Q. Can you explain the Mobile bed model?

Mobile bed models can again be either geometrically similar or vertically exaggerated. Models of the former type permit study of problems of local scour at piers, abutments, spurs, etc. Model scale design is similar to that in case of rigid boundary model except the equality of T/Tc ratio is an additional condition to be satisfied for reproduction of sediment transport. This simple approach is based on the concept that sediment transport is governed primarily by T and Tc values.

In river models where bed changes are required to be studied, mobile bed vertically exaggerated models are used. Scale design in this type of models can be made on basis of Lacey formulae for width, depth and slope. Alternatively more rational procedures due to Einstein(9.2) , Grade(9.3) and others endeavor to satisfy several conditions in addition to Froudian and flow resistance laws for reproduction of specific aspect of sediment transport phenomenon such as incipient motion, bed forms, bed load transport suspended load distribution,