An Investigation of the Effect of Cavitation Bubbles on the Momentum Loss in Transient Pipe Flow

1971 ◽  
Vol 93 (1) ◽  
pp. 1-7 ◽  
Author(s):  
M. E. Weyler ◽  
V. L. Streeter ◽  
P. S. Larsen
Keyword(s):  
Shear Stress ◽  
Physical Model ◽  
Pipe Flow ◽  
Pressure Waves ◽  
Separation Flow ◽  
Column Separation ◽  
Momentum Loss ◽  
Transient Pipe Flow ◽  
Pressure Changes ◽  
Separation Conditions

Based on experimental observations of pressure changes during hydraulic transients in pipe flow with column separation, a physical model was hypothesized and correlated with the data to provide a semiempirical “bubble shear stress” which can be used to predict the increased momentum loss observed under column separation conditions. The “bubble shear stress” arises from the nonadiabatic expansion and collapse of gas bubbles present throughout the low pressure column separation flow, and is found to be proportional to the strength of passing pressure waves, and a weak function of the amount of gas trapped on the pipe walls.

scholarly journals Direct Measurement of Stress at the Base of a Glacier

1979 ◽  
Vol 22 (86) ◽  
pp. 3-24 ◽  
Author(s):  
G. S. Boulton ◽  
E. M. Morris ◽  
A. A. Armstrong ◽  
A. Thomas
Keyword(s):  
Shear Stress ◽  
Volume Concentration ◽  
Normal Pressure ◽  
Spatial Average ◽  
Short Term ◽  
Overburden Pressure ◽  
Basal Ice ◽  
Debris Particles ◽  
Or Groups ◽  
Pressure Changes

AbstractContact stress transducers were placed in subglacial bedrock and used to monitor continuously shear stress and normal pressure changes at the contact with the overriding glacier sole 100 m beneath the surface of the Glacier d’Argentière during periods in summer 1973 and spring 1975. The measured fluctuations in normal pressure and shear stress do not appear to be related to changes in sliding velocity. Analysis of the data reveals short-term fluctuations in normal pressure and shear stress which appear to be related to the passage of individual large debris particles or groups of particles over the transducer. The shear stress appears to be a function of the volume concentration of debris in the ice. The volume concentration at any point appears to be partially dependent on a “streaming” process by which basal debris-rich ice tends to flow around the lateral flanks of hummocks on the glacier bed. Where sub-glacial cavities occur, this streaming effect appears to be dependent on the extent of cavitation and thus on ice overburden pressure and velocity. It is suggested that this process can account for an apparent lag between changes in normal pressure and shear stress.The maximum ratio between shear and normal stress averaged over a period of 10 min was 0.44. This is equivalent to a spatial average over 0.3 cm. Debris concentrations in basal ice of up to 43% by volume occurred. It is suggested that concentrations of this order are common at the base of temperate glaciers and thus that a significant part of the drag at the base of a glacier may be contributed by frictional interactions between the basal-debris load and the bed.

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.

Numerical and experimental investigation of transient pipe flow

1994 ◽  
Vol 32 (5) ◽  
pp. 689-706 ◽  
Author(s):  
Amgad S. Elansary ◽  
M. Hanif Chaudhry ◽  
Walter Silva
Keyword(s):  
Experimental Investigation ◽  
Pipe Flow ◽  
Transient Pipe Flow

scholarly journals Shear stress fluctuation measurements using an electrochemical method in pipe flow

2019 ◽  
Vol 14 (2) ◽  
pp. JFST0013-JFST0013 ◽  
Author(s):  
Tong TONG ◽  
Tatsuya TSUNEYOSHI ◽  
Yoshiyuki TSUJI
Keyword(s):  
Shear Stress ◽  
Pipe Flow ◽  
Electrochemical Method ◽  
Stress Fluctuation

Estimation of gas wall shear stress in horizontal stratified gas-liquid pipe flow

AIChE Journal ◽  
1996 ◽  
Vol 42 (8) ◽  
pp. 2369-2373 ◽  
Author(s):  
Charles H. Newton ◽  
Masud Behnia
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pipe Flow ◽  
Wall Shear

Modification of Shear Stress Transport Turbulence Model Using Helicity for Predicting Corner Separation Flow in a Linear Compressor Cascade

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Yangwei Liu ◽  
Yumeng Tang ◽  
Ashley D. Scillitoe ◽  
Paul G. Tucker
Keyword(s):  
Shear Stress ◽  
Turbulence Model ◽  
Incidence Angle ◽  
Computational Cost ◽  
Separation Flow ◽  
Compressor Cascade ◽  
Production Term ◽  
Corner Separation ◽  
Shear Stress Transport ◽  
Sst Model

Abstract Three-dimensional corner separation significantly affects compressor performance, but turbulence models struggle to predict it accurately. This paper assesses the capability of the original shear stress transport (SST) turbulence model to predict the corner separation in a linear highly loaded prescribed velocity distribution (PVD) compressor cascade. Modifications for streamline curvature, Menter’s production limiter, and the Kato-Launder production term are examined. Comparisons with experimental data show that the original SST model and the SST model with different modifications can predict the corner flow well at an incidence angle of −7 deg, where the corner separation is small. However, all the models overpredict the extent of the flow separation when the corner separation is larger, at an incidence angle of 0 deg. The SST model is then modified using the helicity to take account of the energy backscatter, which previous studies have shown to be important in the corner separation regions of compressors. A Reynolds stress model (RSM) is also used for comparison. By comparing the numerical results with experiments and RSM results, it can be concluded that sensitizing the SST model to helicity can greatly improve the predictive accuracy for simulating the corner separation flow. The accuracy is quite competitive with the RSM, whereas in terms of computational cost and robustness it is superior to the RSM.

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