A Preliminary Report on Experimental Plane Beds under Upper-Flow-Regime Conditions

Abstract

Laboratory experiments aiming to produce plane beds under upper-flow-regime were carried out using a flume of 15 cm × 700 cm and with quartz sands of mean size 0.72 mm. Two types of plane beds were formed : 1) laminae formed and buried by the migration of low-relief asymmetric ripples under near-or sub-critical flow (Froude Number Fr =0.94, Run-5), and 2) laminae formed without producing any low-relief bedform but under super-critical flow (Fr =4.98, Run-12). The mean flow velocity (83 cm/ sec) and the mean depth (8 cm) in Run-5 are larger than those in Run-12 (62 cm/ sec, 1 cm, respectively). Up-current imbrications of detrital grains, however, are more remarkable in Run-12 than in Run-5. Such a imbrication pattern may be useful to recognize the formational processes of plane beds under upper-flow-regime.