Laminar Fluid Flow and Heat Transfer in a Lid-Driven Cavity Due to a Thin Fin

2002 ◽  
Vol 124 (6) ◽  
pp. 1056-1063 ◽  
Author(s):  
Xundan Shi ◽  
J. M. Khodadadi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Computational Study ◽  
Reynolds Numbers ◽  
Left Wall ◽  
Driven Cavity ◽  
Flow And Heat Transfer ◽  
Heat Transfer Capacity ◽  
The Right ◽  
Steady Laminar

A finite-volume-based computational study of steady laminar flow and heat transfer (neglecting natural convection) within a lid-driven square cavity due to a single thin fin is presented. The lid moves from left to right and a fixed thin fin can be positioned perpendicular to any of the three stationary walls. Three fins with lengths equal to 5, 10, and 15 percent of the side, positioned at 15 locations were examined for Re=500, 1000, 2000, and Pr=1 (total of 135 cases). Placing a fin on the right wall brings about multi-cell recirculating vortices compared to the case without a fin that exhibits a primary vortex and two small corner cells. A fin slows the flow near the anchoring wall and reduces the temperature gradients, thus degrading heat transfer capacity. A fin positioned near the top right corner of the cavity can reduce heat transfer most effectively in cases with all three different Reynolds numbers and lengths. Regardless of the Reynolds number, placing a fin on the right wall—compared to putting a fin on the left and bottom walls—can always enhance heat transfer on the left wall and at the same time, reduce heat transfer on the bottom, right and top walls. A long fin has the most marked effect on the system’s heat transfer capabilities. Mean Nusselt number was successfully correlated to the Reynolds number, length of the fin and its position.

Fluid Flow and Heat Transfer in a Lid-Driven Cavity Due to an Oscillatory Thin Fin: Periodic State

2004 ◽  
Author(s):  
Xundan Shi ◽  
J. M. Khodadadi
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Periodic Flow ◽  
Number Range ◽  
Driven Cavity ◽  
Flow And Heat Transfer ◽  
Periodic State ◽  
Wall Impingement ◽  
The Right ◽  
Synchronous Behavior

A computational study of periodic laminar flow and heat transfer within a lid-driven square cavity due to an oscillating thin fin is presented. The lid moves from left to right and a thin fin positioned perpendicular to the right stationary wall oscillates in the horizontal direction. The length of the fin varies sinusoidally with its mean length and amplitude equal to 10 and 5 percent of the side of the cavity, respectively. Two Reynolds numbers of 100 and 1000 with a Pr = 1 fluid were considered. For a given convection time scale (tconv), fin’s oscillation periods (τ) were selected in order to cover both slow (τ/tconv>1) and fast (τ/tconv<1) oscillation regimes, covering a Strouhal number range of 0.005 to 0.5. The number of the cycles needed to reach the periodic state for the flow (Nf) and thermal (Nt) fields increases as the fin oscillates faster with Nf < Nt. The periodic flow field for the case with Re = 1000 and TR = 10 is distinguished by the creation, lateral motion and subsequent wall impingement of a CCW rotating vortex within the lower half of the cavity. Periodic flow and thermal fields of the other nine cases studied were not as varied. Phase diagrams of the stream function and temperature vs. fin’s length clearly exhibit the synchronous behavior of the system. Amplitude of fluctuations of the kinetic energy and temperature are very intense near the fin. As the fin oscillates slower, a greater portion of the cavity exhibits intense fluctuations. For slow to moderate oscillations, the maximum value of Kamp is observed to be greater for Re = 1000 in comparison to Re = 100. For fast oscillations, this behavior is reversed. The maximum values of the amplitude of fluctuations of temperature increase monotonically as the fin oscillates slower. The maximum values of θamp are greater for Re = 1000 compared to Re = 100. The amplitude of fluctuations of the mean Nusselt number on four walls increase as the fin oscillates slower.

scholarly journals Investigation of forced convective heat transfer from a block located staggered cavity with parallel and anti-parallel wall motion

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1281-1288
Author(s):  
Meenakshi Kannan ◽  
Manikandan Gurunathan ◽  
Rajesh Kanna ◽  
Jan Taler ◽  
Dawid Taler ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Wall Motion ◽  
Reynolds Numbers ◽  
Flow And Heat Transfer ◽  
Parallel Wall ◽  
Bottom Side ◽  
Upper Lid ◽  
Block Based ◽  
The Right

The investigation reported in this paper is dealt about the steady-state laminar flow and heat transfer of a lid driven staggered cavity with the heated block. Based on the aspect ratio (AR = H/L = 0.5, H/L = 1, H/L = 2) three different block shapes are introduced for numerical experiments. The solid block with no slip and stationary wall condition is considered and it is located at the geometric center of the cavity. The simulations are carried out for Reynolds numbers 50, 100, 200, 300, 500, and 1000 and temperature of the block is 300 K. A clock-wise momentum is converged to the fluid, by the two driving lids on the top and bottom side of the cavity, lids are set into an anti-parallel wall motion. The upper lid moves to the right, while the lower one to the left, both are consider as same velocities. The results are found to be in good agreement with existing published results. It was found that the dynamics and the structure of the primary vortex and the corner vortices were strongly affected by the Reynolds number. The investigation clearly describes that increasing the Reynolds number values the overall drag coefficient decreases, similarly the value of average Nusselt number also increases with an increasing Reynolds number for all the values of different blocks under studied. The study reveals the important flow physics such as flow separation, boundary-layer and recirculation. The results will be beneficial for similar situation occur in many industrial problems.

LES Investigation of Flow and Heat Transfer in a Channel With Dimples and Protrusions

2007 ◽  
Author(s):  
Mohammad A. Elyyan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Reynolds Numbers ◽  
The Other ◽  
Secondary Effect ◽  
Flow Acceleration ◽  
Heat Transfer Augmentation ◽  
Flow And Heat Transfer ◽  
Separated Shear Layer ◽  
Dimple Surface

LES calculations are conducted for flow in a channel with dimples and protrusions on opposite walls with both surfaces heated at three Reynolds numbers, ReH = 220, 940, and 9300 ranging from laminar, weakly turbulent to fully turbulent, respectively. Turbulence generated by the separated shear layer in the dimple and along the downstream rim of the dimple is primarily responsible for heat transfer augmentation on the dimple surface. On the other hand, augmentation on the protrusion surface is mostly driven by flow impingement and flow acceleration between protrusions, while the turbulence generated in the wake has a secondary effect. Heat transfer augmentation ratios of 0.99 at ReH = 220, 2.9 at ReH = 940, and 2.5 at ReH = 9300 are obtained. Both skin friction and form losses contribute to pressure drop in the channel, with form losses increasing from 45% to 80% with an increase in the Reynolds number. Friction coefficient augmentation ratios of 1.67, 4.82 and 6.37 are obtained at ReH = 220, 940, and 9300, respectively. Based on the geometry studied, it is found that dimples and protrusions may not be viable heat transfer augmentation surfaces when the flow is steady and laminar.

Periodic Fluid Flow and Heat Transfer in a Square Cavity Due to an Insulated or Isothermal Rotating Cylinder

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Y.-C. Shih ◽  
J. M. Khodadadi ◽  
K.-H. Weng ◽  
A. Ahmed
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Rotating Cylinder ◽  
Flow Fields ◽  
Square Cavity ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Rotating Objects

The periodic state of laminar flow and heat transfer due to an insulated or isothermal rotating cylinder object in a square cavity is investigated computationally. A finite-volume-based computational methodology utilizing primitive variables is used. Various rotating objects (circle, square, and equilateral triangle) with different sizes are placed in the middle of a square cavity. A combination of a fixed computational grid and a sliding mesh was utilized for the square and triangle shapes. For the insulated and isothermal objects, the cavity is maintained as differentially heated and isothermal enclosures, respectively. Natural convection heat transfer is neglected. For a given shape of the object and a constant angular velocity, a range of rotating Reynolds numbers are covered for a Pr=5 fluid. The Reynolds numbers were selected so that the flow fields are not generally affected by the Taylor instabilities (Ta<1750). The periodic flow field, the interaction of the rotating objects with the recirculating vortices at the four corners, and the periodic channeling effect of the traversing vertices are clearly elucidated. The simulations of the dynamic flow fields were confirmed against experimental data obtained by particle image velocimetry. The corresponding thermal fields in relation to the evolving flow patterns and the skewness of the temperature contours in comparison to the conduction-only case were discussed. The skewness is observed to become more marked as the Reynolds number is lowered. Transient variations of the average Nusselt numbers of the respective systems show that for high Re numbers, a quasiperiodic behavior due to the onset of the Taylor instabilities is dominant, whereas for low Re numbers, periodicity of the system is clearly observed. Time-integrated average Nusselt numbers of the insulated and isothermal object systems were correlated with the rotational Reynolds number and shape of the object. For high Re numbers, the performance of the system is independent of the shape of the object. On the other hand, with lowering of the hydraulic diameter (i.e., bigger objects), the triangle and the circle exhibit the highest and lowest heat transfers, respectively. High intensity of the periodic channeling and not its frequency is identified as the cause of the observed enhancement.

Transient Leading to Periodic Fluid Flow and Heat Transfer in a Differentially-Heated Cavity Due to an Insulated Rotating Object

2007 ◽  
Author(s):  
Y.-C. Shih ◽  
J. M. Khodadadi ◽  
K.-H. Weng ◽  
H. F. Oztop
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
High Heat ◽  
Thermal Fields ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
Transient Variations ◽  
Rotating Objects

Computational analysis of transient phenomenon followed by the periodic state of laminar flow and heat transfer due to an insulated rotating object in a square cavity is investigated. A finite-volume-based computational methodology utilizing primitive variables is used. Various rotating objects (circle, square and equilateral triangle) with different sizes are placed in the middle of the cavity. A combination of a fixed computational grid with a sliding mesh was utilized for the square and triangle shapes. The cavity is maintained as a differentially-heated enclosure and the motionless insulated object is set in rotation at time t = 0. Natural convection heat transfer is neglected. For a given shape of the object and a constant angular velocity, a range of rotating Reynolds numbers are covered for a Pr = 5 fluid. The Reynolds numbers were selected so that the flow fields are not generally affected by the Taylor instabilities (Ta &lt; 1750). The evolving flow field and the interaction of the rotating objects with the recirculating vortices at the four corners are elucidated. The corresponding thermal fields in relation to the evolving flow patterns and the skewness of the temperature contours in comparison to conduction-only case were discussed. The skewness is observed to become more marked as the Reynolds number is lowered. At the same time, similarity of the thermal fields for various shapes for the same Reynolds number varifies the appropriate selection of the hydraulic diameter. Transient variations of the average Nusselt numbers on the two walls show that for high Re numbers, a quasi-periodic behavior due to the onset of the Taylor instabilities is dominant, whereas for low Re numbers, periodicity of the system is clearly observed. Time-integrated average Nusselt number of the cavity is correlated to the rotational Reynolds number and shape of the object. The triangle object clearly gives rise to high heat transfer followed by the square and circle objects.

Direct Numerical Simulation of Flow and Heat Transfer From a Sphere in a Uniform Cross-Flow

2000 ◽  
Vol 123 (2) ◽  
pp. 347-358 ◽  
Author(s):  
P. Bagchi ◽  
M. Y. Ha ◽  
S. Balachandar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Vortex Shedding ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Flow And Heat Transfer

Direct numerical solution for flow and heat transfer past a sphere in a uniform flow is obtained using an accurate and efficient Fourier-Chebyshev spectral collocation method for Reynolds numbers up to 500. We investigate the flow and temperature fields over a range of Reynolds numbers, showing steady and axisymmetric flow when the Reynolds number is less than 210, steady and nonaxisymmetric flow without vortex shedding when the Reynolds number is between 210 and 270, and unsteady three-dimensional flow with vortex shedding when the Reynolds number is above 270. Results from three-dimensional simulation are compared with the corresponding axisymmetric simulations for Re>210 in order to see the effect of unsteadiness and three-dimensionality on heat transfer past a sphere. The local Nusselt number distribution obtained from the 3D simulation shows big differences in the wake region compared with axisymmetric one, when there exists strong vortex shedding in the wake. But the differences in surface-average Nusselt number between axisymmetric and three-dimensional simulations are small owing to the smaller surface area associated with the base region. The shedding process is observed to be dominantly one-sided and as a result axisymmetry of the surface heat transfer is broken even after a time-average. The one-sided shedding also results in a time-averaged mean lift force on the sphere.

scholarly journals Heat Transfer in an Air-Cooled Rotor-Stator System

1994 ◽  
Author(s):  
Jian-Xin Chen ◽  
Xiaopeng Gan ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Computational Study ◽  
Reynolds Numbers ◽  
Flow Rates ◽  
Nusselt Numbers ◽  
Heated Disc ◽  
Radial Outflow ◽  
Cooling Air

This paper describes a combined experimental and computational study of the heat transfer from an electrically-heated disc rotating close to an unheated stator. A radial outflow of cooling air was used to remove heat from the disc, and local Nusselt numbers were measured, using fluxmeters at seven radial locations, for nondimensional flow rates up to C = 9680 and rotational Reynolds numbers up to Reφ = 1.2 × 106. Computations were carried out using an elliptic solver with a low-Reynolds-number k-ε turbulence model, and the agreement between the measured and computed velocities and Nusselt numbers was mainly good.

Flow and Heat Transfer in Turbine Tip Gaps

1989 ◽  
Vol 111 (3) ◽  
pp. 301-309 ◽  
Author(s):  
J. Moore ◽  
J. G. Moore ◽  
G. S. Henry ◽  
U. Chaudhry
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
High Reynolds Number ◽  
Reynolds Numbers ◽  
Large Separation ◽  
Flow And Heat Transfer ◽  
Blade Tip ◽  
Flow Through ◽  
High Mach ◽  
High Reynolds

The effects of Reynolds number on flow through a tip gap are investigated by performing laminar flow calculations for an idealized two-dimensional tip gap geometry. The results of the calculations aid in understanding and reconciliation of low Much number turbine tip gap measurements, which range in tip gap Reynolds number from 100 to 10,000. For the higher Reynolds numbers, both the calculations and the measurements show a large separation off the sharp edge of the blade tip corner. For a high Reynolds number, fully turbulent flow calculations were also made. These also show a large separation and the results are compared with heat transfer measurements. At high Mach numbers, there are complex shock structures in the tip gap. These are modeled experimentally using a water table.

Two Dimensional Simulation of Flow and Heat Transfer Characteristics of Turbulent Jets

2010 ◽  
Author(s):  
Tarek Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Jets ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Dimensional Simulation

In this study, flow and heat transfer characteristics of two-dimensional impinging jets are investigated numerically. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume CFD code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results show that the Reynolds number has significant effect on the heat transfer rate and has no effect on the location of the maximum Nusselt number.

Investigations on Fluid Flow and Heat Transfer Performances Within a Real Turbine Blade Channel

2014 ◽  
Author(s):  
Zhaoqing Ke ◽  
Jian Pu ◽  
Jianhua Wang ◽  
Lei Wang ◽  
Zhiqiang Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Secondary Flow ◽  
Reynolds Numbers ◽  
Numerical Investigations ◽  
Serpentine Channel ◽  
Flow And Heat Transfer ◽  
Working Medium

The characteristics of fluid flow and heat transfer within a smooth three-pass channel of a real low pressure (LP) turbine blade have been investigated through experimental and numerical approaches. The serpentine channel consists of two inlet passes, two dividing walls, two 180 degree bends, twenty-five exits at the trailing edge, and two exits at the blade tip. In the experiments, purified water was used as working medium, the secondary flow patterns at five cross-sections were captured by a particle image velocimetry (PIV) system, the inlet Reynolds number was controlled by a turbine flow meter, and the mass flow rate ejected from each exit was measured by rotameters. Using the commercial software ANSYS CFX 13.0, numerical investigations were carried out. The practicability of four turbulence models, the SSG RSM, SST k-ω, RNG k-ε and standard k-ε models, were estimated. Through qualitative and quantitative comparisons of the secondary flow patterns, local velocity variation trends and mass flow rates between the experimental data and numerical results, the SSG RSM was selected as the most appropriate model in the following numerical investigations. Using ideal gas as working medium, the impacts of Reynolds numbers and rotation numbers on the heat transfer performances were numerically investigated. The numerical results predicted three interesting phenomena: 1) The locally averaged Nusselt number increases generally with the inlet Reynolds numbers. However, the increasing amplitude is significantly different from the correlation suggested by Dittus-Boelter, Nuo = 0.023Re0.8Pr0.4. The effect of the Reynolds number on the Nusselt number is substantially enhanced due to the serpentine channel design with two 180 degree-bends. The enhancement amplitude is described by two fitted coefficients based on Dittus-Boelter correlation. 2) Under a rotation condition, in the 1st and 3rd passes, the enhancement amplitude of the average Nusselt number on the pressure side (PS) is more significant than that on the suction side (SS), whereas in the 2nd pass, the enhancement amplitude on the PS is lower than that on the SS. 3) In the 3rd pass, a higher rotation number leads to a more uniform distribution of the local Nusselt number along the streamwise direction on both the PS and SS.

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