Surface Flow Image Velocimetry (SFIV) for hydraulics applications

Abstract

Surface Flow Image Velocimetry (SFIV), is a practical extension of Particle Image Velocimetry (PIV), as one of the major effective techniques in hydraulics providing velocity and vorticity fields in fast flow laboratory experiments or in field conditions. SFIV uses similar algorithms than conventional PIV, and these tools have a great deal in common with specific pattern matching used in synthetic schlieren. This paper presents an application to characterize the hydraulic behavior of a grate inlet in the area of urban drainage in order to reproduce the velocity field near the grates, as this is one of the important factors for the design of improved inlet systems and prevention of urban flooding. With a high speed camera it is possible to capture images of very high resolution and speed, which combined with the techniques SFIV for image processing, we may generate dynamic velocity and vorticity fields as well as local fluxes around the grate inlet, and combined with flow depth data, evaluate local Froude numbers. The average surface velocity measured by the imaging technique is a good approximation, especially for shallow flows, but it is also possible to extrapolate the technique to rivers, canals, or other hydraulic structures.