•    Distorted models are those which are not perfectly geometrically similar to the prototype.

•    Different scale ratio is used in different direction.

•    Particularly, in case of shallow rivers, where depth is small compared to the width, without distortion the depth of flow in the model will be so small that measurements may not be accurate and the surface tension effect will be prominent which will not present in prototype. Hence it is necessary to distort the models in the vertical direction.

•    In the design of model, hydraulic similitude is of prime importance and not that the geometric similes. Therefore, by distortion of the model scale, even through the model is not look, like the prototype, but it gives the satisfactory results.

Advantages and Disadvantages of Distorted Models

Advantages

1.    Due to substantial height obtained by distortion, measurement in the vertical direction is fairly accurate.

2.    Hydraulic similitude is achieved due to distortion.

3.    Turbulent flow in the model becomes possible.

4.    Cost of model can be reduced.

5.    Viscous effects absent in the prototype, are eliminated in the model. For example, increase in the bed slope of the model, in an otherwise geometrically similar model, increases the velocity in the model, which decreases the effect of viscosity.

6.    Movement of sand and silt in the model can be simulated to that of the prototype.

7.    Adoption of the distorted model, reduces the sie of the model, which saves the space and facilitates the easy operation of the model.

Disadvantages:

1.    Due to different scales in the different directions, the velocity and pressure distribution in the model is not the same as that in the prototype.

2.    Slopes, curves bends and cutting in earth is not truly represented in the model.

3.    Waves are not simulated in the distorted models.

Eventhough there are many advantages of the distorted models. interpretation of the model results for the application to the prototypes is note direct but it needs some amount of manipulation. However, the due to distortion of models, the accuracy of results can be assured.

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