Initial Research On The Influence Of Time Scale Distorion In River Model Test

The river model test is still the main research method when we make and optimize each kind of hydraulic engineering decision, but the scale effect caused by time distortion in the river model test always can't be obtained a very good solution. At present the usual procedure is to use the time scale of riverbed scour-aggradation to replace the time scale of fluent-movement in order to obtain the similarity of riverbed scour-and-fill simulation as precise as possible, but this method will cause the deviation of water level, river discharge, send content, as well as the capacity of riverbed scour-and-fill. Particularly in the tidal estuary, its influence is extremely not yet being understood. An unsteady 1-D flow and sediment model is used as a tool in this article to carry three kind of different time distortion rate models on the research of the influence of fluent and sediment movement. And then several preliminary adjusted measures have been proposed. The main research results are as follows:1) The time scale distortion makes the lag of stage and discharge. The lag of time is related to the rate of time scale distortion and the model's length. Its value is smaller in tidal flood, larger in tidal ebb. The process curve of tidal elevation and discharge displays flatter. And the distributed time of ebb and flow has been changed with the time of rising tide lasting longer and the time of ebbing tide lasting shorter in the distortion model.2) The lag and deviation of sand content is related to the rate of time scale distortion as well as the distance from the outset cross. The sand content's process curve changes gently. The overall change of silt carrying capacity is that its value is bigger when tide rises anxiously and smaller when tide falls anxiously. The quantity of riverbed scouring enlarges at the import and export section and the quantity of river channel aggradation enlarges at the middle and lower section.3) The influence of time scale distortion on the branch channel is more serious than its influence on the sole river, and its influence is not more serious as to the more obvious branch within two branch channels.4) The influence of time scale distortion on the riverbed deformation is related to the different section of river and the terrain, and it is very complex on the riverbed evolution rule of the river pool or the river shoal and some other partial terrain in the distortion model.5) Lagging adjustment of downstream water level, increasing or reducing the import current capacity, slowing down the sudden-rise or sharp-drop current capacity are the three main methods of adjusted measures proposed in this article.