Turbulent Velocities in a Mountain River

by Graeme M. Smart, Natl Inst of Water and Atmospheric, Research, Christchurch, New Zealand,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


A weighted, electronic Pitot tube was deployed in the swift, boulder-bed Waiho river during a 46 m3/s flow and a 214 m3/s flood. The Pitot device measured velocities and depth at a frequency of 54 Hz, thus providing an indication of the turbulence of flow and the vertical location of the turbulent velocity measurements. The instrument was lowered from a bridge at 3m intervals across the channel. Readings taken continuously during lowering and raising indicate the vertical velocity profile of the flow. Turbulent fluctuations increased with depth, both in terms of amplitude and relative to the mean velocity at the depth under consideration. Turbulence relative to the mean velocity increased when bed material was in motion, especially in the lower third of the profile.

Subject Headings: Turbulent flow | Flow measurement | Fluid velocity | Rivers and streams | Velocity profile | Sediment transport | River flow

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