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A Three Tube Pressure Instrument for Measuring the Local Bed Shear Stress in Smooth and Rough Beds

Author(s): Seyed Hossein Mohajeri; Akbar Safarzadeh; Seyed Ali Akbar Salehi Neyshabouri

Linked Author(s): Seyed Ali Akbar Salehi Neyshabouri

Keywords: No Keywords

Abstract: A new instrument has been developed to measure the local bed shear stress in smooth and rough bed open channel flows. This instrument consists of three small diameter tubes which are vertically placed in the logarithmic part of the turbulent boundary layer. Accurate and high frequency pressure transducers have been used to measure the local dynamic pressures and a specific method has been used to convert the pressure readings to the local bed shear stress. The instrument has been verified against available wind tunnel data. Furthermore, the collected data for smooth bed open channel uniform flow has been compared to the Preston tube data and also with estimated bed shear velocities by indirect methods based on turbulent statistics, measured using ADV. Finally, the rough bed open channel results have been compared with results of indirect shear velocity estimation methods and it was found that results are in fairly agreement.


Year: 2012

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