Time-Mean Wall Static Pressure Distributions and Module Friction Factors for Fully Developed Flows in a Rectangular Duct With Spatially Periodic Interrupted-Plate Inserts

2003 ◽  
Author(s):  
Jose´ A. Candanedo ◽  
Emile Aboumansour ◽  
B. Rabi Baliga
Keyword(s):  
Reynolds Number ◽  
Static Pressure ◽  
Plate Thickness ◽  
Compact Heat Exchangers ◽  
Plate Length ◽  
Plate Spacing ◽  
Pressure Distributions ◽  
Half Height ◽  
Friction Factors ◽  
Spatially Periodic

An experimental study of fully developed flows of air in straight rectangular ducts with interrupted-plate inserts is presented. These flows have features akin to those produced in the cores of plate-fin compact heat exchangers. In all, flows in one plain duct and six different ducts with interrupted-plate inserts were studied. Values of the dimensionless geometric parameters of the interrupted-plate ducts, normalized with respect to its half-height, are the following: width of the duct cross-section between 19.68 and 23.58; plate length between 3.286 and 3.938; plate thickness of 0.062, 0.115, and 0.205; and inter-plate spacing between 3.264 and 7.815. Values of the Reynolds number, based on a nominal average velocity and hydraulic diameter, ranged from 1663 to 30993. The results include graphical and tabular presentations of time-mean static pressure distributions along the axial centerline of the top wall of the duct, and module friction factor versus Reynolds number data, all in the periodic fully developed region.

Module Friction Factors and Intramodular Pressure Distributions for Periodic Fully Developed Turbulent Flow in Rectangular Interrupted-Plate Ducts

1988 ◽  
Vol 110 (2) ◽  
pp. 147-154 ◽  
Author(s):  
R. K. McBrien ◽  
B. R. Baliga
Keyword(s):  
Turbulent Flows ◽  
Static Pressure ◽  
Rectangular Cross Section ◽  
Reynolds Numbers ◽  
Plate Spacing ◽  
Pressure Distributions ◽  
Geometric Configurations ◽  
Friction Factors ◽  
Mean Pressure ◽  
Fully Developed Turbulent Flow

This paper presents detailed time-mean pressure measurements for periodic fully developed turbulent flows in straight interrupted-plate ducts of rectangular cross section. Several combinations of plate spacing and duct aspect ratio are investigated for Reynolds numbers, based on a module hydraulic diameter, in the range 5000 to 45000. The experiments undertaken in this work establish the existence of steady, time-mean, periodic fully developed flows for all flow rates and geometric configurations investigated. The results include graphical and tabular presentations of module friction factor versus Reynolds number data, and intramodular time-mean wall static pressure distributions. The physical implications of these results are also discussed.

Temporally- and Spatially-Periodic Laminar Flow and Heat Transfer in Staggered-Plate Arrays

2007 ◽  
Author(s):  
Alexandre Lamoureux ◽  
B. Rabi Baliga
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Numerical Solutions ◽  
Initial Conditions ◽  
Plate Thickness ◽  
Geometrical Parameters ◽  
Reduced Pressure ◽  
Flow And Heat Transfer ◽  
Spatially Periodic

A computational investigation of temporally- and spatially-periodic laminar two-dimensional fluid flow and heat transfer in staggered-plate arrays is presented in this paper. The objective and the novel aspect of this study is the investigation of the influence (on the numerical solutions) of including single and multiple representative geometric modules in the calculation domain, with spatially-periodic boundary conditions imposed on the instantaneous velocity and temperature fields in both the streamwise and the lateral directions. The following geometrical parameters, normalized with respect to a representative module height, were studied: a dimensionless plate length equal to 1, and a dimensionless plate thickness of 0.250. This relatively high value of dimensionless plate thickness, compared to those commonly encountered in rectangular offset-fin cores of compact heat exchangers, was deliberately chosen to induce and enhance the unsteady features of the fluid flow and heat transfer phenomena. Different specified values of the time-mean modular streamwise gradient of the reduced pressure were investigated, yielding values of Reynolds number (Kays and London definition) in the range of 100 to 625. The Prandtl number was fixed at 0.7. In the multiple-module simulations, for Reynolds number values exceeding 400, it was found that multiple solutions are possible: the particular solution which is obtained in any one simulation depends on the specified initial conditions. The results presented include time-mean modular friction factors, modular Colburn factors, and Strouhal numbers.

Static Pressure Distributions Over 2D Mast/Sail Geometries

1989 ◽  
Vol 26 (04) ◽  
pp. 333-337
Author(s):  
Stuart Wilkinson
Keyword(s):  
Reynolds Number ◽  
Static Pressure ◽  
Incidence Angle ◽  
Flow Regimes ◽  
Two Dimensional ◽  
Test Program ◽  
Flow Parameters ◽  
Pressure Distributions

A variable-camber aerofoil with integral pressure tappings has been built to investigate the nature of the flows around two-dimensional, highly cambered, sail-like aerofoil sections with circular masts. Data have been obtained in the form of static pressure distributions over representative ranges of Reynolds number, camber ratio, incidence angle, mast diameter/chord ratio and mast angle. Two sail shapes—based on the NACA a = 0.8 and NACA 63 mean-line camber distributions—were involved in the test program. All flow regimes present have been identified and related to the salient model and flow parameters.

An Experimental Investigation of Pressure Distributions in a Journal Bearing Operating in the Transition Regime

1986 ◽  
Vol 200 (4) ◽  
pp. 251-264 ◽  
Author(s):  
J B Roberts ◽  
P J Mason
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Journal Bearing ◽  
Transition Regime ◽  
Pressure Measurements ◽  
Eccentricity Ratio ◽  
Clearance Ratio ◽  
Viscosity Parameter ◽  
Pressure Distributions ◽  
Friction Factors

Experimental results are presented, relating to friction factors and circumferential pressure distributions, for a plain cylindrical journal bearing with a central circumferential inlet groove. The length-diameter ratio of each journal bearing land was 0.25 and the clearance ratio was 0.0031. The friction factor results showed the existence of a distinct ‘transition regime’, characterized by a pronounced ‘hump’ in the friction factor-Reynolds number relationship. Pressure measurements recorded when operating in this transition regime revealed the inadequacy of many existing ‘turbulent’ theories for superlaminar lubrication. By using a short-bearing theory a good correlation of the pressure distribution results was obtained, in terms of a non-dimensional viscosity parameter, kz, which is dependent on both the eccentricity ratio and Reynolds number. The magnitude of kz in this regime was considerably higher than the corresponding value for laminar flow, and was similar to the magnitude predicted from a simple theory based on relating kz to the variation of measured friction factor with Reynolds number.

Pressure Distributions in a Superlaminar Journal Bearing

1982 ◽  
Vol 104 (2) ◽  
pp. 187-195 ◽  
Author(s):  
J. B. Roberts ◽  
R. E. Hinton
Keyword(s):  
Reynolds Number ◽  
Total Pressure ◽  
Pressure Field ◽  
Journal Bearing ◽  
Pressure Measurements ◽  
Inertial Effects ◽  
Empirical Theory ◽  
Number Range ◽  
Pressure Distributions ◽  
Friction Factors

The main features of a comprehensive set of pressure measurements, obtained from a short, plain journal bearing, are presented. The pressure field in the lubricant film was measured in both the circumferential and axial directions over a Reynolds number range of 40–50,000. In cases where the film is noncavitating the pressure distributions are separated into viscous and inertial components. The inertial components are found to agree fairly well with an approximate short bearing theory. Axially averaged, total pressure distributions are compared with the predictions of a simple, empirical theory based on measured friction factors and incorporating inertial effects.

Mean velocity and static pressure distributions of a circular jet

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 196-197
Author(s):  
M. T. Islam ◽  
M. A. T. Ali
Keyword(s):  
Static Pressure ◽  
Mean Velocity ◽  
Pressure Distributions

Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Henrique Stel ◽  
Rigoberto E. M. Morales ◽  
Admilson T. Franco ◽  
Silvio L. M. Junqueira ◽  
Raul H. Erthal ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Geometric Configurations ◽  
Corrugated Surfaces ◽  
Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

Experimental and Computational Analyses of Pressure Differentials in Flexible Ducts With Different Bent Angles

2007 ◽  
Author(s):  
Ray R. Taghavi ◽  
Wonjin Jin ◽  
Mario A. Medina
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Complex Geometry ◽  
Analysis Data ◽  
Secondary Flows ◽  
Low Flow ◽  
Pressure Drops ◽  
Pressure Distributions ◽  
Geometrical Effects ◽  
Cfd Analyses

A set of experimental analyses was conducted to determine static pressure drops inside non-metallic flexible, spiral wire helix core ducts, with different bent angles. In addition, Computational Fluid Dynamics (CFD) solutions were performed and verified by comparing them to the experimental data. The CFD computations were carried out to produce more systematic pressure drop information through these complex-geometry ducts. The experimental setup was constructed according to ASHRAE Standard 120-1999. Five different bent angles (0, 30, 45, 60, and 90 degrees) were tested at relatively low flow rates (11 to 89 CFM). Also, two different bent radii and duct lengths were tested to study flexible duct geometrical effects on static pressure drops. FLUENT 6.2, using RANS based two equations - RNG k-ε model, was used for the CFD analyses. The experimental and CFD results showed that larger bent angles produced larger static pressure drops in the flexible ducts. CFD analysis data were found to be in relatively good agreement with the experimental results for all bent angle cases. However, the deviations became slightly larger at higher velocity regimes and at the longer test sections. Overall, static pressure drop for longer length cases were approximately 0.01in.H2O higher when compared to shorter cases because of the increase in resistance to the flow. Also, the CFD simulations captured more pronounced static pressure drops that were produced along the sharper turns. The stronger secondary flows, which resulted from higher and lower static pressure distributions in the outer and inner surfaces, respectively, contributed to these higher pressure drops.

The Relationship Between Frictional Resistance and Roughness for Surfaces Smoothed by Sanding

2002 ◽  
Vol 124 (2) ◽  
pp. 492-499 ◽  
Author(s):  
Michael P. Schultz
Keyword(s):  
Reynolds Number ◽  
Frictional Resistance ◽  
Resistance Coefficient ◽  
Polished Surface ◽  
Average Height ◽  
Freestream Velocity ◽  
Number Range ◽  
Test Fixture ◽  
Plate Length ◽  
The Relationship

An experimental investigation has been carried out to document and relate the frictional resistance and roughness texture of painted surfaces smoothed by sanding. Hydrodynamic tests were carried out in a towing tank using a flat plate test fixture towed at a Reynolds number ReL range of 2.8×106−5.5×106 based on the plate length and freestream velocity. Results indicate an increase in frictional resistance coefficient CF of up to 7.3% for an unsanded, as-sprayed paint surface compared to a sanded, polished surface. Significant increases in CF were also noted on surfaces sanded with sandpaper as fine as 600-grit as compared to the polished surface. The results show that, for the present surfaces, the centerline average height Ra is sufficient to explain a large majority of the variance in the roughness function ΔU+ in this Reynolds number range.

Three-dimensional flow in cavities

1963 ◽  
Vol 16 (4) ◽  
pp. 620-632 ◽  
Author(s):  
D. J. Maull ◽  
L. F. East
Keyword(s):  
Static Pressure ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Three Dimensional Flow ◽  
Large Span ◽  
Dimensional Flow ◽  
Pressure Distributions ◽  
Oil Flow ◽  
Two Dimensional Flow

The flow inside rectangular and other cavities in a wall has been investigated at low subsonic velocities using oil flow and surface static-pressure distributions. Evidence has been found of regular three-dimensional flows in cavities with large span-to-chord ratios which would normally be considered to have two-dimensional flow near their centre-lines. The dependence of the steadiness of the flow upon the cavity's span as well as its chord and depth has also been observed.

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