Properties of Wall Shear Stress Fluctuations in a Turbulent Duct Flow

1977 ◽  
Vol 44 (3) ◽  
pp. 389-395 ◽  
Author(s):  
K. R. Sreenivasan ◽  
R. A. Antonia
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Probability Density ◽  
Duct Flow ◽  
Zero Crossing ◽  
Number Range ◽  
Stress Fluctuation ◽  
Moderate Reynolds Number ◽  
Wall Shear ◽  
Turbulent Duct Flow

Measurements of wall shear stress fluctuations have been made in a fully developed turbulent duct flow, using a surface heat transfer gauge. Measurements, made over a moderate Reynolds number range, include RMS values, probability density functions, spectra, and zero-crossing frequencies of the wall shear stress fluctuation. The ratio of RMS of the fluctuation to the mean value of the wall shear stress is found to be about 0.25. The zero-crossing frequency computed from the measured spectra using the relation derived by Rice for a Gaussian process is found to be a good approximation to the measured value, although the measured probability density function is not Gaussian. The zero crossing frequency and spectra of wall shear stress fluctuations appear to scale with outer variables for asymptotically large Reynolds numbers.

Wall-shear stress patterns of coherent structures in turbulent duct flow

2009 ◽  
Vol 633 ◽  
pp. 147-158 ◽  
Author(s):  
SEBASTIAN GROSSE ◽  
WOLFGANG SCHRÖDER
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Wall Shear Stress ◽  
Coherent Structures ◽  
Shear Stress Distribution ◽  
Duct Flow ◽  
Wall Shear Stress Distribution ◽  
Wall Shear ◽  
Turbulent Duct Flow ◽  
Low Shear

The wall-shear stress distribution in turbulent duct flow has been assessed using the micro-pillar shear-stress sensor MPS3. The spatial resolution of the sensor line is 10.8l+(viscous units) and the total field of view of 120l+along the spanwise direction allows to capture characteristic dimensions of the wall-shear stress distribution at sufficiently high resolution. The results show the coexistence of low-shear and high-shear regions representing ‘footprints’ of near-wall coherent structures. The regions of low shear resemble long meandering bands locally interrupted by areas of higher shear stress. Conditional averages of the flow field indicate the existence of nearly streamwise counter-rotating vortices aligned in the streamwise direction. The results further show periods of very strong spanwise wall-shear stress to be related to the occurrence of high streamwise shear regions and momentum transfer towards the wall. These events go along with a spanwise oscillation and a meandering of the low-shear regions.

Scaling of wall shear stress fluctuations in a turbulent duct flow

AIAA Journal ◽  
1987 ◽  
Vol 25 (1) ◽  
pp. 22-29 ◽  
Author(s):  
D.A. Shah ◽  
R.A. Antonia
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Duct Flow ◽  
Wall Shear ◽  
Turbulent Duct Flow

215 Development of micro-fabricated hot-film sensor by MEMS and study on its validation of the wall shear stress fluctuation measurement

2014 ◽  
Vol 2014.63 (0) ◽  
pp. _215-1_-_215-2_
Author(s):  
Takuya SAWADA ◽  
Osamu TERASHIMA ◽  
Yasuhiko SAKAI ◽  
Kouji Nagata ◽  
Mitsuhiro SHIKIDA ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Film Sensor ◽  
Stress Fluctuation ◽  
Wall Shear ◽  
Hot Film ◽  
Fluctuation Measurement ◽  
Hot Film Sensor

scholarly journals Physiological non-Newtonian blood flow through single stenosed artery

2016 ◽  
Vol 43 (1) ◽  
pp. 99-115 ◽  
Author(s):  
Khairuzzaman Mamun ◽  
Most. Akhter ◽  
Mohammad Ali
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Three Dimensional ◽  
Cross Sectional ◽  
Number Range ◽  
Newtonian Model ◽  
Early Systole ◽  
Wall Shear ◽  
Downstream Flow

A numerical simulation to investigate the Non-Newtonian modeling effects on physiological flows in a three dimensional idealized artery with a single stenosis of 85% severity is given. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Determination of the physiological waveform is performed using a Fourier series with sixteen harmonics. The investigation has a Reynolds number range of 96 to 800. Low Reynolds number k ? w model is used as governing equation. The investigation has been carried out to characterize two Non-Newtonian constitutive equations of blood, namely, (i) Carreau and (ii) Cross models. The Newtonian model has also been investigated to study the physics of fluid. The results of Newtonian model are compared with the Non-Newtonian models. The numerical results are presented in terms of velocity, pressure, wall shear stress distributions and cross sectional velocities as well as the streamlines contour. At early systole pressure differences between Newtonian and Non-Newtonian models are observed at pre-stenotic, throat and immediately after throat regions. In the case of wall shear stress, some differences between Newtonian and Non-Newtonian models are observed when the flows are minimum such as at early systole or diastole. In general, the velocities at throat regions are highest at all-time phase. However, at pick systole higher velocities are observed at post-stenotic region. Downstream flow of all models creates some recirculation regions at diastole.

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 fluctuation in bubbly drag reduction for a 36-m-long flat plate

2020 ◽  
Vol 2020 (0) ◽  
pp. OS12-03
Author(s):  
Yoshihiko OISHI ◽  
Natsumi FUJII ◽  
Taiji TANAKA ◽  
Hyun Jin PARK ◽  
Yuji TASAKA ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Drag Reduction ◽  
Flat Plate ◽  
Stress Fluctuation ◽  
Wall Shear

scholarly journals On the role of secondary motions in turbulent square duct flow

2018 ◽  
Vol 847 ◽  
Author(s):  
Davide Modesti ◽  
Sergio Pirozzoli ◽  
Paolo Orlandi ◽  
Francesco Grasso
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Streamwise Velocity ◽  
Normal Velocity ◽  
Duct Flow ◽  
Mean Flow ◽  
Square Duct ◽  
The Mean ◽  
Wall Shear

We use a direct numerical simulations (DNS) database for turbulent flow in a square duct up to bulk Reynolds number $Re_{b}=40\,000$ to quantitatively analyse the role of secondary motions on the mean flow structure. For that purpose we derive a generalized form of the identity of Fukagata, Iwamoto and Kasagi (FIK), which allows one to quantify the effect of cross-stream convection on the mean streamwise velocity, wall shear stress and bulk friction coefficient. Secondary motions are found to contribute approximately 6 % of the total friction, and to act as a self-regulating mechanism of turbulence whereby wall shear stress non-uniformities induced by corners are equalized, and universality of the wall-normal velocity profiles is established. We also carry out numerical experiments whereby the secondary motions are artificially suppressed, in which case their equalizing role is partially taken by the turbulent stresses.

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