Investigation of the Flow and Heat Transfer around Cylinders at Low Re

2010 ◽  
Vol 156-157 ◽  
pp. 1630-1634
Author(s):  
Lei Yue ◽  
Zhi Guo Zhang ◽  
Da Kui Feng ◽  
Ashvinikumar V. Mudaliar
Keyword(s):  
Heat Transfer ◽  
Strouhal Number ◽  
Excellent Agreement ◽  
Stokes Equations ◽  
Flow Direction ◽  
Incident Angle ◽  
Numerical Results ◽  
Published Data ◽  
Square Cylinder ◽  
Flow And Heat Transfer

2-D computational analyses were conducted for unsteady viscous flow and heat transfer across cylinders of different geometries and different incident angle. Circular, square (both at 0° and 90° angles of incidence) and elliptic cylinders were examined. The calculations were performed by solving the unsteady 2-D Navier-Stokes equations at Re = 100. The calculated results produce drag and lift coefficients, as well as Strouhal number in excellent agreement with published data. Calculations for unsteady, incompressible 2-D flow around a square cylinder at incidence angle of 0° and 45° and for Reynolds number = 100 were carried out. Cycle independence and grid independence results were obtained for the Strouhal number. The results were in excellent agreement with the available experimental and numerical results. Numerical results show that the Strouhal number increases with fluid angle of incidence on the cylinder. The wake behind the cylinder is wider and more violent for a square cylinder at 45° incidence compared to a square at 0° this is due to the increase in the characteristic length in the flow direction. The present studywas carried out for a 2-D single cylinder at fixed location inside a channel for unidirectional velocity. To get more accurate results computation on 3-D geometry should be carried out.

Unsteady Numerical Analysis of Flow Across 2D Cylinder

2010 ◽  
Author(s):  
Yaling Peng ◽  
Zhiguo Zhang ◽  
Fangliang Wu ◽  
Dakui Feng
Keyword(s):  
Strouhal Number ◽  
Excellent Agreement ◽  
Incidence Angle ◽  
Flow Direction ◽  
Incident Angle ◽  
Numerical Results ◽  
Published Data ◽  
Angle Of Incidence ◽  
Square Cylinder ◽  
Navier Stokes Equation

2-D computational analyses were conducted for unsteady viscous flow across cylinders of different geometries and different incident angle. Circular, square and elliptic (both at 0° and 90° angles of incidence) cylinders were examined. The calculations were performed by solving the unsteady 2-D Navier-Stokes equation at Re = 100. The calculated results produce drag and lift coefficients, as well as Strouhal number in excellent agreement with published data. Calculations for unsteady, incompressible 2D flow around a square cylinder at incidence angle of 0° and 45° and for Reynolds number = 100 were carried out. Cycle independence and grid independence results were obtained for the Strouhal number. The results were in excellent agreement with the available experimental and numerical results. Numerical results show that the Strouhal number increases with fluid angle of incidence on the cylinder. The wake behind the cylinder is wider and more violent for a square cylinder at 45° incidence compared to a square at 0° this is due to the increase in the characteristic length in the flow direction. The Strouhal number is highest for elliptic geometry among all cylinders in this research. For the geometries elliptic at 0° at Re = 100, there is not vortex shedding behind the cylinder. This is due to dominance of inertia forces over viscous forces. The present study was carried out for a 2-D single cylinder at fixed location inside a channel for unidirectional velocity. To get more accurate results computation on 3-D geometry should be carried out.

scholarly journals Computational Performance of Disparate Lattice Boltzmann Scenarios under Unsteady Thermal Convection Flow and Heat Transfer Simulation

Computation ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 65
Author(s):  
Aditya Dewanto Hartono ◽  
Kyuro Sasaki ◽  
Yuichi Sugai ◽  
Ronald Nguele
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Lattice Boltzmann ◽  
Numerical Results ◽  
Convection And Heat Transfer ◽  
Steady State Condition ◽  
Physical Systems ◽  
Flow And Heat Transfer ◽  
Computational Performance

The present work highlights the capacity of disparate lattice Boltzmann strategies in simulating natural convection and heat transfer phenomena during the unsteady period of the flow. Within the framework of Bhatnagar-Gross-Krook collision operator, diverse lattice Boltzmann schemes emerged from two different embodiments of discrete Boltzmann expression and three distinct forcing models. Subsequently, computational performance of disparate lattice Boltzmann strategies was tested upon two different thermo-hydrodynamics configurations, namely the natural convection in a differentially-heated cavity and the Rayleigh-Bènard convection. For the purposes of exhibition and validation, the steady-state conditions of both physical systems were compared with the established numerical results from the classical computational techniques. Excellent agreements were observed for both thermo-hydrodynamics cases. Numerical results of both physical systems demonstrate the existence of considerable discrepancy in the computational characteristics of different lattice Boltzmann strategies during the unsteady period of the simulation. The corresponding disparity diminished gradually as the simulation proceeded towards a steady-state condition, where the computational profiles became almost equivalent. Variation in the discrete lattice Boltzmann expressions was identified as the primary factor that engenders the prevailed heterogeneity in the computational behaviour. Meanwhile, the contribution of distinct forcing models to the emergence of such diversity was found to be inconsequential. The findings of the present study contribute to the ventures to alleviate contemporary issues regarding proper selection of lattice Boltzmann schemes in modelling fluid flow and heat transfer phenomena.

scholarly journals Construction of Analytic Solution to Axisymmetric Flow and Heat Transfer on a Moving Cylinder

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1335
Author(s):  
Vasile Marinca ◽  
Nicolae Herisanu
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Stokes Equations ◽  
Nonlinear Differential Equations ◽  
Axisymmetric Flow ◽  
Control Parameters ◽  
Auxiliary Functions ◽  
Flow And Heat Transfer ◽  
Moving Cylinder ◽  
Convergence Control

Based on a new kind of analytical approach, namely the Optimal Auxiliary Functions Method (OAFM), a new analytical procedure is proposed to solve the problem of the annular axisymmetric stagnation flow and heat transfer on a moving cylinder with finite radius. As a novelty, explicit analytical solutions were obtained for the considered complex problem. First, the Navier–Stokes equations were simplified by means of similarity transformations that depended on different parameters and some combinations of these parameters, and the problem under study was reduced to six nonlinear ordinary differential equations with six unknowns. The OAFM proves to be a powerful tool for finding an accurate analytical solution for nonlinear problems, ensuring a fast convergence after the first iteration, even if the small or large parameters are absent, since the determination of the convergence-control parameters is independent of the magnitude of the coefficients that appear in the nonlinear differential equations. Concerning the main novelties of the proposed approach, it is worth mentioning the presence of some auxiliary functions, the involvement of the convergence-control parameters, the construction of the first iteration and much freedom to select the procedure for determining the optimal values of the convergence-control parameters.

Effect of an Oscillating Flow Direction on Leading Edge Heat Transfer

1984 ◽  
Vol 106 (1) ◽  
pp. 222-228 ◽  
Author(s):  
M. L. Marziale ◽  
R. E. Mayle
Keyword(s):  
Heat Transfer ◽  
Strouhal Number ◽  
Large Scale ◽  
Flow Direction ◽  
Leading Edge ◽  
Periodic Variation ◽  
Scale Model ◽  
Transfer Rates ◽  
Large Scale Model ◽  
Turbulence Length

An experimental investigation was conducted to examine the effect of a periodic variation in the angle of attack on heat transfer at the leading edge of a gas turbine blade. A circular cylinder was used as a large-scale model of the leading edge region. The cylinder was placed in a wind tunnel and was oscillated rotationally about its axis. The incident flow Reynolds number and the Strouhal number of oscillation were chosen to model an actual turbine condition. Incident turbulence levels up to 4.9 percent were produced by grids placed upstream of the cylinder. The transfer rate was measured using a mass transfer technique and heat transfer rates inferred from the results. A direct comparison of the unsteady and steady results indicate that the effect is dependent on the Strouhal number, turbulence level, and the turbulence length scale, but that the largest observed effect was only a 10 percent augmentation at the nominal stagnation position.

Numerical Simulation on Heat Transfer and Fluid Flow Characteristics of Arrays With Nonuniform Plate Length Positioned Obliquely to the Flow Direction

1998 ◽  
Vol 120 (4) ◽  
pp. 991-998 ◽  
Author(s):  
L. B. Wang ◽  
G. D. Jiang ◽  
W. Q. Tao ◽  
H. Ozoe
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Numerical Results ◽  
The Body ◽  
Number Range ◽  
Plate Length ◽  
Nonuniform Plate ◽  
Short Plate

The periodically fully developed laminar heat transfer and pressure drop of arrays with nonuniform plate length aligned at an angle (25 deg) to air direction have been investigated by numerical analysis in the Reynolds number range of 50–1700. The body-fitted coordinate system generated by the multisurface method was adopted to retain the corresponding periodic relation of the lines in physical and computational domains. The computations were carried out just in one cycle. Numerical results show that both the heat transfer and pressure drop increase with the increase in the length ratio of the long plate to the short plate, and decrease with the decrease in the ratio of transverse pitch to the longitudinal pitch. The numerical results exhibit good agreement with available experimental data.

scholarly journals Numerical Analysis of Mixed Convective Heat Transfer from a Square Cylinder Utilizing Nanofluids with Multi-Phase Modelling Approach

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5485
Author(s):  
Rajendra S. Rajpoot ◽  
Shanmugam. Dhinakaran ◽  
Md. Mahbub Alam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Richardson Number ◽  
Base Fluid ◽  
Square Cylinder ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Multi Phase ◽  
Modelling Approach

The present study deals with the numerical simulation of mixed convective heat transfer from an unconfined heated square cylinder using nanofluids (Al2O3-water) for Reynolds number (Re) 10–150, Richardson number (Ri) 0–1, and nanoparticles volume fractions (φ) 0–5%. Two-phase modelling approach (i.e., Eulerian-mixture model) is adopted to analyze the flow and heat transfer characteristics of nanofluids. A square cylinder with a constant temperature higher than that of the ambient is exposed to a uniform flow. The governing equations are discretized and solved by using a finite volume method employing the SIMPLE algorithm for pressure–velocity coupling. The thermo-physical properties of nanofluids are calculated from the theoretical models using a single-phase approach. The flow and heat transfer characteristics of nanofluids are studied for considered parameters and compared with those of the base fluid. The temperature field and flow structure around the square cylinder are visualized and compared for single and multi-phase approaches. The thermal performance under thermal buoyancy conditions for both steady and unsteady flow regimes is presented. Minor variations in flow and thermal characteristics are observed between the two approaches for the range of nanoparticle volume fractions considered. Variation in φ affects CD when Reynolds number is varied from 10 to 50. Beyond Reynolds number 50, no significant change in CD is observed with change in φ. The local and mean Nusselt numbers increase with Reynolds number, Richardson number, and nanoparticle volume fraction. For instance, the mean Nusselt number of nanofluids at Re = 100, φ = 5%, and Ri = 1 is approximately 12.4% higher than that of the base fluid. Overall, the thermal enhancement ratio increases with φ and decreases with Re regardless of Ri variation.

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