Question

4. List and describe the THREE (3) necessary conditions for complete similarity between a model and a prototype.

Answer 1

Three necessary conditions for the complete similarity between a model and a prototype.

(1) Geometric similarity—the model must be the same shape as the prototype but may be scaled by some constant scale factor.

It can ve understood as length-scale equivalence.

It is a prerequisite for kinematic similarity.

(2) Kinematic similarity—the velocity at any point in the model flow must be proportional (by a constant scale factor) to the velocity at the corresponding point in the prototype flow. for kinematic similarity, the velocity at corresponding points must scale in magnitude and must point in the same relative direction.

It can ve understood as time-scale equivalence.

It is a necessary but is an insufficient condition for dynamic similarity.

So if a model and prototype achieves both geometric and kinematic similarity but yet cannot be assured of dynamic similarity.

(3) Dynamic similarity—When all forces in the model flow scale by a constant factor to corresponding forces in the prototype flow.

It can be understtod as force-scale equivalence.

With Geometric and Kinematics similarity Dynamic similarity condition must exist to say model and prototype both are similar.