Abstract
Two kinds of Star dunes are simulated numerically in order to make clear the mechanism of their formation. The flow above the sand dune has been investigated by using Large-Eddy Simulation (LES) method. The numerical method employed in this study can be divided in three parts: (i) Calculation of the air flow above the sand dune by using standard MAC method with a generalized coordinate system; (ii) Estimation of the sand transfer caused by the flow through the friction; (iii) Determination of the shape of the sand surface. Since the computational domain is changed due to step (iii), these procedures are repeated until typical shape of the sand dune is formed. Two cases of dunes are simulated. In the first case, when the winds blow from three directions, the sand dune extends at three directions and becomes the shape of a star with three arms. In the second case, when the winds blow from three pairs of opposing directions, the sand dune extends in four directions, becomes the shape of a star with four arms.
