Simplification of the Razor Blade Technique and its Application to the Measurement of Wall-Shear Stress in Wall-Jet Flows

1969 ◽  
Vol 20 (4) ◽  
pp. 355-364 ◽  
Author(s):  
B. R. Pai ◽  
J. H. Whitelaw
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Static Pressure ◽  
Jet Flows ◽  
Adhesive Tape ◽  
Wall Jet ◽  
Razor Blade ◽  
Law Of The Wall ◽  
Wall Shear ◽  
Secondary Injection

SummaryExperiments in a in (6-35 mm) channel have yielded further information on the precision and convenience of the razor blade technique. It is shown that adhesive tape or carefully located cement can be used to secure a segment of razor blade over a static pressure hole: the resulting calibration for shear stress remains valid if the blade is removed and relocated over the same or a different, similar sized hole. Razor blade segments, calibrated in this manner, have been used to measure wall-shear stress in a turbulent boundary layer with tangential, secondary injection: the results indicate that V. C. Patel’s law of the wall is valid for such flows.

Preston-Static Tubes for the Measurement of Wall Shear Stress

1994 ◽  
Vol 116 (3) ◽  
pp. 645-649 ◽  
Author(s):  
Josef Daniel Ackerman ◽  
Louis Wong ◽  
C. Ross Ethier ◽  
D. Grant Allen ◽  
Jan K. Spelt
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Convenient Method ◽  
Pipe Flow ◽  
Total Pressure ◽  
Static Pressure ◽  
Shear Stresses ◽  
Streamline Curvature ◽  
Syringe Needle ◽  
Wall Shear

We present a Preston tube device that combines both total and static pressure readings for the measurement of wall shear stress. As such, the device facilitates the measurement of wall shear stress under conditions where there is streamline curvature and/or over surfaces on which it is difficult to either manufacture an array of static-pressure taps or to position a single tap. Our “Preston-static” device is easily and conveniently constructed from commercially available regular and side-bored syringe needles. The pressure difference between the total pressure measured in the regular syringe needle and the static pressure measured in the side-bored one is used to determine the wall shear stress. Wall shear stresses measured in pipe flow were consistent with independently determined values and values obtained using a conventional Preston tube. These results indicate that Preston-static tubes provide a reliable and convenient method of measuring wall shear stress.

An Experimental Study of Local Wall Shear Stress, Surface Static Pressure, and Flow Visualization Upstream, Alongside, and Downstream of a Blade Endwall Corner

1991 ◽  
Vol 113 (4) ◽  
pp. 626-632 ◽  
Author(s):  
A. K. Abdulla ◽  
R. K. Bhargava ◽  
R. Raj
Keyword(s):  
Experimental Study ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Visualization ◽  
Static Pressure ◽  
Leading Edge ◽  
Chord Length ◽  
Corner Region ◽  
Wall Shear ◽  
Blade Leading Edge

The experimental study reported in this paper was performed to acquire information on the distribution of wall shear stress and surface static pressure in a blade endwall corner. The blade endwall corner region investigated was divided into three sections: 0.4 chord length upstream of the blade leading edge, inside the endwall corner region, and one chord length downstream of the blade trailing edge. The maximum increases in the values of wall shear stress were found to exist on the endwall, in the corner region, between the blade leading edge and the location of maximum blade thickness (≈ 140 percent maximum increase, compared to its far upstream value, at x/D = 6). Surface flow visualization defined the boundaries of the vortex system and provided information on the direction and magnitude of the wall shear stress. The acquired results indicated that the observed variations of wall shear stress and surface static pressure were significantly influenced by the interaction of secondary flows with pressure gradients induced by the presence of blade curvature.

The Law of the Wall for Swirling Flow in Annular Ducts

1989 ◽  
Vol 111 (2) ◽  
pp. 160-164 ◽  
Author(s):  
R. J. Kind ◽  
F. M. Yowakim ◽  
S. A. Sjolander
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Swirling Flow ◽  
Tangential Velocity ◽  
Wall Region ◽  
Law Of The Wall ◽  
Resultant Velocity ◽  
The Law ◽  
Wall Shear ◽  
Near Wall

Expressions for the logarithmic portion of the law of the wall are derived for the axial and tangential velocity components of swirling flow in annular ducts. These expressions involve new shear-velocity scales and curvature terms. They are shown to agree well with experiment over a substantial portion of the flow near both walls of an annulus. The resultant velocity data also agree with the law of the wall. The success of the proposed logarithmic expressions implies that the mixing-length model used in deriving them correctly describes flow-velocity behavior. This model indicates that the velocity gradient at any height y in the near-wall region is determined by the wall shear stress, not by the local shear stress. This suggests that the influence of wall shear stress is dominant and that it determines the near-wall wall flow even in flows with curvature and pressure gradient. A physical explanation is suggested for this.

Measurements and prediction of fully developed turbulent flow in an equilateral triangular duct

1978 ◽  
Vol 85 (1) ◽  
pp. 57-83 ◽  
Author(s):  
A. M. M. Aly ◽  
A. C. Trupp ◽  
A. D. Gerrard
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pipe Flow ◽  
Axial Velocity ◽  
Reynolds Stresses ◽  
Cross Sectional ◽  
Number Range ◽  
Law Of The Wall ◽  
The Cross ◽  
Wall Shear

Fully developed air-flows through an equilateral triangular duct of 12·7 cm sides were investigated over a Reynolds number range of 53 000 to 107 000. Based on equivalent hydraulic diameter, friction factors were found to be about 6% lower than for pipe flow. Mean axial velocity distributions near the wall were describable by the inner law of the wall (when based on local wall shear stress) but the constants differ slightly from those for pipe flow. As expected, the secondary flow pattern was found to consist of six counter-rotating cells bounded by the corner bisectors. Maximum secondary velocities of about 1 ½% of the bulk velocity were observed. The effects of secondary currents were evident in the cross-sectional distributions of mean axial velocity, wall shear stress and Reynolds stresses, and very prominent in the turbulent kinetic energy distribution. For the flow prediction, the vorticity production terms were expressed by modelling the Reynolds stresses in the plane of the cross-section in terms of gradients in the mean axial velocity and a geometrically calculated turbulence length scale. The experimental and predicted characteristics of the flow are shown to be in good agreement.

Wall Shear Stress Inference From Two and Three-Dimensional Turbulent Boundary Layer Velocity Profiles

1973 ◽  
Vol 95 (1) ◽  
pp. 61-67 ◽  
Author(s):  
F. J. Pierce ◽  
B. B. Zimmerman
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Velocity Profile ◽  
Three Dimensional ◽  
Law Of The Wall ◽  
Layer Velocity ◽  
Wall Shear ◽  
Near Wall

A method is developed to infer a local wall shear stress from a two-dimensional turbulent boundary layer velocity profile using all near-wall data with the Spalding single formula law of the wall. The method is used to broaden the Clauser chart scheme by providing for the inclusion of data in the laminar sublayer and transition region, as well as the data in the fully turbulent near-wall flow region. For a skewed velocity profile typical of pressure driven three-dimensional turbulent boundary layer flows, the method is extended to infer a wall shear stress for a three-dimensional turbulent boundary layer. Either wall shear stress or shear velocity values are calculated for two different sets of three-dimensional experimental data, with good agreement found between calculated and experimental results.

Experimental Investigation of Flow Resistance and Wall Shear Stress in the Interior Subchannel of a Triangular Array of Parallel Rods

1979 ◽  
Vol 101 (4) ◽  
pp. 429-434 ◽  
Author(s):  
M. Fakory ◽  
N. Todreas
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Friction Factor ◽  
Static Pressure ◽  
Reynolds Numbers ◽  
Triangular Array ◽  
Flow Area ◽  
Static Pressure Distribution ◽  
The Common ◽  
Wall Shear

A simulated model of a triangular array of rods with pitch to diameter ratio of 1.1 with air flow was used to study the hydraulic parameters of the liquid metal fast breeder reactor (LMFBR) fuel geometry. The wall shear stress distribution, static pressure distribution, turbulence intensity, and friction factor were measured in the central subchannel from Reynolds numbers of 4 × 103 to 36 × 103. Our results show that the maximum wall shear stress occurs at the largest flow area, the static pressure is not uniform around the rod periphery, there is no detectable presence of secondary flow from the wall shear stress measurements, and the friction factor derived from the measured wall shear stress is less than the common friction factor derived from pressure drop measurement.

Theoretical Analysis of Laminar Pipe Flow in a Porous Wall Cylinder

1971 ◽  
Vol 93 (2) ◽  
pp. 102-108 ◽  
Author(s):  
L. S. Galowin ◽  
M. J. Desantis
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Boundary Conditions ◽  
Pressure Difference ◽  
Static Pressure ◽  
Flow Direction ◽  
Axial Flow ◽  
Initial Pressure ◽  
Porous Wall ◽  
Wall Shear

A theoretical investigation was conducted to obtain velocity, pressure, and shear stress distributions for incompressible, steady, fully developed, laminar flow through a cylinder with a uniformly porous wall. Ejection/injection at the walls results from the pressure difference across the porous wall. Fluid flow phenomena in porous tubes and ducts have previously been investigated with the velocity prescribed as the boundary condition at the wall. An accurate wall condition must account for the variable wall velocity being dependent upon the pressure difference across the wall, the properties of the fluid, the thickness and the permeability of the structure. An integral momentum technique was employed to reduce the axisymmetric Navier-Stokes equations in cylindrical coordinates to a nonlinear, second-order ordinary differential equation with appropriate boundary conditions. The velocity condition at the wall was established for the ejection/injection at the surface resulting from the pressure difference across the porous wall derived from Darcy’s law. Numerical solutions were obtained for a range of axial flow Reynolds numbers, wall permeabilities, and initial pressure difference across the porous wall. The calculated static pressure variation in the axial flow direction, the velocity components, and the wall shear stress are presented. For the case of fluid ejection, the results of the analysis show that the wall shear stress and static pressure decrease in the axial flow direction. The rates of decrease are functions of the wall porosity, initial pressure gradient across the wall, and inlet flow Reynolds number. The present analysis treats the realistic problem of flow adjustment to the condition where zero pressure differential across the porous wall occurs (the normal wall velocity vanishes). Previous models are based upon the assumptions of constant radial velocity at the wall and/or prescribed wall shear stress without taking into account the pressure drop through the wall. Such assumptions imply that a variable pressure exists external to the pipe, or that the pipe has walls of variable permeability and thickness rather than the hypothesized condition that the pipe has uniformly porous walls. For one set of boundary conditions it is shown that the outflow through the walls completely discharges the entering flow. As a result no far downstream axial flow occurs. Such effects were not previously discussed by other investigators. For other sets of boundary conditions reductions in centerline velocity and shear stress occur.

scholarly journals A New Wall Shear Stress Model for Atmospheric Boundary Layer Simulations

2013 ◽  
Vol 70 (11) ◽  
pp. 3460-3470 ◽  
Author(s):  
Marcus Hultmark ◽  
Marc Calaf ◽  
Marc B. Parlange
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Atmospheric Boundary Layer ◽  
Large Eddy Simulations ◽  
Stress Model ◽  
Law Of The Wall ◽  
Proposed Model ◽  
Large Eddy ◽  
Wall Shear

Abstract A new wall shear stress model to be used as a wall boundary condition for large-eddy simulations of the atmospheric boundary layer is proposed. The new model computes the wall shear stress and the vertical derivatives of the streamwise velocity component by means of a modified, instantaneous, and local law-of-the-wall formulation. By formulating a correction for the modeled shear stress, using experimental findings of a logarithmic region in the streamwise turbulent fluctuations, the need for a filter is eliminated. This allows one to model the wall shear stress locally, and at the same time accurately recover the correct average value. The proposed model has been applied to both unique high Reynolds number experimental data and a suite of large-eddy simulations, and compared to previous models. It is shown that the proposed model performs equally well or better than the previous filtered models. A nonfiltered model, such as the one proposed, is an essential first step in developing a universal wall shear stress model that can be used for flow over heterogeneous surfaces, studies of diurnal cycles, or analyses of flow over complex terrain.

scholarly journals An Experimental Study of Local Wall Shear Stress, Surface Static Pressure and Flow Visualization Upstream, Alongside, and Downstream of a Blade Endwall Corner

1990 ◽  
Author(s):  
A. K. Abdulla ◽  
R. K. Bhargava ◽  
R. Raj
Keyword(s):  
Experimental Study ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Visualization ◽  
Static Pressure ◽  
Leading Edge ◽  
Chord Length ◽  
Maximum Increase ◽  
Corner Region ◽  
Wall Shear

An experimental study reported in this paper was intended to acquire information on the distribution of wall shear stress and surface static pressure in a blade endwall corner. The blade endwall corner region investigated was divided into three sections: 0.4 chord length upstream of the blade leading edge, inside the endwall corner region, and one-chord length downstream of the blade trailing edge. Maximum increase in the values of wall shear stress were found to exist on the endwall, in the corner region, between the blade leading edge and the location of maximum blade thickness (≈140% maximum increase, compared to its far upstream value, at x/D=6). Surface flow visualization defined the boundaries of the vortex system and provided information on the direction and magnitude of the wall shear stress. The acquired results indicated that the observed variations of wall shear stress and surface static pressure were significantly influenced by the interaction of secondary flows with pressure gradients induced by the presence of blade curvature.

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