Flow Development in a Parallel Plate Channel

1976 ◽  
Vol 98 (1) ◽  
pp. 145-154 ◽  
Author(s):  
A. Z. Szeri ◽  
C. C. Yates ◽  
S. M. Hai
Keyword(s):  
Laminar Flow ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Parallel Plate ◽  
Reynolds Numbers ◽  
Momentum Equation ◽  
Essential Difference ◽  
Eddy Viscosity Model ◽  
Asymptotic Profile ◽  
Plate Channel

The paper presents a study of the flow that occurs in a finite, parallel plate channel. The experimental work consists of velocity profile measurements upstream of and inside the channel of a belt-type apparatus. Theoretical prediction of velocity profile development is made via numerical methods in both laminar and turbulent situations. In the laminar flow case analytical solution of a linearized form of the momentum equation was also possible. Good agreement is shown between prediction and experimental results for all Reynolds numbers tested; in turbulent flow this occurs particularly when employing Reichardt’s eddy viscosity model. For laminar flow the entrance length is estimated to be 0.008–0.01 times the Reynolds number, while in turbulent flow no essential difference was found between an entrance and the corresponding asymptotic profile. Upstream from the entrance the similar laminar profiles of Sakiadis were observed experimentally.

Stability of the developing laminar flow in a parallel-plate channel

1967 ◽  
Vol 30 (2) ◽  
pp. 209-224 ◽  
Author(s):  
T. S. Chen ◽  
E. M. Sparrow
Keyword(s):  
Numerical Methods ◽  
Laminar Flow ◽  
Velocity Profile ◽  
Parallel Plate ◽  
Reynolds Numbers ◽  
Neutral Stability ◽  
Wide Range ◽  
Critical Reynolds Numbers ◽  
The Stability ◽  
Plate Channel

The hydrodynamic stability of the developing laminar flow in the entrance region of a parallel-plate channel is investigated using the theory of small disturbances. The stability of the fully developed flow is also re-examined. A wide range of analytical (i.e. asymptotic) and numerical methods are employed in the stability investigation. Among the asymptotic methods, each of three viscous solutions (singular, regular and composite) is used along with the inviscid solution to provide critical Reynolds numbers and complete neutral stability curves. Two numerical methods, finite differences and stepwise integration, are applied to calculate critical Reynolds numbers. The basic flow in the development region is treated from two stand-points: as a channel velocity profile and as a boundary-layer velocity profile. Extensive comparisons among the various methods and flow models disclose their various strengths and ranges of applicability. As a general result, it is found that the critical Reynolds number decreases monotonically with increasing distance from the channel entrance, approaching the fully developed value as a limit.

Effects of Roughness on Turbulent Flow in Microchannels and Minichannels

2008 ◽  
Author(s):  
Timothy P. Brackbill ◽  
Satish G. Kandlikar
Keyword(s):  
Experimental Study ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Roughness Parameter ◽  
Reynolds Numbers ◽  
Turbulent Regime ◽  
Roughness Effects ◽  
Relative Roughness ◽  
Roughness Elements ◽  
Moody Diagram

The effect of roughness ranging from smooth to 24% relative roughness on laminar flow has been examined in previous works by the authors. It was shown that using a constricted parameter, εFP, the laminar results were predicted well in the roughened channels ([1],[2],[3]). For the turbulent regime, Kandlikar et al. [1] proposed a modified Moody diagram by using the same set of constricted parameters, and using the modification of the Colebrook equation. A new roughness parameter εFP was shown to accurately portray the roughness effects encountered in laminar flow. In addition, a thorough look at defining surface roughness was given in Young et al. [4]. In this paper, the experimental study has been extended to cover the effects of different roughness features on pressure drop in turbulent flow and to verify the validity of the new parameter set in representing the resulting roughness effects. The range of relative roughness covered is from smooth to 10.38% relative roughness, with Reynolds numbers up to 15,000. It was found that using the same constricted parameters some unique characteristics were noted for turbulent flow over sawtooth roughness elements.

Turbulent Flow Over a Facing Step at Several Reynolds Numbers

2011 ◽  
Author(s):  
Jose A. Jimenez-Bernal ◽  
Adan Juarez-Montalvo ◽  
Claudia del C. Gutierrez-Torres ◽  
Juan G. Barbosa Saldan˜a ◽  
Luis F. Rodriguez-Jimenez
Keyword(s):  
Shear Stress ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Reynolds Numbers ◽  
Spatial Average ◽  
Vortex Center ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Image Velocimetry ◽  
Average Velocity Profile

An experimental study was performed over forward facing step (FFS). It was located within a transparent rectangular acrylic channel (1.4 m in length, 0.1 m in width and 0.02 m in height). The step is 0.01 m in height and 0.1 m in width, and was located 0.7 m downstream (fully developed region); a spanwise aspect ratio, w/h = 10 was used. The experiments were carried out using particle image velocimetry (PIV), which is a non intrusive experimental technique. The experimental water flow conditions include three Reynolds numbers based on the step height, Reh = 1124, 1404 and 1685. These flow conditions correspond to turbulent flow. Measurements were carried out in two zones; zone A begins at x = 8 cm (measured from the step base), and zone B starts at x = 0, y = 0, the visualization region corresponds to an area of 22.76 mm × 16.89 mm. 100 instantaneous velocity fields were obtained for each Reh. A temporal and spatial average was performed to obtain a velocity profile in zone A; likewise, the corresponding turbulence intensity and shear stress distribution were evaluated. The average velocity profile was evaluated for each Reh. Regarding the vortex center location, it was observed that as Reh increases, the y-direction coordinate moves towards bottom of wall channel. For zone B, it was also observed a reduction of the shear stress as Reh increases.

Transient Boundary Layers Between Porous Plates

1976 ◽  
Vol 43 (4) ◽  
pp. 555-558 ◽  
Author(s):  
W. A. Fiveland ◽  
P.-C. Lu
Keyword(s):  
Laminar Flow ◽  
Pressure Gradient ◽  
Incompressible Fluid ◽  
Boundary Layers ◽  
Parallel Plate ◽  
Flow Patterns ◽  
Numerical Results ◽  
Sine Transform ◽  
Fourier Sine Transform ◽  
Plate Channel

Analysis is made of a transient, fully developed, laminar flow of an incompressible fluid in a porous, parallel-plate channel. The crossflow through the plates is uniform, but is allowed to vary with time. In addition to a pressure gradient due to pumping, the flow is also under the inducement of the motion of one of the plates. Numerical results are obtained through the (final or nonfinal) use of the finite Fourier sine transform. Asymptotic flow patterns showing transient boundary layers are investigated. Finally, the formation of the flow from the start is described in physical terms.

Laminar flow of a heat-generating fluid in a parallel-plate channel

AIChE Journal ◽  
1963 ◽  
Vol 9 (6) ◽  
pp. 797-804 ◽  
Author(s):  
E. M. Sparrow ◽  
J. L. Novotny ◽  
S. H. Lin
Keyword(s):  
Laminar Flow ◽  
Parallel Plate ◽  
Plate Channel

Linear Spatial Stability of Developing Flow in a Parallel Plate Channel

1981 ◽  
Vol 48 (1) ◽  
pp. 192-194 ◽  
Author(s):  
S. C. Gupta ◽  
V. K. Garg
Keyword(s):  
Reynolds Number ◽  
Velocity Profile ◽  
Parallel Plate ◽  
Critical Reynolds Number ◽  
Two Dimensional ◽  
Spatial Stability ◽  
Percent Change ◽  
Developing Flow ◽  
The Stability ◽  
Plate Channel

It is found that even a 5 percent change in the velocity profile produces a 100 percent change in the critical Reynolds number for the stability of developing flow very close to the entrance of a two-dimensional channel.

scholarly journals MAXIMIZATION OF FLIGHT TIME FOR AIRPLANES WITH ELECTRICAL DRIVE BY POWERPLANT OPTIMIZATION

Aviation ◽  
2007 ◽  
Vol 11 (2) ◽  
pp. 37-40
Author(s):  
Sergey Serokhvostov
Keyword(s):  
Power Plant ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Electrical Power ◽  
Reynolds Numbers ◽  
Flight Time ◽  
Electrical Drive ◽  
Electrical Power Plant

In this paper, the problem of maximizing the flight time of an airplane with an electrical power plant (AEP) by the optimization of the mass of the accumulator in cases of fixed and non‐fixed airframe is considered. Variants of high (turbulent flow) and low (laminar flow) Reynolds numbers are taken into account. Dependence of flight time on airplane parameters is obtained. The behaviour of flight time as a function of accumulator mass near the maximum is also investigated. A comparison between the results obtained and the data for the existing AEP is made. On the basis of the results obtained, the influence of aircraft parameters on flight time is analyzed.

The Steady-State and Dynamic Characteristics of a Full Circular Bearing and a Partial Arc Bearing in the Laminar and Turbulent Flow Regimes

1967 ◽  
Vol 89 (2) ◽  
pp. 143-153 ◽  
Author(s):  
F. K. Orcutt ◽  
E. B. Arwas
Keyword(s):  
Steady State ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Flow Regime ◽  
Dynamic Characteristics ◽  
Reynolds Numbers ◽  
Operating Parameters ◽  
Design Data ◽  
Design Charts ◽  
Laminar And Turbulent Flow

The steady-state and dynamic characteristics of a full circular bearing and a centrally loaded, 100 deg, arc bearing are calculated for a range of eccentricity ratios to 0.95 and of mean Reynolds numbers to 13,300, and presented in design charts. These are compared with the measured performance of these bearings over the same ranges of the operating parameters. There is good correlation between the theoretical and test data, leading to the conclusion that the present turbulent lubrication analysis may be used to obtain general design data for self-acting bearings, operating in the superlaminar flow regime, to supplement that presently existing for laminar flow bearings.

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