Test Papers / Previous Question Papers of Indira Gandhi National Open University ET540B Flow in Open Channel June 2007

B.Tech. Civil (Construction Management)

Term-End Examination

ET-540(B) FLOW lN OPEN CHANNEL

Time: 3 hours
Maximum Marks: 70

Note: Solve any five questions. All questions carry equal marks. Use of calculator is permitted.

June 2007

1. (a) In what ways is the open channel flow different from the flow in closed conduits ? 5

(b) Show that for a given discharge, specific energy is minimum when Q².T / gA³ is unity, where T is the water surface width. Obtain expression or the critical depth and minimum specific energy for a wide rectangular 3+2+2=7

(c) Obtain the relation between Manning's constant and Chezy's constant. 2

2. (a) Calculate the bottom width of a channel required to carry a discharge of 15 m³/sec as a critical flow at a depth of 1.2 m, if the channel section is (a) rectangular, and (b) trapezoidal with side slope of 1.5 horizontal : 1 vertical. 3+3=6

(b) What is a specific energy curve? Draw specific energy curve, and then derive expressions for critical depth and critical velocity. 1+2+3=6

(c) Why is a bed slope provided for an open channel ? 2

3. Classify and characterise the various water surface profiles obtained in a steady gradually varied flow in a prismatic channel under different slopes. 14

4 (a) For a hydraulic jump in a rectangular channel, derive the following relationship. Also state the assumptions involved in the derivation.

(i) y₁y₂(y₁+y₂)=2q₂/g

(ii) E_L=(y₂-y₁)³/4y₁y₂ where, E_L is the energy loss, q is the discharge per unit width. 4+4=8

(b) A rectangular channel carrying a supercritical stream is to be provided with a hydraulic jump type of energy dissipater . If it is desired to have an energy loss of 5.9 m in the jump when the inlet Froude number is 8.5, determine the sequent depth. 6

5. State and discuss the assumptions made in the derivation of the dynamic equation for gradually varied flow. Starting from first principle, derive equation for the slope of the water surface in GVF. Also write down the dynamic equation for wide rectangular channels if (i) Manning's formula is used, and (ii) Chezy's formula is used. 3+7+4=14

6. Discuss the graphical integration method in detail for working out water surface profile in an open channel flow. 14

7. The normal depth of flow of water in a rectangular channel 1.5 m wide is one meter. The bed slope of the channel is 0.0006 and Manning's roughness co-efficient : 0.012. Find the critical depth. At a certain section of the same channel the depth is 0.92 while at a second section the depth is 0.86 m. Find the distance between the two sections. Also find whether the section is located d/s or u/s with respect of the first section. 14

8. Write short notes on any fourof the following : 4x3½=14

(i) Types of open channel flow
(ii) Velocity distribution in open channel flow
(iii) Exponential and non-exponential channels
(iv) Roughness coefficient
(v) Hydraulic gradient
(vi) Hydraulic jump

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