UVP Measurement of Flow around a Baffle in a Rectangular Open Channel

Abstract

The effect of an intermediate standing baffle on the structure of flow in a rectangular open channel has been successfully captured by an Ultrasonic Velocity Profiler (UVP). Various spatial distributions such as on-axis time-averaged velocity profiles and turbulent intensities at different streamwise positions indicate the flow structure of the uprising flow at the upstream of baffle, vortex shedding and flow separation, change of the effective cross-section at immediate downstream of the baffle and recirculation flow at the downstream of the baffle. These phenomena are also reflected in the peak values of the relative turbulent intensity profiles. Space-Time on-axis velocity color-map of upstream and downstream sections confirms the existence of periodic change of flow direction near the edge of the baffle at downstream sections. The captured phenomena were also categorized by observing four types of Phenomenological Zero Crossing Points (PCP). Comparison of space-dependent power spectra of upstream and downstream sections of the baffle indicates the existence of some peak structures concentrated near the edge of the baffle for downstream sections whereas such peak structures have not been observed for the downstream sections. Also for downstream sections mainly the existence of peak values in the space distribution of two frequency modes could be confirmed which can be attributed to the vortex shedding due to the existence of the baffle.

Keywords

• flow measurement
• velocimetry
• flow pattern
• turbulent flow
• separation