96. A jump is to be provided on the channel bed. The maximum height of the jump without affecting the upstream flow condition is

1. 1. 0.50 m

   
   
   

   2. 0.40 m

   
   
   

   3. 0.30 m

   
   
   

   4. 0.20 m

   
   
   

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1. View Hint View Answer Discuss in Forum

   Flow is sub-critical.
   Specific energy, E_c
   z – height
   

   Ec + z = y1 +	v²1
   	2g

   
   

   Ec =	3	× yc
   	2

   
   

   =	3	×		q²		1/3
   	2			g

   
   

   q =	Q	=	16	= 2.67m³/s/m
   	b		6

   
   

   Ec =	3	×		2.67²		1/3	= 1.67 m/s
   	2			9.81

   
   

   V1 =	Q	=	16	= 1.67 m/s
   	A		6 × 1.6

   
   

   ∴ 1.35 + z = 1.6 +	1.67²
   	2 × 9.81

   
   ∴ z = 1.74 – 1.35 = 0.4 m.

   Correct Option: B

   Flow is sub-critical.
   Specific energy, E_c
   z – height
   

   Ec + z = y1 +	v²1
   	2g

   
   

   Ec =	3	× yc
   	2

   
   

   =	3	×		q²		1/3
   	2			g

   
   

   q =	Q	=	16	= 2.67m³/s/m
   	b		6

   
   

   Ec =	3	×		2.67²		1/3	= 1.67 m/s
   	2			9.81

   
   

   V1 =	Q	=	16	= 1.67 m/s
   	A		6 × 1.6

   
   

   ∴ 1.35 + z = 1.6 +	1.67²
   	2 × 9.81

   
   ∴ z = 1.74 – 1.35 = 0.4 m.

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97. For a given discharge, the critical flow depth in an open channel depends on

1. 1. channel geometry only

   
   
   

   2. channel geometry and bed slope

   
   
   

   3. channel geometry, bed slope and roughness

   
   
   

   4. channel geometry, bed slope, roughness and Reynold’s number

   
   
   

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1. View Hint View Answer Discuss in Forum

   We obtain critical flow depth from specific energy equation.
   

   E = y +	V²
   	2g

   
   For E_minimum,
   

   ∂E	= 0
   ∂y

   
   

   Thus,	Q²Te	= 1
   	gA³

   
   A = B. y_c.

   Correct Option: A

   We obtain critical flow depth from specific energy equation.
   

   E = y +	V²
   	2g

   
   For E_minimum,
   

   ∂E	= 0
   ∂y

   
   

   Thus,	Q²Te	= 1
   	gA³

   
   A = B. y_c.

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98. For a body completely submerged in a fluid, the centre of gravity (G) and centre of buoyancy (O) are known. The body is considered to be in stable equilibrium if

1. 1. O does not coincide with the centre of mass of the displaced fluid

   
   
   

   2. G coincides with the centre of mass of the displaced fluid

   
   
   

   3. O lies below G

   
   
   

   4. O lies above G

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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99. The flow in a horizontal, frictionless rectangular open channel is supercritical. A smooth hump is built on the channel floor. As the height of hump is increased, choked condition is attained. With further increase in the height of the hump, the water surface will

1. 1. rise at a section upstream of the hump

   
   
   

   2. drop at a section upstream of the hump

   
   
   

   3. drop at the hump

   
   
   

   4. rise at the hump

   
   
   

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1. View Hint View Answer Discuss in Forum

   After attaining E_min, with further increase in height, the specific energy will increase. That is, y will increase.

   Correct Option: A

   After attaining E_min, with further increase in height, the specific energy will increase. That is, y will increase.

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100. For sub-critical flow in an open channel, the control section for gradually varied flow profiles is

1. 1. at the downstream end

   
   
   

   2. at the upstream end

   
   
   

   3. at both upstream and downstream ends

   
   
   

   4. at any intermediate section

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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