Velocimetry Based on Self-Generated Surface Wave Patterns

Abstract

This paper introduces an image analysis technique applied to an artificially-created disturbance at the free surface of a moving water body as a means of quantifying the average velocity of the water stream for shallow flows. The disturbance was created by a thin object penetrating the free surface with different submerged distances. A V-shaped wake pattern was created by the object of interest through its variation with the water body velocity, the submergence and shape of the piercing body. The angle of the wake pattern decreased with the increase of the velocity for a depth-based Froude number ranging from 0.15 to 0.96. The proof-of-concept experiments presented in this paper, therefore, are usable to quantify the velocity based on the wake angle only in subcritical flow conditions. The results showed the shape of the wake was only slightly influenced by the shape of the object geometry and its submergence. Observations on various types of surface wakes have been documented before, but it is the conversion of these observations into a relatively inexpensive and robust method to estimate the velocity of the moving body that is deemed innovative.

Editorial—Physical Modelling in Hydraulics Engineering

“…This Special Issue contains contributions to the physical and numerical modeling of hydraulics structures, such as dam stilling basing [5][6][7], stepped spillways [8], free falling jets [9] and vortex shaft drops [10]. The development of traditional [11] and novel [12,13] modelling approaches in river engineering are also covered in the Special Issue. Furthermore, contributions in the field of coastal structures and port engineering [14,15], offshore structures [16], and the environmental design of brine discharges [17] are presented in the Special Issue.…”

“…In the paper "Velocimetry Based on Self-Generated Surface Wave Patterns" [12], an innovative image analysis technique was applied to quantify the average velocity of a water stream by introducing an artificially created surface disturbance. The angle of the V-shaped wake pattern created by the object decreased with the increase of the velocity.…”