Contribution of quadrant bursting events to the turbulent flow structure at region close to the mid-channel bar

ABSTRACT

In this paper, the turbulents bursts triggered by the interactions between fluid and bar are investigated using the bursting events technique. The intricate association of scouring that occurred at a region upstream of the bar is reflected by the parameter Dominance Function. It is the ratio of occurrence probability of ejection events to the occurrence probability of sweep event. The results indicate that the high magnitude of scouring is observed in the interaction region of these events. (near bed region, z/h < 0.03). The parameter Dominance Function is successfully predicting the high scouring region. The linkage of deposition process which occurred at locations downstream of the mid-channel bar is signified by the parameter Bursting Index which is the ratio of summation of odd events to the summation of even events. The results indicate that the high magnitude of Bursting Index (BI$\ge$ 1.3) is observed at the high depositional region. The parameter Bursting Index is successfully predicting the high deposition region located downstream of bar. The effect of Submergence Ratio on the turbulent structure of flow is also investigated. The dominance of sweep and ejection events is observed at regions upstream of the mid-channel bar by analyzing the Reynolds stress contours. The high positive value of Reynolds stress is responsible for scouring at regions just upstream of the bar. The negative value of Reynolds stress is observed at regions just downstream of the bar. The velocity fluctuations are modelled using the Gram-Charlier method. The impact of bar on the turbulent flow structure is investigated by plotting the Joint Probability distribution of bursting events. For regions upstream of the bar, the turbulent burst triggered by the interaction of fluid and bar is maximum at a point located closest to the upstream end of bar.

KEYWORDS:

• Dominance function
• mid-channel bar
• Acoustic Doppler Velocimetry
• bursting index
• submergence ratio

Disclosure statement

No potential conflict of interest was reported by the author(s).