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.

Correction: Development of a Two-Dimensional Wall Shear Stress Sensor for Wind Tunnel Applications

2019 ◽  
Author(s):  
Brett Freidkes ◽  
David A. Mills ◽  
Casey Keane ◽  
Lawrence S. Ukeiley ◽  
Mark Sheplak
Keyword(s):  
Shear Stress ◽  
Wind Tunnel ◽  
Wall Shear Stress ◽  
Two Dimensional ◽  
Stress Sensor ◽  
Shear Stress Sensor ◽  
Wall Shear

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.

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 Wind Tunnel Measurements of Surface Shear Stress on an Isolated Dune Downwind a Bridge

2020 ◽  
Vol 10 (11) ◽  
pp. 4022 ◽  
Author(s):  
Wenbo Wang ◽  
Hongchao Dun ◽  
Wei He ◽  
Ning Huang
Keyword(s):  
Shear Stress ◽  
Wind Tunnel ◽  
Wall Shear Stress ◽  
Sand Dune ◽  
Bridge Pier ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Windward Slope ◽  
The Mean ◽  
Wall Shear

As part of a comprehensive environmental assessment of the Dun-Gel railway project located in Dunhuang city, Gansu Province, China, a wind tunnel experiment was proposed to predict surface shear stress changes on a sand dune when a bridge was built upstream it. The results show that the length of the wall shear stress shelter region of a bridge is about 10 times of the bridge height (H). In the cases that the interval of the bridge and sand dune (S) is less than 5 H, normalized wall shear stress on the windward crest is decreased from 1.75 (isolated dune) to 1.0 (S = 5.0 H, measured downwind bridge pier) and 1.5 (S = 5.0 H, measured in the middle line of two adjacent bridge piers). In addition, the mean surface shear stress in the downstream zone of the sand dune model is reduced by the bridge pier and is increased by the bridge desk. As for the fluctuation of surface shear stress ( ζ ) on the windward crest, ζ decreases from 1.3 (in the isolated dune case) to 1.2 (in the case S = 5.0 H, measured just downwind the pier) and increases from 1.3 (in the isolated dune case) to 1.6 (in the cases S = 5.0 H, in the middle of two adjacent piers). Taking the mean and fluctuation of surface shear stress into consideration together, we introduce a parameter ψ ranging from 0 to 1. A low value indicates deposition and a high value indicates erosion. On the windward slope, the value of ψ increases with height (from 0 at toe to 0.98 at crest). However, in the cases of S = 1.5 H, ψ is decreased by the bridge in the lower part of the sand dune at y = 0 and is increased at y = L/2 compared with the isolated dune case. In other cases, the change of ψ on the windward slope is not as prominent as in the case of S = 1.5 H. Downstream the sand dune, erosion starts in a point that exists between x = 10 H and 15 H in all cases.

scholarly journals Unsteady flows measurements using a calorimetric wall shear stress micro-sensor

2019 ◽  
Vol 60 (4) ◽  
Author(s):  
Cecile Ghouila-Houri ◽  
Abdelkrim Talbi ◽  
Romain Viard ◽  
Quentin Gallas ◽  
Eric Garnier ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Unsteady Flows ◽  
Micro Sensor ◽  
Wall Shear

High temperature gradient micro-sensor for wall shear stress and flow direction measurements

2016 ◽  
Vol 109 (24) ◽  
pp. 241905 ◽  
Author(s):  
C. Ghouila-Houri ◽  
J. Claudel ◽  
J.-C. Gerbedoen ◽  
Q. Gallas ◽  
E. Garnier ◽  
...  
Keyword(s):  
Shear Stress ◽  
High Temperature ◽  
Temperature Gradient ◽  
Wall Shear Stress ◽  
Flow Direction ◽  
High Temperature Gradient ◽  
Micro Sensor ◽  
Wall Shear

S053073 Study on the measurement of wall shear stress by using micro sensor

2012 ◽  
Vol 2012 (0) ◽  
pp. _S053073-1-_S053073-5
Author(s):  
Takuya SAWADA ◽  
Osamu TERASHIMA ◽  
Yasuhiko SAKAI ◽  
Koji NAGATA ◽  
Hirotaka HIDA ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Micro Sensor ◽  
Wall Shear

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.

scholarly journals A Computational Study of a Passive Flow Device in a Mechanical Heart Valve for the Anatomic Aorta and the Axisymmetric Aorta

CFD letters ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 69-79
Author(s):  
Nursyaira Mohd Salleh ◽  
Mohamad Shukri Zakaria ◽  
Mohd Juzaila Abd Latif ◽  
Adi Azriff Basri
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Heart Valve ◽  
Heart Valves ◽  
Computational Study ◽  
Mechanical Heart Valve ◽  
Vortex Generator ◽  
Leading Edge ◽  
Jude Medical ◽  
Wall Shear

Artificial heart valves for replacing diseased indigenous heart valves were widely used. The treatment of certain types of heart disease requires mechanical valves to be implanted operatively. Healthy cardiac valves are essential to proper cardiac function. The current study presents an investigation of the pulsatile blood flow through a bileaflet mechanical heart valve (BMHV) with a vortex generator (VG) in fully open position. A St. Jude Medical Regent valve with a diameter of 23 mm was used to mount triangular VGs as a means of improving pressure gradients and reducing turbulence. The anatomic aorta and axisymmetric aorta was computed by large eddy simulation (LES) approached. The implications for both models with VGs were observed in terms of velocity magnitude, vortices and wall shear stress. The results suggested that the anatomic aorta is prone to develop more blood clotting at the leading edge of the leaflets with 2.03 m/s. Furthermore, the anatomic aorta produces higher wall shear stress with 69Pa, which possibly contributes to a high risk of thrombosis.

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