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.

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.

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.

scholarly journals Accurate Measurements of Wall Shear Stress on a Plate with Elliptic Leading Edge

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2682 ◽  
Author(s):  
Guang-Hui Ding ◽  
Bing-He Ma ◽  
Jin-Jun Deng ◽  
Wei-Zheng Yuan ◽  
Kang Liu
Keyword(s):  
Shear Stress ◽  
Wind Tunnel ◽  
Wall Shear Stress ◽  
Leading Edge ◽  
Reynold Number ◽  
Micro Electro Mechanical System ◽  
Flow Speed ◽  
Silicon On Insulator ◽  
Micro Sensor ◽  
Wall Shear

A micro-floating element wall shear stress sensor with backside connections has been developed for accurate measurements of wall shear stress under the turbulent boundary layer. The micro-sensor was designed and fabricated on a 10.16 cm SOI (Silicon on Insulator) wafer by MEMS (Micro-Electro-Mechanical System) processing technology. Then, it was calibrated by a wind tunnel setup over a range of 0 Pa to 65 Pa. The measurements of wall shear stress on a smooth plate were carried out in a 0.6 m × 0.6 m transonic wind tunnel. Flow speed ranges from 0.4 Ma to 0.8 Ma, with a corresponding Reynold number of 1.05 × 106~1.55 × 106 at the micro-sensor location. Wall shear stress measured by the micro-sensor has a range of about 34 Pa to 93 Pa, which is consistent with theoretical values. For comparisons, a Preston tube was also used to measure wall shear stress at the same time. The results show that wall shear stress obtained by three methods (the micro-sensor, a Preston tube, and theoretical results) are well agreed with each other.

Analysis of Laminar Mixed Convective Plumes Along Vertical Adiabatic Surfaces

1984 ◽  
Vol 106 (3) ◽  
pp. 552-557 ◽  
Author(s):  
K. V. Rao ◽  
B. F. Armaly ◽  
T. S. Chen
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Leading Edge ◽  
Vertical Surface ◽  
Stream Velocity ◽  
Thermal Source ◽  
Flow Conditions ◽  
Velocity Overshoot ◽  
Wall Shear ◽  
Prandtl Numbers

Laminar mixed forced and free convection from a line thermal source imbedded at the leading edge of an adiabatic vertical surface is analytically investigated for the cases of buoyancy assisting and buoyancy opposing flow conditions. Temperature and velocity distributions in the boundary layer adjacent to the adiabatic surface are presented for the entire range of the buoyancy parameter ξ (x) = Grx/Rex5/2 from the pure forced (ξ(x) = 0) to the pure free (ξ(x) = ∞) convection regime for fluids having Prandtl numbers of 0.7 and 7.0. For buoyancy-assisting flow, the velocity overshoot, the temperature, and the wall shear stress increase as the plume’s strength increases. On the other hand, the velocity overshoot, the wall shear stress, and the temperature decrease as the free-stream velocity increases. For buoyancy opposing flow, the velocity and wall shear stress decrease but the temperature increases as the plume’s strength increases.

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.

scholarly journals Secondary Flow Development Downstream of a Blade Endwall Corner

1994 ◽  
Author(s):  
A. Karim Abdulla-Altaii ◽  
Rishi S. Raj
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flat Plate ◽  
Secondary Flow ◽  
Total Pressure ◽  
Static Pressure ◽  
Horseshoe Vortex ◽  
Chord Length ◽  
Trailing Edge

The flow downstream of the corner formed by a blade and a flat plate was investigated experimentally. A single dominant horseshoe vortex was identified which persisted more than one chord length downstream of the blade trailing edge. A smaller and weaker corner vortex was also identified. It dissipated and ceased to exist by a downstream axial location of approximately 0.2C (C= chord length). There was no evidence of stress induced vortices in the region of this investigation. The secondary flow system redistributes the mean flow momentum and distorts total pressure profiles and contours. In planes parallel to the flat plate, total pressure values were found to be higher than the undisturbed two-dimensional boundary layer at that height. Surface static pressure was found to be at its maximum at the blade trailing edge location and it decreased in both the downstream and transverse directions. There was no significant static pressure variation in the spanwise direction. Downstream of the blade trailing edge, under the domain of the horseshoe vortex, local wall shear stress increased to values exceeding the values found in the undisturbed boundary layer at that axial location. However, a 20% reduction in the net wall skin-friction (wall shear stress integrated over the flat plate surface) was observed.

Sign in / Sign up

Export Citation Format

Share Document