Fluid Mechanics: fluid statics: pascals law, hydrostatic law

pascals law, hydrostatic law, numericals

1. Course Name: FLUID MECHANICS AND HEAT TRANSFER Fluid statics

2. Fluid statics Fluid pressure at a point: p= dF / dA if the force F is uniformly distributed over are A , then pressure at any point p= F/A F= p X A Units: SI unit N/m 2 or Pa 1bar = 100 kpa or 10 5 N/m 2

3. Pascal’s Law: “Pressure or intensity of pressure at a point in a static fluid is equal in all directions” . P x = P y = P z

4. Pressure Variation in a fluid at rest: “Rate of increase of pressure in a vertical direction is equal to weight density of the fluid at that point”. : Hydrostatic law

5. Integrating on both side p=pressure above atmospheric pressure Z= height of the point from free surfaces Z = pressure head = p/ ρ g

6. Absolute pressure: with reference to absolute vacuum pressure. Gauge pressure: Measured with the help of a pressure measuring instrument , in which atmospheric pressure is taken as datum. Vacuum pressure: pressure below the atmospheric pressure.

7. Relationship between pressures: Absolute pressure = atmospheric pressure + gauge pressure Vacuum pressure = atmospheric pressure – absolute pressure P atm = 101.3 Kpa (at sea level at 15 C) Atmospheric pressure head = 760 mm of Hg or 10.33 m of water