Fluid mechanics Flashcards
Density
Mass per unit of volume of a fluid
Pressure
Force per unit area in a fluid
Viscosity
Force per unit area due to the friction fluid arising from the relative motion of the neighboring elements in a fluid.
Streamlines
The lines of the flow around an object in a fluid. Example: Wind tunnel
Conservation of mass
The mass of fluid is equal at every point of a tube
Mass continuity
conservation of mass
Equation for conservation of mass
ρUA = constant
Flow along a stream tube equation
ρ1U1A1 = ρ2U2A2
Energy conservation in an ideal fluid
Bernoulli’s equation
Bernoulli’s equation
Hydrostatic pressure
The fluid at a given depth z is all at the same pressure p.
(In case the fluid is stationary: u=0)
The significance of Bernoulli’s equation shows:
the pressure in a moving fluid decreases as the speed increases.
coeficient of dynamic viscosicty (greek symbol):
μ
The viscous shear force per unit of area (equation)
Two different kinds of flow in a viscous fluid
- Laminar flow
- Turbulent flow
Laminar flow
the fluid flows along distinct flow tubes and is stable
Turbulent flow
The motion of the flow is disorderly and unstable
Wheter a flow is laminar or turbulent is determined by
the Rennolds number
Reynolds number equation
Drag force
a net force in the direction of motion
Drag force equation
D = 1/2CdρU2A
Lift force
D = 1/2ClρU2A
Drag coefficient
Cd
Lift coefficient
Cl
A fluid can be a
- Liquid
- Gas
Important properties of a fluid
- Density
- Pressure
- Viscosity
Paramaters of a flowing fluid
- Speed
- Volume flow
- Mass flow
2 types of hydro turbines
- uses potential energy to convert to conetic energy
- uses pressure to power turbine
Drag and lift force are
air resistance, fluid resistance in the direction of the flow
