Heat transfer from a cylinder in the wake flow (original) (raw)
Related papers
The present work is an initiative towards improving heat transfer and reducing drag for the case of flow past cylinder by utilizing triangular wake splitter. Flow past circular cylinder and cylinder with triangular and rectangular wake splitter has been studied for low Reynolds number 5, 20, 40, 50, 60, 80, 100,200. Flow and thermal analyses were performed for the case of constant wall temperature. Length of wake splitter in both configurations is taken to be equal to diameter of cylinder. Fluent 6.2.16 is used for the purpose of analysis. An incompressible SIMPLEC finite volume code employing a non-staggered grid arrangement is used. Second order upwind scheme is used for convective terms. Time discretization is implicit and a Second order Crank-Nicholson scheme is employed. Effect of wake splitter on wake formation, vortex generation, Nusselt number, heat transfer has been numerically studied and variations have been plotted. Validation has been carried out for average Nusselt number on single cylinder for Reynolds number 200 and results were found to be in good agreement with available experimental and numerical work. Heat transfer with drag coefficient 8% lower compared to bare cylinder. Performance of triangular wake splitter has been found to be similar to rectangular wake splitter. Results point triangular wake splitter has been found to be 17% more and towards cylinder with triangular wake splitter being more efficient than other configurations.
JSME International Journal Series B, 2004
This paper describes the unsteady and three-dimensional characteristics of heat transfer from a circular cylinder to the cross-flow of air for Reynolds numbers from 120 to 30 000. An infrared camera was used to measure the time-spatial characteristics of heat transfer on the cylinder surface, heated under a condition of constant heat flux. Fluctuating heat transfer was measured using a heat flux sensor. The heat transfer in the separated flow region had a spanwise nonuniformity, the wavelength of which agreed well with that of the streamwise vortices formed in the near-wake. In particular, the streamwise vortices formed at approximately Re = 200 due to "mode-A" instability effectively enhanced the heat transfer at the rear of the cylinder. For Reynolds numbers greater than 6 000, the heat transfer at the rear face was markedly increased by the alternating reattaching flow, caused by the rolling-up of the separated shear layers.
International Journal of Heat and Mass Transfer, 2014
In this paper, a numerical investigation is performed to study the mixed convective flow and heat transfer characteristics past a square cylinder in cross flow at incidence. Utilizing air (Pr = 0.71) as an operating fluid, computations are carried out at a representative Reynolds number (Re) of 100. Angles of incidences are varied as, 0°6 a 6 45°. Effect of superimposed positive and negative cross-flow buoyancy is brought about by varying the Richardson number (Ri) in the range À1.0 6 Ri 6 1.0. The detail features of flow topology and heat transport are analyzed critically for different angles of incidences. The thermo fluidic forces acting on the cylinder during mixed convection are captured in terms of the drag (C D), lift (C L), and moment (C M) coefficients. The results show that the lateral width of the cylinder wake reduces with increasing a and the isotherms spread out far wide. In the range 0°< a < 45°, C D reduces with increasing Ri. The functional dependence of C M with Ri reveals a linear relationship. Thermal boundary layer thickness reduces with increasing angle of incidences. The global rate of heat transfer from the cylinder increases with increasing a.
Fluid Flow and Heat Transfer Around Semi-Circular Cylinder: A Review
2017
Fluid Flow around bluff bodies such as circular, elliptical, square, semi-circular and triangular cylinders was being studies well from several years and there are extensive literatures available on the fluid flow around a circular cylinder because of its practical importance in hydrodynamics and aerodynamics applications and the fundamental significance in the flow physics. On the other hand, semi-circular cylinders are now being studies because of its fluid dynamic features that offers strong engineering applications and tremendous fundamental importance. Fluid flow around a semi-circular cylinder have some practical applications in electronic cooling, heat exchange systems, processing of foodstuffs, etc. The literature available on flow over semi-circular cylinder deals mainly the following parameters i.e. boundary layer separation, forces such as drag and lift and characteristics of the wake region, the nature of the vortex street, the flow separation phenomenon, Nusselt number ...
International Journal of Heat and Mass Transfer, 2020
Three-dimensional direct numerical simulations have been performed to study the influence of gap-ratio (G/D) on wake transition and heat transfer from a square cylinder placed near a moving wall. Value of G/D is varied from 0.1 to 4. Three different values of Re = 160, 180 and 200 are considered, which are slightly less than the critical Re for different flow transitions corresponding to a free-stream flow past a square cylinder. With a decrease in G/D, the transition from one flow regime to another takes place at lower values of Re compared to a free-stream flow. At Re = 160, with a decrease in G/D, an onset of three-dimensionality with the presence of vortex dislocations in flow takes place due to an acceleration of flow in the gap. With a further decrease in G/D, dislocations are suppressed and Mode A only is present in the flow. At G/D = 0.4, streamwise vortices of wavelength 2.5D, called Mode S, appear in flow. These vortices show period doubling phenomenon. For G/D 0.3, three-dimensionality in flow occurs due to interaction of shear-layers formed near the cylinder and moving wall. At low values of G/D, an initial transition occurs from two-dimensional steady state to three-dimensional steady state. Variations in Nusselt number with G/D and Re in the spanwise direction and along the surfaces of the cylinder have been studied. Variation in the global Nusselt number on the cylinder surfaces with G/D can be divided in three parts. For G/D ! 0.5, Nu increases with a decrease in G/D and is maximum at G/D % 0.5. For 0.5 G/D 0.3, it decreases with G/D and is minimum at G/D % 0.3. For G/D 0.3, it again increases with a decrease in G/D. Influences of G/D and Re on force coefficients and Strouhal number (St) are examined. With an increase in Re, the drag coefficient increases and decreases at high and low values of G/D, respectively.
International Journal of Thermal Sciences, 2018
In this paper, a two-dimensional numerical simulation is carried out to understand the effect of confinement (blockage ratio β) on fluid flow and forced convective heat transfer characteristics past a blunt headed cylinder. Utilizing air as an operating fluid, flow simulations are carried out for wide ranges of blockage ratios ≤ ≤ () β 1 10 1 3 and Reynolds numbers ≤ ≤ (60 Re 200). The flow characteristics and heat transport are analysed critically for different β. The functional dependence of C D (Drag Coefficient) and C L (Lift Coefficient) on blockage ratio is examined. It has been found that C D reduces with increasing Re, while the Strouhal number and the average Nusselt number show an increasing trend when the blockage ratio is increased. The average Nusselt number also increases with increasing Re.
STUDY OF TURBULENT FLOW DOWNSTREAM FROM A LINEAR SOURCE OF HEAT PLACED INSIDE THE CYLINDER WAKE
iaeme
A turbulent flow downstream from a linear source of heat placed inside the cylinder wake has been studied numerically in this paper. Special attention has been paid to the cylinder wake effect on the source of heat diffusion in downstream flow. The turbulent model has been applied a standard - two equations model and the two-dimensional Reynolds Averaged Navier–Stokes (RANS) equations are discretized with the second order upwind scheme. The SIMPLE algorithm, which is developed using control volumes, is adopted as the numerical procedure. Calculations were performed for a wide variation of the Reynolds numbers. The investigations reveal that with increasing Reynolds number, the instabilities appear in the wake zone, showing an oscillatory flow, also called von Karman Vortex Street. His geometry has an important influence on the thermal field and the diffusion process. Comparison of numerical results with the experimental data available in the literature is satisfactory.
Flow over and forced convection heat transfer around a semi-circular cylinder at incidence
International Journal of Heat and Mass Transfer, 2012
Wake dynamics and forced convective heat transfer characteristics past a semi-circular cylinder at incidence have been investigated numerically. Utilizing air as an operating fluid computations are carried out for wide ranges of the Reynolds number (80 6 Re 6 180) and angle of incidences (0 6 a 6 180°). Angle of incidence reveals three flow separation zones. Structure properties of shear layer and vortex motions on each flow separation zones are analyzed critically. Functional dependence of drag (C D), lift (C L), and moment (C M) coefficients on the angle of incidence is explored and analyzed in detail. Increase in angle of incidence increases streamline curvature. A structural similarity is observed between the contours of vorticity and the corresponding isotherms. Strouhal number shows a decreasing trend up to certain values of a and thereafter it increases marginally. A new correlation of Strouhal number as a function of Re and a has been established for the present range of Reynolds numbers. At the singularity points a sudden jump in local Nusselt number distribution is observed. The trend of variation of average Nusselt number with a is similar to that of Strouhal number variation. The average Nusselt number is found to vary as Re 0:529 ð1 þ aÞ À0:0476 .
Analysis of low Reynolds number flow around a heated circular cylinder
Journal of Mechanical Science and Technology, 2009
The objective of this study is to investigate the forced convection from and the flow around a heated cylinder. Experimental and computational results are presented for laminar flow around a heated circular cylinder with a diameter of 10 mm. The experiments were carried out using Particle Image Velocimetry (PIV) in a wind tunnel, and numerical simulations using an in-house code and a commercial software package, FLUENT. This paper presents comparisons for vorticity and temperature contours in the wake of the cylinder. Experimental and computational results are compared with those available in the literature for heated and unheated cylinders. An equation is suggested for a temperature-dependent coefficient defining a reference temperature to be used in place of the constant used in other studies. An attempt is also made to correct differences between average cylinder surface temperature and measured interior temperature of the cylinder.