Hydraulics (Chapter 6)

Fluid Flow Measurement

This refers to the quantification of the rate at which fluid flows through a system or pipeline.

Device Coefficients

These are dimensionless values that characterize the performance of hydraulic devices that measure the flow of

fluids.

Coefficient of Discharge, C or Cd

It is the ratio of the actual discharge through the device to the ideal or theoretical discharge which would occur without losses.

Actual discharge

can be obtained by series of observation usually by measuring the total amount of fluid passing through a device for a known period.

Theoretical Discharge

can be obtained using Bernoulli’s Theorem neglecting losses.

Coefficient of Velocity, Cv

It is the ratio of the actual mean velocity to the actual velocity or theoretical velocity which will occur without any losses.

Coefficient of Contraction, Cc

It is the ratio of the actual area of the contracted section of the stream or jet to the area of the opening to which the fluid flows.

Orifice

is an opening, usually circular, with a closed perimeter through which fluid flows.

Orifice

This is usually used to measure or control the flow of fluid.

Short Tubes

This is an orifice with prolonged side such as a piece of pipe having a length two or three times its diameter.

Short Pipes

These are tubes having longer sides than that of a short tube such as culverts.

Circular Orifice

Orifice with round opening.

Square Edged Orifice

Orifice wilh Sharp-Edged rectangular opening

Rounded Edged Orifice

Orifice with Smooth-edged rectangular opening

Conical Orifice

Orifice wilh Tapered Opening

Concentric Orifice

Circular Opening centered within the pipe.

Eccentric Orifice

Circular opening is off-set from the center.

Segmental Orifice

This orifice has partially circular opening.

Free Discharge Orifice

The fluid discharge freely into the atmosphere.

Drowned Orifice

Fluid discharges into another fluid stream.

Submerged Orifice

The fluid discharges under water.

H

total head producing flow in meters or feet of the flowing fluid.

Weirs

These are overflow structures which are built across an open channel for the purpose of measuring or controlling the flow of fluids

Unsteady Flow

A flow in which quantity of fluid flowing per second is not constant.

Nappe

the overflowing stream in a weir

Head, H

the distance between the liquid surface and the crest of the weir

Crest of Weir

the edge or top surface of a weir with which the flowing liquid comes in contact

Drop-Down Curve

the downward curvature of the liquid surface before the weir

Rectangular Weir

This weir has a rectangular opening where the sides are straight up and down. It is generally suitable for larger flowing channels.

Triangular Weir

The shape of the weir is actually reverse triangle like V. so, it is also called V-notch weir. This type of weirs are well suitable for measuring discharge over small flows with greater accuracy.

Trapezoidal Weir

This is trapezoidal in shape and is the modification of rectangular weir with slightly higher capacily for same crest strength.

Cipolletti Weir

a type of trapezoidal weirs with side slope of 1 horizontal by 4 vertical.

Circular Weir

These are circle or half-circle weirs that bolt onto the end of or inserted into conduits and pipes

Parabolic Weir

These are weirs with parabolic cross-sections.

Sharp Crested Weir

The crest of the weir is very sharp such that the water will springs clear of the crest

Broad Crested Weir

These are constructed only in rectangular shape and are suitable for the larger flows. Head loss will be small in case of broad crested weir

Narrow Crested Weir

If is similar to rectangular weir with narrow shaped crest at the top

Ogee Shaped Weir

The crest of the ogee wair is slightly rises and falls into parabolic form.

Contracied Weir

These are weirs having sides sharp-edged, so hat the nappe is contracted in width or having end contractions, either in and or two ends.

Suppressed Weir

Weirs having its length equal to the widih of the channel so that the nappe suffers no end contractions