Author(s): N. Lukerchenko
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Keywords: No Keywords
Abstract: Basset history force is used in several numerical models of bed load sediment transport. Recent investigations show that the Basset force is important for relatively small sediment particles moving close to solid boundaries. In the classical definition, the integral associated with the Basset force and comprising in integrand the relative particle acceleration, must be calculated between the initial and current time. However, since the Basset force calculation requires significant computer resources and since the earlier moments give smaller contributions in the integral, sometimes the integral is calculated approximately during a few of the last particle jumps between the particle-bed collisions. These collisions introduce a new aspect in this problem. During the infinitesimal time of the collision the infinite force, which corresponds to the infinite particle acceleration, acts on the particle so that the impulse of the force remains finite. However, in the known models this aspect isn’t considered. In the present work it is shown that the Basset force can be divided into two parts: first of them due to the particle motion in fluid and second one due to the particle-bed collisions. It is shown that in the case of bed load transport, the values of moduli of both parts are comparable, have opposite directions and substantially compensate one another. For the sand particles saltating in the channel with rough bed the conditions, under which the Basset force can’t be neglected are obtained.
Year: 2010