Abstract
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.
Highlights
Determination of the friction loss is one of the most important problems in hydraulic calculations for pipes and channels [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
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
Summary
Determination of the friction loss is one of the most important problems in hydraulic calculations for pipes and channels [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Till present days the logarithmic velocity profile distribution based on Prandtl theories is used in hydraulic calculations for pipes and channels, that differs for smooth type of resistance: u u* 1 κ ln u* y ν C1 , (1). This velocity distribution has two undefined parameters: Karman parameter κ, often called as “the first turbulence constant”, and parameter C, that is called “the second turbulence constant”. Their values were found by Prandtl and Nikuradze based on the famous series of Nikuradze experiments. The C1 value for smooth type of resistance was equal 5.5 and C2 value for rough type of resistance was close to 8.48
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