LES of Turbulent Separated Flow and Heat Transfer in a Symmetric Expansion Plane Channel

2005 ◽  
Vol 127 (5) ◽  
pp. 865-871 ◽  
Author(s):  
Kazuaki Sugawara ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Finite Difference ◽  
Plane Channel ◽  
Separated Flow ◽  
Expansion Ratio ◽  
Vortical Flow ◽  
Flow And Heat Transfer ◽  
Finite Difference Equations ◽  
Separated And Reattached Flow ◽  
Fundamental Equations

The LES method was applied to analyze numerically an unsteady turbulent separated and reattached flow and heat transfer in a symmetric expansion plane channel of expansion ratio 2.0. The Smagorinsky model was used in the analysis and fundamental equations were discretized by means of the finite difference method, and their resulting finite difference equations were solved using the SMAC method. The calculations were conducted for Re=15,000. It is found that the present numerical results, in general, agree well with the previous experimental ones. The complicated vortical flow structures in the channel and their correlations with heat transfer characteristics are visualized through various fields of flow quantities.

LES of Turbulent Separated Flow and Heat Transfer in a Symmetric Expansion Plane Channel

2004 ◽  
Author(s):  
Kazuaki Sugawara ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Finite Difference ◽  
Plane Channel ◽  
Separated Flow ◽  
Expansion Ratio ◽  
Vortical Flow ◽  
Flow And Heat Transfer ◽  
Finite Difference Equations ◽  
Separated And Reattached Flow ◽  
Fundamental Equations

LES method is applied to simulate numerically a turbulent separated and reattached flow and heat transfer in a symmetric expansion plane channel of expansion ratio 2.0. Smagorinsky model is used in the analysis and fundamental equations are discretized by means of the finite difference method, and their resulting finite difference equations are solved using SMAC method. The calculations are conducted for Re = 15000. It is found that the present numerical results, in general, agree well with the previous experimental ones. The complicated vortical flow structures in the channel and their correlations with heat transfer characteristics are visualized through various fields of flow quantities.

Turbulent Flow and Heat Transfer in a Symmetric Expansion Plane Channel

2005 ◽  
Author(s):  
Terukazu Ota ◽  
Takuma Suzuki ◽  
Hiroyuki Yoshikawa
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Large Scale ◽  
Plane Channel ◽  
Flow Region ◽  
Expansion Ratio ◽  
Open Circuit ◽  
Temperature Fields ◽  
Flow And Heat Transfer ◽  
Separated And Reattached Flow

Experimental results of turbulent flow and heat transfer in the separated and reattached flow in a symmetric expansion plane channel are presented. Experiments were conducted using a low speed open circuit wind tunnel, the expansion ratio of channel was 2.0 and the Reynolds number 15000, respectively. The flow and temperature fields were measured using split film probes and a cold wire. The conditional sampling techniques were employed in order to investigate the large scale vortex structure shed from the reattachment flow region and its correlation with the heat transfer behavior. It is found that the local Nusselt number profile is considerably different on the upper and lower walls due to the Coanda effect. Two large scale vortices shed from the reattachment regions on two walls are combined into one large vortex in the redeveloping region, whose configuration is estimated to be an ellipse inclined to the main flow.

LES of Turbulent Separated and Reattached Flow Around a Surface-Mounted Plate

2003 ◽  
Author(s):  
Hiroyuki Yoshikawa ◽  
Masakazu Konno ◽  
Ryuta Okamoto ◽  
Terukazu Ota
Keyword(s):  
Finite Difference ◽  
Vortical Flow ◽  
Flow Structures ◽  
Smagorinsky Model ◽  
Finite Difference Equations ◽  
Time Variations ◽  
Separated And Reattached Flow ◽  
Volume Method ◽  
Fundamental Equations ◽  
Smac Method

LES method is applied to simulate numerically a turbulent separated and reattached flow around a surface-mounted plate. Smagorinsky model is used in the analysis and fundamental equations are discretized by means of the finite volume method, and their resulting finite difference equations are solved using SMAC method. The calculations are conducted for Re = 105. It is found that the present numerical results, in general, agree well with the previous experimental ones. The complicated vortical flow structures around the plate and their time variations are visualized through various fields of flow quantities.

DNS of Expansion Ratio Effects on Three-Dimensional Unsteady Separated Flow and Heat Transfer Around a Downward Step

2005 ◽  
Author(s):  
Aya Kito ◽  
Kazuaki Sugawara ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Side Wall ◽  
Separated Flow ◽  
Flow Region ◽  
Expansion Ratio ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Channel Expansion

The direct numerical simulation methodology was employed to analyze the unsteady features of a three-dimensional separated flow and heat transfer around a downward step in a rectangular channel, and to clarify systematically the channel expansion ratio effects upon them. Numerical calculations were carried out using the finite difference method. The Reynolds number Re based on the mean velocity at inlet and the step height was varied from 300 to 1000. The channel expansion ratio ER is 1.5, 2.0 and 3.0 under a step aspect ratio of 36.0. It is found that the flow is steady upto Re = 500 but becomes sensibly unsteady at Re = 700 for all the three expansion ratios. In the case of ER = 2.0, the separated shear layer is most unstable. In the case of ER = 1.5, the longitudinal vortices formed near the side walls of channel are strongest. Nusselt number reaches its maximum in the reattachment flow region and also in the neighborhood of the side wall, and their locations depend greatly upon ER and Re.

DNS of Three-Dimensional Unsteady Separated Flow and Heat Transfer in a Sudden-Expansion Channel

2005 ◽  
Author(s):  
Hiroyuki Yoshikawa ◽  
Kimitake Ishikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Separated Flow ◽  
Expansion Ratio ◽  
Sudden Expansion ◽  
Number Range ◽  
Simulation Methodology ◽  
Flow And Heat Transfer ◽  
Unsteady Separated Flow

Numerical results of a three-dimensional unsteady separated flow and heat transfer in a sudden expansion rectangular channel are presented. A direct numerical simulation methodology was employed in the calculations using the finite difference method. Treated in the present study is a rectangular channel of aspect ratio AR = 4.0 and expansion ratio ER = 2.5 in a Reynolds number range from 200 to 1000. It is found that the flow becomes unsteady at Re = 400 and severely complicated at Re = 500 to 1000. The heat transfer characteristics are presented and discussed in relation to the flow ones.

Numerical Simulation of Three-Dimensional Separated Flow and Heat Transfer Around a Surface-Mounted Square Plate

2003 ◽  
Author(s):  
Hiroyuki Yoshikawa ◽  
Keisuke Shimizu ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Boundary Layer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Separated Flow ◽  
Numerical Calculations ◽  
Flow And Heat Transfer ◽  
Square Plate ◽  
Separated And Reattached Flow

Direct Numerical Simulation results of three-dimensional laminar separated and reattached flow and heat transfer around a surface-mounted square plate are presented in this paper. Numerical calculations of Navier-Stokes equations and energy one are carried out using the finite difference method with SMAC method. A square plate is presumed to be mounted in a laminar boundary layer developing on a flat surface and to be heated under a constant heat flux. Numerical calculations are made on two boundary layer thicknesses at the plate, and the Reynolds number is varied from 300 to 1000. Details of the separated and reattached flow and the thermal field therein are clarified.

DNS of Three-Dimensional Unsteady Separated Flow and Heat Transfer Around a Downward Step

2005 ◽  
Author(s):  
Kazuaki Sugawara ◽  
Eiji Kaihara ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Side Wall ◽  
Separated Flow ◽  
Flow Region ◽  
Expansion Ratio ◽  
Temperature Fields ◽  
Mean Velocity ◽  
Flow And Heat Transfer

The direct numerical simulation methodology was employed to analyze the unsteady features of a three-dimensional separated flow and heat transfer around a downward step in a rectangular channel. Numerical calculations were carried out using the finite difference method. The Reynolds number Re based on the mean velocity at inlet and the step height was varied from 300 to 1000. The channel expansion ratio ER is 2.0 under a step aspect ratio of 36.0. It is found that the flow is steady upto Re = 500, but becomes sensibly unsteady at Re = 600 as accompanying a remarkable increase of the three-dimensionality of the flow and temperature fields. Nusselt number reaches its maximum in the reattachment flow region and also in the neighborhood of the side wall, and their locations depend greatly upon Re.

Expansion Ratio Effects on Three-Dimensional Separated Flow and Heat Transfer Around Backward-Facing Steps

2006 ◽  
Vol 129 (9) ◽  
pp. 1141-1155 ◽  
Author(s):  
Aya Kitoh ◽  
Kazuaki Sugawara ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Separated Flow ◽  
Expansion Ratio ◽  
Temperature Fields ◽  
Number Range ◽  
Flow And Heat Transfer

Direct numerical simulation methodology clarified the three-dimensional separated flow and heat transfer around three backward-facing steps in a rectangular channel, especially effects of channel expansion ratio ER upon them. ER treated in the present study was 1.5, 2.0, and 3.0 under a step aspect ratio of 36.0. The Reynolds number Re based on the mean velocity at inlet and the step height was varied from 300 to 1000. The present numerical results for ER=2.0 were found to be in very good agreement with the previous experimental and numerical ones in the present Reynolds number range for both the steady and unsteady flow states. The time averaged reattachment length on the center line increases with a decrease of ER. The flow became unsteady at RE=700, 600, and 500 for ER=1.5, 2.0, and 3.0, respectively, accompanying the remarkable increase of the three-dimensionality of the flow and temperature fields in spite of a very large step aspect ratio of 36.0. The Nusselt number increases in the reattachment flow region, in the neighborhood of the sidewalls, and also in the far downstream depending on both Re and ER.

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