In this work, we present a new optimal control approach to fluid-structure interaction parameter estimation problems. The goal is to obtain the desired deformation by controlling the solid material properties, such as the Young modulus. We consider a stationary monolithic FSI problem where solid and liquid forces at the interface are automatically balanced. We consider inequality constraints in order

A numerical study of stably stratified flows past spheres at Reynolds numbers Re=200 and Re=300 is reported. In these flow regimes, a neutrally stratified laminar flow induces distinctly different near-wake features. However, the flow behaviour changes significantly as the stratification increases and suppresses the scale of vertical displacements of fluid parcels. Computations for a range of Froude

In this paper, the Implicit Large-Eddy Simulation (ILES) is investigated on the flow around a square cylinder incorporating an unstructured Weighted Essential Non-Oscillatory (WENO) reconstruction method for a Reynolds number of 22,000. Simulations are undertaken in the framework of open-source package OpenFOAM and additional implicit 2nd/3rd-order WENO scheme on the convective term of the viscous

Accurately predicting unsteady wakes and vortex-dominated flows is essential to a wide range of engineering applications, including aircraft, rotorcraft, shipboard operations, bio-inspired unsteady flight and propulsion, wind turbines, and urban flows. While current CFD software can model the complete flow field and wake system, the computational costs incurred in high Reynolds number unsteady turbulent

For a long time, people hold an idea that vorticity is equivalent to vortex for fluid flow since vorticity represents rotation for rigid body. Nevertheless, many experimental results do not support this opinion. So, several improved methods have been proposed, including Q, λci, λ2, Δ methods and etc, which are all based on the eigenvalues of the velocity gradient tensor. These methods share a common

This study presents a direct aeroacoustic simulation using a cumulant lattice Boltzmann method that provides very high stability without modifying the bulk viscosity compared to the Bhatnagar–Gross–Krook model. It is shown with the Chapman–Enskog analysis that the numerical model recovers the compressible Navier–Stokes equations for low Mach number flows to second-order accuracy. The low dissipation

Three-dimensional direct numerical simulations (DNS) of Rayleigh-Taylor instability (RTI) at the interface of two masses of air with a sharp temperature gradient of 149 K are performed by solving the compressible Navier-Stokes equation (NSE). The flow is studied in an isolated box with non-periodic walls along the three directions. A non-conducting interface separating the two air masses is impulsively

One of the main limitations in computational aerodynamics lies in the ability of CFD solvers to handle complex geometries while maintaining their accuracy. Among the currently available strategies, the Zonal Immersed Boundary Conditions (ZIBC) has shown its capability to introduce complex geometrical details for the simulations of high Reynolds turbulent flows. In this context, this work aims to extend

In this short note we apply the recently proposed data-driven RANS closure modelling framework of Schmelzer et al.(2020) to fully three-dimensional, high Reynolds number flows: namely wall-mounted cubes and cuboids at Re=40,000, and a cylinder at Re=140,000. For each flow, a new RANS closure is generated using sparse symbolic regression based on LES or DES reference data. This new model is implemented

The dynamic programming interface reconstruction (DPIR) method introduced by Dumas et al.[1] is a volume-preserving and continuous interface reconstruction method. It is a two-step method, which comprises of an optimized step and a correction step. At first, in the optimized step, it minimizes a target function by the dynamic programming method to obtain a continuous interface. Then, it corrects the

Reconstruction of turbulent flow based on data assimilation methods is of significant importance for improving the estimation of flow characteristics by incorporating limited observations. Existing works mainly focus on using only one observation data source, e.g., velocity, wall pressure, lift or drag force, to reconstruct the flow. In practical applications observations are disparate data sources

We discuss the applicability of a unified hyperbolic model for continuum fluid and solid mechanics to modeling non-Newtonian flows and in particular to modeling the stress-driven solid-fluid transformations in flows of viscoplastic fluids, also called yield-stress fluids. In contrast to the conventional approaches relying on the non-linear viscosity concept of the Navier-Stokes theory and representation

A continuous adjoint formulation for shape optimization in steady-state, cavitating flows is developed. A Transport Equation-based mixture model, extended with the Kunz cavitation model, is implemented to incorporate phase transition due to cavitation and for which the adjoint equations are derived. Flow and adjoint equations are discretized on 2D Cartesian meshes with cut-cells. In the cut-cell method

To improve the modeling quality of pollutant transport in shallow waters, different reconstruction schemes have been proposed to better link the edge values to the centroid values of a pollutant concentration in finite-volume shallow water models: a scheme of higher (lower) order generally has a better (poorer) quantitative accuracy but lower (higher) computational efficiency. Here, a numerical comparative

Deep reinforcement learning (DRL) has recently been adopted in a wide range of physics and engineering domains for its ability to solve decision-making problems that were previously out of reach due to a combination of non-linearity and high dimensionality. In the last few years, it has spread in the field of computational mechanics, and particularly in fluid dynamics, with recent applications in flow

In this paper we develop a family of very high-order central (up to 6th-order) non-oscillatory schemes for mixed-element unstructured meshes. The schemes are inherently compact in the sense that the central stencils employed are as compact as possible, and that the directional stencils are reduced in size therefore simplifying their implementation. Their key ingredient is the non-linear combination

We report the first high-order eddy-resolving simulation of flow over a marine propeller using a recently developed high-order sliding-mesh method. This method employs the flux reconstruction framework and a new dynamic curved mortar approach to handle the complex rotating geometries. For a wide range of working conditions, it is validated to predict the loads very accurately against experiments. The

The present paper deals with the development of a numerical scheme for the solution of two-dimensional Boltzmann transport equation (BTE) under electronic nonequilibrium conditions. A two-dimensional explicit modal discontinuous Galerkin (DG) method with uniform meshes is developed for solving the BTE in conjunction with the relaxation time approximation. The spatial discretization is carried out using

Three-dimensional Orr-Sommerfeld equation is analyzed by compound-matrix method to explain the relevance of two- and three-dimensional wall excitations with respect to three-dimensional direct simulation results presented in Sharma and Sengupta, Effect of frequency and wavenumber on the three-dimensional routes of transition by wall excitation, Phys. Fluids, 31 (6), 064107 (2019). Physical variables

A new conservative symmetry-preserving second-order time-accurate PISO-based pressure-velocity coupling for solving the incompressible Navier-Stokes equations on unstructured collocated grids is presented in this paper. This new method for implicit time stepping is an extension of the conservative symmetry-preserving incremental-pressure projection method for explicit time stepping and unstructured

We present a high–order discontinuous Galerkin (DG) discretization for the three–phase Cahn–Hilliard model of [Boyer, F., & Lapuerta, C. (2006). Study of a three component Cahn–Hilliard flow model]. In this model, consistency is ensured with an additional term in the chemical free–energy. The model considered in this work includes a wall boundary condition that allows for an arbitrary equilibrium contact

In this paper we present an efficient numerical method for locating material interfaces in multi-fluid simulations. Starting from a detailed investigation of the moment-of-fluid reconstruction problem, we develop an efficient procedure for the interface reconstruction, based on pre-computing certain values and mapping the domain of the function describing the interface reconstruction onto these values

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 different grids that overlap each other (typically, a highly

The semi-Lagrangian Vortex method (VM) and the Lattice Boltzmann method (LBM) are used to investigate flows simulations in the incompressible regime. In this study, a proven version of each method is used and compared on different three dimensional benchmarks in terms of numerical accuracy, convergence, numerical diffusion and dissipation. The first comparisons are made on a convected vortex to study

The interaction of a reflected shock with the boundary layer inside the shock tubes is an important engineering problem. Studies related to shock wave mitigation and attenuation are performed inside the shock tubes. A proper understanding of the flow behind the reflected shock and the separated zone involving multiple vortical structures is highly essential for estimating the effectiveness of the shock

One dimensional troubled cell indicator, which is based on the extreme point of approximated polynomial, was proposed by Zhu and Qiu (SIAM J. Sci. Comput. 39:A1089-A1113, 2017). This troubled cell indicator performs well, but still has two shortcomings. First, it calculates the extreme point of high-degree polynomial, however the calculation is not simple. The reason is that, the explicit formula of

In this paper, we discuss the usage and implementation of the compressive sensing (CS) for the efficient measurement and analysis of the von Krmn vortices. We consider two different flow fields, the flow fields around a circle and an ellipse. We solve the governing k−ϵ transport equations numerically in order to model the flow fields around these bodies. Using the time series of the drag, CD, and the

In the numerical simulation of multimaterial flows, Lagrangian method was applied widely, and fluid-particle multiphase flows phenomenon often existed when elastic-plastic material was impacted intensively. Most of the previous studies about the fluid-particle flows in Lagrangian hydrodynamics framework only focused on the dilute flow. It is very necessary to establish a Lagrangian-Lagrangian coupling

Within this study, a prediction of free surface flow during the gravity casting of shear-thinning fluids is of interest. An experimental test setup which enables analysis of the casting flow by means of optical measurements is designed and an in-house computational fluid dynamics solver based on the lattice Boltzmann method is implemented. The model of isothermal free surface flow of non-Newtonian

Volume of fluid (VOF) methods are extensively used to track fluid interfaces in numerical simulations, and many VOF algorithms require that the interface be reconstructed geometrically. For this purpose, the Piecewise Linear Interface Construction (PLIC) technique is most frequently used, which for reasons of geometric complexity can be slow and difficult to implement. Here, we propose an alternative

Verification and validation are crucial steps for the development of any numerical model. While suitable processes have been established for commercial Computational Fluid Dynamics (CFD) codes, more difficult challenges must be faced for high-fidelity solvers. Benchmarks have been proposed in a series of dedicated conferences for non-reacting configurations. However, to our knowledge, no suitable approach

We present maDG, a newly developed code designed for the efficient parallel implicit solution of the 3D unstructured nodal discontinuous Galerkin discretization of the unsteady compressible Navier–Stokes equations. The code is being developed to provide an efficient, modular, and maintainable software platform for studying algorithmic and modeling issues arising in high-resolution CFD. In this paper

This paper presents a new method to perform output error estimation and mesh adaptation in computational fluid dynamics (CFD) using machine-learning techniques. The error of interest is the functional output error induced by the numerical discretization, including the finite computational mesh and approximation order. Given the data of adaptive flow simulations guided by adjoint-based error estimates

Herein, we develop a totally decoupled, linear, and temporally second-order accurate numerical scheme for the Cahn–Hilliard–Darcy system which models the two-phase incompressible fluid flows in porous medium or in Hele–Shaw cells. Our proposed scheme is based on a simple and efficient stabilized multiple scalar auxiliary variables (S-MSAV) approach. Two time-dependent variables are defined to change

What do you get a distinguished Englishman (who has everything) for his birthday? Another publication, but of course! The dilemma is in how to keep it a surprise, while developing a document which warrants his authorship. No problem, Antony and I have collaborated on several subjects over the years which we have yet to publish. The topic chosen for this gift is: Inverse Aerodynamic Design. The examples

A new set of aerodynamic correlations are proposed for an ellipsoidal particle in the free molecular regime by carrying out flow simulations using the Direct Simulation Monte Carlo (DSMC) method. The in-house DSMC solver is modified to be consistent with free molecular flow assumptions as well as to reduce computational cost. The solver is validated against an open-source DSMC solver, viz., SPARTA

Generalized polynomial chaos a reliable framework for many problems of uncertainty quantification in computational fluid dynamics. However, it fails for long-time integration of unsteady problems with stochastic frequency. In this work, the asynchronous time integration technique, introduced in previous works to remedy this issue for systems of ODEs, is applied to the Kármán vortex street problem.

A large eddy simulation (LES) study of the flow around a 1/4 scale squareback Ahmed body at ReH=33,333 is presented. The study consists of both wall-resolved (WRLES) and wall-modelled (WMLES) simulations, and investigates the bimodal switching of the wake between different horizontal positions. Within a non-dimensional time-window of 1050 convective flow units, both WRLES and WMLES simulations, for

In this paper, we present a conservative sharp interface numerical method for compressible reactive flows. This method is developed by modified finite volume scheme in Eulerian framework. Applying the level set method, discretized scheme is obtained for each material separated by material interface, and small cut cells are merged into neighboring cells. To get accurate interface exchanges for reactive

Spurious pressure oscillations are a numerical instability that is commonly observed in multiphase and multicomponent flow problems near the critical point. A diffuse-interface model has been created to simulate transcritical mixing in multispecies and multiphase systems where spurious pressure oscillations pose a serious challenge in achieving convergence. To reduce the spurious pressure oscillations

Immersed boundary methods (IBMs) are an interesting alternative to the usual body-fitted mesh approach when dealing with complex geometries as they allow simpler mesh generation. The volume penalization method (an IBM) is commonly used for incompressible and compressible viscous flows but only one application to compressible inviscid flows can be found, which uses the characteristic-based volume penalization

The flux reconstruction (FR) approach offers a flexible framework for describing a range of high-order numerical schemes; including nodal discontinuous Galerkin and spectral difference schemes. This is accomplished through the use of so-called correction functions. In this study we employ a weighted Sobolev norm to define a new extended family of FR correction functions, the stability of which is affirmed

In the present study, a hybrid RANS/LES model and a correlation-based transition model were coupled for simulating flow involving massive flow separation and laminar-turbulent transition including crossflow direction. For this purpose, blending of IDDES model and the γ−Reθt−CF+ transition model was accomplished in a tightly coupled manner. For validations, numerical simulations around a circular cylinder

In order to obtain the influence law and microscale mechanism of droplet wetting state in microgravity, the model of nano-droplet on array micro-structured surface with different wettability and gravity was built and simulated by molecular dynamics. In conditions of no gravity, it was found that critical point of wetting state transition was closer to weak wettability surface with the decrease of low

A new immersed boundary approach for high order Weighted Essentially non-Oscillatory (WENO) schemes is proposed. The schemes is based on the main ideas from both the general immersed boundary algorithms and the level–set approach and can be easily applied to both finite difference and finite volume formulation. Although formally only second order accurate, numerical tests prove that the use of higher

Direct simulation at the pore-scale is crucial to unravel rarefaction effect on gas transport in tight porous media. To satisfy the dual demands on modeling accuracy and computation effort, an appropriate method must be chosen. This work, therefore, evaluates four numerical methods for pore-scale rarefied gas flows in a two-dimensional (2D) model porous media over a wide range of rarefaction. These

We develop an augmented discontinuous Galerkin method for wall-modeled large-eddy simulations. This method is motivated by the enrichment method that has been formulated for finite-element method, by statistically augmenting the variational solution of the near-wall element with a simple wall function to model the effects of the unresolved momentum-carrying near-wall eddies on the resolved scales.

This research presents numerical modeling of the spray process using the Euler-Eulerian multi-fluid approach where the standard WAVE secondary breakup model was improved and validated. The standard WAVE model tends to overestimate the creation of smaller diameter droplets in the Eulerian multi-fluid framework, which reflects as an inaccurate droplet distribution. Improvements include an introduction

The cohesion and adhesion parameters are the two essential parameters in the Shan-Chen multicomponent and multiphase lattice Boltzmann models for determining the separation of fluids and the wettability of surfaces, and thus should be carefully chosen. In this study, we propose a systematic method of determining these parameters from a physical point of view. The cohesion parameters of different water/alkane

This paper presents an efficient high-order finite volume method for solution of compressible Navier-Stokes equations on unstructured grids. In this method, a high-order polynomial which is based on Taylor series expansion is applied to approximate the solution function within each control cell. The derivatives in the Taylor series expansion are approximated by the functional values at the cell centers

Lagrangian simulation coupled with large eddy simulation (LES) is studied for turbulent scalar mixing in compressible flows, where Lagrangian simulation solves advection-diffusion equations with computational particles. In Lagrangian simulation, a molecular diffusion term needs to be modeled with a so-called mixing model, which also requires modeling the dissipation rate of scalar fluctuations. The

The present work is focused on the analysis of cloud cavitation, i.e. high-speed unsteady liquid /vapor flows characterized by periodical large-scale shedding. The study relies on the numerical modeling of cavitating flows with a homogeneous approach coupled with the Reynolds-Averaged Navier-Stokes (RANS) framework. A new algorithm based on an implicit fractional step method is used to solve the time-dependent

This numerical work investigates the potential of a high-order finite-difference spectral vanishing viscosity approach to simulate gravity currents at high Reynolds numbers. The method introduces targeted numerical dissipation at small scales through altering the discretisation of the second derivatives of the viscous terms in the incompressible Navier-Stokes equations to mimic the spectral vanishing

This paper is devoted to the simulation of the three-phase flow model [20], in order to account for immiscible components. The whole model is first recalled, and the main properties of the closed set are given, with particular focus on the Riemann problem associated with the convective subset that contains non-conservative terms, and also on the relaxation process. The model is hyperbolic, far from

We report the development of a discontinuous spectral element flow solver that includes the implementation of both spectral difference and flux reconstruction formulations. With this high order framework, we have constructed a foundation upon which to provide a fair and accurate assessment of these two schemes in terms of accuracy, stability, and performance with special attention to the true spectral

The concept of projection applied to explicit discontinuous Galerkin (DG) schemes is investigated. The two explicit DG methods in this study are based on a ‘predictor-corrector’ formulation, the first introduced by Lörcher, Gassner, and Munz called space–time expansion discontinuous Galerkin or STE-DG scheme (Lörcher et al. 2007, Gassner et al. 2008), and the second, introduced independently by the

Computational Fluid Dynamics (CFD) discretisation errors are generally present in any simulation result, with the main issues lying in the mesh generation stage. Despite this, CFDsoftware has widespread use in the industrial design procedure. To improve modelling reliability, mesh adaptation proposes to automatically modify grids to better their accuracy, while minimising their overall size. Regardless

We develop in this paper a fifth-order nonlinear spectral difference method for solving hyperbolic conservation laws, whose solutions often admit discontinuities. To avoid instability caused by the Gibbs phenomenon arising from interpolation across discontinuities, a fifth-order nonlinear interpolation scheme is proposed within a single cell, keeping the compactness of the original linear spectral

In this paper, a fourth-order multi-dimensional weighted essentially non-oscillatory (WENO) reconstruction is developed, which is aiming at the complicated flows. In corporate with two-stage fourth-order temporal discretization, a high-order gas-kinetic scheme is proposed for the direct numerical simulation (DNS) and large eddy simulation (LES) of turbulence. In such WENO scheme, a simple strategy

Solution of the pressure Poisson equation is often the most expensive aspect of solving the incompressible form of Navier-Stokes. For a single phase deterministic model the pressure calculation is costly. Expanded to an intrusive stochastic multiphase framework, the simulation expense grows dramatically due to coupling between the stochastic pressure field and stochastic density. To address this issue