In the context of turbulent flows, this study presents a new methodology for the high-fidelity simulation of conjugate heat transfer between solid and fluid. The numerical strategy is mainly based on the immersed boundary method to ensure the expected thermal boundary condition at the fluid/solid interface. The approach is dual since the solid domain is the immersed region for the fluid and, conversely

We present an adaptive reduced-order model for the efficient time-resolved simulation of fluid–structure interaction problems with complex and non-linear deformations. The model is based on repeated linearizations of the structural balance equations. Upon each linearization step, the number of unknowns is strongly decreased by using modal reduction, which leads to a substantial gain in computational

This paper presents a sensitivity analysis of structural turbulence uncertainty estimates to time and space resolution of numerical computations. Turbulence uncertainty estimates are obtained by means of the Eigenspace Perturbation Method (EPM). Results show that, in general, one cannot expect the turbulence uncertainty estimates to be mesh and time-step independent based on the sole sensitivity analysis

The early-time dynamics of Rayleigh-Taylor instability with a premixed density gradient layer was investigated by three-dimensional implicit large eddy simulation. Compared with the classic Rayleigh-Taylor instability, it was found that the mixing layer undergoes an inactive stage when the mixing width of the layer is nearly unchanged. The development of hydrodynamic instability with a premixed layer

In this paper we propose to revisit the notion of simple Riemann solver both in Lagrangian and Eulerian coordinates following the seminal work of Gallice ”Positive and entropy stable Godunov-type schemes for gas dynamics and MHD equations in Lagrangian or Eulerian coordinates” in Numer. Math., 94, 2003. We provide in this work the relation between the Eulerian and Lagrangian forms of systems of conservation

In the present study, the shock-disturbances interaction in hypersonic inviscid flows with real gas effects is studied by applying a high-order accurate numerical method with the shock capturing technique. To consider real gas effects, the equilibrium air model is utilized here. The strong conservative form of the two-dimensional unsteady compressible Euler equations in the 2D generalized curvilinear

This paper focuses on the extension of the Weighted Average Flux (WAF) scheme for the numerical simulation of two-phase gas-liquid flow by imposing velocity equilibrium and without mechanical equilibrium of the transient drift-flux model. The model becomes a hyperbolic system of conservation laws with realistic closure relations where both phases are strongly coupled during their motion. Exploiting

In this paper, we propose a hybrid kinetic weighted group velocity control - weighted essentially non-oscillatory (WGVC-WENO) scheme which combines the WGVC-WENO reconstruction technique Sun et al. (2011) with the hybrid kinetic method proposed in Lv et al. (2016). The new scheme is based on the idea of hybridization. The hybrid kinetic method is adopted for flux calculations, and the WGVC-WENO technique

In this article, we propose a practical and highly efficient finite difference approach for two-phase fluid simulations on three-dimensional (3D) surfaces. The hydrodynamically coupled interfacial motion is captured by using the conservative Allen–Cahn–Navier–Stokes (CACNS) equations. By adopting the closest point method and the pseudo-Neumann boundary condition, the direct computations on curved surfaces

In this study, the control parameters related to the strength of the backward energy transfer in turbulence shell models were optimized using a genetic algorithm. Control parameters of 0.5 and 1.25 produced helicity and enstrophy scaling, respectively. I examined the optimization from the perspective of energy spectra reproducibility. The optimization objective function was the error between the energy

This paper presents a formulation of a general form of an equation for pressure using thermodynamic principles. The motivation for this is in large part due to the need for a pressure equation for smoothed particle hydrodynamics, SPH, that takes into account the role of entropy. This is necessary because the use of physical and artificial viscosity leads to an increase in entropy. While such an increase

We develop a direct numerical framework for simulating the incompressible multiphase flow. This approach combines our recent high accuracy interfacial jump capturing method (Qin et al., 2020) with a topology preserving interface tracking method in a semi-implicit setting. With the help of a composite solution for the individual fluid phases within the interfacial cells, the interfacial jump capturing

The Reynolds number for the onset of flow unsteadiness is determined for several canonical geometries (triangles, rectangles, ellipses and lozenges) at different sectional breadth (L) to height (d) ratios (aspect ratio AR=L∕d), for more than 70 shapes. The flow is modeled using a direct Navier–Stokes incompressible two-dimensional solver and the shape is defined by an Immersed Boundary Method. The

The Stokes eigenmodes on two-dimensional regular polygons of N apexes, 3≤N≤40, are studied numerically using two different solvers: the lattice Boltzmann equation and the Legendre–Galerkin spectral element method. In particular, the lowest 55 eigenmodes on regular N-polygons have been computed and investigated for the following properties including (a) symmetries, (b) the asymptotic behaviour of the

We perform particle-resolved simulations of ice slurry flows in a square duct by using the thermal immersed boundary–lattice Boltzmann method. We investigate the effects of Reynolds number, ice packing factor, and density ratio of the ice particle to the carrier fluid on the cooling performance of ice slurry flows. In addition, we compare two collision models, i.e., a repulsion model and an adhesion

Gas-liquid two-phase flows in pipes are present in a variety of engineering applications. These applications require transient one-dimensional mathematical models coupled with robust numerical methods to simulate the flow behavior in time and space. As there exist several possible combinations of models and numerical methods, questions arise as to the suitability of these numerical models to best accommodate

Menter SST k-ω is a Reynolds-averaged Navier–Stokes based two-equation turbulence model routinely used in industry for predicting aerodynamic flows. It shows excellent performance for low-speed flows, but gives inconsistent predictions for high-speed shock-induced separated flows. The model assumption of using a constant value of 0.31 for the structure parameter contradicts experimental observations

An unstructured, shock-fitting algorithm, originally developed to simulate inviscid flows, has been further developed to make it capable of dealing with shock-wave/boundary-layer interactions (SWBLI). This paper illustrates the newly implemented algorithmic features of this technique and its application to two-dimensional flow-configurations representative of three different SWBLI patterns. A detailed

Nowadays, as industrial designs are close to their optimal configurations, the challenge lies in the extraction of the last percentages of improvement. This necessitates accurate evaluations of the performance and represents a significant higher computational cost. The present work aims at integrating Large Eddy Simulations in the optimization framework for an accurate evaluation of the flow field

A three-dimensional (3D) lattice Boltzmann method based on the Allen-Cahn equation (A-C LBM) is employed to study the spreading dynamics of impacting droplets on the hydrophobic flat and textured surfaces. At first, the simulation of the equilibrium state of a droplet and also the impacting droplet spreading on a flat surface are considered at various wetting conditions to examine the accuracy and

The breakup of a periodic jet is examined computationally, using a front-tracking/finite-volume method, where the interface is represented by connected marker points moving with the fluid, while the governing equations are solved on a fixed grid. Tracking the interface allows control of whether topology changes take place or not. The Reynolds and Capillary numbers are kept relatively low (Re=150 and

Precise modeling of contact angle is ubiquitous in capillary driven multiphase flow simulations. From a simple 2D rectangular capillary benchmark, we demonstrate and discuss the dependence of capillary dynamics on the mesh size with respect to Washburn’s equation. Mesh-dependency is dominated by an underestimation of viscous losses for coarser meshes and transits to ever increasing stress-related errors

The supersonic near-wake flow experiment conducted by Dutton on a cylinder with 10 degrees angle of attack was studied numerically with Delayed Detached Eddy Simulation (DDES) method. The wind tunnel test section were included in the geometry model to examine if its omission led to the unsuccessful prediction of several important flow features in previous studies. Flow structures were compared to experiment

Large-eddy simulations (LES) of the flow over a semi-circular cylinder at a diameter-based Reynolds number 50000 and zero angle of attack are presented. In comparison with the prominent benchmark flows past circular and square cylinders, this test problem has been less investigated in the literature from both numerical and experimental perspectives. Also, this case can be even more challenging for

Hydrophobic and superhydrophobic coatings are of great interest to the aerospace community as a measure to mitigate performance losses due to ice formation in flight. To numerically investigate the supercooled large droplets (SLDs) impacting such coated surfaces, a multiphase smoothed particle hydrodynamics (SPH) solver is developed by solving the Euler momentum equations for fluid dynamics, the energy

We seek to assess the key aspects of two modern moving mesh approaches for simulating two-phase flows where a thin explicit interface separates the two fluids within the context of “one-fluid” formulation. Both methods discretize the fluid equations through the Finite Element (FE) method using the Arbitrary Lagrangian-Eulerian (ALE) framework, therefore a complex moving mesh scheme is achieved. These

The article deals with an improved treatment of wall models for the simulation of turbulent flows in the framework of Immersed Wall Boundaries on Cartesian grids. The emphasis is put on the implementation in a Lattice-Boltzmann Method solver without loss of generality, since the proposed approach can be used in Navier–Stokes-based solvers in a straightforward way. The proposed improved wall model implementation

The purpose of this paper is to present results of an uncertainty and sensitivity analysis study of commonly used turbulence models in Reynolds-Averaged Navier–Stokes codes due to the epistemic uncertainty in closure coefficients for a set of turbulence model validation cases that represent the structure of several canonical flow problems. The study focuses on the analysis of a 2D Zero Pressure Gradient

This paper is devoted to the development and application of hybrid methods combining, on the one hand, semi-lagrangian methods for the advection-diffusion of scalars, and, on the other hand, either finite volume or spectral methods, depending on the flow geometry, for the Navier-Stokes equations. A particular focus is made on the accuracy and scalability of the methods. These methods are then used

In this work, the Harten-Lax-van Leer Contact (HLLC) approximate Riemann solver is extended to two-phase flow through ducts with discontinuous cross-sections. Two main strategies are explored regarding the treatment of the non-conservative term arising in the governing equations. In the first, labelled HLLC+S, the non-conservative term is discretized separately. In the second, labelled HLLCS, the non-conservative

In this paper we propose a dual-time stepping scheme for the Smoothed Particle Hydrodynamics (SPH) method. Dual-time stepping has been used in the context of other numerical methods for the simulation of incompressible fluid flows. Here we provide a scheme that combines the entropically damped artificial compressibility (EDAC) along with dual-time stepping. The method is accurate, robust, and demonstrates

In this study we couple a family of AUSM-flux splitting schemes with the CENO high-order scheme and evaluate the overall performance of the developed in-house solver in terms of modeling the flow physics accurately for a wide range of benchmark problems. The solver uses reconstructed conservative variables. The problems include inviscid and viscous flows that cover low subsonic through transonic and

In this paper we present the implementation and the validation of the Diffusion Mixture Model as a valuable alternative to other popular models for the simulation of gas-liquid systems. The Diffusion Mixture Model treats the gas-liquid system as if it consists of only one phase: the gas-liquid mixture. The difference between the Diffusion Mixture Model and others lies in the minor simplification made

An adaptive time spectral viscosity (TSV) approach is proposed to stabilize the time-spectral method (TSM) by dealiasing its solution. Instead of being assigned uniformly in space, the cut-off wave number for TSV is determined locally by spectrum analysis of the flow variables. On each grid cell, the significant low-frequency modes are adaptively separated from the TSV targeted high-frequency ones

In this paper, a hybrid computational aero/hydro-acoustic approach is proposed to deal with acoustic scattering and flow-induced noise problems based on the sharp interface immersed boundary method (IBM). For the flow field, the incompressible Navier–Stokes equations are solved by an in-house direct numerical simulation solver. The acoustic field is predicted by solving acoustic perturbation equations

This work deals with the numerical simulation of aeroacoustic sound generated by flexible structures in low Mach number turbulent flows. A partitioned computation scheme is investigated to solve the coupled fluid-solid problem. A hybrid method based on the acoustic/viscous splitting technique is applied for aeroacoustic computation using large eddy simulations (LES) to resolve the incompressible turbulent

A discrete adjoint method implemented in a coupled pressure-based RANS solver is presented in this paper. The adjoint equations are solved using an adjoint fixed point iteration that inherits the convergence properties of the primal solver. Automatic differentiation is used extensively for the construction of the adjoint fixed point iteration. The concept of Krylov subspace methods was adopted to stabilize

A new numerical flux scheme is proposed for compressible multi-phase flows at all Mach numbers. The hybrid AUSM-family scheme (HAUS) combines various AUSM-type schemes. HAUS is facilitated by reconstructing the mass flux term present in AUSM-family schemes such as AUSMPW, SLAU-type, and AUSM+ up, and subsequently rebuilding the pressure flux term. Numerical validations are performed under various conditions

The FORCE-type centred schemes are simple and efficient and do not explicitly require the wave propagation information of the system to calculate the numerical flux. However, their poor resolution for contact discontinuities seriously affects their applications. In the present work, a simple FORCE-type centred scheme accurate for contact discontinuities is proposed and applied to calculations of compressible

We present a Stochastic Galerkin (SG) scheme for Uncertainty Quantification (UQ) of the compressible Navier-Stokes and Euler equations. For spatial discretization, we rely on the high-order Discontinuous Galerkin Spectral Element Method (DGSEM) in combination with an explicit time-stepping scheme. We simulate complex flow problems in two- and three-dimensional domains using curved unstructured hexahedral

The present study focuses on applying different metrics to assess accuracy, robustness and sensitivity of scale-resolving simulations of turbulent channel flow, when the numerical parameters are systematically varied. Derived by combining well-established uncertainty quantification techniques and computer experiments, the metrics act as powerful tools for understanding the behavior of flow solvers

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

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

The simplified lattice Boltzmann method (SLBM) is relatively new in the LBM community, which lowers the cost in virtual memories significantly and has better numerical stability compared with the single-relaxation-time (SRT) LBM. Recently, SLBM has been extended to simulate thermal flows based on the simplified thermal energy distribution function model. However, the existing thermal models developed

A fourth-order finite difference algorithm is developed for the direct simulation of two-dimensional Rayleigh-Bénard convection in a horizontally periodic domain of aspect ratio Γ. The free-slip condition prevents the formation of kinetic boundary layers and allow the implementation of an efficient long-stencil scheme for the vorticity equation without additional risk of instability. The required grid

We introduce a numerical framework to study the fluid-structure interaction between two helical filaments rotating under low Reynolds number condition, motivated by the propulsion of bacteria using helical flagella. Our numerical framework couples the elasticity of the thin filaments, nonlocal hydrodynamic loading, and the contact between multiple elastic rods. Each of these three ingredients is respectively

This paper presents the study of the losses generated in a Counter Rotating Open Rotor (CROR) configuration at three different operating conditions (approach, cutback and sideline). Unsteady Reynolds Averaged Navier-Stokes (URANS) and Large-Eddy Simulation (LES) approaches are used and compared to describe the flow field and the mechanisms of loss. Since no common circumferential periodicity occurs

Reynolds Averaged Navier-Stokes (RANS) simulations and wind tunnel testing have become the go-to tools for industrial design of Low-Pressure Turbine (LPT) blades. However, there is also an emerging interest in use of scale-resolving simulations, including Direct Numerical Simulations (DNS). These could generate insight and data to underpin development of improved RANS models for LPT design. Additionally

Shale gas flow at the pore scale is very challenging to simulate due to high Knudsen numbers (Kn), low speeds and complicated pore geometries. The direct simulation BGK (DSBGK) method and the discrete velocity method (DVM) are promising methods to simulate three-dimensional (3D) gas flows in the shale rock. As the grid-convergence accuracy and computational cost highly depend on the spatial and molecular

This numerical study based on high-order finite-difference schemes presents LES-NWR (Large Eddy Simulation with near-wall resolution) of turbulent channel flows up to Reτ=5200 using non-explicit approaches for which numerical dissipation is introduced via the discretisation of viscous terms of the Navier-Stokes equations. These models are cheaper than explicit LES models as no extra terms are needed

Particle-laden flows can be encountered in a plethora of engineering applications, e.g., sediment transport, fluidized beds, vehicle soiling, and aircraft icing. The latter is caused by supercooled water droplets or ice crystals impacting and adhering to an aerodynamic surface during flight. Simulating such flows requires proper application of physical models through the use of particle flow solvers

Motivated by the interest in accurate simulation of dense fluid-particle flows, a resolved CFD-DEM method is developed by incorporating computational fluid dynamics and discrete element method (CFD-DEM) with the immersed boundary method (IBM). In this approach, the fluid phase is simulated by the CFD while the individual particles are analyzed by means of the DEM. The direct-forcing IBM, which satisfies

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

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

In this paper, we discuss the usage and implementation of the compressive sensing (CS) for the efficient measurement and analysis of the von Kármán 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

From the previous works, we found that the stability of the pressure solution obtained by using particle-based method can be improved by solving the pressure equation on a stationary Eulerian grid. In this study, the Multiquadric Radial Basis Function (RBF-MQ) interpolation technique is applied for the data transfer between Lagrangian particles and Eulerian grids in solving the incompressible Navier-Stokes

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

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

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