We propose in this paper a technique to accelerate the convergence of the Newton method to solve non-linear unsteady CFD problems. The principle relies on an effective way to obtain a better solution for the current time step than the solution of the previous time step. This is performed on a reduced model computed with a Proper Orthogonal Decomposition of some solution computed at some previou...

Research involving the interaction of flow with morphological instability during directional solidification of binary alloys is reviewed. In general, flow may arise during the solidification process from thermal and solutal buoyancy, changes in density upon solidification, thermocapillary forces at free boundaries, or external forcing of the system. We focus primarily on the last of these, givi...

We present a new algorithm to simulate unsteady viscoelastic flows in abrupt contraction channels. In our approach we split the viscoelastic terms of the Oldroyd-B constitutive equation using Duhamel s formula and discretize the resulting PDEs using a semi-implicit finite difference method based on a Lax–Wendroff method for hyperbolic terms. In particular, we leave a small residual elastic term...

This paper presents a new method for simulating ship airwake flow fields. These flows are inherently unsteady, and very difficult to predict. The method presented (NLDE) is fourth-order accurate in space and time. In this method we first solve for the steady state flow field, then we solve for the unsteady fluctuations. Steady and unsteady results are presented for a generic frigate shape. Cons...

The objective of this paper is to evaluate the predictive capability of three turbulence models for the simulation of unsteady cavitating flows around a 2D Clark-y hydrofoil. Three turbulence models were standard k-ε model, hybrid model of density correction model (DCM) and filter-based model (FBM) and an improved partially-averaged Navier-Stokes model (PANS) based on k-ε model. Using the above...

This chapter reviews techniques of model reduction of fluid dynamics systems. Fluid systems are known to be difficult to reduce efficiently due to several reasons. First of all, they exhibit strong nonlinearities – which are mainly related either to nonlinear convection terms and/or some geometric variability – that often cannot be treated by simple linearization. Additional difficulties arise ...

An unsteady sampling routine for a general parallel direct simulation Monte Carlo method called PDSC is introduced, allowing the simulation of time-dependent flow problems in the near continuum range. A post-processing procedure called DSMC rapid ensemble averaging method (DREAM) is developed to improve the statistical scatter in the results while minimising both memory and simulation time. Thi...

In the present paper, we have studied MHD free convective two dimensional unsteady viscous incompressible flows through a porous effect bounded by an infinite vertical porous plate with constant suction. The permeability of the porous medium fluctuates in time about a constant mean, and the viscosity of fluid is assumed to vary as a linear function of temperature. The flow is permitted under th...

Time-dependent flows of a Newtonian fluid through periodic arrays of spheres were simulated using the lattice-Boltzmann scheme. By applying a constant body force per unit mass to the fluid, a steady background fluid flow through the array of stationary spheres was first established. Subsequently, a small-amplitude perturbation to the body force, which varied periodically in time, was added and ...

The high cost of wind tunnel testing and the ongoing reduction in national wind tunnel facilities are forcing the aerospace engineering community to increasingly rely on computational fluid dynamics (CFD) to predict the performance of new aircraft designs. However, most aerospace applications are characterized by flows that exhibit large-scale unsteady turbulence and the accurate prediction of ...