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...

In this study, the homogeneity of the continuum model of a fixed bed reactor operated in steady state and unsteady state systems for lean CH4 oxidation is investigated. The steady-state fixed bed reactor system was operated under once-through direction, while the unsteady-state fixed bed reactor system was operated under flow reversal. The governing equations consisting of mass and energy balan...

The present study deals with the analysis of unsteady boundary layer flow and heat transfer of an incompressible micropolar fluid over a stretching sheet when the sheet is stretched in its own plane. The velocity and temperature are assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x-axis so that the sheet is stretched, k...

The paper presents an adjoint based approach for determining global error in the time domain that is relevant to scalar outputs computed as functions of the unsteady flow solution. The algorithm is derived for the unsteady Euler equations and takes into account the effect of dynamic meshes. Two primary components of the total error are specifically identified, namely, the error due to temporal ...

This paper presents an Euler and boundary-layer method capable of unsteady flow and aeroelastic simulations. An integral boundary-layer solver is coupled with an Euler solver in a “semi-inverse” manner. For the inviscid part, approximate wall boundaryconditions are implemented on non-moving mean chord positions, whereas the full nonlinear Euler equation is solved in the field for accurate resol...

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...

Flood waves resulting from dam breaks and flash floods have been responsible for numerous losses. In the present study, sudden flood releases were investigated down a large stepped waterway initially dry. A new experimental technique was developed to obtain instantaneous void fractions, bubble count rates and velocities. Unsteady air-water flow properties were recorded with arrays of conductivi...

The purpose of the present study is to clarify the effects of unsteady glottal flow on the phonation. We numerically simulate the speech production process within the larynx and the vocal tract based on our proposed glottal sound source model. The simulation shows amplitude and waveform fluctuations in pressure within the larynx caused by unsteady fluid motion. In order to investigate the unste...

The present paper describes how to apply the Chebyshev orthogonal collocation technique to solve steady-state and unsteady-steady two-dimensional problems. All problems are solved using one single computer algebra, Mathematica . The problems include: (1) steady-state heat transfer in a rectangular bar, (2) steady-state flow in a rectangular duct, (2) steady-state heat transfer in a cooling cyli...

Unsteady boundary layer flow of an incompressible micropolar fluid over a stretching sheet when the sheet is stretched in its own plane is studied in this paper. The stretching velocity is assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x-axis so that the sheet is stretched, keeping the origin fixed in a micropolar flui...