# GATE Questions & Answers of Flow measurements in channels and pipes

## What is the Weightage of Flow measurements in channels and pipes in GATE Exam?

Total 16 Questions have been asked from Flow measurements in channels and pipes topic of Hydraulics subject in previous GATE papers. Average marks 1.62.

For a given discharge in an open channel, there are two depths which have the same specific energy. These two depths are known as

In a 5 m wide rectangular channel, the velocity $u$ distribution in the vertical direction $y$ is given by $u=1.25y^\frac16$ . The distance y is measured from the channel bed. If the flow depth is 2 m, the discharge per unit width of the channel is

A rough pipe of 0.5 m diameter, 300 m length and roughness height of 0.25 mm, carries water (kinematic viscosity $0.9\times10^{-6}$ m2/s) with velocity of 3 m/s. Friction factor ($f$) for laminar flow is given by $f=64/R_e$, and for turbulent flow it is given by $\frac1{\sqrt f}=2\;\log_{10}\left(\frac rk\right)+1.74$, where, $R_e$ = Reynolds number, r = radius of pipe, k = roughness height and $g=9.81$ m/s2 . The head loss (in m, up to three decimal places) in the pipe due to friction is ______

Water is pumped at a steady uniform flow rate of 0.01 m3/s through a horizontal smooth circular pipe of 100 mm diameter. Given that  the Reynolds number is 800 and g is 9.81 m/s2, the head loss (in meters, up to one decimal place) per km length due to friction would be ____________

The pre-jump Froude Number for a particular flow in a horizontal rectangular channel is 10. The ratio of sequent depth (i.e., post-jump depth to pre-jump depth) is ____________.

A 4 m wide rectangular channel, having bed slope of 0.001 carries a discharge of 16 m3/s. Considering Manning's roughness coefficient = 0.012 and g = 10 m/s2, the category of the channel slope is

A hydraulically efficient trapezoidal channel section has a uniform flow depth of 2 m. The bed width (expressed in m) of the channel is __________

A 3 m wide rectangular channel carries a flow of 6 m3/s. The depth of flow at a section P is 0.5 m. A flat-topped hump is to be placed at the downstream of the section P. Assume negligible energy loss between section P and hump, and consider g as 9.81 m/s2. The maximum height of the hump (expressed in m) which will not change the depth of flow at section P is _________

For steady incompressible flow through a closed-conduit of uniform cross-section, the direction of flow will always be :

A circular pipe has a diameter of 1 m, bed slope of 1 in 1000, and Manning’s roughness coefficient equal to 0.01. It may be treated as an open channel flow when it is flowing just full, i.e., the water level just touches the crest. The discharge in this condition is denoted by $Q_{full}$. Similarly, the discharge when the pipe is flowing half-full, i.e., with a flow depth of 0.5m, is denoted by $Q_{half}$. The ratio $Q_{full}/Q_{half}$ is:

Two reservoirs are connected through a 930 m long, 0.3 m diameter pipe, which has a gate valve. The pipe entrance is sharp (loss coefficient= 0.5) and the valve is half-open (loss coefficient = 5.5). The head difference between the two reservoirs is 20 m. Assume the friction factor for the pipe as 0.03 and g =10 m/s2. The discharge in the pipe accounting for all minor and major losses is _________ m3/s.

A short reach of a 2 m wide rectangular open channel has its bed level rising in the direction of flow at a slope of 1 in 10000. It carries a discharge of 4 m3/s and its Manning’s roughness coefficient is 0.01. The flow in this reach is gradually varying. At a certain section in this reach, the depth of flow was measured as 0.5 m. The rate of change of the water depth with distance, dy/dx, at this section is ___(use g = 10 m/s2)

A pipe of 0.7 m diameter has a length of 6 km and connects two reservoirs A and B. The water level in reservoir A is at an elevation 30 m above the water level in reservoir B. Halfway along the pipe line, there is a branch through which water can be supplied to a third reservoir C. The friction factor of the pipe is 0.024. The quantity of water discharged into reservoir C is 0.15 m3/s. Considering the acceleration due to gravity as 9.81 m/s2 and neglecting minor losses, the discharge (in m3/s) into the reservoir B is ___________.

Group-I gives a list of devices and Group-II the list of uses

 Group-I Group-II P. Pitot tube 1. Measuring pressure in a pipe Q. Manometer 2. Measuring velocity of flow in a pipe R. Venturimeter 3. Measuring air and gas velocity S. Anemometer Measuring discharge in a pipe The correct match of Group-I with Group-II  is

Water ($\gamma$w = 9.879 kN/m3) flows with a flow rate of 0.3 m3/sec through a pipe AB of 10m length and of uniform cross section. The end ‘B’ is above end ‘A’ and the pipe makes an angle of 30º to the horizontal. For a pressure of 12 kN/m2 at the end ‘B’, the corresponding pressure at the end ‘A’ is
At two points 1 and 2 in a pipeline the velocities and V and 2V, respectively. Both the points are at the same elevation. The fluid density is $\mathrm{\rho }$. The flow can be assumed to be in compressible, inviscid, steady and irrotational. The difference in pressures P1 and P2 at poiunts 1 and 2 is