Chapter 2 Fluid Statics

1. Engineering Mechanics Fluid Mechanics (Week 4) Chapter 2: Fluid Statics Chapter 2 Fluid Statics Hsin-Yuan Miao, Ph. D.Assistant ProfessorDepartment of Mechanical EngineeringNational Kaohsiung University of Applied Science415 Chien-Kung Road, Kaohsiung, 80778, Taiwan R. O. C.TEL : 886-7-381-4526 ext. 5351FAX : 886-7-3831373Mobile : 886-937-215-638E-MAIL : kenymiao@cc.kuas.edu.twhttp://www2.kuas.edu.tw/prof/kenymiao/index.html

2. Chapter 2: Fluid Statics Introduction • The problem in this chapter : • No matter the fluid is either at rest or moving in such a manner that there is no relative motion between adjacent particles. • 2. There is no shearing stress in fluid, and the only forces that develop on the surface of the particle will be due to the pressure. • 3. All have to investigate are pressure and its variation throughout a fluid, and the effect of pressure on submerged surface.

3. Chapter 2: Fluid Statics 2.1 Pressure at a Point 2.2 Basic Equation for Pressure Field 2.3 Pressure Variation in a Fluid at Rest 2.4 Standard Atmosphere 2.5 Measurement of Pressure 2.6 Manometry 2.8 Hydrostatic Force on a Plane Surface 2.9 Pressure Prism 2.10 Hydrostatic Force on a Curved Surface 2.11 Buoyancy, Flotation, and Stabilityotion 2.12 Pressure Variation in a fluid with Rigid-Body Motion

4. Chapter 2: Fluid Statics 2.1 Pressure at a Point Figure 2.1 Forces on an arbitrary wedged-shaped element of fluid How about “Pressure”? The normal force per unit area at a given point acting on a given plane within the fluid mass of interest Free-body diagram 重力(weight)

5. Chapter 1: Introduction ---1.4 Measure of Fluid Mass and Weight Chapter 2: Fluid Statics 1.4.2 Specifics Weight (lb/ft3, N/m3)(比重量) = γ (gamma) = is defined as its weight per unit volume. = is related to density through the equation γ= ρg = is used to characterize the weight of the system. 1.4.3 Specific Gravity(沒單位) = SG = is defined as the ratio of the density of the fluid to the density of water at some specified temperature. = SG = ρ/ ρH2O 4ºC ρHg = (13.55)(1.94 slugs/ft3) = 26.3 slugs/ft3 ρHg = (13.55)(1000 kg/m3) = 13.6x103 kg/m3 Hg 20 ºC SG= 13.55

6. Chapter 1: Introduction ---1.4 Measure of Fluid Mass and Weight Chapter 2: Fluid Statics 1.41 Density 密度 1.42 Specific weight 比重量 1.43 Specific gravity 比重 1.4.1 Density 密度 (sluds/ft3, kg/m3) = ρ (rho) =is defined as its mass per unit volume. = used to characterize the mass of a fluid system. = 不同流體，其值變化極大 = 但對單一流體，隨壓力與溫度之變化極小(氣則不然)

7. Chapter 2: Fluid Statics

8. Chapter 2: Fluid Statics 2.2 Basic Equation for Pressure Fluid How about the “Pressure” from point to point in a fluid? Figure 2.2 Surface and body forces acting on small fluid element p = f (x, y, z) Surface force Body force

9. Chapter 2: Fluid Statics (壓力的統御方程式)

10. Chapter 2: Fluid Statics 2.3 Pressure Variation in a Fluid at Rest 1。(2-4)是為靜態流體的方程式，可計算隨高度改變時的壓力值。 2。負值表往下壓力變小。 3。 γ不一定為定值(水為定值)。如氣体，可先求得γ對高度的變化函 數後，再代入(2-4)。

11. Chapter 2: Fluid Statics 2.3-1 Incompressible Fluid 2.3-1 Incompressible Fluid 2.3-2 Compressible

12. Chapter 2: Fluid Statics 2.3-1 Incompressible Fluid 1. 因為γ=ρg。g設為定值，ρ設為不變 === Incompressible Fluid Figure 2.3 Notation for pressure variation in a fluid at rest with a free surface

13. Chapter 2: Fluid Statics

14. Chapter 2: Fluid Statics Example Figure 2.1

15. Chapter 2: Fluid Statics

16. Chapter 2: Fluid Statics 2.3-2 Compressible γ=ρg + (2-4式)