Strouhal numbers of rectangular cylinders
TL;DR: In this article, experiments on the vortex shedding frequencies of various rectangular cylinders were conducted in a wind tunnel and in a water tank and the results show how Strouhal number varies with a width-to-height ratio of the cylinders in the range of Reynolds number between 70 and 2 × l04.
Abstract: Experiments on the vortex-shedding frequencies of various rectangular cylinders were conducted in a wind tunnel and in a water tank. The results show how Strouhal number varies with a width-to-height ratio of the cylinders in the range of Reynolds number between 70 and 2 × l04. There is found to exist a certain range of Reynolds number for the cylinders with the width-to-height ratios of 2 and 3 where flow pattern abruptly changes with a sudden discontinuity in Strouhal number. The changes in flow pattern corresponding to the discontinuity of Strouhal number have been confirmed by means of measurements of velocity distribution and flow visualization. These data are compared with those of other investigators. The experimental results have been found to show a good agreement with those of numerical calculations.
Citations
More filters
TL;DR: In this paper, an incompressible SIMPLEC code is used with a non-staggered grid arrangement for the convective terms and the time discretization is implicit and a second-order Crank-Nicolson scheme is employed.
Abstract: Calculations of unsteady 2D flow around a square cylinder at incidence (α=0°−45°) are presented. The Reynolds numbers are low (Re=45–200) so that the flow is presumably laminar. A von Karman vortex sheet is predicted behind the cylinders with a periodicity which agrees well with experiments. An incompressible SIMPLEC code is used with a non-staggered grid arrangement. A third-order QUICK scheme is used for the convective terms. The time discretization is implicit and a second-order Crank–Nicolson scheme is employed. At the outlet of the computational domain a convective Sommerfeld boundary condition is compared with a traditional Neumann condition. The convective boundary condition is shown to be more effective in reducing the CPU time, reducing the upstream influence of the outlet and thus reducing the necessary downstream extent of the domain. A study of the effects of spatial resolution and blockage is also provided. The onset of vortex shedding is investigated by using the Stuart–Landau equation at various angles of incidence and for a solid blockage of 5%. A number of quantities such as Strouhal number and drag, lift and moment coefficients are calculated. © 1998 John Wiley & Sons, Ltd.
540 citations
TL;DR: In this article, the authors re-introduce the consistent mass matrix into some semi-implicit projection methods in such a way that the cost advantage of lumped mass and the accuracy advantage of consistent mass are simultaneously realized.
Abstract: Ever since the expansion of the finite element method (FEM) into unsteady fluid mechanics, the «consistent mass matrix» has been a relevant issue. Applied to the time-dependent incompressible Navier-Stokes equations, it virtually demands the use of implicit time integration methods in which full «velocity-pressure coupling» is also inherent. We re-introduce the consistent mass matrix into some semi-implicit projection methods in such a way that the cost advantage of lumped mass and the accuracy advantage of consistent mass are simultaneously realized
527 citations
TL;DR: In this paper, an experimental investigation of the flow around and pressure forces on fixed (non-vibrating) rectangular cylinders at angles of attack 0°-90° was conducted.
427 citations
TL;DR: The confined flow around a cylinder with square cross-section mounted inside a plane channel was investigated in detail by two entirely different numerical techniques, namely a lattice-Boltzmann automata (LBA) and a finite-volume method (FVM).
411 citations
Cites background from "Strouhal numbers of rectangular cyl..."
...The onset of this phenomenon is not clearly de®ned in the literature; only a wide range of Re 100 to 150 is given (Okajima, 1982; Franke, 1991)....
[...]
TL;DR: In this article, an implicit fractional step method finite-volume code with second-order accuracy in space and time was used to simulate 2D and 3D shedding flow around a square cylinder for moderate Reynolds numbers.
Abstract: Direct numerical simulations of two-dimensional (2D) and 3-D unsteady flow around a square cylinder for moderate Reynolds numbers (Re=150–500) are performed, employing an implicit fractional step method finite-volume code with second-order accuracy in space and time. The simulations, which are carried out with a blockage ratio of 5.6%, indicate a transition from 2-D to 3-D shedding flow between Re=150 and Re=200. Both spanwise instability modes, A and B, are present in the wake transitional process, similar to the flow around a circular cylinder. However, seemingly in contrast to a circular cylinder, the transitional flow around a square cylinder exhibits a phenomenon of distinct low-frequency force pulsations (Re=200–300). For 3-D simulations, the Strouhal number and the mean drag coefficient are in general agreement with existing experiments. Between Re=300 and 500, an increase in the spanwise coupling of fluctuating forces is indicated. The influence of the spanwise aspect ratio using periodic boundary conditions, a finer grid, and a finer time step is also investigated.
355 citations
References
More filters
01 Jul 1954
TL;DR: In this paper, a semi-empirical study of the bluff body problem is presented, where interference elements in the wake close behind a cylinder demonstrate the need for considering that region in any complete theory.
Abstract: Note presenting a semiempirical study of the bluff-body problem. Some experiments with interference elements in the wake close behind a cylinder demonstrate the need for considering that region in any complete theory.
702 citations
TL;DR: In this article, the mean and fluctuating pressure field acting on a two-dimensional square cylinder in uniform and turbulent flows was measured and the addition of turbulence to the flow was shown to raise the base pressure and reduce the drag of the body.
Abstract: Measurements are presented of the mean and fluctuating pressure field acting on a two-dimensional square cylinder in uniform and turbulent flows. The addition of turbulence to the flow is shown to raise the base pressure and reduce the drag of the body. It is suggested that this is attributable to the manner in which the increased turbulence intensity thickens the shear layers, which causes them to be deflected by the downstream corners of the body and results in the downstream movement of the vortex formation region. The strength of the vortex shedding is shown to be reduced as the intensity of the incident turbulence is increased.
441 citations
TL;DR: In this paper, the authors present the results of measurements of fluctuating lift and drag on a long square cylinder and find that the presence of large-scale turbulence in the stream had a marked influence on both the steady and the fluctuating forces.
Abstract: The paper presents the results of measurements of fluctuating lift and drag on a long square cylinder. The measurements include the correlation of lift along the cylinder and the distribution of fluctuating pressure on a cross-section. The magnitude of the fluctuating lift was found to be considerably greater than that for a circular cross-section and the spanwise correlation much stronger.It was found that the presence of large-scale turbulence in the stream had a marked influence on both the steady and the fluctuating forces. The most significant changes were at small angles of attack (%alpha; < 10°) and included a reduction in base suction and a decrease in fluctuating lift of about 50%.
362 citations
TL;DR: In this article, the Strouhal number of rectangular cylinders was measured and the base pressure coefficient, drag coefficient and the number of cylinders per cylinder was found to be strongly influenced by the presence of the trailing edge corners.
Abstract: Measurements are presented of the base pressure coefficient, drag coefficient and Strouhal number of rectangular cylinders. The results confirm a finding in Japan that the drag coefficient rises to nearly 3 when the depth of the section is just over half the width. The flow around the sections is found to be strongly influenced by the presence of the trailing-edge corners.
334 citations
195 citations