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Experimental Investigation on Drag Reduction of Surface Coat for Turbulent Gas Pipe Flow

Author: ChaiYaBin
Tutor: JiangZuo
School: Tianjin University
Course: Fluid Mechanics
Keywords: Wavelet analysis Probability density function Intermittent Multi - scale coherent structures Conditional phase-averaged waveform drag reduction
CLC: O357.5
Type: Master's thesis
Year: 2004
Downloads: 177
Quote: 0
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Abstract


Pipeline wall coating drag reduction technology in order to meet the West-East Gas Transmission Project application Hotline velocimetry, experimental study of the turbulent boundary layer wind tunnel wall covering the drag-reducing coatings for drag reduction mechanism. Hot-wire anemometer and monofilament boundary layer micro hotline probe IFA300 intelligent fine measurements in the wind tunnel with the mean velocity profile of the different wall paint wall turbulence, logarithmic law of the mean velocity profile and wall friction velocity, fluid viscosity coefficient of wall turbulence , etc. the inner scale physical relationship as well as the wall friction velocity and wall friction shear stress relationship, through nonlinear iterative fitting wall friction velocity, average velocity profile measurement of wall turbulence skin friction and wall friction coefficient, kinds of paint wall drag reduction performance were compared with experimental studies provide experimental basis for further understanding of the wall drag reduction mechanism. The three coatings are a polyurethane, an epoxy resin, asphalt, three thickness of each paint coating, and the contrast wall surface, and a total of ten experimental model. Each an experimental model in the wind tunnel using three Reynolds number (flow speed) hair. u? wavelet analysis of the turbulent boundary layer to the position of the flow speed time series signal is decomposed autocorrelation method to determine the time scales of the turbulent structures of different scales, with the the instantaneous intensity factor of the wavelet coefficients, multi-scale coherent structures in wall turbulence in the flatness factor detection. Phase average waveforms extracted different position multiscale coherent structure of the turbulent boundary layer conditions, to study the kinetics of the process of multi-scale coherent structure burst. Intermittent analysis of multi-scale coherent structures with the probability density function of the wavelet coefficients. It was found that the drag reduction effect paint flow to the near wall region increase in average speed, buffer layer thickness, the shift of the law of large numbers on a drag reduction effect. Turbulent boundary layer by changing the energy distribution of the different scale coherent structures in the condition phase of the average waveform, the flatness factor, relative intensity, the probability of occurrence, so that the turbulence structure coherence enhancement, flow orderly improved, thus the turbulent boundary layer Zhongyuan Some multi-scale coherent structure control, in order to achieve the purpose of the wall drag reduction. Logarithmic law outside the paint on the nature of the flow structure basically no impact.

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CLC: > Mathematical sciences and chemical > Mechanics > Fluid Mechanics > Viscous fluid > Turbulence ( turbulence )
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