Physical model experiments can be scaled down from field size(prototype) according to similarity law. The main purpose of physical model experiments is to observe and measure complicated flow and sediment transport phenomena. The measured data from experiments can be translated back to prototype size. Besides, physical model experiments provide visualized flow and sediment transport phenomena. Therefore physical model experiment is an important method to provide hydraulic information for engineering design and decision. The procedure of physical model experiments are as below(flowchart as in Figure 2):
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Confirmation of demand
The first step of physical model experiments is to confirm demand. For example, focus on flow hydraulics of structure or bed change et al. For bed type, model can be divided into fixed bed and movable bed. For experimental target, model can be roughly divided into river model, reservoir model and hydraulic structure model. In addition, collection of field hydrology, geology, topography and designed case is necessary.
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Model design and construction
Model design must consider as follows: similarity law, movable/fixed bed, undistorted/distorted model, model scale and particle size.
Besides main part of model, water supply system and sediment supply system are also a part of model. Physical models usually are constructed by contour lines or profiles of cross-sections to simulate field topography.
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Validation
After experiments under real events, water level, velocity, and bed are usually checked to compare with field data. The idea is to verify the correctness of topography, chosen particle, and similarity law. The validation is necessary for physical model.
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Experiments with different cases
Different cases are usually tested to compare the performances by different engineering design cases (Figure 1 as an example). Thus results can be a reference for decision. Another type of experiments is fundamental experiments for fundamental research. The series experiments are usually based on different parameters, for example, discharge, slope, and particle size to obtain the results by different parameters. The experimental data also can be provided for dimensionless analysis.
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Figure.1 Experimental photo: (a) bend scour without protection; (b) bend scour with protection
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Analysis
After experiments, measured data can be a reference for engineering design. The data analysis can help us to understand physical mechanism and even dimensionless analysis can be done if data is enough.
Figure.2 Procedure of physical model experiments