scholarly journals NEAR-BOTTOM VELOCITIES IN WAVES WITH A CURRENT

1978 ◽  
Vol 1 (16) ◽  
pp. 82 ◽  
Author(s):  
W.T. Bakker ◽  
Th. Van Doorn
Keyword(s):  
Mathematical Model ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Experimental Verification ◽  
Velocity Profiles ◽  
Horizontal Direction ◽  
Numerical Accuracy ◽  
A Current ◽  
Bottom Velocities

Bakker (1974) developed a mathematical model concerning the sand concentration and velocity distribution in an oscillatory turbulent flow, with or without resultant current. The flow is assumed to be uniform in horizontal direction. The present paper reports on an experimental verification of this theory. Furthermore, the numerical accuracy of the model has been investigated and diagrams are presented which enable the computation by hand of global velocity profiles.

scholarly journals Assessment of Steady and Unsteady Friction Models in the Draining Processes of Hydraulic Installations

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1888
Author(s):  
Óscar E. Coronado-Hernández ◽  
Ivan Derpich ◽  
Vicente S. Fuertes-Miquel ◽  
Jairo R. Coronado-Hernández ◽  
Gustavo Gatica
Keyword(s):  
Mathematical Model ◽  
Turbulent Flow ◽  
Water Velocity ◽  
Experimental Facility ◽  
Governing Equations ◽  
Pressure Oscillations ◽  
Air Pocket ◽  
Friction Models ◽  
The Mathematical Model

The study of draining processes without admitting air has been conducted using only steady friction formulations in the implementation of governing equations. However, this hydraulic event involves transitions from laminar to turbulent flow, and vice versa, because of the changes in water velocity. In this sense, this research improves the current mathematical model considering unsteady friction models. An experimental facility composed by a 4.36 m long methacrylate pipe was configured, and measurements of air pocket pressure oscillations were recorded. The mathematical model was performed using steady and unsteady friction models. Comparisons between measured and computed air pocket pressure patterns indicated that unsteady friction models slightly improve the results compared to steady friction models.

scholarly journals Distribution of velocity and temperature between concentric rotating cylinders

1935 ◽  
Vol 151 (874) ◽  
pp. 494-512 ◽  
Keyword(s):  
Turbulent Flow ◽  
Velocity Distribution ◽  
The Other ◽  
Momentum Transport ◽  
Rotating Cylinders ◽  
Simultaneous Measurements ◽  
Other Hand ◽  
Vorticity Transport

It is not possible to distinguish between the Momentum Transport and the Vorticity Transport theories of turbulent flow by measurements of the distribution of velocity in a fluid flowing under pressure through pipes or between parallel planes. Only simultaneous measurements of temperature and velocity distribution are capable of distinguishing between the two theories in these cases. On the other hand, it will be seen later that measurements of the distribution of velocity between concentric rotating cylinders are capable of distinguishing between the two theories; in fact the predictions of the two theories in this case are sharply contrasted and mutually exclusive.

scholarly journals EROSION AROUND A PILE DUE TO CURRENT AND BREAKING WAVES

1988 ◽  
Vol 1 (21) ◽  
pp. 102 ◽  
Author(s):  
E.W. Bijker ◽  
C.A. De Bruyn
Keyword(s):  
Shear Stress ◽  
Breaking Waves ◽  
Velocity Profiles ◽  
Long Waves ◽  
Orbital Velocity ◽  
Bottom Shear Stress ◽  
Normal Waves ◽  
Short Waves ◽  
A Current

Tests have been performed on a vertical pile subject to current only and to a combination of current with normal waves and current with breaking waves. The scour around the pile produced by current only is decreased by normal short waves superimposed upon that current and increased when breaking waves are superimposed upon the current. After analysis of the velocity profiles in the undisturbed area upstream of the pile and next to the pile, the following explanation is found for this phenomenon. When normal short waves are superimposed upon a current, the bottom shear stress of the combination of current with waves is increased more in the undisturbed area than next to the pile in the scour area. This results in a decrease of the scour around the pile. Due to the large values of the orbital velocity under breaking waves this effect is reversed for the combination of a current with breaking and relatively long waves. This results in an increase of the scour around the pile.

On Turbulent Flow Between Parallel Plates

1953 ◽  
Vol 20 (1) ◽  
pp. 109-114
Author(s):  
S. I. Pai
Keyword(s):  
Turbulent Flow ◽  
Velocity Distribution ◽  
Poiseuille Flow ◽  
The Other ◽  
Turbulent Velocity ◽  
Parallel Plates ◽  
Mean Velocity ◽  
Reynolds Equations ◽  
Mean Pressure ◽  
The Mean

Abstract The Reynolds equations of motion of turbulent flow of incompressible fluid have been studied for turbulent flow between parallel plates. The number of these equations is finally reduced to two. One of these consists of mean velocity and correlation between transverse and longitudinal turbulent-velocity fluctuations u 1 ′ u 2 ′ ¯ only. The other consists of the mean pressure and transverse turbulent-velocity intensity. Some conclusions about the mean pressure distribution and turbulent fluctuations are drawn. These equations are applied to two special cases: One is Poiseuille flow in which both plates are at rest and the other is Couette flow in which one plate is at rest and the other is moving with constant velocity. The mean velocity distribution and the correlation u 1 ′ u 2 ′ ¯ can be expressed in a form of polynomial of the co-ordinate in the direction perpendicular to the plates, with the ratio of shearing stress on the plate to that of the corresponding laminar flow of the same maximum velocity as a parameter. These expressions hold true all the way across the plates, i.e., both the turbulent region and viscous layer including the laminar sublayer. These expressions for Poiseuille flow have been checked with experimental data of Laufer fairly well. It also shows that the logarithmic mean velocity distribution is not a rigorous solution of Reynolds equations.

On the Velocity Distribution of Turbulent Flow in Pipes and Channels of Constant Cross Section

1946 ◽  
Vol 13 (2) ◽  
pp. A85-A90
Author(s):  
Chi-Teh Wang
Keyword(s):  
Turbulent Flow ◽  
Velocity Distribution ◽  
Length Distribution ◽  
Critical Examination ◽  
Large Reynolds Number ◽  
Good Picture ◽  
Von Karman ◽  
Von Kármán ◽  
New Formula ◽  
Good Agreement

Abstract This paper follows the Prandtl conception of momentum transport and gives a critical examination of the so-called Prandtl-Nikuradse formula and the von Kármán formula for the velocity distribution of the turbulent flow in tubes or channels at large Reynolds number. It shows that both formulas would not give a good picture of the turbulent flow near the center of the conduit, and indeed they actually do not. A new formula for the velocity distribution is developed from a study of the mixing-length distribution across the section. This new formula checks quite well with the experiments and yields the same skin-friction formula as derived by von Kármán and Prandtl, which itself is in very good agreement with experiments.

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