Increasing Richardson Number Research Articles

Buoyancy Effect on the Wake of a Confined Circular Cylinder during Opposing Laminar Mixed Convection Heat Transfer

Particle image velocimetry (PIV) measurements are carried out in an experimental investigation of transient laminar opposing mixed convection to assess the thermal effects on the wake of an isothermal circular cylinder placed horizontally and confined inside a vertical closed-loop downward rectangular water channel. The buoyancy effect on the flow distributions are revealed for flow conditions with Reynolds number based on cylinder diameter of Re=170, blockage ratio D/H=0.287, aspect ratio, L/D=6.97 and values of the buoyancy parameter (Richardson number) of Ri=0 and 1. Results show that the wake closure length and Strouhal number slightly decrease for increasing Richardson number.

Finite element modeling of conjugate mixed convection flow of Al2O3–water nanofluid from an inclined slender hollow cylinder

Steady laminar mixed convection flow and heat transfer characteristics of Al2O3–water nanofluid about a vertical slender hollow cylinder are investigated numerically, under the effect of wall conduction. The transformed, non-dimensional, nonlinear governing equations (obtained with the Boussinesq approximation) are solved, using a robust, extensively validated, Galerkin finite element method for spherical-shaped nanoparticles with volume fraction ranging up to 4%, with associated boundary conditions. Nine-node quadrilateral finite elements are employed. Experimental models for thermal conductivity and viscosity incorporating Brownian motion terms have been taken into consideration. The influence of physical parameters, namely wall conduction parameter, Richardson number (buoyancy parameter) and nanoparticle volume fraction, on velocity profile, temperature profile and on Nusselt number is shown graphically. Excellent validation of the present numerical results has been achieved with earlier published results. Both skin friction coefficient and Nusselt number are enhanced with increasing Richardson number. With increasing inclination angle there is a decrease in average Nusselt number. Furthermore, average Nusselt number and interfacial temperature are both reduced with nanoparticle diameter. The flow is accelerated with increasing Richardson number whereas the bulk temperature is found to be suppressed. The study has important applications in thermal enhancement of solar energy systems.

Evaluation of Mixed Convection in Inclined Square Lid-Driven Cavity Filled with AL2O3/Water Nano-Fluid

To study the mixed convection flows in a square double lid-driven cavity with various inclination angles, a numerical method based on the finite volume method is used. In this investigation Al2O3/water nanofluid with particle diameter of 47 nanometers in different solid volume fractions have been utilized. Flow is obtained by the top and bottom walls, which slide in opposite direction at constant speed. The study has been conducted for the Richardson number of 0.1 to 10, Reynolds number (Re) of 1 to 100, while solid volume fraction φ of nanoparticles altered from 0 to 0.06. The heat transfer increases with increasing solid volume fraction for a constant Re. It also increases with increasing Richardson number and Reynolds number for a particular volume fraction. Also at low Reynolds number, the solid volume fraction does not have much effect on flow and heat transfer.

Numerical Investigation of Nanofluid Mixed Convection and Entropy Generation in an Inclined Ventilating Cavity

This paper presents results of a numerical study of mixed convection and entropy generation of Cu–water nanofluid in a square ventilating cavity at different inclination angles. Except a piece of bottom wall with a uniform heat flux, all of the cavity walls are insulated. The inlet port is placed at the bottom of the left wall and the outlet port is positioned at the top of the right wall. Entropy generation, Bejan number, average Nusselt number and heat source temperature have been investigated for Richardson numbers between 0.1 and 10, Reynolds numbers in the range of 1 and 300, solid volume fractions between 0 and 0.06 and cavity inclination angles between ԟ90o and 90o . The results show that the average Nusselt number increases with increasing Richardson number for cavity inclination angle of 30o , 60o and 90o but decreases with increasing Richardson number for inclination angle of ԟ30o , ԟ60o and ԟ90o . Total entropy generation and entropy generation due to heat transfer decreases with increasing Richardson and Reynolds numbers, but the Bejan number increases with increasing Reynolds and Richardson numbers.

Momentum Flux and Flux Divergence of Gravity Waves in Directional Shear Flows over Three-Dimensional Mountains

Abstract Linear mountain wave theory is used to derive the general formulas of the gravity wave momentum flux (WMF) and its vertical divergence that develop in directionally sheared flows with constant vertical shear. Height variations of the WMF and its vertical divergence are studied for a circular bell-shaped mountain. The results show that the magnitude of the WMF decreases with height owing to variable critical-level height for different wave components. This leads to continuous—rather than abrupt—absorption of surface-forced gravity waves, and the rate of absorption is largely determined by the maximum turning angle of the wind with height. For flows turning substantially with height, the wave momentum is primarily trapped in the lower atmosphere. Otherwise, it can be transported to the upper levels. The vertical divergence of WMF is oriented perpendicularly to the right (left) of the mean flow that veers (backs) with height except at the surface, where it vanishes. First, the magnitude of the WMF divergence increases with height until reaching its peak value. Then, it decreases toward zero above that height. The altitude of peak WMF divergence is proportional to the surface wind speed and inversely proportional to the vertical wind shear magnitude, increasing as the maximum wind turning angle increases. The magnitude of the peak WMF divergence also increases with the maximum wind turning angle, but it in general decreases as the ambient flow Richardson number increases. Implications of the findings for treating mountain gravity waves in numerical models are discussed.

Flushing a finite volume of dense fluid from a square street canyon by a turbulent overflow

Experimental results are presented for the shear-driven flushing of a dense fluid from a square street canyon. The flow is both qualitatively and quantitatively influenced by the density of the fluid in the canyon, which is parameterized in terms of the flow Richardson number. A total of 26 experiments were conducted for Richardson numbers ranging from 0.08 to 4.5. For low Richardson numbers the canyon remains well mixed during the flushing process and the density difference decays exponentially (as observed in previous studies flushing a neutrally buoyant tracer). As the Richardson number increases the canyon becomes more stably stratified and the decay rate reduces. For very high Richardson numbers, a two-layer stratification is observed. Over time, for the two-layer case, the lower dense layer gets thinner, indicating that dense fluid is being skimmed from the top of the layer, and less dense, indicating that ambient fluid is being mixed down into the dense layer. Previous studies only observed flushing by skimming. The layer buoyancy decreases linearly over time until the shear layer reaches the bottom of the canyon at which point the rate of layer buoyancy reduction dramatically increases. Results also indicate that the density interface is thinner than the shear layer that is driving the mixing, and that the difference in thicknesses increases with an increasing Richardson number. This result is consistent with previous studies of mixing in stratified shear flows. The initial exponential decay rate was calculated for each experiment and is given by k=1/(18+84Ri)1.21. Following the initial period of exponential decay, the decay rate increases as the stratification weakens.

Mixed convection in a lid driven square cavity with an isothermally heated square blockage inside

Laminar mixed convection characteristics in a square cavity with an isothermally heated square blockage inside have been investigated numerically using the finite volume method of the ANSYS FLUENT commercial CFD code. Various different blockage sizes and concentric and eccentric placement of the blockage inside the cavity have been considered. The blockage is maintained at a hot temperature, Th, and four surfaces of the cavity (including the lid) are maintained at a cold temperature, Tc, under all circumstances. The physical problem is represented mathematically by sets of governing conservation equations of mass, momentum, and energy. The geometrical and flow parameters for the problem are the blockage ratio (B), the blockage placement eccentricities (ɛx and ɛy), the Reynolds number (Re), the Grashof number (Gr), and the Richardson number (Ri). The flow and heat transfer behavior in the cavity for a range of Richardson number (0.01–100) at a fixed Reynolds number (100) and Prandtl number (0.71) is examined comprehensively. The variations of the average and local Nusselt number at the blockage surface at various Richardson numbers for different blockage sizes and placement eccentricities are presented. From the analysis of the mixed convection process, it is found that for any size of the blockage placed anywhere in the cavity, the average Nusselt number does not change significantly with increasing Richardson number until it approaches the value of the order of 1 beyond which the average Nusselt number increases rapidly with the Richardson number. For the central placement of the blockage at any fixed Richardson number, the average Nusselt number decreases with increasing blockage ratio and reaches a minimum at around a blockage ratio of slightly larger than 1/2. For further increase of the blockage ratio, the average Nusselt number increases again and becomes independent of the Richardson number. The most preferable heat transfer (based on the average Nusselt number) is obtained when the blockage is placed around the top left and the bottom right corners of the cavity.

Numerical study of mixed convection flow in a lid-driven cavity with sinusoidal heating on sidewalls using nanofluid

Mixed convection flow of Cu–water nanofluid inside a lid-driven square cavity with adiabatic horizontal walls and sinusoidal heating on sidewalls has been investigated numerically. The effects of increase in shear force for a fixed buoyancy force and effects of increase in buoyancy force for a fixed shear force were investigated. Effects of variations of Richardson number, phase deviation of sinusoidal heating, and volume fraction of nanoparticles on flow and temperature field were studied. The obtained results showed that for a constant Grashof number at all Richardson numbers, a clockwise eddy was developed inside the cavity, also the rate of heat transfer increases with decrease in Richardson number and increase of volume fraction of nanoparticles. For a constant Reynolds number the clockwise eddy is observed up to Ri=1. For Ri=10 a multicellular flow pattern is formed inside the cavity. Moreover it was found that when the Reynolds number is kept constant, the rate of heat transfer increases with increase in Richardson number.

Mixed convection flow and heat transfer across a square cylinder under the influence of aiding buoyancy at low Reynolds numbers

In this paper, mixed convection flow and heat transfer around a long cylinder of square cross-section under the influence of aiding buoyancy are investigated in the vertical unconfined configuration (Reynolds number, Re=1–40 and Richardson number, Ri=0–1). The semi-explicit finite volume method implemented on the collocated grid arrangement is used to solve the governing equations along with the appropriate boundary conditions. The onset of flow separation occurs between Re=1–2, between Re=2–3 and between Re=3–4 for Ri=0, 0.5 and 1, respectively. The flow is found to be steady for the range of conditions studied here. The friction, pressure and total drag coefficients are found to increase with Richardson number, i.e., as the influence of aiding buoyancy increases drag coefficients increase at the constant value of the Reynolds number. The temperature field around the obstacle is presented by isotherm contours at the Prandtl number of 0.7 (air). The local and average Nusselt numbers are calculated to give a detailed study of heat transfer over each surface of the square cylinder and an overall heat transfer rate and it is found that heat transfer increases with increase in Reynolds number and/or Richardson number. The simple expressions for the wake length and average cylinder Nusselt number are obtained for the range of conditions covered in this work.

Mixed convection from a heated semi-circular cylinder to power-law fluids in the steady flow regime

Steady mixed convection heat transfer from a heated semi-circular cylinder immersed in power-law fluids is considered here with its curved surface facing upstream. The imposed flow and the buoyancy act in the same direction thereby resulting in the so-called aiding-buoyancy configuration. The momentum and thermal energy equations have been solved numerically over the following ranges of conditions: 0 ⩽ Ri ⩽ 2 , 0.2 ⩽ n ⩽ 1.8 , 1 ⩽ Re ⩽ 30 and 1 ⩽ Pr ⩽ 100 . The combined effects of the forced and free convection on the flow and thermal fields are visualized in terms of the streamline and isotherm contours. Further insights are provided in terms of the distribution of pressure coefficient and local Nusselt number along the cylinder surface. Finally, the overall macroscopic characteristics are reported in terms of the individual and total drag coefficients and the average Nusselt number as functions of the pertinent dimensionless parameters. The influence of the power-law index is strongly modulated by the value of the Reynolds number. Broadly, drag coefficient shows a monotonic increase as the value of the Richardson number or Reynolds number increases. At low Reynolds numbers, such as Re = 1, the local value of the Nusselt number is found to be maximum at corners and for high values of the Reynolds number, it shifts towards the front stagnation point. The average Nusselt number increases with an increase in the value of the Reynolds number, Prandtl number and Richardson number. Broadly, shear-thinning viscosity facilitates heat transfer whereas shear-thickening has an adverse effect on it.

Thermal effects on the wake of a heated circular cylinder operating in mixed convection regime

AbstractThe thermal effects on the wake flow behind a heated circular cylinder operating in the mixed convection regime were investigated experimentally in the present study. The experiments were conducted in a vertical water channel with the heated cylinder placed horizontally and the flow approaching the cylinder downwards. With such a flow arrangement, the direction of the thermally induced buoyancy force acting on the fluid surrounding the heated cylinder would be opposite to the approach flow. During the experiments, the temperature and Reynolds number of the approach flow were held constant. By adjusting the surface temperature of the heated cylinder, the corresponding Richardson number ($\mathit{Ri}= \mathit{Gr}/ {\mathit{Re}}^{2} $) was varied between 0.0 (unheated) and 1.04, resulting in a change in the heat transfer process from forced convection to mixed convection. A novel flow diagnostic technique, molecular tagging velocimetry and thermometry (MTV&T), was used for qualitative flow visualization of thermally induced flow structures and quantitative, simultaneous measurements of flow velocity and temperature distributions in the wake of the heated cylinder. With increasing temperature of the heated cylinder (i.e. Richardson number), significant modifications of the wake flow pattern and wake vortex shedding process were clearly revealed. When the Richardson number was relatively small ($\mathit{Ri}\leq 0. 31$), the vortex shedding process in the wake of the heated cylinder was found to be quite similar to that of an unheated cylinder. As the Richardson number increased to${\ensuremath{\sim} }0. 50$, the wake vortex shedding process was found to be ‘delayed’, with the wake vortex structures beginning to shed much further downstream. As the Richardson number approached unity ($\mathit{Ri}\geq 0. 72$), instead of having ‘Kármán’ vortices shedding alternately at the two sides of the heated cylinder, concurrent shedding of smaller vortex structures was observed in the near wake of the heated cylinder. The smaller vortex structures were found to behave more like ‘Kelvin–Helmholtz’ vortices than ‘Kármán’ vortices, and adjacent small vortices would merge to form larger vortex structures further downstream. It was also found that the shedding frequency of the wake vortex structures decreased with increasing Richardson number. The wake closure length and the drag coefficient of the heated cylinder were found initially to decrease slightly when the Richardson number was relatively small ($\mathit{Ri}\lt 0. 31$), and then to increase monotonically with increasing Richardson number as the Richardson number became relatively large ($\mathit{Ri}\gt 0. 31$). The average Nusselt number ($ \overline{\mathit{Nu}} $) of the heated cylinder was found to decrease almost linearly with increasing Richardson number.

Unsteady wake dynamics and heat transfer in forced and mixed convection past a circular cylinder in cross flow for high Prandtl numbers

This paper investigates the combined effect of Prandtl number and Richardson number on the wake dynamics and heat transfer past a circular cylinder in crossflow using a SUPG based finite element method. The computations are carried out for 80 < Re < 180, 0.7 < Pr < 100 and 0 ⩽ Ri ⩽ 2 . The results have been presented for both forced and mixed convection flows. In the case of forced convection, crowding of temperature contours with reduced spatial spread is observed for increasing Prandtl numbers. The local and average Nusselt numbers are found to increase with increasing Reynolds number and Prandtl number. The average Nusselt number and Colburn factor are found to vary as Re 0.548 Pr 0.373 and Re −0.452, respectively. The extrapolated results of the average Nusselt number for low and high Reynolds numbers are found to match quite well with the available results in literature. Effect of Prandtl number shows various interesting phenomena for the mixed convective flows. Increasing the Prandtl numbers resulted in decreasing deflection and strength in the wake structures. The effect of baroclinic vorticity production during vortex shedding has been demonstrated at the vicinity of the cylinder and near wake. The Strouhal number is found to decrease with increasing Prandtl number, in the case of buoyancy induced flow. The effect of increasing Prandtl number is manifested as the stabilizing effect in the flow. This is, perhaps, the first time that such behavior for the Prandtl number is being reported. Additionally it is observed that the average Nusselt number decreases with increasing Richardson number.

The effect of stable stratification and thermophoresis on fine particle deposition in a bounded turbulent flow

Small inertial particle transfer and deposition in a thermally stratified turbulent channel flow is studied by large eddy simulation. The Lagrangian tracking approach is used to describe the dynamics of particles. The objective of this study is to examine the influences of thermal stratification and the thermophoresis on the preferential concentration and deposition of small particles with different particle relaxation time scales. The diameters of particle are ranged from 0.6μm to 5μm. Numerical results show that the thermophoresis strengthens the deposition of particles near the cold wall while it weakens the deposition near the hot wall. With the Richardson number increases, the particle mean velocity increases regularly in the core of the channel, and the particle fluctuation intensities decrease due to the re-laminarization tendency of stably stratified turbulent boundary layer. The magnitude of the thermophoretic force on particles decreases in the stable stratified flow, which results in smaller deposition rate with increasing the Richardson number.

Effects of buoyancy on turbulent premixed V-flames by large-eddy simulation

Buoyancy effects on turbulent premixed V-flames are investigated under normal gravity (+g) and reversed gravity (–g). Numerical simulations employ large eddy simulation (LES) with a dynamic model for sub-grid scale stress. With the assumption of fast chemistry combustion, a progress variable c-equation is applied to describe the flame front propagation. The equations are solved using a projection-based fractional step method in two dimensions for low-Mach number flows. Computed LES results of buoyancy effects on flame angle and flame brush thickness are consistent with those obtained from experiments. In both +g and –g conditions, the effects of buoyancy become important with increase in Richardson number (Ri). Buoyancy force tends to close up the flame under +g, but has the opposite effect under –g. Buoyancy force also suppresses flame wrinkling in +g and enhances wrinkling in –g. While there is a lack of experimental data available, computed axial velocity is shown to be significantly affected by buoyancy downstream from the flame holder under moderate Reynolds number.

Numerical study of the fin effect on mixed convection heat transfer in a lid-driven cavity

In this study, the mixed convective heat transfer in a lid-driven cavity was investigated numerically. The finite volume discritization method was used to solve the momentum and energy equations by using the classic Boussinesq incompressible approximation. The cavity vertical walls are insulated whereas the bottom (hot wall) and top (cold wall) surface are maintained at a uniform temperature and fins are located on bottom wall. The effect of fin numbers over the flow field and heat transfer was investigated at various Richardson numbers. Study was carried out for Richardson numbers ranging from 0.01 to 10, fin numbers between 1 and 7, fin height ratio change from 0.05 to 0.3, and thermal conductivity ratio (fin to fluid) from 10 to 104, respectively. The results are presented in the form of streamlines, temperature contours, and Nusselt number distributions. The results show that the Nusselt number increases when the number of fin and fin height decrease. In addition, in all cases an increasing Richardson number caused increasing the relative Nusselt number ( Nu / Nu0). The heat transfer enhancement was observed at low fin numbers (1 and 3) and high Richardson number in comparison with the cavity without fins.

Wake Flow and Heat Transfer Due to a Spherical Viscous Droplet

A numerical study on the buoyancy-assisted flow and heat transfer from a liquid spherical droplet falling in fluid medium is made. The investigation is based on the solution of the Navier-Stokes equations together with the energy equation inside and outside the droplet, along with a suitable interface condition. The governing equations for three-dimensional flow and heat transfer are solved through the pressure correction based iterative algorithm, SIMPLE. The Reynolds number for the exterior flow is considered below 300 with the Richardson number in the range 0 ≤ Ri ≤ 1.5. The form of the wake due to the viscous droplet and its influence on heat transfer and drag coefficient are analyzed for a wide range of physical parameters. It is found that by increasing the Reynolds number, the predicted rate of heat transfer is significantly increased for a liquid droplet compared to a solid sphere. The increment of viscosity of the droplet increases the drag experienced by the droplet but reduces the rate of heat transfer. An increase in Richardson number produces an increment in drag coefficient as well as in heat transfer. In order to establish a simplified model for heat transfer due to a viscous droplet, we compared our computed solutions with several empirical correlations for conjugate heat transfer and proposed a model (in absence of buoyancy). We have also investigated the validity of several empirical correlations for the drag coefficient.

Transition to turbulence in the wake of a fixed sphere in mixed convection

The thermal effect on axisymmetry breaking and transition to turbulence in the wake of a fixed heated sphere is investigated in the mixed convection configurations commonly known as ‘assisting’ and ‘opposing’ flows in which the buoyancy tends, respectively, to accelerate and decelerate the flow. The study is carried out in the Ri–Re parameter plane (Ri being the mixed convection parameter – the Richardson number) for two values of Prandtl number – 0.72 (≈air and many gases) and 7 (≈water). We show that convection affects considerably the transition (as compared to that observed in the wake of an unheated sphere) even at moderate Richardson numbers. The latter are taken to be positive in assisting flow and negative in opposing one. In this notation, it can be said that convection shifts the primary-instability threshold to higher Reynolds numbers with increasing Richardson number. In assisting flow, the primary bifurcation is always regular, but at Ri ≥ 0.6 it appears in azimuthal subspaces associated with higher azimuthal wavenumbers m &gt; 1. The transition scenario is characterized by a large variety of regimes explainable by nonlinear interactions between different azimuthal subspaces. On the side of higher (positive) Richardson numbers the axisymmetric flow is found stable up to Re = 1400 at Pr = 0.72 and Ri = 0.7. In opposing flow, the m = 1 subspace is always the most unstable, but the regular bifurcation gives way to a Hopf one at Ri &lt; −0.1. Close to the junction of both bifurcations a similar variety of regimes precedes the transition to chaos as in assisting flow. On the side of negative Richardson numbers the primary (Hopf) bifurcation threshold is found as low as Re = 100 at Ri = −0.25 and at both investigated Prandtl numbers. After a primary periodic regime characterized by vortex shedding with a symmetry plane, the transition proceeds via a series of increasingly irregular helical regimes.

Destratification by Mechanical Mixers: Mixing Efficiency and Flow Scaling

Experiments have been performed to assess the efficiency of mechanical mixers in destratifying water bodies. The effects of Reynolds number, physical scale, and Richardson number were all considered. The results demonstrated that the variation of mixing efficiency with Richardson number was well described by two different power-law regimes. At low Richardson numbers, the efficiency increased with increasing Richardson number. Above a critical value, however, the efficiency decreased rapidly with further increases in Richardson number. The experiments further showed that, over the range of Reynolds numbers considered, the results collapsed fairly well. Finally, experiments at different physical scales showed reasonable agreement. The main conclusion of the present technical note is that the destratification efficiency of mechanical mixers can be well parameterized by an overall Richardson number. The results, however, are specific to the particular geometric configuration studied. It is hoped that the present technical note will help to guide future studies of destratification systems in small lakes and reservoirs and fluid mixing in the chemical and process industries.

Linear stability analysis of inclined two-layer stratified flows

Two-layer stratified flows are commonly observed in geophysical and environmental contexts. At the interface between the two layers, both velocity shear and buoyancy interplay, resulting in various modes of instability. Results from a temporal linear stability analysis of a two-layer stratified exchange flow under the action of a mean advection are presented, investigating the effect of a mild bottom slope on the stability of the interface. The spatial acceleration is directly included in the governing stability equations. The results demonstrate that increasing the bottom slope has a similar effect on the stability of the flow as does increasing the ratio R of the thickness of the velocity mixing layer δν to that of the density layer δρ as it causes the flow to be more unstable to the Kelvin–Helmholtz instabilities. The transition from Kelvin–Helmholtz modes to stable flow occurs at lower Richardson numbers and wavenumbers compared to the horizontal two-layer flow. Kelvin–Helmholtz modes are decreasingly amplified for 1&amp;lt;R&amp;lt;2. When 2&amp;lt;R&amp;lt;2, Kelvin–Helmholtz modes are first amplified and then damped as the Richardson number increases. This suggests that the behavior of the Richardson number alone is not sufficient to predict the stability tendency of the interface.

Effect of buoyancy on the wakes of circular and square cylinders: a schlieren-interferometric study

Wakes behind heated cylinders, circular, and square have been experimentally investigated at low-Reynolds numbers. The electrically heated cylinder is mounted in a vertical airflow facility such that buoyancy aids the inertia of main flow. The operating parameters, i.e., Reynolds number and Richardson number are varied to examine flow behavior over a range of experimental conditions from forced to mixed convection regime. Laser schlieren-interferometry has been used for visualization and analysis of flow structures. Complete vortex shedding sequence has been recorded using a high-speed camera. The results on detailed dynamical characteristics of vortical structures, i.e., their size, shape and phase, Strouhal number, power spectra, convection velocity, phase shift, vortex inception length, and fluctuations are reported. On heating, alteration of organized (coherent) structures with respect to shape, size and their movement is readily perceived from instantaneous Schlieren images before they reduce to a steady plume. For both cylinders, Strouhal number shows a slow increase with an increase in Richardson number. At a critical value, there is complete disappearance of vortex shedding and a drop in Strouhal number to zero. The corresponding spectra evolve from being highly peaked at the vortex shedding frequency to a broadband appearance when vortex shedding is suppressed. The geometry of vortex structures transforms to a slender shape before shedding is suppressed. At this heating level, absence of multiple peaks in power spectra at cylinder centerline indicates absence of interaction between opposite shear layers. The convection velocity of vortices increases in stream wise direction to an asymptotic value and its variation is a function of Richardson number. The convection speed abruptly falls to zero at critical Richardson number. The phase difference of shed vortices between upstream and downstream location increases with an increase in Richardson number. Velocity profiles show an increase in fluid speed and beyond the critical point, buoyancy forces add enough momentum to cancel momentum deficit due to the cylinder. Overall, the combined effect of temperature gradient on the separating shear layer velocity profile in near field and vortical structures interaction in far field influences wake instability of a heated cylinder.