(27) Bedforms under polydirectional flow: a preliminary experiment using pure oscillatory flow
Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Ts ukuba 305-8577, Japan
Bedforms attain their equilibrium states when hydraulic conditions are constant for sufficiently long duration. What would bedforms be if hydraulic conditions periodically changes and duration of each condition is not long enough for bedforms to become equilibrium? From this point of view, this preliminary experimental study examined bedforms under one-dimensional pure oscillatory flow, which periodically change its direction. The experiment employed a two-directional oscillatory bed with a circler sand tray 1 m in diameter. Properties of oscillatory flow, but its direction, were the same: the oscillatory period was 1.0 s, and total amplitude (= orbital diameter), 5.0 cm. Direction of oscillatory flow was changed and top view photographs were taken every 10 oscillatory cycles. The experiment developed some types of quasi equilibrium bedforms. In the presentation, I will show their developments by movies.