ERSC 2P16 Lecture 22: Bed forms and stratification under unidirectional flows pt 3
7 Aug 2015
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Bed forms and stratification under unidirectional flows 3: bedform stability diagrams: john. Southard and his group at mit have developed the following scheme for defining the hydraulic conditions for bed form stability. The conditions under which a given bed form will develop depends on a combination of fluid and sediment properties: Water temperature (specifically fluid density and viscosity), grain size (d), grain density (rs). Stability diagrams are based on a very large number of experimental observations and observations in natural settings. Stability fields are shown on velocity versus grain size diagrams or depth versus velocity diagrams. All diagrams apply to quartz-density sand and are normalized to water at. Important points to remember: ripples form only in fine sand or finer. Lower plane bed only forms in coarse sand or coarser. Upper plane bed and dunes stability fields become larger with increasing depth: Limits the range of velocity over which they are stable.
