Fluid Mechanics & Hydraulics
"Future ME! Fluid Mechanics - ang pag-aaral ng fluids (liquid & gas) whether moving or at rest. Essential sa pumps, turbines, pipes!"
1. Fluid Properties ๐
Fluids (liquids & gases) have distinct properties that govern behavior in systems.
| Property | Definition | Effect |
|---|---|---|
| Density (ฯ) | Mass per unit volume (kg/mยณ) | Water: 1000, Air: 1.2 kg/mยณ. Affects pressure & buoyancy |
| Viscosity (ฮผ) | Resistance to flow (Paยทs) | Honey: thick (high ฮผ), Water: thin (low ฮผ). Causes friction losses |
| Surface Tension | Cohesive force at liquid surface | Causes water to form drops, capillary action |
| Pressure (P) | Force per unit area (Pa or bar) | Drives fluid flow, critical in hydraulics (pumps, actuators) |
| Compressibility | Ability to change volume under pressure | Liquids: incompressible, Gases: highly compressible |
2. Fluid Mechanics Equations ๐
Key Equations
Continuity Equation: AโVโ = AโVโ (Flow rate constant in pipe)
Bernoulli's Principle: P + ยฝฯVยฒ + ฯgh = constant (Energy conservation in fluids)
Pressure Drop (Darcy-Weisbach): ฮP = f ร (L/D) ร (ฯVยฒ/2) (Friction losses in pipes)
Power (Hydraulic): P = Q ร ฮP (Flow rate ร pressure difference)
3. Bernoulli's Principle ๐ง
Energy conservation in fluid flow: Total energy (pressure + kinetic + potential) remains constant along streamline.
High Velocity
Faster water = Lower pressure (airfoil lift)
Low Velocity
Slower water = Higher pressure (dam bottom pressure)
Height Change
Pressure increases at lower heights (water tower)
4. Fluid Flow Types ๐
| Flow Type | Characteristic | Application |
|---|---|---|
| Laminar | Smooth layers, Re < 2300, predictable | Oil flow, low-speed systems, accurate calculations |
| Turbulent | Chaotic, eddies, Re > 4000, high friction | Water in pipes, river flow, higher pressure drop |
| Transitional | Between laminar & turbulent, 2300 < Re < 4000 | Design challenges, unpredictable |
5. Hydraulic Systems โ๏ธ
Hydraulics Applications
- Hydraulic Pumps: Convert mechanical energy โ fluid energy (pressure, flow)
- Hydraulic Actuators: Convert fluid energy โ mechanical motion (cylinders, motors)
- Pascal's Law: Pressure applied to enclosed fluid transmits equally in all directions - basis of hydraulic power
- Mechanical Advantage: Small force on small piston = large force on large piston
- Applications: Excavators, bulldozers, aircraft landing gear, ship steering systems
6. Pipe & Channel Flow ๐ง
Pipe Flow (Closed)
- Pressure-driven flow
- Lower pressure drop
- Can handle high pressure
- Industrial systems
Channel Flow (Open)
- Gravity-driven flow
- Free surface (water level visible)
- Rivers, canals, irrigation
- Atmospheric pressure on surface
7. Practice Questions ๐
Common Exam Questions
Q1: State and explain Bernoulli's Principle.
A: Total energy (pressure + kinetic + potential) remains constant in flowing fluid. Higher velocity โ lower pressure (airfoils), lower velocity โ higher pressure (dams)
Q2: What is the Continuity Equation?
A: AโVโ = AโVโ. Flow rate is constant in pipe. Smaller cross-section = faster velocity.
Q3: Explain Pascal's Law and its application.
A: Pressure applied to enclosed incompressible fluid transmits equally in all directions. Basis of hydraulic systems - small pump pressure on small piston can move large load on large piston
Q4: Differentiate laminar and turbulent flow.
A: Laminar (Re < 2300): smooth, predictable, low friction. Turbulent (Re > 4000): chaotic eddies, high friction. Turbulent has higher pressure drop.
Q5: What is viscosity and how does it affect flow?
A: Resistance to flow. High viscosity (honey) = slower flow, more friction losses. Low viscosity (water) = faster flow, less loss. Increases with pressure, decreases with temperature
Q6: How do hydraulic systems work?
A: Pump creates pressure. Incompressible fluid transmits this pressure through pipes to actuators. Small force on pump โ large force on actuator (mechanical advantage)
๐ฅ ME Challenge ๐ฅ
Master fluid mechanics! Bernoulli's principle, flow equations, hydraulics, pump/turbine design!
Fluids power the world - learn the physics!
Test Your Knowledge! ๐ง
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