Digital particle velocimetry technique for free-surface boundary layer measurements: Application to vortex pair interactions

2001 ◽  
Vol 31 (2) ◽  
pp. 127-139 ◽  
Author(s):  
A. H. Hirsa ◽  
M. J. Vogel ◽  
J. D. Gayton
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Vortex Pair ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Pair Interactions

Free-Surface Boundary-Layer Approach to Study the Bow Vortices Generation Ahead of a Semisubmerged Horizontal Circular Cylinder

1995 ◽  
Vol 39 (04) ◽  
pp. 284-296
Author(s):  
L. R. Raheja
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Circular Cylinder ◽  
The Body ◽  
Instability Criterion ◽  
Surface Boundary ◽  
Surface Shear ◽  
Surface Boundary Layer ◽  
Surface Separation ◽  
Horizontal Circular Cylinder

In the light of experimental observation of a free-surface shear layer, the flow ahead of a semisubmerged horizontal circular cylinder is modeled as a free-surface boundary layer of concentrated vorticity joining the potential flow below it with the aim to study the generation of bow vortices theoretically. The boundary-layer equations are linearized subject to a suitable assumption and are integrated using basically the Kármán Pohlhausen method. It is found that the free surface moves slower than the layer beneath it, but there is more likelihood of bow vortices being generated by instability of velocity profile rather than by separation and backflow. This is confirmed by the nonmonotonicity in the vorticity profile and the fulfillment of the Görtler instability criterion for flow along curved boundaries, near the body upstream. The position of the point of onset of instability, as stipulated from the above observations, compares well with the position of the free-surface separation point as observed in the experiments.

The laminar free surface boundary layer of a solitary wave

2012 ◽  
Vol 696 ◽  
pp. 423-433 ◽  
Author(s):  
Christian A. Klettner ◽  
Ian Eames
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Solitary Wave ◽  
Numerical Simulations ◽  
Numerical Results ◽  
Analytical Models ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Good Agreement

AbstractThe laminar free surface boundary layer beneath a solitary wave is investigated using numerical simulations. Across the boundary layer $\partial {u}_{s} / \partial {x}_{n} $ and $\partial {u}_{n} / \partial {x}_{s} $ are comparable in magnitude, where $u$ is the velocity, $x$ position and subscripts $s$ and $n$ refer to components tangential and normal to the free surface. In this region $\partial {u}_{n} / \partial {x}_{s} $ is approximately constant across the boundary layer while $\partial {u}_{s} / \partial {x}_{n} $ varies with ${x}_{n} $ and outside the boundary layer tends to ${\ensuremath{-} } \mathop{ (\partial {u}_{s} / \partial {x}_{n} )} \nolimits _{n= 0} $. The numerical results are compared to analytical models and good agreement is found.

Prediction of Atmospheric Turbulence Characteristics for Surface Boundary Layer using Empirical Spectral Methods

2020 ◽  
Author(s):  
Yagya Dutta Dwivedi ◽  
Vasishta Bhargava Nukala ◽  
Satya Prasad Maddula ◽  
Kiran Nair
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Surface Roughness ◽  
Wind Speed ◽  
Atmospheric Turbulence ◽  
Surface Boundary ◽  
Low Frequencies ◽  
Surface Boundary Layer ◽  
Power Spectral ◽  
Mean Wind Speed

Abstract Atmospheric turbulence is an unsteady phenomenon found in nature and plays significance role in predicting natural events and life prediction of structures. In this work, turbulence in surface boundary layer has been studied through empirical methods. Computer simulation of Von Karman, Kaimal methods were evaluated for different surface roughness and for low (1%), medium (10%) and high (50%) turbulence intensities. Instantaneous values of one minute time series for longitudinal turbulent wind at mean wind speed of 12 m/s using both spectra showed strong correlation in validation trends. Influence of integral length scales on turbulence kinetic energy production at different heights is illustrated. Time series for mean wind speed of 12 m/s with surface roughness value of 0.05 m have shown that variance for longitudinal, lateral and vertical velocity components were different and found to be anisotropic. Wind speed power spectral density from Davenport and Simiu profiles have also been calculated at surface roughness of 0.05 m and compared with k−1 and k−3 slopes for Kolmogorov k−5/3 law in inertial sub-range and k−7 in viscous dissipation range. At high frequencies, logarithmic slope of Kolmogorov −5/3rd law agreed well with Davenport, Harris, Simiu and Solari spectra than at low frequencies.

scholarly journals A global perspective on Langmuir turbulence in the ocean surface boundary layer

2012 ◽  
Vol 39 (18) ◽  
Author(s):  
Stephen E. Belcher ◽  
Alan L. M. Grant ◽  
Kirsty E. Hanley ◽  
Baylor Fox-Kemper ◽  
Luke Van Roekel ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ocean Surface ◽  
Global Perspective ◽  
Surface Boundary ◽  
Langmuir Turbulence ◽  
Surface Boundary Layer
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