Turbulence Diffusion Mechanism in Submerged Vegetation Flows

Many aquatic plants are often observed, and the submerged canopy flow appears in natural rivers. Complex flow patterns such as Karman vortex and related coherent motions are formed behind vegetation. In particular, mass and momentum transfers and the vertical mixing process are promoted significantly between the within‐canopy layer and over‐canopy layer. Therefore, it is very important for river ecosystem to reveal turbulent diffusion in submerged vegetated open‐channel flows. The present study conducted simultaneously PIV and laser‐induced fluorescence (LIF) measurements using a pair of high‐speed cameras to analyze the contribution of coherent vortex to the turbulent diffusion property

Development of Automated Velocity Measurement Method in Natural Rivers

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Effect of Submergence Depth on Turbulence Structure in Vegetated Canopy Open-Channel Flows

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Coherent turbulence structure generated by wind-induced water waves

River engineeringInnovative field and laboratory instrumentatio

Experiments on Relationship between Gas Transfer in River Stream

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

PIV Measurement of Turbulence Structure and Monami Phenomena in Open-Channel Flows with Flexible Vegetations

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Space-time correlation and momentum exchanges in compound open-channel flow by simultaneous measurements of two-sets of ADVs

River hydrodynamicsOverbank flows and vegetatio

PIV and PTV measurements in hydro-sciences with focus on turbulent open-channel flows

PIV is one of the most popular measurement techniques in hydraulic engineering as well as in fluid sciences. It has been applied to study various turbulent phenomena in laboratory experiments related to natural rivers, e.g., bursting phenomena near the bed, mixing layers observed at confluences, wake turbulence around dikes and piers, and so on. In these studies, PIV plays important roles in revealing the space-time structure of velocity fluctuations and coherent vortices. This review article focuses particularly on the applications of PIV to turbulent open-channel flows, which have been conducted for the past decade in Hydraulics Laboratory of Kyoto University. In Section 2, we introduce our experimental setup and PIV/PTV algorithm. In Section 3, we apply the PIV measurements to reveal turbulence characteristics and coherent structures in open-channel flows as well as in vegetated canopy flows. For complex flow situations, various applications of PIV to compound open-channel flows and wind-induced water waves are considered to reveal coherent vortices. In Section 4, we discuss some advanced PIV measurements in open-channel flows. The free-surface-elevation fluctuations and velocity components were measured simultaneously with two sets of cameras to examine phase-averaged parameters of turbulence. A multi-layer scanning PIV was developed to reveal 3D turbulence structure in compound open-channel flows. Our discriminator PIV/PTV was applied successfully to sediment-laden open-channel flows and revealed the fluid/particle interaction and the relationship between coherent structures and sediment concentration. Finally, we conducted simultaneous measurements of velocity and dye concentration with a combination of PIV and LIF in vegetated open-channel flow, which enables us to examine turbulent scalar flux of a passive contaminant

Hydrodynamic characteristics and related mass-transfer properties in open-channel flows with rectangular embayment zone

Consecutive groynes and embayments form dead water zones, where sedimentation and high concentrations of pollutants are often observed. It is thus very important to understand the mass and momentum exchange between the main channel and side cavities in rivers and hydraulic engineering structures. The spanwise gradient of the streamwise velocity near the junction produces small-scale turbulent vortices because of shear instability. Furthermore, large-scale horizontal circulation is also generated in the cavity zone. These coherent turbulent structures play a significant role in mass and sediment transfer at the boundary between the mainstream and embayment. However, the relation between turbulence and mass transfer is poorly understood. In this study, we performed particle image velocity and laser-induced fluorescence experiments using a laboratory flume, laser light sheets and a high-speed CMOS camera. We examined the exchange properties of a dye as a function of bed configuration and sedimentation effect. Both primary and secondary gyres were observed in the flat bed and downward-sloping bed, whereas the primary gyre was prevalent in the upward-sloping bed. Moreover, the horizontal circulation strongly affected the mass-transfer properties between the mainstream and side cavity