Miniature Pressure Probe for Measuring the Surface-Shear-Stress Vector in Turbulent Flow

1981 ◽  
Vol 32 (1) ◽  
pp. 43-47 ◽  
Author(s):  
N. Pontikos ◽  
P. Bradshaw
Keyword(s):  
Shear Stress ◽  
Pressure Difference ◽  
Three Dimensional ◽  
Pressure Probe ◽  
Surface Shear Stress ◽  
Pressure Gradients ◽  
Stress Vector ◽  
Three Dimensional Flow ◽  
Surface Shear ◽  
Plan View

SummaryIf two small fences are arranged approximately at right angles in plan view, the magnitude and direction of surface shear stress can be deduced from measurements of the pressure difference across each fence. Fence heights as small as 0.05 mm are easily achieved. The device is simpler to use than null-seeking arrangements, and is accurate even in the presence of strong pressure gradients, which are shown to have large effects on other types of surface obstacle in three-dimensional flow.

New methodology for the measurement of surface shear stress vector distributions

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 608-614
Author(s):  
Daniel C. Reda ◽  
Michael C. Wilder ◽  
Dino J. Farina ◽  
Greg Zilliac
Keyword(s):  
Shear Stress ◽  
Surface Shear Stress ◽  
Stress Vector ◽  
Surface Shear

A Comprehensive Method to Predict Wear and to Define the Optimum Geometry of Fretting Surfaces

2006 ◽  
Vol 128 (3) ◽  
pp. 476-485 ◽  
Author(s):  
L. Gallego ◽  
D. Nélias ◽  
C. Jacq
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Rolling Contact ◽  
Dissipated Energy ◽  
Surface Shear Stress ◽  
Surface Geometry ◽  
Surface Shear ◽  
Normal Loading ◽  
Slip Regime ◽  
The One

This paper presents a fast and robust three-dimensional contact computation tool taking into account the effect of cyclic wear induced from fretting solicitations under the gross slip regime. The wear prediction is established on a friction-dissipated energy criteria. The material response is assumed elastic. The contact solver is based on the half-space assumption and the algorithm core is similar to the one originally proposed by Kalker (1990, Three Dimensional Elastic Bodies in Rolling Contact, Kluwer, Dordrecht) for normal loading. In the numerical procedure the center of pressure may be imposed. The effect of surface shear stress is considered through a Coulomb friction coefficient. The conjugate gradient scheme presented by Polonsky and Keer (1999, Wear, 231, pp. 206–219) and an improved fast Fourier transform (FFT) acceleration technique similar to the one developed by Liu et al. (2000, Wear, 243, pp. 101–111) are used. Results for elementary geometries in the gross slip regime are presented. It is shown that the surface geometry influences the contact pressure and surface shear stress distributions found after each loading cycle. It is also shown that wear tends to be uniformly distributed. This process continuously modifies the micro- and macrogeometry of the rubbing surfaces, leading after a given number of cycles to (i) an optimum or ideal contact geometry and (ii) a prediction of wear.

New Methodology for the Measurement of Surface Shear Stress Vector Distributions

AIAA Journal ◽  
10.2514/2.165 ◽  
1997 ◽  
Vol 35 (4) ◽  
pp. 608-614 ◽  
Author(s):  
Daniel C. Reda ◽  
Michael C. Wilder ◽  
Dino J. Farina ◽  
Greg Zilliac
Keyword(s):  
Shear Stress ◽  
Surface Shear Stress ◽  
Stress Vector ◽  
Surface Shear

Areal measurements of surface shear stress vector distributions using liquid crystal coatings

1996 ◽  
Author(s):  
D. Reda ◽  
M. Wilder ◽  
D. Farina ◽  
G. Zilliac ◽  
R. McCabe ◽  
...  
Keyword(s):  
Shear Stress ◽  
Liquid Crystal ◽  
Surface Shear Stress ◽  
Stress Vector ◽  
Surface Shear

Measurement of surface shear stress vector beneath high-speed jet flow using liquid crystal coating

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840029
Author(s):  
Cheng-Peng Wang ◽  
Ji-Song Zhao ◽  
Yun Jiao ◽  
Ke-Ming Cheng
Keyword(s):  
Shear Stress ◽  
Liquid Crystal ◽  
Wind Tunnel ◽  
High Speed ◽  
Jet Flow ◽  
Test Surface ◽  
Surface Shear Stress ◽  
Stress Vector ◽  
Surface Shear ◽  
Coating Color

The shear-sensitive liquid crystal coating (SSLCC) technique is investigated in the high-speed jet flow of a micro-wind-tunnel. An approach to measure surface shear stress vector distribution using the SSLCC technique is established, where six synchronous cameras are used to record the coating color at different circumferential view angles. Spatial wall shear stress vector distributions on the test surface are obtained at different velocities. The results are encouraging and demonstrate the great potential of the SSLCC technique in high-speed wind-tunnel measurement.

Laboratory-scale investigation of a periodically forced stratified basin with inclined endwalls

2021 ◽  
Vol 932 ◽  
Author(s):  
Sara Marković ◽  
Vincenzo Armenio
Keyword(s):  
Shear Stress ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Boussinesq Approximation ◽  
Laboratory Scale ◽  
Navier Stokes ◽  
Fundamental Wave ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Vertical Mode

We present results of numerical simulations of a stratified reservoir with a three-layer stratification, subject to an oscillating surface shear stress. We investigate the effect of sloped endwalls on mixing and internal wave adjustment to forcing within the basin, for three different periods of forcing. The simulations are carried out at a laboratory scale, using large-eddy simulation. We solve the three-dimensional Navier–Stokes equations under the Boussinesq approximation using a second-order-accurate finite-volume solver. The model was validated by reproducing experimental results for the response of a reservoir to surface shear stress and resonant frequencies of internal waves. We find interesting combinations of wave modes and mixing under variation of the forcing frequencies and of the inclination of the endwalls. When the frequency of the forcing is close to the fundamental mode-one wave frequency, a resonant internal seiche occurs and the response is characterized by the first vertical mode. For forcing periods twice and three times the fundamental period, the dominant response is in terms of the second vertical mode. Adjustment to forcing via the second vertical mode is accompanied by the cancellation of the fundamental wave and energy transfer to higher-frequency waves. The study shows that the slope of the endwalls dramatically affects the location of mixing, which has a feedback on the wave field by promoting the generation of higher vertical modes.

Visualization of separation and reattachment in an incident shock-induced interaction

2021 ◽  
pp. 095441002098349
Author(s):  
Yun Jiao ◽  
Chengpeng Wang
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Shear Stress ◽  
Separation Bubble ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Bottom Wall ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Oil Flow

An experimental study is conducted on the qualitative visualization of the flow field in separation and reattachment flows induced by an incident shock interaction by several techniques including shear-sensitive liquid crystal coating (SSLCC), oil flow, schlieren, and numerical simulation. The incident shock wave is generated by a wedge in a Mach 2.7 duct flow, where the strength of the interaction is varied from weak to moderate by changing the angle of attack α of the wedge from 8° and 10° to 12°. The stagnation pressure upstream was set to approximately 607.9 kPa. The SSLCC technique was used to visualize the surface flow characteristics and analyze the surface shear stress fields induced by the initial incident shock wave over the bottom wall and sidewall experimentally which resolution is 3500 × 200 pixels, and the numerical simulation was also performed as the supplement for a clearer understanding to the flow field. As a result, surface shear stress over the bottom wall was visualized qualitatively by SSLCC images, and flow features such as separation/reattachment and the variations of position/size of separation bubble with wedge angle were successfully distinguished. Furthermore, analysis of shear stress trend over the bottom wall by a hue value curve indicated that the relative magnitude of shear stress increased significantly downstream of the separation bubble compared with that upstream. The variation trend of shear stress was consistent with the numerical simulation results, and the error of separation position was less than 2 mm. Finally, the three-dimensional schematic of incident shock-induced interaction has been achieved by qualitative summary by multiple techniques, including SSLCC, oil flow, schlieren, and numerical simulation.

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