Heat and fluid flow around two co-rotating cylinders in tandem arrangement (original) (raw)
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Analysis of heat and fluid flow around two co-rotating side-by-side cylinders
Sādhanā, 2019
Analysis of the heat and fluid flow around two co-rotating side-by-side cylinders is the subject of this numerical study which is done at constant Reynolds and Prandtl numbers of 200 and 7.0, respectively. Both cylinders rotate in the counterclockwise direction with an identical rotating speed (RS) in the range from 0 to 4. On the other hand, several gap spaces between the rotating cylinders such as G/D = 1.5, 2.0, and 3.0 are considered in the present study. The obtained results are validated against the available data in the open literature. Many different results have been reported in this investigation. It is observed that co-rotating the cylinders deforms the wake region downstream of both cylinders which the vortex strength of the lower cylinder against the rotation is stronger than that of the upper cylinder. On the other hand, co-rotating the cylinders develops a negative lift force on both cylinders. Finally, it was concluded that rotating the side-by-side cylinders reduces the heat transfer rate between the fluid flow and cylinders in general. At whole RS and G/D values, the heat transfer rate of the upper cylinder is realized to be less than that of the lower cylinder.
Convective heat transfer and fluid flow of two counter-rotating cylinders in tandem arrangement
Acta Mechanica, 2017
This paper discusses the forced convective heat transfer and fluid flow around two counter-rotating cylinders in tandem arrangement at a constant Reynolds number of 200. The upstream and downstream cylinders rotate in counterclockwise and clockwise directions, respectively, with an identical non-dimensional rotating speed (RS) in the range of 0 ≤ RS ≤ 4. Computations are carried out at various non-dimensional gap spaces between the cylinders such as the G/D = 1.5, 2.0, and 3.0. It is found that counter-rotating the tandem cylinders deforms the wake region downstream of both cylinders in which the vortex strength of the upstream cylinder is realized to be stronger at larger gap spaces. On the other hand, it is stated that the instabilities of the shear layer of both cylinders become maximum and minimum at RS = 1 and RS = 2, respectively. Examination of the Nusselt number distributions on the cylinders indicates that at the high RS values, more or less, all points on the each individual cylinder have identical roles in the heat dissipation rate. Finally, it is concluded that the maximum heat transfer occurs at RS = 1 for both cylinders.
Heat Transfer-Asian Research, 2018
This study presents details of the heat and fluid flow around two counter-rotating cylinders. For this goal, three different nondimensional gap spaces such as G/D = 1.5, 2.0, and 3.0 are examined in the constant Reynolds number of 200 and Prandtl number of 7.0. In addition, computations are carried out at various nondimensional rotating speeds (R.S) in the range from 0 to 4. The obtained results are validated against the available data in the open literature for stationary cases. The results showed that the flow structure, vortex shedding process, and exerted forces on the cylinders strongly depended on the R.S and G/D. Reductions of the drag coefficients are observed for both cylinders with increasing the R.S due to suppression of the wake
Analysis of flow dynamics around two rotating circular cylinders in tandem and side by side
In this paper, the flow dynamics around two rotating circular cylinders arranged in two different configurations, in turbulent and laminar regimes are analyzed through the Immersed Boundary Methodology. The Large Eddy Simulation with dynamic Smagorinsky sub-grid scale is also used here. For the side by side and in tandem configurations, the simulations are performed, for Re 100, specific rotation 0.5 and spacing ratio varying between 1.5 and 5.0. For the first arrangement, simulations are also carried out, for Re and spacing ratio constant, and the specific rotation varying between 0 and 2. For in tandem configuration, the Re ranges from 200 to 105 and the others parameters are maintained constant. The results showed that the cylinder arrangements, in addition to the mentioned parameters, play an important role in the mechanism of the vortex shedding, as well as in the wake pattern and in the fluctuations of drag and lift coefficients. The rotation mechanism inhibits the vortex shedding process for different values of spacing ratio depending on the arrangement of the cylinders. Vorticity contours, time evolutions of fluid dynamics coefficients as well as pressure distribution along the cylinder are presented.
Convective transport around two rotating tandem circular cylinders at low Reynolds numbers
Sādhanā
The convective transport around two rotating circular cylinders kept in a tandem configuration to an unconfined flow of an incompressible fluid (Prandtl number, Pr = 0.717) is investigated through two-dimensional numerical simulation. The flow Reynolds number is considered constant at Re = 100. Four different gap spacings between the tandem cylinders such as 0.2, 0.7, 1.5 and 3.0 are chosen for simulation. The cylinders are rotating about their centroidal axes for a range of dimensionless speed 0 X 2:75 ð Þ. The rotation to the objects causes the unsteady periodic flow around them to become stabilized and at some critical rotational speed, the vortex shedding stops completely resulting in a steady flow pattern. The critical speed of rotation at which the vortex shedding completely stops is a function of the cylinder spacing. Overall, it is observed that increasing the gap increases the critical rotation rate. The thermal fields are also strongly stabilized as a result of the cylinder rotation. The rotating cylinders actually create a zone in their proximity which acts like a buffer to the convective transport. The conduction mode of heat transfer predominates in these regions causing the heat transfer rate to assume a decaying pattern with increasing the rotational speed at all cylinder spacings.
Heat Transfer Research, 2010
This paper presents a numerical investigation of the characteristics of two-dimensional heat transfer in a steady laminar flow around two rotating circular cylinders in a side-by-side arrangement. The simulation is validated by comparing our computational results for the large gap-spacing between cylinder surfaces with the available numerical and experimental data for a single cylinder. Numerical simulations were carried out for the Reynolds number range 10≤Re ≤40, for the Prandtl number range 0.7≤Pr ≤50, and for a variety of absolute rotational speeds (|α|≤2.5) at different gap spacings. The study revealed that for the range of parameters considered the rate of heat transfer decreases with the increasing speed of rotation. An increase of the Prandtl number resulted in an increase in the average Nusselt number. The streamlines and isotherms are plotted for a numbers of cases to show the details of the velocity and thermal fields. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20293
Physics of Fluids
Flow-induced vibration (FIV) on two tandem cylinders with forced convection is numerically investigated at a constant Re = 150. Elastically mounted cylinder with four different values of corner radii ( r* = r/R: r = radius of fillet; R = radius of circle) = 0 (square cylinder), 0.25, 0.75, and 1 (circular cylinder) with two spacing ratio ([Formula: see text]) = 4 and 2 is studied. Transverse oscillations are generated from the cylinder having non-dimensional mass ([Formula: see text]) = 10. The structural damping coefficient is assigned a zero value with varying reduced velocity [Formula: see text]. The two-dimensional incompressible Navier–Stokes and energy equations are solved together with Newton's second law governing the motion of the cylinders. Both cylinders' surfaces are maintained at a higher constant temperature of [Formula: see text], and incoming flow is set to be at [Formula: see text] with Prandtl number (Pr) = 0.7. The effect of r* and [Formula: see text] is o...
Low Reynolds number flow characteristics for two side by side rotating cylinders
Journal of Fluids Engineering, 2015
Numerical simulations were performed for two-dimensional viscous incompressible flow past two stationary side-by-side rotating circular cylinders at Reynolds number (Re) 100 by varying center-to-center distance between the cylinders from 1.1 to 3.5 times the diameter (D) of a cylinder and different rotational speed ratio (α) = 0.5, 1.0, and 1.25. The incompressible Navier–Stokes equations were solved using consistent flux reconstruction (CFR) technique of Roy and Bandyopadhyay (2006, “A Finite Volume Method for Viscous Incompressible Flows Using a Consistent Flux Reconstruction Scheme,” Int. J. Numer. Methods Fluids, 52(3), pp. 297–319). Eight different flow regimes were observed within the investigated parametric space. An attempt has been made to characterize the different flow regimes using vorticity contours, λ2 criterion, and force coefficients. All these above stated methods confirm the existence of eight different regimes in the flow.
Influence of Rotating Speed Ratio on the Annular Turbulent Flow between Two Rotating Cylinders
Journal of Modern Physics, 2013
Rotating flows represent a very interesting area for researchers and industry for their extensive use in industrial and domestic machinery and especially for their great energy potential, annular flows are an example that draws the attention of researchers in recent years. The best design and optimization of these devices require knowledge of thermal, mechanical and hydrodynamic characteristics of flows circulating in these devices. An example of hydrodynamic parameters is the speed of rotation of the moving walls. This work is to study numerically the influence of the rotating speed ratio Γ of the two moving cylinders on the mean and especially on the turbulent quantities of the turbulent flow in the annular space. The numerical simulation is based on one-point statistical modeling using a low Reynolds number second-order full stress transport closure (RSM model), simulation code is not a black box but a completely transparent code where we can intervene at any step of the calculation. We have varied Γ from −1.0 to 1.0 while maintaining always the external cylinder with same speed Ω. The results show that the turbulence structure, profiles of mean velocities and the nature of the boundary layers of the mobile walls depend enormously on the ratio of speeds. The level of turbulence measured by the kinetic energy of turbulence and the Reynolds stresses shows well that the ratio Γ is an interesting parameter to exploit turbulence in this kind of annular flows.
LES of the flow around two cylinders in tandem
Journal of Fluids and Structures, 2008
The flow around an arrangement of two-in-tandem cylinders exhibits a remarkably complex behaviour that is of interest for many engineering problems, such as environmental flows or structural design. In the present paper, a Large Eddy Simulation using a staggered Cartesian grid has been performed for the flow around two-in-tandem cylinders of diameter D=20mm and height H=50mm submerged in an open channel with height h=60 mm. The two axes have a streamwise spacing of 2D. The Reynolds number is 1500, based on the cylinder diameter and the free-stream velocity u . The results obtained show that no vortex shedding occurs in the gap between the two cylinders where the separated shear layers produced by the upstream cylinder reattach on the surface of the downstream one. The flow separates on the top of the first cylinder with the presence of two spiral nodes known as owl-face configuration. On top of the downstream cylinder, the flow is attached. A complex mean flow develops in the gap and also behind the second cylinder. Comparisons with PIV measurements reveal good general agreement, but there are differences concerning some details of the flow in the gap between the cylinders.