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The moving least square meshfree method is used to solve the Reynolds-averaged Navier-Stokes equations with two different turbulence models: the renormalisation group (RNG) κ-ε model and the Wilcox κ-ε model. The moving least square approach with clouds-of-points reconstruction, which can provide results from highly anisotropic clouds of points, is adopted to approximate the spatial derivatives. Both the subsonic and transonic viscous flows around RAE2822 airfoil are simulated. The pressure coefficients of the airfoil surface are calculated, the Mach number contours of the flow fields are presented, and the mean velocity profiles of the boundary layer at different locations are investigated. Some unsteady viscous flow simulation results are also presented. The simulation results show a good agreement with the experiment results and other numerical simulation results. Overall, the simulation results demonstrate that the proposed meshfree numerical algorithm is accurate and capable of modelling turbulence flows around airfoils. [ABSTRACT FROM AUTHOR]

The numerical simulation of the flow around the moving body requires a flexible computational grid; a grid which can adapt itself to the displacements of moving body. In the present study, it is shown that with the concentration of the deformations caused by the body motion in a limited number of elements (deformable layer) and the regular manipulation in the connections of these elements, any type of body motion can be modelled. In this method, the quality of the grid is maintained and there is no need to delete/insert any node in the domain. The ability to model the large motions of the body without the need for re-meshing or interpolation are among the other advantages of this method. To demonstrate the correct performance of the presented method, the unsteady form of the Euler equations is solved and the properties over each cell edges are evaluated using an averaging method. For time integration of equations used an implicit dual time method. Several test cases are solved and the results are compared with experimental and other numerical data. [ABSTRACT FROM AUTHOR]

In this paper, in order to design a useful computational flow simulation for the governing equation of two phase incompressible (water and oil), a robust and efficient scheme is proposed. This hybrid method consisting of IMPES technique for the linearisation, control volume finite element method on hexagonal grids for spatial discretisation, backward Euler method for time discretisation and stable variant (adaptive-simpler-GMRES) of simpler generalised minimum residual technique with incomplete factorisation preconditioners is used to solve the corresponding linear system. Moreover, we proposed the general Courant Friedrich Levy condition for two phase immiscible flow with Von Neumann method. Numerical results for oil pressure, oil and water production rates and water saturation in the injection and production wells are illustrated. [ABSTRACT FROM AUTHOR]

We develop a low-dimensional tool to predict the effects of unsteadiness in the inflow on force coefficients acting on a circular cylinder using proper orthogonal decomposition (POD) modes from steady flow simulations. The approach is based on combining POD and linear stochastic estimator (LSE) techniques. We use POD to derive a reduced-order model (ROM) to reconstruct the velocity field. To overcome the difficulty of developing a ROM using Poisson's equation, we relate the pressure field to the velocity field through a mapping function based on LSE. The use of this approach to derive force decomposition coefficients (FDCs) under unsteady mean flow from basis functions of the steady flow is illustrated. For both steady and unsteady cases, the final outcome is a representation of the lift and drag coefficients in terms of velocity and pressure temporal coefficients. Such a representation could serve as the basis for implementing control strategies or conducting uncertainty quantification. [ABSTRACT FROM AUTHOR]

In the present study, an efficient numerical method to deform an unstructured polyhedral grid for accurate simulations of a flow induced by a moving solid object is proposed. In order to overcome inefficiency of the existing methods based on the vertices of a computational cell, the present approach deforms the polyhedral grids adaptively using a network based on the centre of each computational cell. It is shown that the proposed method provides with an improved efficiency for an arbitrary Lagrangian-Eulerian (ALE) simulation of a flow with a moving solid object compared to the existing methods based on the vertices. It is also shown that a polyhedral grid results in a better numerical accuracy than a triangular grid. The present numerical methods were applied to flows around a fixed and oscillating circular cylinder with various Reynolds numbers and oscillating frequencies. The produced numerical results were verified against aerodynamic characteristics of the previous numerical studies. [ABSTRACT FROM AUTHOR]

A second-order accurate coupling algorithm for Thermal Fluid-Structure Interaction (TFSI) is presented. An implicit partitioned solution approach, which combines the advantages of weakly and strongly coupled schemes, is used. The framework consists of a finite-volume solver in arbitrary-Lagrangian-Eulerian formulation for the flow simulation, a finite-element code for the structural part and a commercial, black-box coupling interface. The thermal coupling is realised by a Schwarz decomposition method. Several elementary configurations are considered, to test the accuracy and to investigate the numerical characteristics of the system. By applying different grid configurations, we show that the results are of second-order accuracy. We also discuss the convergence properties of the method. [ABSTRACT FROM AUTHOR]

A comparative study was carried out on numerical methods for simulating a flow inside a torque converter. To investigate the effect of different methods for handling the relative motion of the parts, three methods were considered - the frozen rotor, sliding mesh and mixing plane methods. To improve the accuracy of performance prediction, the influence of viscosity variation with the temperature was studied by a thermo-fluid analysis. From parametric studies on the numerical scheme and the mesh resolution, it is observed that the results with the frozen rotor and sliding mesh methods agree well with the experimental data, whereas the mixing plane method induces a larger difference. The effect of viscosity variation on the accuracy of simulation is also investigated. [ABSTRACT FROM AUTHOR]

A nanofluid is a suspension consisting of a base liquid and nanoparticles, which has great potential for heat transfer enhancement. By considering the external and internal forces acting on the suspended nanoparticles as well as mechanical and thermal interactions among the nanoparticles and fluid particles, a thermal Lattice Boltzmann model is proposed for simulating flow and energy transport process of the nanofluid. The Nusselt number of the nanofluid is defined. By taking a nanofluid flowing through a channel as an example, some numerical computations are carried out and the enhancement mechanism of heat transfer of the nanofluid is discussed. [ABSTRACT FROM AUTHOR]

A novel boundary reconstruction scheme is developed utilising the reinitialisation scheme of the Level Set Method (LSM). The proposed scheme transfers usual digitally defined step-like boundary data to continuously smooth surface data. It is confirmed that the lattice boltzmann simulation by the Interpolated Bounce-Back (IBB) Boundary Condition (BC) with the present scheme well reproduces the drag coefficients of a cylinder and a sphere. Then this numerical scheme is applied to simulate flows in porous media which have the body-centred cubic structure. The results indicate that the present scheme improves the shape representation and thus the prediction accuracy is less sensitive to grid resolutions. [ABSTRACT FROM AUTHOR]

A discrete-element model (spring-dumbbell model) is used to investigate the mechanism of drag-reduction by adding polymer in a turbulent channel flow of Newtonian fluid by Direct Numerical Simulations (DNSs). By using this model, the spatial concentration of the polymer can be obtained numerically. In this paper, the effect of the spring coefficient on the drag-reduction is studied in detail. The quantitative relations between the drag-reduction rate and viscoelastic and Reynolds shear stress, etc., are obtained. Discussions are performed to clarify the relation between the turbulent structure of the polymer drag-reducing flow and the spring coefficient of the discrete-element model. [ABSTRACT FROM AUTHOR]

This paper is concerned with simulation of flows with interface between two incompressible and immiscible fluids on a fixed grid using what is called the single fluid formalism. This formalism views flow of two fluids as that of a single fluid whose density and viscosity change abruptly at the interface. The location of the interface is apriori not known but is to be discovered as part of the solution. Problems of these types are typically solved using two main approaches: a) Interface Capturing and b) Interface Tracking. The present contribution is of a former variety. The governing Navier-Stokes equations in primitive variables are solved on collocated grids with a specially derived smoothing pressure correction that satisfies volume conservation whereas superficial density is determined from mass conservation equation. It is shown that the latter equation can be cast in the form of a well known volume fraction equation. The convective terms are represented by a TVD scheme. The overall methodology is tested against few problems for which experimental data and/or numerical predictions are available. [ABSTRACT FROM AUTHOR]

The finite-difference method is combined with the Lattice Boltzmann Method (LBM) to simulate compressible flows with shock waves. The LBM model used here is based on a polynomial kernel function in the phase space, and can be recovered to the compressible Navier-Stokes equations with a flexible specific-heat ratio and Prandtl number. The third-order implicit-explicit Runge-Kutta scheme and the fifth-order weighted essentially non-oscillatory scheme are adopted for time and space discretisation, respectively. Three problems, including the Sod and the Lax shock tubes, and the strong shock wave problem, are simulated. Numerical solutions agree well with the exact solutions. [ABSTRACT FROM AUTHOR]