Correlating Flow Pattern with Force Coefficients in Air Flow past a Tandem Unit of Three Circular Cylinders

2013 ◽  
Vol 40 (3) ◽  
pp. 235-253 ◽  
Author(s):  
A. R. Vasel-Be-Hagh ◽  
David Ting ◽  
Rupp Carriveau
Keyword(s):  
Flow Pattern ◽  
Air Flow ◽  
Circular Cylinders ◽  
Force Coefficients ◽  
Flow Past

scholarly journals Buoyancy Effect on the Flow Pattern and the Thermal Performance of an Array of Circular Cylinders

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Francesco Fornarelli ◽  
Antonio Lippolis ◽  
Paolo Oresta
Keyword(s):  
Nusselt Number ◽  
Flow Pattern ◽  
Richardson Number ◽  
Near Field ◽  
Circular Cylinders ◽  
Momentum Exchange ◽  
Force Coefficients ◽  
The Earth ◽  
Spacing Ratio ◽  
Oscillatory Character

In this paper, we found, by means of numerical simulations, a transition in the oscillatory character of the flow field for a particular combination of buoyancy and spacing in an array of six circular cylinders at a Reynolds number of 100 and Prandtl number of 0.7. The cylinders are isothermal and they are aligned with the earth acceleration (g). According to the array orientation, an aiding or an opposing buoyancy is considered. The effect of natural convection with respect to the forced convection is modulated with the Richardson number, Ri, ranging between −1 and 1. Two values of center-to-center spacing (s = 3.6d–4d) are considered. The effects of buoyancy and spacing on the flow pattern in the near and far field are described. Several transitions in the flow patterns are found, and a parametric analysis of the dependence of the force coefficients and Nusselt number with respect to the Richardson number is reported. For Ri=−1, the change of spacing ratio from 3.6 to 4 induces a transition in the standard deviation of the force coefficients and heat flux. In fact, the transition occurs due to rearrangement of the near-field flow in a more ordered wake pattern. Therefore, attention is focused on the influence of geometrical and buoyancy parameters on the heat and momentum exchange and their fluctuations. The available heat exchange models for cylinders array provide a not accurate prediction of the Nusselt number in the cases here studied.

Numerical simulation of flow past two circular cylinders in cruciform arrangement

2018 ◽  
Vol 848 ◽  
pp. 1013-1039 ◽  
Author(s):  
Ming Zhao ◽  
Lin Lu
Keyword(s):  
Standard Deviation ◽  
Drag Coefficient ◽  
Flow Pattern ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Circular Cylinders ◽  
Local Flow ◽  
Wake Vortices ◽  
Flow Past ◽  
The Mean

Flow past two circular cylinders in cruciform arrangement is simulated by direct numerical simulations for Reynolds numbers ranging from 100 to 500. The study is aimed at investigating the local flow pattern near the gap between the two cylinders, the global vortex shedding flow in the wake of the cylinders and their effects on the force coefficients of the two cylinders. The three identified local flow patterns near the gap: trail vortex (TV), necklace vortex (NV) and vortex shedding in the gap (SG) agree with those found by flow visualization in experimental studies. As for the global wake flow, two modes of vortex shedding are identified: K mode with inclined wake vortices and P mode where the wake vortices are parallel to the cylinders. The K mode occurs when the gap is slightly greater than the boundary gap between the NV and SG. It also coexists with the SG gap flow pattern if the Reynolds number is very small ($Re=100$). The flow pattern affects the force coefficient. The K mode increases the mean drag coefficient and the standard deviation of the lift coefficient at the centre of the upstream cylinder because the wake vortices converge towards the centre. The mean drag coefficient and standard deviation of the lift coefficient of the downstream cylinder decreases because of the shedding effect from the upstream cylinder.

The supersonic and low-speed flows past circular cylinders of finite length supported at one end

1962 ◽  
Vol 12 (3) ◽  
pp. 367-387 ◽  
Author(s):  
D. M. Sykes
Keyword(s):  
Mach Number ◽  
Finite Length ◽  
Central Region ◽  
Diameter Ratio ◽  
Circular Cylinders ◽  
Form Drag ◽  
Drag Coefficients ◽  
Low Speed ◽  
Flow Past ◽  
Length To Diameter Ratio

The flow past circular cylinders of finite length, supported at one end and lying with their axes perpendicular to a uniform stream, has been investigated in a supersonic stream at Mach number 1.96 and also in a low-speed stream. In both stream it was found that the flow past the cylinders could be divided into three regions: (a) a central region, (b) that near the free end of the cylinder, and (c) that near the supported end. The locations of the second and third regions were found to be almost independent of the cylinder length-to-diameter ratio, provided that this exceeded 4, while the flow within and the extent of the first region were dependent on this ratio. Form-drag coefficients determined in the central region in the supersonic flow were in close agreement with the values determined at the same Mach number by other workers. In the low-speed flow the local form-drag coefficients were dependent on length-to-diameter ratio and were always less than that of an infinite-length cylinder at the same Reynolds number.

The Impact of Urbanization on Air Flow Pattern: The Case of Rio de Janeiro

2014 ◽  
Vol 12 (9) ◽  
pp. 908-916 ◽  
Author(s):  
Marilia Ramalho Fontenelle ◽  
Sylvie Lorente ◽  
Leopoldo Eurico Gonçalves Bastos
Keyword(s):  
Flow Pattern ◽  
Rio De Janeiro ◽  
Air Flow ◽  
Impact Of Urbanization ◽  
The Impact

Steady approach of unsteady low-Reynolds-number flow past two rotating circular cylinders

2013 ◽  
Vol 736 ◽  
pp. 414-443 ◽  
Author(s):  
Y. Ueda ◽  
T. Kida ◽  
M. Iguchi
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Stokes Equations ◽  
Low Reynolds Number ◽  
Vortex Method ◽  
The Self ◽  
Circular Cylinders ◽  
Far Field ◽  
Flow Past ◽  
Low Reynolds

AbstractThe long-time viscous flow about two identical rotating circular cylinders in a side-by-side arrangement is investigated using an adaptive numerical scheme based on the vortex method. The Stokes solution of the steady flow about the two-cylinder cluster produces a uniform stream in the far field, which is the so-called Jeffery’s paradox. The present work first addresses the validation of the vortex method for a low-Reynolds-number computation. The unsteady flow past an abruptly started purely rotating circular cylinder is therefore computed and compared with an exact solution to the Navier–Stokes equations. The steady state is then found to be obtained for $t\gg 1$ with ${\mathit{Re}}_{\omega } {r}^{2} \ll t$, where the characteristic length and velocity are respectively normalized with the radius ${a}_{1} $ of the circular cylinder and the circumferential velocity ${\Omega }_{1} {a}_{1} $. Then, the influence of the Reynolds number ${\mathit{Re}}_{\omega } = { a}_{1}^{2} {\Omega }_{1} / \nu $ about the two-cylinder cluster is investigated in the range $0. 125\leqslant {\mathit{Re}}_{\omega } \leqslant 40$. The convection influence forms a pair of circulations (called self-induced closed streamlines) ahead of the cylinders to alter the symmetry of the streamline whereas the low-Reynolds-number computation (${\mathit{Re}}_{\omega } = 0. 125$) reaches the steady regime in a proper inner domain. The self-induced closed streamline is formed at far field due to the boundary condition being zero at infinity. When the two-cylinder cluster is immersed in a uniform flow, which is equivalent to Jeffery’s solution, the streamline behaves like excellent Jeffery’s flow at ${\mathit{Re}}_{\omega } = 1. 25$ (although the drag force is almost zero). On the other hand, the influence of the gap spacing between the cylinders is also investigated and it is shown that there are two kinds of flow regimes including Jeffery’s flow. At a proper distance from the cylinders, the self-induced far-field velocity, which is almost equivalent to Jeffery’s solution, is successfully observed in a two-cylinder arrangement.

Natural-Ventilation Flow in a 3-D Room Fitted With Solar Chimney

2012 ◽  
Author(s):  
B. P. Huynh
Keyword(s):  
Heat Flux ◽  
Flow Pattern ◽  
Natural Ventilation ◽  
Air Flow ◽  
Ventilation Rate ◽  
High Heat Flux ◽  
Solar Chimney ◽  
Solar Heat ◽  
Solar Heat Flux ◽  
Inlet Opening

Natural-ventilation flow induced in a real-sized rectangular-box room fitted with a solar chimney on its roof is investigated numerically, using a commercial CFD (Computational Fluid Dynamics) software package. The chimney in turn is in the form of a parallel channel with one plate being subjected to uniform solar heat flux. Ventilation rate and air-flow pattern through the room are considered in terms of the heat flux for two different locations of the room’s inlet opening. Chien’s turbulence model of low-Reynolds-number K-ε is used in a Reynolds-Averaged Navier-Stokes (RANS) formulation. It is found that ventilation flow rate increases quickly with solar heat flux when this flux is low, but more gradually at higher flux. At low heat flux, ventilation rate is not significantly affected by location of the inlet opening to the room. On the other hand, at high heat flux, ventilation rate varies substantially with the opening’s location. Location of the inlet opening to the room also affects strongly the air-flow pattern. In any case, ample ventilation rate is readily induced by the chimney.

Solution of Levi Civita’s Problem by Infinite Matrix Inversion

1973 ◽  
Vol 40 (1) ◽  
pp. 31-36 ◽  
Author(s):  
M. Bentwich
Keyword(s):  
Flow Pattern ◽  
Flow Direction ◽  
Leading Edge ◽  
Arbitrary Cross Section ◽  
Matrix Inversion ◽  
Infinite Matrix ◽  
Algebraic Equations ◽  
Flow Past ◽  
Linear Algebraic Equations ◽  
Wet Surface

The author proposes a new method by which one can solve for the two-dimensional irrotational fully cavitating flow past a cylinder of arbitrary cross section. Unlike the available solutions, it is in the form of two expansions each valid in part of the complex potential plane w = Φ + iΨ. The a priori unknown coefficients in the two expansions are linked by infinitely many linear algebraic equations. By inverting the associated matrix and utilizing the boundary condition, that represent the geometry of the wet surface, the coefficients in the expansions are evaluated and the solution is completed. Cases in which the wet surface is circular, the pressure along the free streamlines is constant, and the entire flow pattern is symmetric with respect to flow direction at infinity are considered in detail. Also, the well-known solution for the flow past a flat plate is compared to that obtained by the method of matrix inversion. Judging from these results, the convergence of the series appears to be very rapid. The author finally discusses the applicability of the method to cases in which the obstacle has a sharp leading edge, the pressure in the cavity is not uniform, or the flow pattern is not symmetric.

Three-dimensional flow past two stationary side-by-side circular cylinders

2022 ◽  
Vol 244 ◽  
pp. 110379
Author(s):  
Weilin Chen ◽  
Chunning Ji ◽  
Md. Mahbub Alam ◽  
Yuhao Yan
Keyword(s):  
Three Dimensional ◽  
Circular Cylinders ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Flow Past
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