Chapter 6 Flow Measurement
|Venturimeter||rate of flow (discharge)|
|Flow nozzle||rate of flow|
|Orifice meter||rate of flow|
|Bend meter||rate of flow|
|Rotameter||rate of flow|
|Hot wire anemometer||air & gas velocity|
|Current meter||velocity in open channels|
-Cone angle of convergence side (20°) is greater than cone angle of divergence side (5° to 7°).
-Position of venturimeter does not play any role in discharge thus it is constant for horizontal, inclined or vertical position.
-Qac = Cd Qth
-Cd = coefficient of discharge = 0.95 to 0.98
-h = venturi head which is difference between pressure heads
-Throat diameter is known as size of the venturimenter.
-It is a cheaper arrangement but has more energy loss.
-Cd for orifice meter = 0.68 - 0.74
-a1 = πd2/4
-a2 = πdc2/4
-It is based on principle of conversion of kinetic head into pressure head. The point at which velocity reduces zero is called stagnation point.
-Vac = Cv .Vth
-Cv = Coefficient of velocity = 0.99
-ps/γ = stagnation head & static head.
-Velocity head is indicated by the difference in liquid level between the Pitot tube and the piezometer.The Pitot tube measures the total head and therefore known as total head tube.
- Contraction coefficient (Cc) =
- Coefficient of velocity of (Cv) =
- Coefficient of discharge (Cd) =
- Cd = Cv . Cc
Flow through orifice in the tank:
Discharge through orifice when head over orifice is h
Time required to lower the level from H to h
L = length of crest
H = head above crest
Flow over cippoletti weir or trapezoidal weir:
-Trapezoidal weir is also called as Cippoletti weir. This is trapezoidal in shape and is the modification of rectangular weir with slightly higher capacity for same crest strength.
-The sides are inclined outwards with a slope 1:4 (horizontal : vertical)