| Abstract: | This paper deals with the effects of average flow velocity, obstacle length and sediment size on time evolution of scour depth near thin, vertical obstacles, protruding at right angle from movable bed channel side-walls. These effects are studied in the framework of the "generalised equations" of Ettema (1980), Franzetti et al. (1982) and Whitehouse (1997). The results show that i) coefficients included in the first two equations depend on flow velocity as well as on obstacle length; ii) those coefficients are independent of bed material size; iii) the coefficients involved in the equation of Whitehouse (1997) are independent of flow velocity, obstacle length and bed material size. A new method for the evaluation of Whitehouse's time scale was obtained and a new method for the characterisation of equilibrium time was established in the framework of the equation of Franzetti et al. (1982). |
