Numerical simulation of the turbulent wake behind a normal flat plate
TL;DR: In this paper, the three-dimensional wake flow behind a flat plate placed normal to the free stream has been investigated by means of direct numerical simulations and the Reynolds number Re based on the homogeneous inflow velocity and the uniform width d of the plate was 750.
About: This article is published in International Journal of Heat and Fluid Flow.The article was published on 2009-12-01. It has received 81 citations till now. The article focuses on the topics: Strouhal number & Reynolds number.
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TL;DR: In this article, the authors evaluate the validity of 2D URANS simulations with k- ω Shear Stress Transport (SST) turbulence model for the flow around rectangular cylinders and discuss the effects of aspect ratios on the vortex formation.
53 citations
TL;DR: In this paper, the authors investigate the effect of the rounded corners on the development of the separated and transitional flow past the cylinder in terms of time-averaged statistics, time-dependent behavior, turbulent statistics and three-dimensional flow patterns.
40 citations
TL;DR: In this article, the authors investigated the properties of asymmetric wake patterns behind a flat plate inclined at angles of attack 20°, 25°, and 30° by direct numerical simulations.
Abstract: The properties of asymmetric wake patterns behind a flat plate inclined at angles of attack 20°, 25°, and 30° are investigated. The Reynolds number based on the inflow velocity and the plate width is 1000. Both two-dimensional and three-dimensional calculations are performed by direct numerical simulations. Compared to the three-dimensional simulations, the two-dimensional calculations predict a significantly lower pressure on the rear surface of the plate, which consequently leads to very high drag and lift forces on the plate. The asymmetric mean wake flow, turbulence properties, and coherent patterns in the three-dimensional simulations are analysed by time- and phase-averaged techniques. Unlike the symmetric wake flow, the vortices shed from the leading and trailing edges of an inclined plate possess unequal strength with the trailing edge vortex having higher strength. It is observed that the present three-dimensional simulations predict results which compare well with the experimental data. In addit...
39 citations
TL;DR: In this paper, the effects of thermal radiation and moisture content on the pyrolysis and gas-phase ignition of a solid fuel element containing high moisture content were investigated using the coupled Gpyro3D/FDS models.
39 citations
TL;DR: In this paper, the authors investigate the incompressible flow past an isolated NACA0012 airfoil at the angle of attack of 5 degrees and Reynolds number 5 × 10 4.
35 citations
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TL;DR: In this article, the authors propose a definition of vortex in an incompressible flow in terms of the eigenvalues of the symmetric tensor, which captures the pressure minimum in a plane perpendicular to the vortex axis at high Reynolds numbers, and also accurately defines vortex cores at low Reynolds numbers.
Abstract: Considerable confusion surrounds the longstanding question of what constitutes a vortex, especially in a turbulent flow. This question, frequently misunderstood as academic, has recently acquired particular significance since coherent structures (CS) in turbulent flows are now commonly regarded as vortices. An objective definition of a vortex should permit the use of vortex dynamics concepts to educe CS, to explain formation and evolutionary dynamics of CS, to explore the role of CS in turbulence phenomena, and to develop viable turbulence models and control strategies for turbulence phenomena. We propose a definition of a vortex in an incompressible flow in terms of the eigenvalues of the symmetric tensor ${\bm {\cal S}}^2 + {\bm \Omega}^2$ are respectively the symmetric and antisymmetric parts of the velocity gradient tensor ${\bm \Delta}{\bm u}$. This definition captures the pressure minimum in a plane perpendicular to the vortex axis at high Reynolds numbers, and also accurately defines vortex cores at low Reynolds numbers, unlike a pressure-minimum criterion. We compare our definition with prior schemes/definitions using exact and numerical solutions of the Euler and Navier–Stokes equations for a variety of laminar and turbulent flows. In contrast to definitions based on the positive second invariant of ${\bm \Delta}{\bm u}$ or the complex eigenvalues of ${\bm \Delta}{\bm u}$, our definition accurately identifies the vortex core in flows where the vortex geometry is intuitively clear.
5,837 citations
TL;DR: In this article, the authors examined the flow in the wake of a two-dimensional model with a blunt trailing edge at Reynolds numbers (based on model chord) between 1·4 × 105 and 2·56 × 105.
Abstract: The flow in the wake of a two-dimensional model with a blunt trailing edge was examined at Reynolds numbers (based on model chord) between 1·4 × 105 and 2·56 × 105. The ratio of total boundary-layer thickness at the trailing edge to model base height was approximately 0·5. Measurements were taken of base pressure and vortex shedding frequency together with traverses of the wake using a hot-wire anemometer. Traverses carried out along the wake showed a peak in the root-mean-square velocity-fluctuation at a distance equal to one base height from the model rear face. The position of the peak is referred to as the position of the fully formed vortex. The investigation was extended to a model fitted with splitter plates up to four base heights long. For each plate tested, a position of the fully formed vortex was found, and its distance from the model base was discovered to be inversely proportional to the base pressure coefficient. The flow about the model with splitter plates is described as being separated into five regimes of flow.
532 citations
TL;DR: In this article, the authors investigated the resistance of a flat plate to the general flow, in terms of the dimensions of the vortex system at some distance behind the plate and the rate at which vorticity is leaving the edges of the plate.
Abstract: The general form of the flow behind an infinitely long thin flat plate inclined at a large angle to a fluid stream of infinite extent has been known for many years past. The essential features of the motion are illustrated in the smoke photograph given in fig. 1, Plate 6. At the edges, thin bands of vorticity are generated, which separate the freely-moving fluid from the “dead-water” region at the back of the plate; and at some distance behind, these vortex bands on account of their lack of stability roll up and form what is now commonly known as a vortex street (see fig. 2). Various theories for calculating the resistance of the plate have also been advanced from time to time. One of the earliest is the theory of “discontinuous” motion due to Kirchhoff and Rayleigh, who obtained the expression π sin α/4 + π sin α ρV2 b (see symbols) for the normal force per unit length of the plate. More recently Karman has obtained a formula for the resistance of a plate normal to the general flow, in terms of the dimensions of the vortex system at some distance behind the plate. In spite, however, of these and other important investigations, much more remains to be discovered before it can be said that the phenomenon of the flow is completely understood. No attempt has hitherto been made, as far as the writers are aware, to determine experimentally, at incidences below 90°, the frequency and speed with which the vortices pass downstream; the dimensions of the vortex system; the average strength of the individual vortices; or the rate at which vorticity is leaving the edges of the plate. The present investigation has been undertaken to furnish information on these features of the flow.
382 citations
TL;DR: It is shown, using several dierent databases, that this hypothesis is almost never verified and the analogy with kinetic theory, and the reason why this analogy cannot be applied in general for turbulent flows is addressed.
280 citations
TL;DR: In this paper, a three-dimensional numerical simulation of the Navier-Stokes equations system in the Reynolds number range 100-300 is presented, which predicts the frequency modulation and the formation of a discontinuity region delimited by two frequency steps within the present Reynolds number ranges.
Abstract: The transition to turbulence of the flow around a circular cylinder is studied by a three-dimensional numerical simulation of the Navier–Stokes equations system in the Reynolds number range 100–300. The numerical method is second-order accurate in space and time and Neumann boundary conditions are used at the two boundaries in the spanwise direction; non-reflecting boundary conditions are specified for the outlet downstream boundary. This study predicts the frequency modulation and the formation of a discontinuity region delimited by two frequency steps within the present Reynolds number range. These features are related to the birth of streamwise vorticity and to the kinetic energy distribution in the near wake. The development of the mean dynamic quantities, the Reynolds stress correlations and the variation of their maximum values are provided in this region, where the similarity laws do not hold. The spatial evolution of the von Karman mode and of its spectral amplitude are quantified and the variation laws of the maximum spectral amplitude and of its location as a function of Reynolds number are established. The critical Reynolds number for the appearance of the first discontinuity in the present flow system is evaluated by the fully nonlinear approach.
270 citations