The Study Of The Law Of Similarity For Models Of Flood Flows Of The Lower Reach Of The Yellow River

This thesis reviewed at first the existing research results of the law of similarity for river models carrying sediment. In order that the similarity criteria established be based on sound foundation, fundamental properties of flow with heavy sediment load, such as the vertical distributions of velocity and suspended sediment and the sediment carrying capacity of the flow, were studied. The proposed equations describing these properties have been checked upon satisfactorily with large amount of flume or field data. Besides, a stability criterion for different river regimes has been suggested. A set of similarity law for flood flows of the lower reach of the Yellow River was then proposed.The salient points of our method of modelling the lower reach of the Yellow River are as follows:(1)The critical (i.e.,the lowest) effective Reynolds number for flows with heavy sediment concentrations to remain turbulent without the effect of Bingham limiting shearing stress TB is 8000.(2)By introducing a new factor a. , called the distribution factor of saturated sediment concentration , we are able to determine more appropriately the scale of the fall velocities of the suspended sediment between the prototype and the model.(3)A new criterion for river regime is introduced in order that the river regime in the model be the same as in the prototype.(4)The discussions and the method of determination for the scale of sediment concentration and the time scale of river channel deformation are also worthy of note.The proposed model law has been used in a model of the lower reach of the Yellow River from Huayuankou to Dongbatou. The test results of this model for the floods of 1988 and 1992 show that the flow pattern, the sediment movement and the channel deformation all conform very well with the field data of these floods.