# Flow Rate

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## flow rate

[′flō ‚rāt]## Flow Rate

in hydraulics, the volume of fluid flowing through a cross section of a stream per unit time. The flow rate *Q* of a fluid for a given cross section ω is determined by the formula

*Q* = ∫_{ω}*u dω*

where *u* is the flow velocity within the limits of *d,* an elementary segment of the cross section. In steady flow, the flow rate of a dropping liquid is constant along a given stream. The average flow velocity of the fluid can be determined from the known values of the flow rate and cross-sectional area: *v* = *Q/ω.* The mass of fluid flowing per unit time through a cross section of the stream is called the mass flow rate *M.* This rate is related with the volume flow rate by the equation *M* = ρ *Q,* where *ρ* is the density of the fluid. The flow rate of a fluid is measured with water meters, measuring spillways, hydrometers, rate-of-flow meters, and other instruments.

### REFERENCES

Al’tshul’, A. D., and P. G. Kiselev.*Gidravlika i aerodinamika.*Moscow, 1965.

Chugaev, R. R.

*Gidravlika,*2nd ed. Leningrad, 1970.