Fluid Dynamics Flashcards
Uniform flow
the velocity has the same magnitude and direction at every point
Non-uniform flow
At a given instant, the velocity is not the same everywhere
Steady flow
Velocity, pressure and cross section may differ from point to point but do not change with time
Unsteady flow
Velocity, pressure and cross section may differ with time
One dimensional flow
Parameters at given instant in time only vary in the direction of flow
Two dimensional flow
Flow parameters vary in the direction of flow and in one direction at right angles to this direction.
Three dimensional flow
Flow parameters vary in direction of flow and in the two directions at right angles to this direction.
Streamlines
Path of imaginary particles in a fluid
3 facts about streamlines
Close to a solid boundary, streamlines are parallel to that boundary
Streamlines can not cross each other
Any particle starting in one streamlines will stay in the same streamline
Streamtube
Collection of streamlines
Key difference between streamlines and streamtubes
Streamlines are two dimensional while streamtubes are three dimensional
Volume flow rate
Volume of fluid flowing per unit time
Mass flow rate
Mass of fluid flowing per unit time
Mean velocity flow
Discharge (Q) divided by cross section area (A)
Inviscid flow
Flow of fluid with no viscosity
Continuity equation
Conservation of mass
Bernoulli’s equation
Conservation of energy
Momentum equation
Conservation of momentum
Energies
0.5mV²=>0.5(ρAV)xV²
mgh=>(ρAV)gh
(pA)xV
Total energy power unit weight
V²/2g+h+p/ρg=constant
Bernoulli’s equation
V²/2g+h+p/ρg before = V²/2g+h+p/ρg after
Volume of flow through small orifice
V₂=√(2gh)
Conservation of momentum so
F=d(mV)/dt
Force equals momentum change rate
All the forces equation
FT=FR+FP+FB
As an application of the momentum equation, what does the control column include?
Faces at inlet and outlet of bend and pipe walls
As an application of the momentum equation, why is the coordinates system
An axis is pointing in the direction of the inlet velocity
Total force equation
F=ρ(Q₂V₂-Q₁V₁)
Force on a pelton wheel blade
FTX=ρQ(V₂cosβ+V₁)
