Fluid Mechanics

Step 1: Understanding the Grashof number.
The Grashof number (Gr) is used in fluid dynamics and heat transfer to characterize the ratio of buoyancy forces to viscous forces in a fluid. It is an important dimensionless number in natural convection and helps determine the flow regime (laminar or turbulent). It is defined as: Where: - is the acceleration due to gravity
- is the thermal expansion coefficient
- is the temperature difference
- is the characteristic length
- is the kinematic viscosity
Step 2: Conclusion.
The Grashof number compares buoyancy forces (due to temperature difference) and viscous forces. Thus, the correct answer is (4).