Euler equations for fluid dynamics, the energy equation for heat transfer, and

The Smoothed Particle Hydrodynamics code SPHERA (RSE SpA) is validated on a laboratory urban dam-break flood. Comparisons with a porous Shallow Water Equations - Finite Volume Method 2D model are also reported. SPHERA provides a performance comparable with the state-of-the-art code, with results closer to the measured values during the most risky flood stage. Some improvements of SPHERA predictions

A new computational methodology is developed for large eddy simulation (LES) of turbulent reacting flows using graphic processing units (GPUs). The LES is based on the filtered density function (FDF) of the scalar-composition in conjunction with a discontinuous Galerkin (DG) discretisation scheme on a structured rectangular mesh. This hybrid solver is developed in a manner suitable for GPU computing

This paper presents results of Artificial Neural Networks (ANN) applications to sub-grid Large Eddy Simulation (LES) model. The training data for the ANN is provided by simulation of Homogeneous Isotropic Turbulence at different Reynolds numbers. The results show that the correlation coefficients are superior to other sub-grid models, using a similar set of input variables. As the ANN model extrapolates

This paper facilitates the integration of TRIZ and CFD techniques to resolve design challenges and drive innovation in flow handling equipment new product development processes. A new methodology is proposed based on an integrated product lifecycle suited for flow handling equipment product development processes. The methodology accomplishes novel design solutions by designing geometrical flow paths

In this paper a characteristics-based open boundary condition (CBC) is proposed for the magnetohydrodynamic (MHD) system of equations. The algorithm is carefully designed and implemented in the context of a high-order flux reconstruction (FR) scheme under the Generalised Lagrange Multiplier (GLM)-MHD system of equations. It is implemented by adding the contribution of the characteristic equation directly

(2020). Correction. International Journal of Computational Fluid Dynamics: Vol. 34, No. 6, pp. I-I.

We have examined the effects on fluid and particle motion due to solid particles passing around circular obstacles in particulate flows. Particle interaction with internal obstacles, outer boundary and with the fluid is inspected. Eulerian approach using a fixed computational mesh is used across which the solid particles move freely in fluid. Treatment of fluid and particle interaction inside the whole

The vorticity confinement (VC) method was used with total variation diminishing (TVD) schemes to reduce possible over-confinement and applied to convected and stationary vortices. The optimal VC parameter was determined by application to 2-D vortices. The conservativity of the scheme is investigated in terms of kinetic energy and momentum. Grid convergence study was conducted for the range of grid

This paper discusses selected features of the Smoothed Particle Hydrodynamics (SPH) method when used in combination with a Finite Element (FE) software tool. Special attention is paid to the implementation of wall boundary conditions in view of their relevance to the simulation of fluid-structure interaction (FSI). Several industrial applications of the hybrid SPH-FE method are reviewed in detail.

Canard is one of the aerodynamic add-on devices which can reduce drag coefficient of the car. In this paper, different parameters of the canard geometry are determined using a multi-objective optimisation. Design variables are entrance velocity (U), geometrical parameters of canard (L 1, L 2, r, α) and canard angle from horizontal axis (θ). The objective functions include magnitude of drag and lift

Aerodynamic characteristics of tilt-rotor UAVs are usually simulated by computational fluid dynamics (CFD) only, and the fuselage/wing is fixed in simulations. It is difficult for this method to consider drastic changes of the aerodynamic forces and flowfield originating from conversion of flight modes. And during flight-mode conversions, the rapid changes of postures of tilt-rotors will unavoidably

ABSTRACT For complex engineering and scientific applications, Computational Fluid Dynamics (CFD) simulations require a huge amount of computational power. As such, it is of paramount importance to carefully assess the performance of CFD codes and to study them in depth for enabling optimisation and portability. In this paper, we study three complex CFD codes, OpenFOAM, Alya and CHORUS representing

The design process is a critical issue in order to improve rocket engine performance. Indeed, the prediction of the aerodynamic forces acting on the nozzle, in particular the off-axis loads, is challenging even for modern methods. In this study, the flow of an exit Mach number M d = 3.5 Truncated Ideal Contour (TIC) nozzle is numerically investigated by means of Large-Eddy Simulation (LES), using the

Multiphysics problems involve the couplings of different sets of partial differential equations. Partitioned methods consider the individual solutions of each set, which upon iterating, converge to the monolithic solution. The main drawback of partitioned methods is the additional iterative loop, which can be done a la Jacobi (parallel) or a la Gauss–Seidel (sequential). The latter method has worse

This paper addresses the MPI parallelisation of a 3D multiphase smoothed particle hydrodynamics (SPH) solver, focusing on supercooled large droplets (SLD) impingement. SPH uses moving particles to represent fluid flows, demanding particular parallelisation strategies. A cell system provides a spatial reference to generate dynamical neighbour lists, and to pack, send and receive particles. A re-indexing

ABSTRACT In this work, we propose an efficient ‘r-to-h’ adaptation algorithm for moving boundary problems using only vertex displacements and some local h-adaptation operations. Moving boundary algorithms usually require the regeneration of the mesh to avoid his invalidation in particular when the motion is large and/or several bodies are involved. The proposed approach aims to move the mesh nodes

Aerodynamic characteristics of tilt-rotor UAVs are usually simulated by computational fluid dynamics (CFD) only, and the fuselage/wing is fixed in simulations. It is difficult for this method to consider drastic changes of the aerodynamic forces and flowfield originating from conversion of flight modes. And during flight-mode conversions, the rapid changes of postures of tilt-rotors will unavoidably

Fault-tolerant computing options based on the use of restart information stored on and off node and the use of reserve processes have been developed, implemented and tested in a large-scale, production field solver taken from the domain of computational fluid dynamics. The tests conducted to date have shown good results, with recovery rates approaching 100% under realistic node failure scenarios. Even

High fidelity multiphysics simulations are ubiquitous in science and engineering but still face many challenges to run efficiently in today's supercomputers. This work reports advanced technologies present in EdgeCFD, a hybrid parallel variational multiscale multiphysics finite element software capable of running industrial problems involving turbulent incompressible, compressible, free-surface flows

The shark-skin-inspired riblets could effectively reduce the turbulence wall-skin friction compared with the smooth surface. Nevertheless, computations of the flow field over riblets in the practical configurations (e.g., airplanes and wind turbines) remain unfeasible for its huge computational cost. In this study, a general strategy for modelling the effects of riblets in turbulent flows is proposed

We analyse and study instability problems related to the solution of the advection–diffusion–reaction equation (ADR) using a standard finite element scheme. With this aim, this work has been carried out in the following way: first, three weak formulations are obtained from the general problem. In specific, we study the existence and uniqueness of the solution for each of the aforementioned formulations

(2020). Special Issue on Reduced Order Models in CFD. International Journal of Computational Fluid Dynamics: Vol. 34, Advances in reduced order methods in CFD (GRSP). Guest Editors: Simona Perotto and Gianluigi Rozza, pp. 91-92.

In-flight ice accretion code predictions depend on heat loss over rough surfaces. The equivalent sand grain roughness models the friction coefficient, but an additional model is needed for heat transfer predictions. In this paper, a two parameters model based on a turbulent Prandtl number correction is derived from the sublayer Stanton-based model. For flow over rough surfaces, the new model predictions

In this contribution we consider cardiovascular hemodynamic modelling in patient-specific artery branches. To this aim, we first propose a procedure based on non-uniform rational basis splines (NURBS) to parametrise the artery volume which identifies the computational domain. Then, we adopt an isogeometric hierarchically reduced model which suitably combines separation of variables with a different

The resolution and robustness properties of a numerical scheme are two mutually restricted aspects for the detailed simulation of complex flows. In the present paper, an improved seventh-order finite difference weighted essentially non-oscillatory scheme (WENO-PR) is developed by distributing larger weights to the less smooth stencils. To meet the optimization requirements, the high-order smoothness

A coupling technique for interface simulations applied to the fields of ship hydrodynamics and multiphase flow computations is presented. The technique takes advantages of mass conservation property of the volume-of-fluid method and sharpened interface computation of the Level-Set approach. An improved scheme for the gradient computation of the Level-Set function during re-initialisation is also introduced

The multi-mesh, multi-solver paradigm makes use of multiple Computational Fluid Dynamics (CFD) solvers in a single overset framework. A framework-level implementation of the Generalised Minimal Residual algorithm applied to the full implicit overset system is presented. The method requires only minimal changes to existing, Python-wrapped CFD solvers and demonstrates improved convergence compared to

When the Reynolds number exceeds approximately 10, drag from porous media becomes nonlinear and cannot be handled by Darcy's theory. The Darcy–Forchheimer law, which considers drag through porous media as a quadratic function, covers this region up to the Reynolds number of the order 102. In this research, we study the optimal shape of a porous unit cell based on this law and topology optimisation

A combination of the lattice-Boltzmann and immersed-boundary methods is used to simulate the behaviour of circular particles in fluids, including their behaviour in stationary and flowing fluids. This method simulates the fluid domain with a regular Eulerian grid, and the non-grid uniform boundaries with a Lagrangian grid. The no-slip boundary condition of the fluid and particle boundaries is enforced

Additive Manufacturing (AM) is a rapidly developing new technology which allows the manufacture of arbitrarily complex geometries, and which is likely to transform heat exchanger design. To drive this transformation we need to develop computer modelling techniques to model fluid flow, heat exchange and phase change in arbitrarily complex domains, such as can be manufactured using AM. The present work

A linear stability analysis is performed to explain the formation of coherent structures in the narrow regions of a rectangular channel containing a cylindrical rod and a channel formed by two rectangular ducts connected through a narrow slot. This stability analysis introduces small perturbations of the velocity and the pressure in the governing equations. The linearised equations are transformed

In the paper, an improved third-order finite difference weighted essentially non-oscillatory scheme is presented for achieving the optimal order near critical points. A new global smoothness indicator is obtained with the way of Taylor expansion for the local smoothness indicator. In the framework of the conventional WENO-Z scheme, we present an improved third-order finite difference WENO scheme. The

Since the discovery of vortex structures in turbulence, research in the area of vortex visualisation methods has been of interest. The prevalent Galilean invariant visualisation methods, like Q, Lambda2, and Omega methods, are based on the local pointwise analysis of invariants of the velocity gradient tensor. When plotting the vortex iso-surfaces, different methods will introduce different thresholds

Accurate modelling of fluid and particle flow is essential for reliable predictions of gas–solid reactions in the multiphase reactor. Due to the promising features such as short contact time, less back mixing of solids and low residence time, downer column has been used in industries than conventional riser configuration. However, the effective simulation and validation of the hydrodynamic characteristics

Multi-physics simulations are at the heart of today's engineering applications. The trend is towards more realistic and detailed simulations, which demand highly resolved spatial and temporal scales of various physical mechanisms to solve engineering problems in a reasonable amount of time. As a consequence, numerical codes need to run efficiently on high-performance computers. Therefore, the framework

This paper presents an isogeometric (IGA) solver for time-dependent, incompressible magnetohydrodynamics (MHD). In this paper, a combination of inf-sup stable mixed discretisations is considered to discretise the hydrodynamic pair (i.e. velocity and pressure) and magnetic pair (i.e. magnetic field and magnetic pressure). The one step θ-method is used for the temporal discretisation. Manufactured and

The sensitivity of a large range of turbulence closures to the near-wall grid resolution is assessed through analytical and numerical techniques. We determine model boundedness, limiting behaviour, and solution dependence of channel flow simulations to the near-wall cell size y 1 + . The sensitivity of present simulations to y 1 + is strongly dependent on the choice of scale determining variable; ε

This paper demonstrates how, by means of Reduced Order Modelling (ROM), CFD cost can be drastically reduced and, in addition, a more complete investigation of a continuous design space obtained by adding experimental fluid dynamics (EFD) and flight fluid dynamics (FFD) data. The ‘Gappy’ Proper Orthogonal Decomposition (GPOD) method is used to enrich the EFD and FFD data to the size of their companion

This paper investigates the recently introduced data-driven correction reduced order model (DDC-ROM) in the numerical simulation of the quasi-geostrophic equations. The DDC-ROM uses available data to model the correction term that is generally used to represent the missing information in low-dimensional ROMs. Physical constraints are added to the DDC-ROM to create the constrained data-driven correction

Reversible axial flow fans, used in tunnel ventilation systems are designed in a way that as the direction of impeller rotation changes, suction and discharge directions change without any sensible change in flow rate and pressure. Also, their reversibility must be higher than 90%. Therefore, the blade profiles of these fans (S-shaped or elliptic) are designed symmetrically. In the current work, a

A typical weighted compact nonlinear scheme (WCNS) uses a convex combination of several low-order polynomials approximated over selected candidate stencils of the same width, achieving non-oscillatory interpolation near discontinuities and high-order accuracy for smooth solutions. In this paper, we present a new multi-resolution fifth-order WCNS by making use of the information of polynomials on three

(2019). Discontinuous Galerkin methods – new trends and applications. International Journal of Computational Fluid Dynamics: Vol. 33, No. 8, pp. 333-334.