ANS:C - Grashhoff number

In forced convection, all three parameters mentioned - Reynolds number, Prandtl number, and Grashof number - are important for characterizing the flow.

• Reynolds number (Re) is crucial as it determines the flow regime (whether laminar or turbulent) and provides information about the fluid behavior.
• Prandtl number (Pr) is important as it relates the momentum diffusivity (kinematic viscosity) to the thermal diffusivity, affecting the thickness of the thermal boundary layer and thus the heat transfer characteristics.
• Grashof number (Gr) is significant as it represents the ratio of buoyancy forces to viscous forces and influences the onset of natural convection.