1. What is Fluid Mechanics?
Fluid mechanics is the branch of science that studies the behavior of fluids (liquids and gases) at rest and in motion. It deals with fluid properties, forces, and flow characteristics.
Types of Fluids
| Type of Fluid | Definition |
|---|---|
| Ideal Fluid | No viscosity and no frictional losses; imaginary fluid for theory. |
| Real Fluid | Has viscosity; actual fluids we see in real life. |
| Newtonian Fluid | Viscosity remains constant; follows Newton’s law of viscosity (e.g., water, air). |
| Non-Newtonian Fluid | Viscosity changes with applied shear (e.g., toothpaste, blood). |
| Incompressible Fluid | Density remains constant during flow (e.g., liquids). |
| Compressible Fluid | Density changes significantly with pressure (e.g., gases). |
2.Fluid Properties ?
| Fluid Property | Simple Definition (2–3 lines) |
|---|---|
| Density (ρ) | Mass per unit volume of a fluid. Indicates how heavy the fluid is. |
| Specific Weight (γ) | Weight per unit volume. Shows how strongly gravity acts on the fluid. |
| Specific Gravity (SG) | Ratio of fluid density to water density. No units. |
| Viscosity (μ) | Internal resistance to flow. Higher viscosity → thicker fluid. |
| Kinematic Viscosity (ν) | Ratio of viscosity to density. Represents flow behavior without gravity effect. |
| Pressure (p) | Force applied by the fluid per unit area. |
| Temperature (T) | Measure of fluid heat energy affecting viscosity and density. |
| Vapor Pressure | Pressure at which fluid starts to vaporize. |
| Surface Tension | Force acting on the fluid surface causing it to behave like a stretched film. |
| Capillarity | Rise or fall of fluid in a narrow tube due to surface tension. |
3.Dynamic Viscosity Vs Kinematic Viscosity ?
| Property | Dynamic Viscosity (μ) | Kinematic Viscosity (ν) |
|---|---|---|
| Definition | Resistance offered by a fluid to shear or flow. | Ratio of dynamic viscosity to fluid density. |
| Formula | μ = τ / (du/dy) | ν = μ / ρ |
| Units | N·s/m² or Pa·s | m²/s |
| Depends on | Fluid’s internal friction. | Viscosity and density both. |
| Meaning | Indicates how “thick” or sticky the fluid is. | Indicates how easily the fluid flows under gravity. |
| Example | Honey has high μ, water has low μ. | Kinematic viscosity of oil > water because of higher μ/ρ. |