Quiz: Civil Engineering

Exam: UPPSC-AE

Topic: Hydraulics & Fluid Mechanics

Each question carries 1 mark

Negative marking: 1/3 mark

Time: 10 Minutes

Q1. In open channel flows, the characteristic length commonly used in defining the Reynolds number is the

(a) depth of flow

(b) wetted perimeter

(c) hydraulic radius

(d) area /top width

Q2. The height of hydraulic jump is equal to:

(a) Sequent depth

(b) Difference in conjugate depths

(c) Difference in alternate depths

(d) Initial depth

Q3. During the formation of hydraulic jump

(a) the specific energy and specific force remains constant

(b) the specific energy increase and specific force decreases

(c) the specific energy decrease and specific force increase

(d) the specific energy decrease and specific force remains constant

Q4. The total number of possible GVF profiles in open channel are

(a) 12

(b) 11

(c) 9

(d) 15

Q5. If the Froude number of a hydraulic jump is more than 9, this jump is classified as –

(a) Weak jump

(b) Strong jump

(c) Oscillating jump

(d) None of these

Q6. For an open channel, chezy’s formula is (symbol’s have their usual meanings)

(a) V = √CRS

(b) V =C √RS

(c) V = CRS

(d) V = C/√RS

Q7. The sequent depth ratio of a hydraulic jump in a rectangular horizontal channel is a 10.30. The Froude number at the beginning of the jump is

(a) 5.64

(b) 7.63

(c) 8.05

(d) 13.61

Q8. For open channel, Manning’s formula with usual notations is –

(a) V = 1/N R^(1/3 ) S^(1/2 )

(b) V = 1/N R^(2/3 ) S^(1/2 )

(c) V = 1/N R^(1/3 ) S^(1/3 )

(d) None of the above

Q9. The critical depth at a section of a rectangular channel is 1.5m. The specific energy at that section is

(a) 0.75m

(b) 1.00m

(c) 1.50m

(d) 2.2m

Q10. For best triangular section the hydraulic radious should be:

(a) y

(b) y/√8

(c) y/2

(d) 2/√3 y

SOLUTION

S1. Ans. (c)

Sol. Reynold Number (Re) = ρVD/μ

Where, D = 4 × A/P

= 4 × hydraulic radius

S2. Ans. (b)

Sol. Height of hydraulic jump equal to difference in conjugate or sequent depth. Conjugate depth having same specific force

S3. Ans. (d)

Sol. During the formation of hydraulic jump specific energy decreases and specific force remains constant

S4. Ans. (a)

Sol. Number of GVF profile in open channel flow equal to twelve

S5. Ans. (b)

Sol. Classification of hydraulic jump –

Jump Froude Number

Undular Jump 1 to 1.7

Weak Jump 1.7 to 2.5

Oscillating Jump 2.5 to 4.5

Steady Jump 4.5 to 9

Strong Jump > 9

S6. Ans. (b)

Sol. According to chezy formula –

V = C √RS

S7. Ans. (b)

Sol. y_2/y_1 = 10.30

y_2/y_1 = (-1+√(1+8 Fr_1^2 ))/2

10.30 = (-1+√(1+8 ×Fr_1^2 ))/2

Fr_1^2 = 7.62

S8. Ans. (b)

Sol. Mannings formula –

v=1/n R^(2/3) S^(1/2)

n → Manning Coefficient

S9. Ans. (d)

Sol. Critical depth (y_c) = 1.5m

Specific Energy (E_c) = ?

E_c = 3/2 y_c

= 3/2 × 1.5

E_c = 2.25 m

S10. Ans. (b)

Sol. For most efficient triangular channel

Hydraulic Radiaus (R) = y/(2√2)

R=y/√8