Fundamentals of Fluid Flow Flashcards
Amount of fluid passing through a section per unit of time
Discharge/Flow Rate
Formula of Volume Flow Rate
Q = Av
Formula of Mass Flow Rate
Mf = pQ
Formula of Weight Flow Rate
W = yQ
Q is
discharge
A is
cross-sectional area of flow
v is
mean velocity of flow
p is
mass density
y is
unit weight
Occurs when the discharge Q passing a given cross-section is constant with time
Steady Flow
If the flow Q at the cross-section varies with time
Unsteady Flow
Occurs if, with steady flow for a given length, the average velocity of flow is the same at every cross-section
Uniform Flow
If the average velocity of flow varies at every cross-section
Non-uniform Flow
Occurs when at any time, the discharge Q at every section of the stream is the same
Continuous Flow
Formula of Continuous Flow for Incompressible Fluids
Q = A1v1 = A2v2 = A3v3 = constant
Formula of Continuous Flow for Compressible Fluids
Q = p1A1v1 = p2A2v2 = p3A3v3 = constant
When the path of individual fluid particles do not cross or intersect
Laminar Flow
Occurs when the Reynolds number Re is less than (approximately) 2100
Laminar Flow
When the path of individual particles are irregular and continuously cross each other
Turbulent Flow
Occurs when the Reynolds number exceeds 2100 (most common situation is when it exceeds 4000)
Turbulent Flow
The energy possessed by a flowing fluid
kinetic and potential energy
Potential energy may be subdivided into
energy due to position or elevation above a given datum and energy due to pressure in the fluid
The ability of the fluid mass to do work by virtue of its velocity
Kinetic energy
Amount of energy per pound or Newton of fluid
Head
Formula of Kinetic Energy
KE = ½mv² = ½(W/g)v²
Formula of Kinetic Head or Velocity Head
Hv = v²/2g
Formula of Potential Energy for Elevation
PE = mgh = Wh = Wz
Formula of Elevation Head
Hz = z
Formula of Potential Energy for Pressure
PE = mgh = W(p/y)
Formula of Pressure Head
Hp = p/y
Formula of Total Energy/Total Head
E = v²/2g + p/y + z
Results from the application of the
principles of conservation of energy
Bernoulli’s Energy Theorem
Bernoulli’s Energy Theorem
E1 + Eadded - Eextracted = E2
Energy Equation w/out Head Lost
E1 = E2
v1²/2g + P1/y + z1 = v2²/2g + P2/y + z2
Energy Equation w/ Head Lost
E1 - HL = E2
v1²/2g + P1/y + z1 - HL = v2²/2g + P2/y + z2
Energy Equation w/ Pump
E1 + HA - HL = E2
Energy Equation w/ Turbine
E1 - HE - HL = E2
Also known as pressure gradient
Hydraulic Grade Line
The graphical representation of the total potential energy of flow
Hydraulic Grade Line
A graphical representation of the total energy of flow
Energy Grade Line
The rate at which work is done
Power
Formula of Power
P = yQE
1 hp in Watts and ft-lb/sec
746 Watts
550 ft-lb/sec
1 Watt in N-m/s and J/s
1 N-m/s
1 J/s
Formula of Power for Pump
Poutput = yQ(HA)
Formula of Efficiency for Pump
Effpump = Poutput/Pinput x 100%
Formula of Power for Turbine
Pinput = yQ(HE)
Formula of Efficiency for Turbine
Effpump = Poutput/Pinput x 100%
The input power of the pump is the ___ and its output power is ____.
electrical energy, flow energy
The ratio of the inertia force to viscous force
Reynolds Number
Formula of Reynolds Number
Re = vDρ/μ
