Distorted models are those which are not perfectly geometrically 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 be 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 similarly therefore by distortion of the model scale, even through the model is not look like the prototype, but it give the satisfactory results

Advantages and Disadvantages if Distorted Models

Advantages:

1). Due to substantial heigh obtained by distorted, measurements in a vertical direction is fairly accurate

2). Hydraulic similitude is actived due to distortion

3) Turbulent flow in the model becomes activated

4) cost of model can be reduced

5). Viscous effects absent in the prototype , are eliminated in the model for example, increases 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). Adaption of the distorted model. reduces the size of the model, which saves the space and facilitates the easy operation of the model

Disadvantages:

1). Due to different scales in the different direction the velocity and pressure distribution in the model is not 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 stimulated in distorted model

Even though there are many advantages of the distorted models interpretation of the model result for the application to the prototype is not direct but it needs some amount of manipulation . However, due to distortion of models, the accuracy of results can be assured