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PIV EXPERIMENTAL RESEARCH OF flow STRUCTURE IN RECTANGULAR CHANNEL WITH TRANSVERSELY PLACED SPIRAL COIL INSERT

Journal of Hydrodynamics 2012年第4期24卷 518-525页

作者： TANG Yu-feng TIAN Mao-cheng ZHANG Guan-min School of Energy Source and Power Engineering Shandong UniversityJinan 250061China

The flow field in a rectangular channel with a transversely placed spiral coil insert is investigated by Particle Image Velocimetry （PIV） measurements in both transverse and longitudinal sections. The experimental results show that multi-longitudinal vortices are induced downstream of the spiral coil and are distributed as a symmetrical vortex array along the horizontal central line of the transverse section. Along the mainstream, due to the spiral motion of the longitudinal vortices, the velocity fluctuates in a manner of the damped sinusoidal curve and the velocity component in the wall normal direction is improved in the channel. Com- pared with the flow field in a smooth channel it is found that the movement of the longitudinal vortices can cause a continuous dis- turbance near the channel walls and thus enhances the fluid velocity in the near wall region, which consequently leads to the redu- ction of the velocity gradient and a more uniform velocity distribution. With the increase of the Reynolds number, the induced longitudinal vortices gain strength and become straighter and closer to the channel walls, thus the turbulence intensity is further enha- nced in this area.

关键词： Particle Image Velocimetry (PIV) spiral coil longitudinal vortices flow disturbance

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flow-induced vegetation uprooting in a meandering bend:Experimental investigation

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International Journal of Sediment Research 2022年第3期37卷 399-410页

作者： Donatella Termini Alice Di Leonardo Department of Engineering University of Palermo

Vegetation uprooting is a complex process which depends on many interrelated factors. In this paper,attention is focused on the flow-induced uprooting in river bends, where the flow characteristics vary as effected by the channel's curvature and its continuous changing in the downstream direction. Results are presented by an experimental work done in a high-amplitude meandering flume with mature herbaceous vegetation on the bed. In the first part of the paper, the variation along the bend of the geometrical(length, thickness, and radical architecture) and the mechanical(resistance force) characteristics of the roots are analyzed. In the second part of the paper, the transition from the condition of vegetation distributed on the bed to the condition of vegetation uprooted by the flow is experimentally *** results show that the flow-induced uprooting varies along the bend depending on the roots' geometrical and mechanical characteristics which are, in turn, influenced by the variation of the water surface elevation along the bend itself. It has been found that lower values of the resistance force occur at the apex section where the roots are characterized by higher values of length and lower values of thickness and have radical apparatuses characterized by limited encumbrance, a high number of roots,and low bushyness. The flow-induced uprooting especially develops close to the outer bank along the channel reach between the bend entrance and the apex section, where the root resistance force and the water surface slope tend to decrease in value.

关键词： Physical experiment River bend Resistance flow disturbance Vegetation Uprooting

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