Unit 2 Hydrostatics-b.pptx Unit 2 Hydrostatics-b.pptx

Unit 2 Hydrostatics-b.pptxUnit 2 Hydrostatics-b.pptxUnit 2 Hydrostatics-b.pptxUnit 2 Hydrostatics-b.pptxUnit 2 Hydrostatics-b.pptxUnit 2 Hydrostatics-b.pptx

1. Unit 2 : Hydrostatics CE 205 : ENGG. FLUID MECHANICS Unit 2

2. CE 205 : ENGG. FLUID MECHANICS Unit 2 Hydrostatics is the study of fluid bodies that are • At rest • Moving slowly so there is no relative motion between adjacent parts of the body What is hydrostatics ? For hydrostatic situations • There are no shear stresses • There are only pressure forces that act perpendicular to any surface.

3. CE 205 : ENGG. FLUID MECHANICS Unit 2 Pressure For example, the pressure felt by a man is the weight of the column of fluid above his body divided by the area the fluid is resting on. P = (Weight of column)/(Area of base) Standard Atmospheric Pressure : 1 atmosphere ( atm ) = 101.3 kPascals 1Pa = 1N/m 2 Pressure = Force per Unit Area

4. Basic Principles : Fluid is at rest : no shear forces Pressure is the only force acting What are the forces acting on the block? Air pressure on the surface - neglect Weight of the water above the block Atmospheric pressure CE 205 : ENGG. FLUID MECHANICS Unit 2 Pressure is a function of depth only h A = Area of the block parallel to the surface of fluid Pressure =

5. Pascal’s Law : CE 205 : ENGG. FLUID MECHANICS Unit 2 The pressure at any point is the same in all directions Note that the pressure depends only on the depth and is equal for any two points at the same level. The shape of the container does not matter! h The height of the fluid column (h) in all the limbs are same The height “h” depends up on the pressure at the centre of the vessel OR h : Pressure Head

6. CE 205 : ENGG. FLUID MECHANICS Unit 2 Absolute, Gauge and vacuum pressure Actual Pressure at a given point is called the absolute pressure. Absolute vacuum is the datum for the measurement Pressure measured keeping atmospheric pressure as a datum is called gauge pressure. Most pressure measuring devices are calibrated to read zero in the atmosphere. P gauge = P abs – P atm Pressure below atmospheric is called vacuum pressure. P vac = P atm – P abs

7. CE 205 : ENGG. FLUID MECHANICS Unit 2 Absolute, Gauge and vacuum pressure Absolute Pressure Gauge Pressure Absolute Pressure Vacuum Pressure Atmospheric Pressure Atmospheric Pressure = 101.3 KPa Absolute vacuum

8. Exercise : CE 205 : ENGG. FLUID MECHANICS Unit 2 2.1: If a mercury barometer reads 700 mm and a Bourden Gauge at a point in a flow system reads 500 kN /m 2 , What is the absolute pressure at the point ? [ SG Hg = 13.6]

9. Exercise : CE 205 : ENGG. FLUID MECHANICS Unit 2 2.2 : Find the depth of a point below water surface in sea where the pressure intensity is 100.55 kN /m 2 . Specific gravity of sea water is 1.025.