Showing papers in "International Journal of Computational Fluid Dynamics in 2019"
TL;DR: Four adaptive sampling methods of a multi-fidelity (MF) metamodel, based on stochastic radial basis functions (RBF), for global design optimisation based on expensive CFD computer simulations and adaptive grid refinement are presented.
Abstract: The paper presents a study on four adaptive sampling methods of a multi-fidelity (MF) metamodel, based on stochastic radial basis functions (RBF), for global design optimisation based on expensive ...
50 citations
TL;DR: From an informal survey conducted in January of 2018, it appears that simple Cartesian Finite Difference codes or, equivalently, Lattice Boltzmann codes may be the first to achieve industrial LES.
Abstract: Industrial large-eddy simulation (LES), i.e. overnight runs with O(109) degrees of freedom (DOFs) and O(107) timesteps, has been one of the top priorities of CFD research over the last two decades....
37 citations
TL;DR: In this paper, the OpenACC heterogeneous parallel programming model is successfully applied to modification and acceleration of the three-dimensional Tokamak magnetohydrodynamical code (CLT).
Abstract: In this paper, the OpenACC heterogeneous parallel programming model is successfully applied to modification and acceleration of the three-dimensional Tokamak magnetohydrodynamical code (CLT). Throu...
18 citations
TL;DR: The main computing phases of numerical methods for solving partial differential equations are the algebraic system assembly and the iterative solver as discussed by the authors, and the first task, in this paper, is the first one.
Abstract: The main computing phases of numerical methods for solving partial differential equations are the algebraic system assembly and the iterative solver. This work focuses on the first task, in...
16 citations
TL;DR: The results show that the aerodynamic resistance of the optimised vehicle is further reduced, the drag reduction rate reaches 5.52%, and the speed of the Kantrowitz limit phenomenon is delayed from 760 to 860 km/h.
Abstract: The vacuum pipeline vehicle system is a novel conceptual system aimed to provide a high-speed public transportation service in the future, featured with a reduced-pressure tube in which pressurised capsules ride on a cushion of air that is driven by a combination of linear induction motors and air compressor. The capsule body has a great influence on the aerodynamic performance of vehicles. This work involves numerical simulations based on finite volume method to study the optimisation method for the parameter design of the vehicle body. The results show that the aerodynamic resistance of the optimised vehicle is further reduced, the drag reduction rate reaches 5.52%, and the speed of the Kantrowitz limit phenomenon is delayed from 760 to 860 km/h. The drag reduction effect is obvious.
14 citations
TL;DR: An approach for shape optimisation of the flow through a diffuser by simultaneously increasing the static pressure recovery across the geometry and the flow uniformity at the outflow using the Computational Fluid Dynamics software OpenFOAM.
Abstract: An approach for shape optimisation of the flow through a diffuser is presented in this work. This multi-objective problem focuses on maximising the diffuser performance by simultaneously increasing...
11 citations
TL;DR: The numerical results show that, when the polynomial degree is sufficiently high and the mesh is sufficiently dense, the hp-multilevel preconditioner can be fruitfully exploited.
Abstract: In this work, we investigate the performance of {h−p−hp}-multilevel preconditioners for discontinuous Galerkin (dG) discretisations of elliptic operators with constant coefficients. Recent publicat...
10 citations
TL;DR: A high-order hybridisable discontinuous Galerkin (HDG) formulation to solve the immiscible and incompressible two-phase flow problem in a heterogeneous porous media is developed and numerical evidence of the convergences rates is shown.
Abstract: We develop a high-order hybridisable discontinuous Galerkin (HDG) formulation to solve the immiscible and incompressible two-phase flow problem in a heterogeneous porous media. The HDG meth...
10 citations
TL;DR: In this article, the coupled level set and volume of fluid method was applied to the numerical study on the successive impact of double droplets on a super-hydrophobic tube.
Abstract: The coupled level set and volume of fluid method is applied to the numerical study on the successive impact of double droplets on a super-hydrophobic tube. The impact velocity varies from 0.25 to 2...
9 citations
TL;DR: A new multigrid preconditioning strategy for use in Jacobian-free Newton–Krylov (JFNK) methods for the solution of algebraic equation systems arising from implicit Discontinuous Galerkin (DG) discretisations is suggested.
Abstract: We suggest a new multigrid preconditioning strategy for use in Jacobian-free Newton–Krylov (JFNK) methods for the solution of algebraic equation systems arising from implicit Discontinuous ...
9 citations
TL;DR: The first CFD-enabled multi-objective design optimisation methodology for continuous oscillatory baffled reactors (COBRs), used for flow chemistry-based process development, is described, where performance is quantified in terms of two metrics: a mixing efficiency index and the variance of the residence time distribution.
Abstract: The first CFD-enabled multi-objective design optimisation methodology for continuous oscillatory baffled reactors (COBRs), used for flow chemistry-based process development, is described, where per...
TL;DR: In this paper, an overset grid method was developed to investigate the interaction between a particle-laden flow and a circular cylinder, which is implemented in the Pencil Code, a high-order finite-difference code for compressible flow simulation.
Abstract: An overset grid method was developed to investigate the interaction between a particle-laden flow and a circular cylinder. The method is implemented in the Pencil Code, a high-order finite-difference code for compressible flow simulation. High-order summation-by-parts operators were used at the cylinder boundary, and both bi-linear Lagrangian and bi-quadratic spline interpolation were used to communicate between the Cartesian background grid and the body-conformal cylindrical grid. The performance of the overset grid method was assessed to benchmark cases of steady and unsteady flows past a cylinder. Results show high-order accuracy and good agreement to the literature. Particle-laden flow simulations were performed, with inertial point particles impacting on a cylinder. The simulations reproduced results from the literature at a significantly reduced cost. Further, an investigation into blockage effects on particle impaction revealing that the previously published DNS data is less accurate than assumed f...
TL;DR: Two hybridized methods are considered in addition to DG: hybridized DG (HDG) and embedded DG (EDG).
Abstract: This paper assesses the benefits of hybridization on the accuracy and efficiency of high-order discontinuous Galerkin (DG) discretizations. Two hybridized methods are considered in addition to DG: ...
TL;DR: This article compares an adjoint-assisted gradient-based and a metamodel- assisted gradient-free method with respect to convergence, local/global optima and especially the computational time.
Abstract: Design processes nowadays rely more and more on automated optimisation methods to shorten the development cycle. Within those optimisation methods, gradient-free ones converge slower but rather to ...
TL;DR: A hierarchical geometry handling approach is demonstrated which makes use of the lower order modelling, overset meshes and zonal blocking for efficient preprocessing of complex geometries for flow simulations.
Abstract: Preprocessing remains one the main bottlenecks in the computational fluid Dynamics simulations of flows involving complex geometries as advances in the algorithm development, turbulence modelling a...
TL;DR: The use of and interest in Computational Fluid Dynamics (CFD) and their variants have been growing at an everincreasing rate over the last five decades and applied in numerous industries as mentioned in this paper.
Abstract: The use of and interest in Computational Fluid Dynamics (CFD) and their variants have been growing at an ever-increasing rate over the last five decades and applied in numerous industries. The futu...
TL;DR: In this paper, the primitive variable-based approach does not strictly preserve time accuracy and a dual-time stepping technique, which uses an inner iteration of pseudo-time within the physical time, is used to correct the issue.
Abstract: A class of Computational Fluid Dynamics codes uses primitive variable-based formulation to solve the conservative form of the governing equations. Under certain specific conditions, the approach yields inaccurate results for unsteady problems. Here, Euler equations are used to numerically analyse time accuracy when using such an approach. It is demonstrated, using a simple shock tube problem, that the primitive variable-based approach does not strictly preserve time accuracy. A dual-time stepping technique, which uses an inner iteration of pseudo-time within the physical time, is used to correct the issue. The method is applied to the shock tube problem, which eliminates the time-dependent discrepancies. The problem, and the correction, is also applied to a supersonic flow over a wedge. In both cases, the results are shown to be identical to the solution obtained using a conservative variable-based approach.
TL;DR: In this article, a set of shallow water equations based on a k−e^ Reynold stress model is established to simulate the turbulent flows over a complex roughness bed, and the fundamental equations are discretized.
Abstract: A set of shallow-water equations (SWEs) based on a k^−e^ Reynold stress model is established to simulate the turbulent flows over a complex roughness bed. The fundamental equations are discretized ...
TL;DR: Computational fluid dynamics simulations employing eddy-viscosity turbulence models remain the baseline numerical tool in the aerospace industry, mainly due to their numerical stability and robustness.
Abstract: Computational fluid dynamics simulations employing eddy-viscosity turbulence models remain the baseline numerical tool in the aerospace industry, mainly due to their numerical stability and...
TL;DR: A new hybrid RANS/LES approach with scale-adaptive capabilities is developed that reflects local vortex structures instead of grid spacing in the turbulent wake and is validated for a subcritical flow past a circular cylinder and a supersonic base flow.
Abstract: A new hybrid RANS/LES approach with scale-adaptive capabilities is developed. The blending function in the SST model is adopted to prevent the invasion of the von Karman length scale to the RANS re...
TL;DR: Turbulence models are widely accepted in CFD codes in order to close Reynolds Averaged Navier Stokes equations as mentioned in this paper, and more and more complex models were proposed to improve the reliability of...
Abstract: Turbulence models are widely accepted in CFD codes in order to close Reynolds Averaged Navier Stokes equations. In the years more and more complex models were proposed to improve the reliability of...
TL;DR: This plugin therefore combines respectively ParaView's scalability in parallel and Gmsh's ability to apply h-refinement of the initial mesh followed by solution interpolation on the resulting visualisation grid, thus enabling parallel visualisation of any arbitrary high-order polynomial solutions in client–server mode.
Abstract: This paper presents two recent numerical tools developed respectively to perform traditional post-processing and more advanced in situ processing of high-order polynomial data generated by ...
TL;DR: The MDA–MDO project of IRT Saint-Exupéry aims at performing an aircraft engine pylon MDO, and a parametrised and differentiated CAD of the pylon has been developed, demonstrating the ability to handle the 3D pylon geometry with its intersections.
Abstract: The MDA–MDO project of IRT Saint-Exupery aims at performing an aircraft engine pylon MDO. A bi-level formulation is enabling the reuse of the disciplinary optimisation software for aerodynamic, str...
TL;DR: In this article, a novel, efficient method to account for multivariate probability density functions (PDFs) in the context of the flamelet generated manifolds (FGM) approach in a large eddy simulation (LES) framewo
Abstract: A novel, efficient method to account for multivariate probability density functions (PDFs) in the context of the flamelet generated manifolds (FGM) approach in a large eddy simulation (LES) framewo
TL;DR: A simple iterative geometry-based interface-preserving reinitialization is proposed to reconstruct a signed distance function (SDF) while fixing the interface location with the combination of the external and internal iterations.
Abstract: The iterative reinitialization, as an important process for the standard level set method, is flexible and straightforward in large-scale computing but has problems of interface movement and seriou...
TL;DR: The high-order hybridisable discontinuous Galerkin (HDG) method is used to find steady-state solution of gas kinetic equations on two-dimensional geometry to solve the Boltzmann equation with full collision operator, which can produce accurate results for shear-driven and thermally induced flows.
Abstract: The high-order hybridisable discontinuous Galerkin (HDG) method is used to find steady-state solution of gas kinetic equations on two-dimensional geometry. The velocity distribution functio...
TL;DR: A method where the control points of the BRep are used to automatically derive parametrisations suitable for shape optimisation with gradient-based methods, with particular focus on ensuring geometric continuity between the NURBS patches through formulation of discrete constraints.
Abstract: CAD geometries are most often exchanged between analysis tools using NURBS patches to represent the boundary (BRep). We present a method where the control points of the BRep are used to automatical...
TL;DR: In this paper, a problem-independent nonlinear switch was proposed to avoid the problem-dependent nature of this switch, which was mainly dependent on the trial-and-error threshold value of a switch parameter.
Abstract: The uniformly third-order WENO-BO-Z scheme has been proposed previously in an attempt to restore third-order accuracy at the second-order critical point via the reduction of nonlinear dissipation followed by the modification of nonlinear weights as well as to improve the intermediate bandwidth property of the linear optimal stencil of the classical WENO-JS scheme with respect to both dispersion and dissipation. However, a problem-dependent nonlinear switch was employed to turn on in the intermediate range of wavenumbers to avoid unnecessary nonlinear adaption of the WENO scheme and was mainly dependent on the trial-and-error threshold value of a switch parameter. In order to avoid the problem-dependent nature of this switch, a problem-independent nonlinear switch is suggested and investigated in this work. Benchmark problems, ranging from non-broadband to broadband, are solved using the WENO-BO-Z scheme, and a comparison of the suggested switch with the problem-dependent switch is made.
TL;DR: In this article, the density flow in adiabatic two-phase fluids through the characteristic finite element method is analyzed, where the fluids are assumed to be liquids and the equations of conse...
Abstract: The purpose of this study is to analyze the density flow in adiabatic two-phase fluids through the characteristic finite element method. The fluids are assumed to be liquids. The equations of conse...
TL;DR: Discontinuous Galerkin (DG) methods are a class of finite element methods that use discontinuous basis functions that enables the use of non-conforming meshes and facilitates the development of discrete star grammars.
Abstract: Discontinuous Galerkin (DG) methods are a class of finite element methods that use discontinuous basis functions. This particular feature enables the use of non-conforming meshes and facilitates th...