Self-Preservation of Turbulence Statistics in the Wall-Wake Flow of a Bed-Mounted Horizontal Pipe

Abstract

This research article analyzed the self-preserving behaviour of wall-wake region of a circular pipe mounted horizontally over a flat rigid sand bed in a shallow flow in terms of mean velocity, RSS, and turbulence intensities. The study aims to investigate self-preservation using appropriate length and velocity scales.in addition to that wall-normal distributions of the third-order correlations along the streamwise direction in the wake region are analyzed. An ADV probe was used to record the three-dimensional instantaneous velocities for four different hydraulic and physical conditions corresponding to four cylinder Reynolds numbers. The results revealed that the streamwise velocity deficits, RSS deficits, and turbulence intensities deficits distributions displayed good collapse on a narrow band when they were non-dimensionalized by their respective maximum deficits. The wall-normal distance was non-dimensionalized by the half velocity profile width for velocity distributions, while the half RSS profile width was used in the case of the RSS deficits and turbulence intensities deficits distributions. The results indicate the self-preserving nature of streamwise velocity, RSS, and turbulence intensities in the wall-wake region of the pipe. The third-order correlations distributions indicate that sweep is the dominant bursting event in the near-bed zone. At the same time, ejection is the dominant bursting event in the region above the cylinder height.

Wake flow field of a wall-mounted pipe with spoiler on a rough channel bed

“…The locations of the peak in the RSSs profiles are corresponding to the locations of the points of inflection (d 2 u/dz 2 = 0) in the velocity distributions. The results obtained in this study are similar to those of Dey et al (2018) and Devi et al (2021a). The magnitudes of the peaks increase with the increase in the streamwise distance downstream of the cylinder up to the flow reattachment point.…”

“…3b). This location is similar to the location of the point of inflection by Dey et al (2018), Devi et al (2021a), Devi et al (2022) for a wall-mounted horizontal cylinder and Nepf and Ghisalberti (2008) for a dense canopy of vegetation. On inner scaling, the streamwise velocity distributions are not showing any effects of the Reynolds numbers.…”

Environmental Hydraulics, Turbulence and Sediment Transport

“…To add to the complexity, any obstruction like wood-log or boulder, in particular those obstructions across channel width, can attach with the bedform during its formation to cause floods. To study the impact of the horizontal obstruction in rough bed flow, Devi et al [4,5] have run a series of experiments by bedmounted cylinder to investigate their flow velocity [4] and turbulence [5]. Using an acoustic Doppler velocimetry (ADV) measurement approach, Devi et al [4] concentrated on comparison between flow properties impacted by sand and gravel-formed beds, while Devi et al [5] considered the turbulence of flow above sand bed by high-order bursting analysis.…”

“…To study the impact of the horizontal obstruction in rough bed flow, Devi et al [4,5] have run a series of experiments by bedmounted cylinder to investigate their flow velocity [4] and turbulence [5]. Using an acoustic Doppler velocimetry (ADV) measurement approach, Devi et al [4] concentrated on comparison between flow properties impacted by sand and gravel-formed beds, while Devi et al [5] considered the turbulence of flow above sand bed by high-order bursting analysis. The findings by [4,5] are crucial for consolidating the knowledge of turbulence field induced by the horizontally laying cylindrical obstacle and predicting its actual flow characteristic over a rough bed.…”