Aim:- To measure the flow rate of a fluid for its flow in closed pipe with the help of a head meter (venturimeter).

Apparatus:- Venturimeter.


The head flow meter consists of a primary element such as an orifice , venturi, or pitot tube based with a differential – pressure meter to measure the differential head caused by the flowing fluid at the primary element. The differential – pressure meter may be any of the various meters such as the enlarged – leg mercury manometer, the bell gage, the bellows gage, the diaphragm gage, the ring gage, or the tilting U –tube gage.

The flow of fluid through the venturi tube establishes the pressure differential which can then be measured and related the flow rate.



  1. Fill the storage tank with the water.
  2. Switch on the pump and keep the delivery valve fully open and close the by pass valve to have maximum flow rate through the meter.
  3. Open the vent cocks provided at the top of the manometer to drive out the air from the manometer limbs and close both of them as soon as water start coming out.
  4. Note down the difference of level in the manometer limbs.
  5. Keep the drain valve of the collection tank closed till its time to start collecting tank and note down the initial level of the water in the collection tank.
  6. Collect about 40 liter of water in the collection tank and note down the time required for the same.
  7. Change the flow rate of water through the meter with the help of delivery valve and repeat the above procedure.
  8. Take about 5-6 readings for different flow rates.Results:-Conclusion:-Observations:
    1. Inner dia of pipe =            cm
    2. Venturi throat dia =           cm
    3. Venturi co-efficient =________
    4. Density of water =________
    5. Density of manometer fluid =________
    6. Diameter ratio =________
    7. Temperature =________

    Observation table:

    Sr. No. Volume collected,


    Manometer reading (h)


    Vol. flow rate (Q)


    Venturi meter discharge  co-efficient CVT


    Volumetric flow rate from venturi co-efficient (Q)

    Q         =        {Π*CVT2 * D2 * √ 2*g*(ρm-ρ)*h/ρ }/ {4 *√(1-β4)}


    Q= flow meter, m3/sec

    CVT= Venturi meter discharge co-efficient

    β=dia ratio, d/D

    d=venturi throat diameter

    D=pipe diameter, m

    ρm=density of manometer fluid , kg/m3

    ρ=density of flowing fluid, kg/m3

    h=manometer differential, m


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