Low Reynolds Number Turbulent Flow in Large Aspect Ratio Rectangular Ducts

1971 ◽  
Vol 93 (2) ◽  
pp. 296-299 ◽  
Author(s):  
G. S. Beavers ◽  
E. M. Sparrow ◽  
J. R. Lloyd
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Equivalent Diameter ◽  
Large Aspect Ratio ◽  
Number Range ◽  
Aspect Ratios ◽  
Reynolds Number Range ◽  
Low Reynolds

Experiments are reported on fully developed turbulent flows at low Reynolds numbers in rectangular ducts of large aspect ratio. Six ducts, with aspect ratios between 15.5:1 and 35.0:1, were employed for the investigation, covering a Reynolds number range from 5,000 to 27,000. A friction factor, Reynolds number relation expressed as f = 0.507 R−0.30 was found to be an excellent representation of the experimental data when the equivalent diameter was used as the characteristic length dimension. The Blasius and Prandtl circular tube friction factor relations, generalized by use of the equivalent diameter, gave results within 5 percent or better of the aforementioned correlation over the Reynolds number range of this investigation.

Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces

2013 ◽  
Author(s):  
Matthew A. Smith ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios ◽  
Parallel Configuration

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter. While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently. The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.

Reynolds Number Effect on Regenerative Pump Performance in Low Reynolds Number Range

2008 ◽  
Vol 1 (1) ◽  
pp. 101-108 ◽  
Author(s):  
Hironori Horiguchi ◽  
Daisuke Yumiba ◽  
Yoshinobu Tsujimoto ◽  
Masaaki Sakagami ◽  
Shigeo Tanaka
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Number Range ◽  
Pump Performance ◽  
Reynolds Number Effect ◽  
Reynolds Number Range ◽  
Low Reynolds

Forced Convection in a Uniformly Heated Enclosure With Different Aspect Ratios: Effect of the Inlet and Two Outlet Port Locations

2008 ◽  
Author(s):  
A. I. Botello-Arredondo ◽  
A. Hernandez-Guerrero ◽  
C. Rubio-Arana ◽  
M. Pen˜a-Taveras
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Forced Convection ◽  
Flow Behavior ◽  
Temperature Fields ◽  
Transfer Enhancement ◽  
Number Range ◽  
Outlet Port ◽  
Aspect Ratios

This paper presents a numerical investigation on forced convection in a cavity with one inlet and two outlet ports. For the present study three different aspect ratios between height (H) and length (L), (H ≠ L)were considered (AR = H/L), AR = 1, 1.3 and 2.5. Different conditions and geometric arrays for the position of the ports are analyzed. The walls of the cavity are considered to be isothermal warming-up the incoming cold fluid. A Reynolds number range of 10 < Re < 500 is considered, clearly within the laminar regimen. The flow and temperature fields are obtained as part of the solution. As expected, the aspect ratio affects the flow behavior in the cavity. An increment of vorticity leads to a heat transfer enhancement. The different aspect ratios of the cavity and the effect of the outlet ports and their location are discussed.

A note on vortex streets behind circular cylinders at low Reynolds numbers

1971 ◽  
Vol 45 (1) ◽  
pp. 203-208 ◽  
Author(s):  
D. J. Tritton
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Current State ◽  
Reynolds Number Range ◽  
Vortex Streets ◽  
Low Reynolds

A discussion is given of the current state of knowledge of vortex streets behind circular cylinders in the Reynolds number range 50 to 160. This was prompted by Gaster's (1969) report that he could not find the transition at a Reynolds number of about 90 observed by Tritton (1959) and Berger (1964a). A further brief experiment confirming the existence of the transition is described Reasons for rejecting Gaster's interpretation are advanced. Possible (mutually alternative) explanations of the discrepant observations are suggested.

Flexible ring flapping in a uniform flow

2012 ◽  
Vol 707 ◽  
pp. 129-149 ◽  
Author(s):  
Boyoung Kim ◽  
Wei-Xi Huang ◽  
Soo Jai Shin ◽  
Hyung Jin Sung
Keyword(s):  
Reynolds Number ◽  
Stable State ◽  
Uniform Flow ◽  
Bending Stiffness ◽  
Immersed Boundary ◽  
Number Range ◽  
Aspect Ratios ◽  
Reynolds Number Range ◽  
Internal Volume ◽  
Flexible Ring

AbstractAn improved version of the immersed boundary (IB) method for simulating an initially circular or elliptic flexible ring pinned at one point in a uniform flow has been developed. The boundary of the ring consists of a flexible filament with tension and bending stiffness. A penalty method derived from fluid compressibility was used to ensure the conservation of the internal volume of the flexible ring. At $\mathit{Re}= 100$, two different flapping modes were identified by varying the tension coefficient for a fixed bending stiffness, or by changing the bending coefficient for a fixed tension coefficient. The optimal tension and bending coefficients that minimize the drag force of the flexible ring were found. Visualization of the vorticity field showed that the two flapping modes correspond to different vortex shedding patterns. We observed the hysteresis property of the flexible ring, which exhibits bistable states over a range of flow velocities depending on the initial inclination angle, i.e. one is a stationary stable state and the other a self-sustained periodically flapping state. The Reynolds number range of the bistability region and the flapping amplitude were determined for various aspect ratios $a/ b$. For $a/ b= 0. 5$, the hysteresis region arises at the highest Reynolds number and the flapping amplitude in the self-sustained flapping state is minimized. A new bistability phenomenon was observed: for certain aspect ratios, two periodically flapping states coexist with different amplitudes in a particular Reynolds number range, instead of the presence of a stationary stable state and a periodically flapping state.

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