scholarly journals Velocity profile development and friction in compressible micro-flows

2019 ◽  
Author(s):  
Marco Cavazzuti ◽  
Mauro A. Corticelli ◽  
Tassos G. Karayiannis
Author(s):  
E. Hauser ◽  
J. Regan ◽  
H. Estrada

This paper discusses the nature of flow velocity profiles in nuclear plant feedwater system piping, and the impact of flow profile development on flow measurement. The mechanism for flow velocity profile development is described, and the influence of upstream pipe fittings and the relative roughness of the piping inside diameter on flow development is illustrated. The paper defines fully developed flow profiles and illustrates, using several practical applications, how velocity profiles in nuclear plant feedwater piping are rarely fully developed.


Author(s):  
Anatoly Kusher

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.


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