Experimental study on the formation of subaqueous barchan dunes in closed conduits

School of Mechanical Engineering - University of Campinas - UNICAMP, Rua Mendeleyev, 200 - Campinas - SP - CEP : 13083-860, Brazil

^* Corresponding author: calvarez@fem.unicamp.br

Published online: 4 June 2018

Abstract

The present paper reports the formation of subaqueous barchan dunes by analyzing the temporal evolution of their main geometrical characteristics (width W, length L and horn lengths Lh). After certain time, the dunes reach an equilibrium state and it is possible to study the relation between W versus L, and the dependence of the dune velocity on L. The barchan dunes were formed from spherical glass and zirconium beads. An initial conical heap of beads was placed on the bottom wall of a rectangular channel and it was entrained by a water turbulent flow. The evolution of the dunes was filmed with a CCD camera placed above the channel and mounted on a traveling system. Our results show that after a characteristic time the dune shape does not change and it travels with a roughly constant velocity. Once the equilibrium state is reach, W and L are measured, showing linear dependence. Furthermore, we show that the dune velocity V_d scales with the inverse of the dune length.