scholarly journals Logarithmic velocity profile of quantum turbulence of superfluidHe4

2015 ◽  
Vol 92 (22) ◽  
Author(s):  
Satoshi Yui ◽  
Kazuya Fujimoto ◽  
Makoto Tsubota
Keyword(s):  
Velocity Profile ◽  
Quantum Turbulence ◽  
Logarithmic Velocity Profile

A simple method to include vertical resolution in a river model, and results from an implementation

2005 ◽  
Vol 36 (2) ◽  
pp. 163-174 ◽  
Author(s):  
Flemming Jakobsen ◽  
Kim Wium Olesen ◽  
Mads Madsen
Keyword(s):  
Velocity Profile ◽  
Solution Technique ◽  
Test Cases ◽  
Vertical Resolution ◽  
Simple Method ◽  
One Dimensional ◽  
Accelerated Flow ◽  
Bed Friction ◽  
Logarithmic Velocity Profile ◽  
Good Agreement

A simple method to include vertical resolution in a one-dimensional river model is outlined. The equations on which the method is based are the width-averaged continuity, momentum and transport equations. Some details are given on how to formulate the bed friction in a river model with vertical resolution. The equations are transformed to be in sigma coordinates. The numerical techniques, which make maximum use of an already implemented numerical solution technique in an existing river model, are described. The method is used to implement vertical resolution in the existing river model, MIKE 11. The implementation is tested on the following cases: logarithmic velocity profile, wind driven velocity profile, rapid accelerated flow, lock exchange and finally wind-forced entrainment. All test cases showed good agreement.

scholarly journals The regularities of resistance and flow in pipes and wide channels

2018 ◽  
Vol 193 ◽  
pp. 02034
Author(s):  
Ilya Bryansky ◽  
Yuliya Bryanskaya ◽  
Аleksandra Оstyakova
Keyword(s):  
Comparative Analysis ◽  
Velocity Profile ◽  
Hydraulic Resistance ◽  
Cross Section ◽  
Resistance Coefficient ◽  
Hydraulic Structures ◽  
Hydraulic Characteristics ◽  
Hydraulic Resistance Coefficient ◽  
Logarithmic Velocity Profile

The data of hydraulic characteristics of flow are required to be more accurate to increase reliability and accident-free work of water conducting systems and hydraulic structures. One of the problems in hydraulic calculations is the determination of friction loss that is associated with the distribution of velocities over the cross section of the flow. The article presents a comparative analysis of the regularities of velocity distribution based on the logarithmic velocity profile and hydraulic resistance in pipes and open channels. It is revealed that the Karman parameter is associated with the second turbulence constant and depend on the hydraulic resistance coefficient. The research showed that the behavior of the second turbulence constant in the velocity profile is determined mainly by the Karman parameter. The attached illustrations picture the dependence of logarithmic velocity profile parameters based on different values of the hydraulic resistance coefficient. The results of the calculations were compared to the experimental-based Nikuradze formulas for smooth and rough pipes.

scholarly journals Featuresof velocity distribution in a turbulent flow

Vestnik MGSU ◽  
2015 ◽  
pp. 103-109
Author(s):  
Valeriy Stepanovich Borovkov ◽  
Valeriy Valentinovich Volshanik ◽  
Irina Aleksandrovna Rylova
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Drag Coefficient ◽  
Viscous Flow ◽  
Measured Velocity ◽  
Displacement Thickness ◽  
Logarithmic Velocity Profile

In this article the questions of kinematic structure of steady turbulent flow near a solid boundary are considered. It has been established that due to friction the value of the local Reynolds number decreases and always becomes smaller than the critical value of the Reynolds number, which leads to formation of viscous flow near a wall. Velocity profiles for the area of viscous flow with constant and variable shear stress are obtained. The experimental investigations of different authors showed that in this area the flow is of unsteady character, where viscous flow occurs intermittently with turbulent flow. With increasing distance from the wall the flow becomes fully turbulent. In the area where generation and dissipation of turbulence are very intensive, there is a developed turbulent flow with increasing distance from the wall. Dissipation of turbulence is an action of viscous force. The logarithmic velocity profile was obtained by L. Prandtl disregarding the viscous component and the linear variation of the shear stress in the depth flow. The profile parameters C and k were determined from Nikuradze’s experiments. The detailed investigations of Nikuradze’s experiments established the part of the flow where the logarithmic velocity profile is correctly confirmed.This part of the flow was called “Prandtl layer”. The measured velocity distribution above this layer deviates in the direction of greater values. Processing of experimental data revealed that the thickness of the “Prandtl layer”, normalized to the radius of a pipe, depend on a drag coefficient. The formula for determining the thickness of the “Prandtl layer” with the known value of the drag coefficient is obtained. It is shown that the thickness of “Prandtl layer” almost coincides with the boundary layer displacement thickness formed on the wall of the pipe.

Multi-mode models of flow and of solute dispersion in shallow water. Part 2. Logarithmic velocity profiles

1995 ◽  
Vol 286 ◽  
pp. 277-290 ◽  
Author(s):  
R. Smith
Keyword(s):  
Velocity Profile ◽  
Shallow Water ◽  
Solute Concentration ◽  
Transverse Flow ◽  
Exact Results ◽  
Solute Dispersion ◽  
Water Flows ◽  
Shallow Water Flows ◽  
Multi Mode ◽  
Logarithmic Velocity Profile

A two-mode model for velocity and solute concentration in shallow-water flows is derived which allows for departures from the logarithmic velocity profile and from vertically well-mixed concentrations. The modelling is tested against exact results for a buoyancy-driven transverse flow and for a modified logarithmic velocity profile.

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