Stably stratified turbulent channel flow (STCF) is a canonical flow that is representative of shear-driven boundary mixing processes in geophysical settings. We examine the performance of a turbulence modeling framework composed of residual-based variational multiscale method (RBVMS) and isogeometric analysis (IGA) applied to STCF at friction Reynolds number Reτ=180. The framework is implemented with

Transition modelling represents a key ingredient for improving the performance predictions of many industrial applications. Among transition models, local formulations seem to guarantee better robustness, accuracy and easiness of implementation in modern CFD solvers. These models have been proposed in the finite volume context to predict the laminar-turbulent transition, but only few attempts have

In this paper, an efficient, unified finite difference method for imposing mixed Dirichlet, Neumann and Robin boundary conditions on irregular domains is proposed, leveraging on our previous work [Chai et al., J. Comput. Phys. 400 (2020): 108890]. The level set method is applied to describe the arbitrarily-shaped interface, and the ghost fluid method is utilized to address the complex discontinuities

In this paper we will show that the Runge-Kutta-Legendre (RKL) super-time-step methods are built up in stages by combining forward Euler steps with linear extrapolation steps. For second order, we will show that linear interpolation is also used. By using these characteristics a simplified algorithm will be presented. The effect of different types of external boundary conditions are shown. For Neumann

We study periodic solutions to the Navier-Stokes equations. The transition phase of a dynamic Navier-Stokes solution to the periodic-in-time state can be excessively long and it depends on parameters like the domain size and the viscosity. Several methods for an accelerated identification of the correct initial data that will yield the periodic state exist. They are mostly based on space-time frameworks

In this work, a mixing cell closure model was derived in a Lagrangian formulation based on the hypothesis of isentropic compression or expansion. The proposed closure model is used to construct a five-equation model for the simulation of multifluid and multiphase flows. Thereafter a global ALE(Arbitrary Lagrangian-Eulerian) method was developed for the five-equation model. The five-equation based ALE

Considering the current advances in experimental capabilities in fluid mechanics and the advances in computing power and numerical methods in computational fluid mechanics, a question that naturally arises is whether the two sets of techniques are approaching a level of sophistication sufficiently high to deliver results on turbulent flows in realistic geometries that are comparable. The purpose of

The dual-mesh finite domain method (DMFDM) proposed by Reddy (2019)[1] is used to study the steady-state convection–diffusion problems in 1D and 2D. In the DMFDM, one mesh of finite elements for the approximation of the domain and primary variables and another mesh of control domains, which also covers the whole domain, to satisfy the governing differential equations are used. The approach is distinguished

Computer-Aided Engineering (CAE) has supported the industry in its transition from trial-and-error towards physics-based modelling, but our ways of treating and exploiting the simulation results have changed little during this period. Indeed, the business model of CAE centers almost exclusively around delivering base-case simulation results with a few additional operational conditions. In this contribution

A comparative study of SST RANS and three hybrid approaches (SAS, DDES and SBES methods) is performed to analyse the flow around the 25∘ Ahmed body. The DDES approach is then selected as the reference model, based on comparison of numerical results. The main study is based on grid and time step influence over the simulation results. All results are compared to in-house experiments. The three grids

The present paper concerns the study of the nonconservative bitemperature Euler system with transverse magnetic field. We firstly introduce an underlying conservative kinetic model coupled to Maxwell equations. The nonconservative bitemperature Euler system with transverse magnetic field is then established from this kinetic model by hydrodynamic limit. Next we present the derivation of a finite volume

The quest for new portable implementations of simulation algorithms is motivated by the increasing variety of computing architectures. Moreover, the hybridization of high-performance computing systems imposes additional constraints, since heterogeneous computations are needed to efficiently engage processors and massively-parallel accelerators. This, in turn, involves different parallel paradigms and

During large-scale simulations, intermediate data products such as image databases have become popular due to their low relative storage cost and fast in-situ analysis. Serving as a form of data reduction, these image databases have become more acceptable to perform data analysis on. We present an image-space detection and classification system for extracting vortices at multiple scales through wavelet-based

In this paper, a prediction-correction algorithm, built on the method proposed in [1], uses the adjoint method to trace the Pareto front. The method is initialized by a point on the Pareto front obtained by considering one of the objectives only. During the prediction and correction steps, different systems of equations are derived and solved by treating the Karush-Kuhn-Tucker (KKT) optimality conditions

A mesh adaptation methodology for wall-modeled turbomachinery Large Eddy Simulation (LES) is proposed, simultaneously taking into account two quantities of interest: the average kinetic energy dissipation rate and the normalized wall distance y+. This strategy is first tested on a highly loaded transonic blade with separated flow, and is compared to wall-resolved LES results, as well as experimental

This paper aims to present the extension of the non-hydrostatic wave-flow model SWASH with the covolume method to build discretization schemes on unstructured triangular grids. Central to this method that is free of spurious pressure modes, is the use of dual pairs of meshes that are mutually orthogonal, such as the Delaunay-Voronoi mesh systems. The approximants sought are the components of the flow

Coupling techniques that take advantage of the mass conservation property of the volume-of-fluid (VOF) method and the sharpened interface computation of the Level Set (LS) approach are widely used for computations with high accuracy order demands. In this paper, an enhanced coupling method for interface computations in incompressible two-phase flows is presented. In the proposed method, the solution

A simultaneous impact of three water drops (aligned with equidistant spacing) onto a solid wall covered by a thin liquid film is predicted by direct numerical simulation using the multiphase code Free Surface 3D (FS3D) which is based on the volume-of-fluid (VOF) method and uses the piecewise linear interface calculation (PLIC) method to reconstruct the interface. The numerically reproduced splashing

Discontinuous Galerkin (DG) methods due to their robustness properties, e.g. local conservation, low numerical dispersion, and well-capturing strong shocks and physical discontinuities, are well-suited for the simulation of Variable Density Flow (VDF) in porous media. This paper aims at introducing, in a unified format, the general class of Interior Penalty DG (IPDG) methods to solve the VDF equations

Collision process, the most complicated evolution term in the Boltzmann or Kac stochastic equations, is treated statistically in the direct simulation Monte Carlo (DSMC) method. The treatment of collision pair selection is of crucial importance in DSMC. A subsequent of several collision algorithms called Bernoulli-trials family schemes have been put forward, which were mathematically based on the Kac

This paper addresses the design of linear and nonlinear stabilization procedures for high-order continuous Galerkin (CG) finite element discretizations of scalar conservation laws. We prove that the standard CG method is entropy conservative for the square entropy. In general, the rate of entropy production/dissipation depends on the residual of the governing equation and on the accuracy of the finite

In this study, we present a novel Cahn–Hilliard–Navier–Stokes (CHNS) system with a nonstandard variable mobility for two-phase incompressible fluid flow. Unlike the classical constant mobility, the developed variable mobility has decreasing values nearby the interface and increasing values away from the interface, which minimizes the dynamics of the Cahn–Hilliard (CH) model nearby the interface. An

This paper studies RANS turbulence modelling for a linear compressor cascade corner separation flow, using large-eddy simulation results as reference. The Boussinesq and the quadratic constitutive relations are investigated with two versions of Wilcox’s k−ω turbulence model through a priori and a posteriori analyses. In the a priori analysis the quadratic constitutive relation shows improvement on

The improved coupled finite element material point (ICFEMP) method is an effective way to deal with fluid-structure interaction problems. However, the FEM-MPM contact algorithm employed in ICFEMP suffers from the contact penetration problem which limits its application in engineering. In this paper, the reason leading to the penetration phenomenon is revealed. The singularity of the normal vector of

A multiphase flow numerical approach for performing large-eddy simulations of three-dimensional (3D) wave-structure interaction is presented in this study. The approach combines a volume-of-fluid method to capture the air-water interface and a Cartesian cut-cell method to deal with complex geometries. The filtered Navier–Stokes equations are discretised by the finite volume method with the PISO algorithm

Direct numerical simulation of turbulent Rayleigh-Bénard convection up to Rayleigh number 108 is performed using a fully-implicit, non-dissipative, discrete kinetic energy-conserving algorithm and a parallel flow solver based on it. The algorithm is especially suitable for simulating low-Mach number, variable density/viscosity, transitional and turbulent flows with or without heat transfer. Furthermore

The construction of limiter functions is a crucial factor in total-variation-diminishing (TVD) schemes to achieve high resolution and numerical stability. In this paper, three symmetrical limiter functions are constructed by introducing the MAX function into the classical van Albada, van Leer, and PR-κ limiters. The analysis and numerical results demonstrate that the MUSCL scheme equipped with the

In this paper we present a simplified discussion of the Smoothness-Increasing Accuracy-Conserving (SIAC) filter. We demonstrate the importance of appropriately initializing the data in order to be able to extract higher orders of accuracy by comparing the nodal and modal forms of a discontinuous Galerkin approximation applied to a simplified cubic polynomial. Using the modal form, we are able to exactly

In this work, the local correlation-based one-equation transition model (Menter, F.R., Smirnov, P.E., Liu, T. and Avancha, R., A one-equation local correlation-based transition model. Flow, Turbulence and Combustion, vol. 95, no. 4, pp. 583-619, 2015.) is transformed into a zero-equation transition model. The new model provides an attractive choice in terms of quick implementation of a transition model

This article discusses the use of numerical optimization procedures to aid in the calibration of turbulence model coefficients. Such methods would increase the rigor and repeatability of the calibration procedure by requiring clearly defined and objective optimization metrics, and could be used to identify unique combinations of coefficient values for specific flow problems. The approach is applied

The fractional step method is an efficient time advancement scheme for problems involving transient incompressible flow. The method is desirable over traditional SIMPLE-like algorithms for its non-iterative nature. This paper presents a technique that extends the fractional step method to low-Mach number compressible flow problems. The proposed pressure-velocity coupling and a transient SIMPLEC algorithm

Fractured geologic media can yield anisotropies in solute and heat diffusion due to the formation of changing fluid network connectivity in a rock matrix. In this paper we model Steady-state anisotropic heat diffusion as an elliptic partial differential equation with a symmetric positive definite second rank thermal conductivity tensor. We model diffusive flux as a non-diagonal symmetric tensor, which

In this paper, we present a new finite difference (FD) two stage boundary variation diminishing (BVD) P4T2 (fourth-degree polynomial (P4) and Tangent of Hyperbola for Interface Capturing (THINC) function with a two-level steepness (T2)) scheme for the compressible Euler equations. First, after splitting the flux vector into positive and negative flux vectors using an appropriate flux vector splitting

In this work, we report on the development and initial validation of a new hybrid numerical model for the simulation of incompressible flow. A kinetic Lattice Boltzmann method (LBM) model using a reduced domain is nested within an inviscid flow field to provide increased simulation fidelity where desired, while leveraging the computational efficiency of inviscid solutions. We formulate a fully (or

A detailed numerical investigation of temperature effects on both aerodynamics and acoustics of a dual-stream jet including a central plug is carried out. The geometry is representative of a realistic turbofan with a high by-pass-ratio (BPR) close to 9. Two take-off high-subsonic operating points are investigated numerically by compressible large-eddy simulation. For these two selected points, the

Free surfaces and fluid interfaces are encountered in a wide variety of gas-liquid configurations. Although many numerical approaches exist to solve such flows, there is still a need for improved simulation methods. Recently, a new efficient geometric VoF method for general meshes, called isoAdvector, was implemented in OpenFOAM®. More recently, the isoAdvector method was significantly improved by

For the simulation of compressible flow with a broadband of length scales and discontinuities, the WENO schemes using incremental stencil sizes other than uniform ones are promising for more robustness and less numerical dissipation. However, in smooth region, large weights may be assigned to smaller stencils due to the lack of high-order derivatives in the smoothness indicator compared with that of

A domain-decomposed method to simultaneously couple the classical Molecular Dynamics (MD) and Direct Simulation Monte Carlo (DSMC) methods is proposed. This approach utilises the MPI-based general coupling library, the Multiscale Universal Interface. The method provides a direct coupling strategy and utilises two OpenFOAM based solvers, mdFoam+ and dsmcFoam+, enabling scenarios where both solvers assume

A finite volume method based on the artificial compressibility scheme has been developed to simulate incompressible two-phase flows. In this method, the level set equation, used to capture the interface between two phases, is solved by coupling with the Navier-Stokes equations. The HLLC approximate Riemann solver, capable of resolving contact discontinuity accurately, is proposed to compute the intercell

When using the conventional direction splitting method to calculate multidimensional high speed gasdynamical flows, Riemann solvers capable of resolving contact surface and shear wave accurately will suffer from different forms of shock instability, such as the notorious carbuncle phenomenon. The stability analysis shows that the lack of dissipation in the direction transverse to the shock front leads

A new quasi-direct numerical simulation (q-DNS) solver named combustionFoam, capable of simulating reacting flows at arbitrary Mach number with a detailed chemical reaction mechanism, has been developed. This solver is implemented based on reactingFoam-solver from OpenFOAM-v7. The main improvements are a mixture-averaged formula transport model and ability to simulate reacting flows at arbitrary Mach

The level set (LS) method is a popular approach to represent interfaces owing to its smooth description of interfaces, accurate interface information and the convenience of applying to 3D, but it suffers from severe mass loss/gain mainly due to the reinitialization. To address this problem, an efficient 3D iterative interface-correction reinitialization for the LS method is proposed to maintain mass

Large Eddy Simulations are reported on the flow around a rudder operating in the wake of a propeller. Results demonstrate the production of important spanwise flows within the boundary layer on the hydrofoil, mainly tied to the behavior of the largest coherent structures populating the propeller wake. The two branches of the hub vortex are shifted from the pressure towards the suction sides of the

We present a novel hyperbolic reformulation of the Serre-Green-Naghdi (SGN) model for the description of dispersive water waves. Contrarily to the classical Boussinesq-type models, it contains only first order derivatives, thus allowing to overcome the numerical difficulties arising from higher order derivative terms, especially in the context of high order discontinuous Galerkin finite element schemes

Interface-resolved direct numerical simulations are performed to examine the combined effects of soluble surfactant and viscoelasticity on the structure of a bubbly turbulent channel flow. The incompressible flow equations are solved fully coupled with the FENE-P viscoelastic model and the equations governing interfacial and bulk surfactant concentrations. The latter coupling is achieved through a

Membrane distillation is an emerging desalination process with important applications to the energy-water nexus. Its performance depends, however, on heat and mass transport phenomena that are uniquely challenging to simulate. Difficulties include two adjacent channel flows coupled by heat and mass transport across a semi-permeable membrane. Within the channels, heat and mass boundary layers interact

Accurate methods to solve the Reynolds-Averaged Navier-Stokes (RANS) equations coupled to turbulence models are still of great interest, as this is often the only computationally feasible approach to simulate complex turbulent flows in large engineering applications. In this work, we present a novel discontinuous Galerkin (DG) solver for the RANS equations coupled to the k−ϵ model (in logarithmic form

We provide a comparison of the dispersion properties, specifically the time-amplification factor, the scaled group velocity, the error in the phase speed and scaled numerical diffusion coefficient of four spatiotemporal discretization schemes utilized for solving a linear, one-dimensional (1D) as well as a linear/nonlinear, two-dimensional (2D) advection diffusion reaction (ADR) equation: (a) Explicit

A technique based on the finite element method (FEM) is developed to precisely predict the pressure jump due to the surface tension forces in two-phase flow problems. In this method, the FEM shape functions of the active elements (the elements containing both phases) are enhanced by the aid of the moving least-squares (MLS) interpolation functions and used in the FEM calculations. Therefore, this technique

This article introduces a new vertex-centered quasi-Lagrangian discontinuous Galerkin method for two-dimensional compressible flows that is third-order accurate both in space and time. The computational domain is divided into structured quadrilateral cells with straight edges. Nodal control volumes with curved edges are constructed surrounding the grid vertices. The Euler equations in arbitrary Lagrangian-Eulerian

In this study, to simulate the pollution treatment as a separated phase a 3D incompressible turbulence model under isothermal conditions was considered. The hybrid RANS-LES method with a sub-grid scale(SGS) technique within the framework of two-phase flow was used to study pollution distribution in urban street canyons. An area source of pollutant with a constant concentration, located in the ground

We present a diffuse-interface model for simulating compressible three-fluid flows with surface tension. In this model different fluids are separated with resolved interfaces. We first deduce the jump conditions across the material interfaces under surface tension. The interfaces are represented with the advection equations for volume fractions. Traditional methods for solving these equations result

This paper presents a spatially and temporally adaptive boundary condition to specify the volumetric flow rate for lattice Boltzmann methods. The approach differs from standard velocity boundary conditions because it allows the velocity to vary over the boundary region provided that the total flux through the boundary satisfies a prescribed constraint, which is a typical scenario for laboratory experimental

This research work deals with the computational simulation of the transitions of dripping to jetting which occurs during the flow of Newtonian Fluid. Herein, Volume of Fluid (VOF) model is mapped for the detention of various regimes of drop formation. The transition of drop formation from dripping to jetting is easily categorised through Weber number. The present work reveals that jetting regimes are

The paper addresses a new method for approximately solving the Riemann problem for an arbitrary non-conservative hyperbolic system of partial differential equations. The method is based on the reconstruction of the complete wave structure in the Riemann problem with using the Borel measures interpretation (path-representation) of the non-conservative products. In contrast to alternative approximate

The research on hypersonic boundary layer transition is a recent focal point in fluid dynamics. One of the effective numerical methods for transition study is the high-order shock-fitting method, which is especially suitable for dealing with shock-related interactions and removing post-shock oscillations as compared with shock-capturing methods. Currently, explicit time-stepping schemes are mainly

The two-dimensional hexagonal Fourier transform is introduced to reduce the background anisotropy in the numerical calculations with periodic conditions. Comparing to traditional Fourier transform with cartesian mesh, the large-scale background anisotropy is significantly reduced under different energy spectra. In addition, the phenomenon of small-scale background anisotropy is found to be related

When a shock passes through an ionized plasma, a question exists about how much of the shock energy should go to the ions and how much should go to the electrons. Until recently, we have used the simplest possible model (based on Zel’dovich and Raizer [1], dumping all of the shock energy into the ions and ignoring the electronic fluid completely. However, we have become aware of work from the early

Despite the significant breakthrough of neural networks in the last few years, their spreading in the field of computational fluid dynamics is very recent, and many applications remain to explore. In this paper, we explore the drag prediction capabilities of convolutional neural networks for laminar, low-Reynolds number flows past arbitrary 2D shapes. A set of random shapes exhibiting a rich variety

The rise of bubbles in viscous liquids is not only a widespread process in many industrial applications but also an essential fundamental problem in fluid physics. The modeling and simulation of such problems is still an area of active research, mainly when surface tension is present, as in the case of single and multiple bubbles rising in viscous liquids. We treat the interface between the two fluids