Buoyancy Strength Research Articles

Simulations of local heat islands in Zürich with coupled CFD and building energy models

Due to the urban heat island (UHI) effect the air temperatures in urban areas are most of the time higher compared to the temperatures in rural areas. Further the wind speeds are lower due to wind sheltering. In the past decades cities and therefore also the urban heat islands have been continuously growing. The local microclimate has a strong impact on the energy demand of buildings and the human comfort and health. Only few guidelines exist for urban planners to mitigate UHI effects or its impacts. This study aims at simulating the effect of new buildings on the local urban microclimate for a building site in Zürich (Switzerland). One-way coupled CFD and building energy simulations are conducted to determine the increase in air and surface temperatures due the presences of new buildings. The daytime local air temperatures for weather conditions with high ambient air temperatures, which are considered to be most critical for thermal comfort, are studied. The results show that the formation of local hot spots strongly depend on the building geometries, building materials, the strength of buoyancy and the wind directions and wind speeds.

Transient mixed convection heat transfer for opposing flow from two discrete flush-mounted heaters in a rectangular channel of finite length: Effect of buoyancy and inclination angle

An experimental investigation in a vertical rectangular channel using water as the working fluid is carried out to study the transient laminar opposing mixed convection heat transfer from two flush-mounted, symmetric and discrete heat sources subjected to a constant wall heat flux boundary condition while the other bounding walls are insulated and adiabatic. The experiments are done under different values of buoyancy strength or modified Richardson number Ri∗ = Gr∗/Re2, Reynolds number of 300 ≤ Re ≤ 900 and channel inclination of 0° ≤ γ ≤ 90°. From experimental measurements, surface temperature distributions and averaged Nusselt number for each heat source are obtained. In general, for a fixed value of the buoyancy parameter, the averaged Nusselt number increases for increasing values of the Reynolds number. In the vertical channel configuration, it is observed that for fixed values of Re and high Ri∗ number, because buoyancy acts directly against convective flow, higher heat transfer rates are achieved. As the duct approaches the horizontal configuration, buoyancy strength is reduced and the averaged Nusselt number decreases for decreasing values of the inclination angle with marked variations. Here, the effect on the heat transfer rates is more pronounced at γ = 60° for low Ri∗. For the horizontal configuration, because buoyancy only acts indirectly, higher threshold values of Ri∗ are required to induce instability. The results show that for relatively large values of buoyancy strength, the surface temperature presents strong spanwise and axial variations, and for all of the inclination angles considered in this study, the values of the surface temperatures achieve higher values at the middle spanwise positions of both heaters than those registered at other spanwise locations. This indicates that because of the secondary three-dimensional flow, heat transfer augmentation takes place close to the channel corners while the higher surface temperatures and hence, lower heat transfer rates are achieved at the centerline of the discrete heat sources.

Effects of buoyancy and inclination for opposing mixed convection in a symmetrical heated duct with a plane symmetric sudden contraction–expansion

In this work, transient laminar opposing mixed convection is studied experimentally in an open vertical rectangular channel configuration with plane symmetric forward–backward facing steps located at the middle of the test section with uniform heat flux imposed to the lateral walls of each step while the other bounding walls are treated as adiabatic surfaces. The effect of opposing buoyancy and the geometrical configuration of partial blockage on the heat transfer behavior for the double stepped wall is analyzed for a Reynolds number of 300⩽Re⩽900, channel inclination of 0°⩽γ⩽90°, and different values of buoyancy strength or modified Richardson number. From experimental measurements, space-averaged surface temperatures and overall Nusselt number of each simulated electronic chip are obtained for a wide range in the parametric space. Also, phase-space plots of the self-oscillatory system, characteristic times of temperature oscillations and spectral distribution of the fluctuating energy are presented. Results show that for relatively large values of buoyancy strength, strong three-dimensional secondary flow oscillations develop in the axial and spanwise directions. The temperature measurements show that for a fixed value of the modified Richardson number, there is not a linear dependence between the duct orientation and the heat transfer rates achieved. Also, when the duct is inclined with respect to the horizontal, the right (upper) and left (lower) oscillating vortical structures present large and small amplitude thermal fluctuations, respectively. In addition, it is pointed out that the highest flow reversal takes place at the channel corners of the upper heater block, and that higher surface temperatures are reached at the centerline of the latter. The analysis brings out the significance of the three-dimensional configuration of the vortical structure and how the buoyancy induced secondary flow is affected by the partial blockage.

Steady and oscillatory laminar opposing mixed convection in a vertical channel of finite length subjected to symmetrical isothermal discrete heat sources

Transient laminar opposing mixed convection in a gravity driven downward flow confined inside a vertical rectangular channel has been investigated, with both walls suddenly subjected to symmetrical isothermal heat sources over a finite portion of the channel walls. The unsteady two-dimensional Navier-Stokes and energy equations have been solved numerically for a wide parametric set. Studies are carried out for Reynolds numbers of 100 and 200 and several values of buoyancy strength or Richardson number. The effect of Reynolds number and opposing buoyancy on the temporal evolution of the overall flow structure, temperature field, and Nusselt number from the heated surfaces is investigated using fixed geometrical parameters and considering heat losses to the channel walls. In this parameter space, for a given Reynolds number and relatively small values of the buoyancy parameter, the transient process leads to a final symmetric or asymmetric steady-state. However, as the value of buoyancy strength increases, the flow and temperature fields become more complex and an oscillatory flow with a fundamental frequency sets in when a critical value of the Richardson number is reached. Numerical predictions show that the critical value of the Richardson number between the two regimes strongly depends on the value of the Reynolds number, and the time scales, natural frequencies, and phase-space portraits of flow oscillation are presented and discussed in detail. Stability of the symmetric response has been analyzed. The results include the effects of Prandtl number and heat losses to the channel walls on the evolution of the final flow and thermal responses.

A GLOBAL RELATION OF FIRE SMOKE RE-CIRCULATION BEHAVIOUR IN URBAN STREET CANYONS

Street canyon, formed by buildings along two sides of a road, is an important and ubiquitous architectural element in the metropolises. When a fire occurs in an urban street canyon, a critical serious phenomenon is found to happen where the uprising fire smoke is re-circulated back into the base of the street canyon by the wind flow beyond a critical velocity. Theoretical analysis is derived based on Froude number (Fr), by balancing the inertial force of the wind flow to the buoyancy strength of the fire smoke. It is found that the critical re-circulation wind velocity is proportional to an integrated global parameter . Large Eddy Simulations (LES) are carried out by Fire Dynamics Simulator (FDS). The critical Froude number (Fr) is found to be about 0.7~0.8. The simulation results are well collapsed by the generalized theoretical relation. It is further revealed that the non-dimensional critical re-circulation wind velocity . against aspect ratio of street canyons in the skimming flow pattern (W/H < 1.43) falls into two behavioural regimes, where it firstly increases then remains constant with the increase in street canyon aspect ratio (W/H) with a turning point at W/H = 1. A global non-dimensional relation is finally achieved for the critical re-circulation wind velocity (u), fire heat release rate (Q) and its height (H) to the top of the street canyon as well as the street canyon aspect ratio (W/H).

Numerical study on buoyancy and inclination effects on transient laminar opposing mixed convection in rectangular channels with symmetric and discrete heating

Detailed numerical simulations are carried out for transient laminar opposing mixed convection in a rectangular inclined channel with both walls suddenly subjected to discrete isothermal flush-mounted heat sources simulating electronic components. Using the vorticity-stream function formulation of the unsteady two-dimensional Navier–Stokes and energy equations, the governing equations are solved numerically using the control volume method. Simulations are performed for fixed values of the geometrical parameters, Reynolds number of Re=500, Prandtl number of Pr=7 and channel inclination of 0°⩽γ⩽90°. Results illustrate the effects of buoyancy strength or Richardson number Ri=Gr/Re2 and channel inclination angle on the overall flow structure and nondimensional heat flux (Nusselt number) from the heated slabs. It is found that for the horizontal configuration (γ=0°), due to the indirect effect of buoyancy, much higher threshold values of buoyancy strength are required for the appearance of the recirculation flows that take place downstream of the heated slabs. However, for increasing values of the inclination angle, vortex migration to higher positions inside the channel occurs and higher heat transfer rates are obtained. In addition, transition from steady to time-periodic flow takes place for values of the buoyancy parameter larger than a critical one, and the threshold value between the two regimes strongly depends on the value of the Reynolds number and channel orientation. The results include the effects of Reynolds and Prandtl numbers along with heat losses to the channel walls on the evolution of the final flow and thermal response.

A unifying framework for parameterizing stably stratified shear-flow turbulence

An alternative framework for parameterizing stably stratified shear-flow turbulence is presented. Using dimensional analysis, four non-dimensional parameters of interest are identified that consider the independent effects of stratification, shear, viscosity, and scalar diffusivity. In the interest of geophysical applications, the problem is further simplified by considering only high Reynolds number flow. This leads to a two-dimensional parameter space based on a buoyancy strength parameter (i.e., an inverse Froude number) and a shear strength parameter. Consideration for the gradient Richardson number allows the space to be divided into an unforced regime, a shear-dominated regime, and a buoyancy-dominated regime. On this basis, a large database of direct numerical simulation and laboratory data from various sources is evaluated. Of particular interest is the observed length scale of overturning. Overturns are found to scale with k1/2/N in the buoyancy-dominated regime, k1/2/S in the shear-dominated regime, and k3/2/ε in the unforced regime, where k, N, S, and ε are the turbulent kinetic energy, buoyancy frequency, mean shear rate, and turbulent kinetic energy dissipation rate, respectively. Implications for estimates of diapycnal mixing in the ocean are discussed and a new parameterization for eddy diffusivity is presented.

Multiple thermal and moisture removals from the moving plate opposite to the impinging slot jet

This study presents the numerical model of convective heat and moisture transfer of an impinging jet with a moving plate, taking thermal buoyancy effects into account by the formulation of Boussinesq approximation. Effects of thermal buoyancy strength (Gr), separation between slot and plate (H), impingement jet flow speed (Vjet), and the plate moving speed (Um) on the heat and moisture transport have been investigated. Contours of stream-function, heat-function and moisture-function, skin friction coefficient, and heat and moisture transfer rates are presented and analyzed for different flow situations. Multiple steady flow solutions are observed through continuously changing the impingement jet flow speed or varying the moving speed of the plate. In the regime of forced convection dominated flow, natural solution obtained from the rest state is coinciding with upward solution as Um < 1. In the heat transfer driven flow dominated regime, two flow solution branches are observed within the range of 0.4 ≤ Vjet ≤ 1.6, whereas three solution branches are obtained and the upward solutions are sustained only at the range of Um ≤ 0.7. The present researches will benefit the optimization design and operation control of cooling and drying systems with moving belts.

Relevance of the Thorpe length scale in stably stratified turbulence

Direct numerical simulations of stably stratified turbulence are used to compare the Thorpe overturn length scale, LT, with other length scales of the flow that can be constructed from large-scale quantities fundamental to shear-free, stratified turbulence. Quantities considered are the turbulent kinetic energy, k, its dissipation rate, ε, and the buoyancy frequency, N. Fundamental length scales are then the Ozmidov length scale, LO, the isotropic large scale, Lkε, and a kinetic energy length scale, LkN. Behavior of all three fundamental scales, relative to LT, is shown to be a function of the buoyancy strength parameter NTL, where TL = k/ε is the turbulence time scale. When buoyancy effects are dominant (i.e., for NTL &amp;gt; 1), LT is shown to be linearly correlated with LkN and not with LO as is commonly assumed for oceanic flows. Agreement between LO and LT is only observed when the buoyancy and turbulence time scales are approximately equal (i.e., for the critical case when NTL ≈ 1). The relative lack of agreement between LT and LO in strongly stratified flows is likely due to anisotropy at the outer scales of the flow where the energy transfer rate differs from ε. The key finding of this work is that observable overturns in strongly stratified flows are more reflective of k than ε. In the context of oceanic observations, this implies that inference of k, rather than ε, from measurements of LT is fundamentally correct when NTL ≈ 1 and most appropriate when NTL &amp;gt; 1. Furthermore, we show that for NTL &amp;lt; 1, LT is linearly correlated with Lkε when mean shear is absent.

A new mathematical quantification of wind-blown flame tilt angle of hydrocarbon pool fires with a new global correlation model

A new mathematical methodology is brought forward in this paper to objectively quantify the flame tilt angle based on flame appearance intermittency spatial distribution obtained from the flame images series recorded in the experiments, in counteracting the uncertainty in traditional method due to the fact of extensive vibration nature of the flame in a wind. The flame tilt angle is determined based on a proposed sum function of the product of multiplication of p(x, y) as probability of flame appearance at each pixel, by D(x, y) as perpendicular distance from the pixel to a threshold line originated from the flame base center. The flame tilt angle is solved mathematically as the angle of the threshold line when the above sum function at the two sides of the threshold line in the flame intermittency distribution contour are early equal. Experiments are carried out for ethanol and heptane square pool fires with dimensions of 10cm, 15cm, 20cm and 25cm in wind speed of 0–2.5m/s. The tilt angles of the flames in the experiments determined by above mathematical method are compared with previous models reported in the literatures. A new dimensionless global parameter, equating the wind speed by a characteristic uprising velocity of the flame supported by the buoyancy strength of the pool fire, is further proposed, which is shown to better converge and correlate the flame tilt angle data than previous models.

Transient flows in enclosures: A generalised approach for modelling the effects of geometry, heat gains and wind

Transient flows in a confined ventilated space induced by a buoyancy source of time-varying strength and an external wind are examined. The space considered has varying cross-sectional area with height. A generalised theoretical model is proposed to investigate the flow dynamics following the activation of an external wind and an internal source of buoyancy. To investigate the effect of geometry, we vary the angle of the wall inclination of a particular geometry in which a point source of constant buoyancy is activated in the absence of wind. Counter-intuitively the ventilation is worse and lower airflow rates are established for geometries of increasing cross-sectional areas with height. We investigate the effect of the source buoyancy strength by comparing two cases: (1) when the buoyancy input is constant and (2) when the buoyancy input gradually increases over time so that after a finite time the total buoyancy inputs for (1) and (2) are identical. The rate at which the source heat gains are introduced has a significant role on the flow behaviour as we find that, in case (2), a warmer layer and a more pronounced overshoot are obtained than in case (1). The effect of assisting and opposing wind on the transient ventilation of an enclosure of constant cross-sectional area with height and constant heat gains is examined. A Froude number Fr is used to define the relative strengths of the buoyancy-induced and wind-induced velocities and five different transient states and their associated critical Fr are identified.

The dynamics of two interacting compositional plumes

The dynamics of two compositionally buoyant columns of fluid rising in an infinite less buoyant fluid is studied. The fluid within and outside the columns is thermally stably stratified and has a kinematic viscosity, ν, and a thermal diffusivity, κ. The mean vertical flow and the associated temperature profiles depending on the horizontal coordinate normal to the surfaces of the columns are obtained and the associated buoyancy, heat and material fluxes are discussed. The stability of the mean state to infinitesimal disturbances is governed by the five dimensionless parameters: the number R (=UL/ν, where U and L are characteristic velocity and length, respectively) which measures the strength of the compositional buoyancy, the dimensionless measures of the thickness of the two plumes and the distance between them, respectively, and Γ representing the ratio of the strengths of the two plumes. The stability is examined for small values of R. The preferred mode of instability is studied in the space (, Γ). When a single plume is present (and x 1, d, Γ = 0), it is already known that the perturbations are neutral at O(R 0) and linearly unstable at O(R 1) for all values of x 0 and Prandtl number, σ(=ν/κ). It is shown here that at , the presence of a second interacting plume has the significant effect that the system of two plumes becomes unstable for a certain range of the parameters while it remains neutrally stable for the others. In contrast with the instability of the single plume, the instability of the two interacting plumes does not depend, at the level, on the Prandtl number of the fluid. However, the neutrally stable two plumes might suffer instability at and that instability may depend on the Prandtl number. The instability is found to be driven by the gradients of all of the concentration of light material, the flow and temperature of the basic state. The presence of the second plume destroys the definite parity of the perturbations' solution and this can lead to non-zero total helicity.

Visualization of Mixed Convective Rolls of a Slot Jet in a Fluid-Superposed Metallic Porous Foam Heated from below

Flow visualization and numerical study of a slot jet in a horizontal channel partially filled with FeCrAlY foam is carried out to observe the flow structure under buoyancy effect. The flow patterns in the fluid region for different jet velocity (0 ≤ Pe ≤ 548.9) are captured using particle imaging velocimetry. The flow patterns obtained from simulations are similar to the experimental results. The flow patterns for 219.5 ≤ Pe ≤ 548.9 with buoyancy strength of Ra = 1.024 × 106 and Ra = 1.048 × 106 for dimensionless height of 0.6 and 0.8, respectively, demonstrated mixed convective flows. Buoyancy driven roll is observed near the edge of the metal foam, and jet driven roll is observed above the metal foam.

Buoyancy Dominated He–O2 Separated Jet Mixing in a Tubular Reactor

Mixing of two variable-density jets, one of which is essentially a negatively buoyant jet (He) and the other a nonbuoyant jet (O2) is studied experimentally using digital particle image velocimetry technique for separated nozzle geometry. Two jets are separated from each other, i.e., He jet exit plane is located upstream of the O2 jet exit plane. Experiments were carried out keeping the nonbuoyant O2 jet at constant Reynolds number (Re2=245) and varying the Richardson number (Ri1=1.8,4.7,16.4) of the buoyant He jet. The interaction between two jets as a function of buoyancy strength of helium jet is investigated. The flow visualization images clearly demonstrate the growth and shape of buoyant jet as a function of Richardson number. Mean velocity and vorticity field results provide quantitative picture about the mixing and interaction between the two jets. The stream trace results show the flow structures, i.e., recirculation zone and foci of vortex structures as a function of Richardson number. The mixing between two jets takes place at far downstream region for low Richardson number (Ri1=1.8). At high Richardson number (Ri1=16.4), the buoyant He jet is located near its exit plane without any direct interaction with the O2 jet. At the intermediate Richardson number (Ri1=4.7), the buoyant jet encroaches the nonbuoyant O2 jet at a favorable penetration distance and a good amount of mixing between the two jets take place. The jet growth results based on the y0.5-location development in the streamwise direction clearly demonstrate the interaction between the He and O2 jets in the interjet region. The entrainment coefficient, vorticity magnitude, and turbulent kinetic energy magnitude are maximum at the intermediate Richardson number (Ri1=4.7) demonstrating direct relationship among each other. The mixing between buoyant He jet and nonbuoyant O2 jet is a function of both shear between the two jets and the strength of buoyant plume.

Transient laminar opposing mixed convection in a differentially and asymmetrically heated vertical channel of finite length

Transient laminar mixed convection in an asymmetrically and differentially heated vertical channel of finite length subject to an opposing buoyancy is investigated by solving the unsteady two-dimensional Navier–Stokes and energy equations. Results illustrate the effects of buoyancy strength or Richardson number Ri = Gr / Re 2 and Reynolds number Re on the overall flow structure and the nondimensional heat flux (Nusselt number) from the heated surface. Final steady or oscillatory flow response is obtained depending on the value of the Reynolds and Richardson numbers. The critical value of the buoyancy strength between the two regimes strongly depends on the value of the Reynolds number.

Effects of Buoyancy on Electrohydrodynamic-Enhanced Forced Convection in a Vertical Channel

Buoyancy effects on heat transfer enhancement using an electrohydrodynamic (EHD) technique is numerically examined for laminar forced convection in a horizontal channel. Attention is also focused on the effect of added buoyancy on the flow stability. The flow Reynolds numbers and thermal buoyancy strength considered are in the range of 6 x 10 2 ≤ Re ≤ 1.8 x 10 3 and 10 4 ≤ Gr ≤ 10 6 , respectively. The electrical field is generated by positive corona from a wire electrode charged with dc high-voltage (10 ≤ V 0 ≤ 17.5 kV). In terms of an EHD number, this corresponds to 0.36 < N ehd ≤ 23.56. The results show that heat transfer enhancement increases with the applied voltage. For a given electric field, oscillation in the flow and temperature fields is observed for flows at small Reynolds numbers. In addition, the flow and temperature fields become more unstable with an increase in the thermal buoyancy strength. Because of the existence of secondary flows, there is an improvement in heat transfer. However, it is observed that thermal buoyancy has a negligible effect on the heat transfer enhancement for Gr < 10 6

A numerical simulation of residual circulation in Tampa Bay. Part I: Low-frequency temporal variations

The residual (time-average) salinity and circulation in a numerical ocean model of the Tampa Bay estuary are shown to experience significant temporal variation under realistic forcing conditions. A version of the Estuarine Coastal Ocean Model developed for Tampa Bay with 70 by 100 horizontal grid points and 11 sigma levels is examined for the years 2001–2003. Model output variables are averaged over the entire time of the simulation to generate long-term residual fields. The residual axial current is found to be dominated by the buoyancy-driven baroclinic circulation with an outflow (southwestward) at the surface and to the sides of the shipping channel, and an inflow (northeastward) usually occurring subsurface within or above the shipping channel. Averages over 30 d are used to examine variations in the residual fields. During the simulation the average surface salinity near the head of Tampa Bay varies with the freshwater inflow, from 12‰ to 33%. At the bay mouth salinity varies from 30%. to 36%.. A localized measure of the baroclinic circulation in the shipping channel indicates the residual circulation can vary strongly, attaining a magnitude triple the long-term mean value. The baroclinic circulation can be disrupted, going to near zero or even reversing, when the buoyancy-driven flow is weak and the surface winds are to the northeast. Three time periods, representing different environmental conditions, are chosen to examine these results in detail. A scaling argument indicates the relative strength of buoyancy versus wind as ΔρgH2(LC Dω2)−1, where δρ is head-to-mouth density difference across the bay,g is gravitational acceleration,H is depth,L is bay length,C D is the surface wind drag coefficient, andw is wind speed. Tampa Bay is usually in the buoyancy dominated regime. The importance of winds in the weak-buoyancy case is demonstrated in an additional simulation without wind stress.

Numerical simulation of axi-symmetric fire plumes: accuracy and limitations

Abstract The objective of this work was to determine the accuracy and limitations of a new version of Fire Dynamics Simulator (FDS), developed by McGrattan et al., on axi-symmetric fire plumes. The current version uses LES for turbulence, a mixture-fraction-based infinitely fast chemistry model for combustion, and a constant radiative loss fraction. These sub-models have been tested for unconfined fires of different sizes, based on a dimensionless heat release rate QD* in the range of 0.1 to 10.0, which covers most natural fire scenarios. No adjustment of constants or algorithms in the model FDS2.0 have been made. An examination of plume theory is made first to find the benchmark correlations. This shows a generalization for a collection of correlations based on theory, and which might be “the best”. Using the characteristic length as the scaling factor, it is found that the optimum resolution of a pool fire simulation is around 0.05. With this resolution, the flame height prediction is found to fit well with flame height correlations. Some other parameters such as temperature and mixture fraction are found to be close to the empirical estimations at flame tips. The Froude number, which describes the relative strength of momentum and buoyancy, falls within the measurement range of many researchers. The simulation also reveals that the temperature near the burner is over-predicted, while the centerline temperature and velocity in the non-combusting region is predicted well.

Experimental and numerical investigation of buoyancy driven convection during PDAMNA thin film growth

This paper presents results from numerical simulations as well as laboratory experiments of buoyancy driven convection in an ampoule under varying heating and gravitational acceleration loadings. The modeling effort in this work resolves the large scale natural convective motion that occurs in the fluid during photodeposition of polydiacetelene films which is due to energy absorbed by the growth solution from a UV source. Consequently, the growth kinetics of the film are ignored in the model discussed here, and also a much simplified ampoule geometry is considered. The objective of this work is to validate the numerical prediction on the strength and structure of buoyancy driven convection that could occur under terrestrial conditions during nonlinear optical film growth. The validation is used to enable a reliable predictive capability on the nature and strength of the convective motion under low gravity conditions. The ampoule geometry is in the form of a parallelepiped with rectangular faces. The numerical results obtained from the solution to the Boussinesq equations show that natural convection will occur regardless of the orientation of the UV source with respect to the gravity vector. The least strong convective motion occurred with the UV beam directed at the top face of the parallelepiped. The strength of the convective motion was found to be almost linearly proportional to the total power of the UV source. Also, it was found that the strength of the convective motion decreased linearly with the gravity due to acceleration. The pattern of the convection flow on the other hand, depended on the source location.

Heat Transfer Characteristics of Ice Melting in Water and Salt Solutions

Ice cubes were placed in identical beakers, one containing tap water and the other containing a sodium chloride salt solution. Both beakers and their original contents were at 20°C. As expected, the ice cubes floated and slowly melted, however, it was found that the ice cube in the water melted 25% faster than in the brine, contrary to expectation. A second series of tests were undertaken in which the ice cubes were made to sink to the bottom by placing them in a coarse string bag with weights attached. It was found that the submerged ice cube in the brine solution melted four times faster than that submerged in tap water. Computational Fluid Dynamics, has shown that the paradoxical experimental findings can all be explained by considering the strength and direction of buoyancy driven currents.