Fluid mechanics: definition of geometric similarity between model and prototype Compare model and prototype for geometric similarity in hydraulic/thermal machinery modeling. Choose the correct statement that defines geometric similarity.

Concept

• Geometric similarity means the model and prototype are the same shape; all corresponding linear dimensions are in a constant ratio (scale). Size may differ, but shape must be identical.
• Dynamic or kinematic similarity adds matching force/velocity ratios, but those are separate requirements.

Why the other options are incorrect

• Identical velocities or forces are aspects of kinematic or dynamic similarity, not strictly geometric.
• Equal size and shape implies the same object, not a scale model.

Final Answer
Identical in shape but different in size according to a constant scale.