Sanjay Giri

THE EFFECT OF THE INITIAL BED PERTURBTION TO THE SAND BAR FORMATION AND EVOLUTION PROCESS

This paper presents investigations, performed to assess the effect of the initial bed perturbation on the sand bar formation and evolution process. Computations were conducted with two different kind of initial bed perturbations. In the series of first computations, the influence of the amplitude of random field of perturbations was tested. The time to reach an equilibrium state was found to be depending on the amplitude of the initial random bed perturbation. It was found that the larger the amplitude, the shorter the time to reach an equilibrium state. The second test was conducted with the initial bed perturbation in the form of a double row bar. During the first stage of the computation, double row bar type bed configurations were formed, however the modes of bed configurations appeared to be reduced and finally turned into single mode type bed configurations. Since the hydraulic condition of the numerical experiment is single-bar regime, this experiment corresponds to the transformation of bar conditions from the doublemodes to the single-mode during the flood in the natural rivers.