Test 29 - Spillway Hydraulics and Energy Dissipation

Question 1 ప్రశ్న 1

What is the principal purpose of an energy dissipator downstream of a spillway carrying high-velocity flow?

A To increase reservoir storage by raising the spillway crest B To reduce the excessive kinetic energy of the released water so that downstream scour and structural damage are controlled C To increase the velocity before the flow enters an erodible riverbed D To replace the spillway control structure

Question 2 ప్రశ్న 2

For an uncontrolled overflow spillway, use Q = C L H^(3/2). If C = 2.10, effective crest length L = 18 m and total head H = 2.5 m, what is the discharge?

A 94.5 m³/s B 118.1 m³/s C Approximately 149.4 m³/s D 189.0 m³/s

Question 3 ప్రశ్న 3

At the spillway head-measurement section, the static water head above the crest is 3.0 m and the average approach velocity is 4.0 m/s. Taking g = 9.81 m/s² and using total head H = h + V²/(2g), what total head should be used in the stated idealized discharge relation?

A Approximately 3.82 m B Approximately 3.20 m C Exactly 4.00 m D Approximately 6.26 m

Question 4 ప్రశ్న 4

Why can poor or highly nonuniform approach conditions upstream of an ogee spillway affect its hydraulic performance?

A Because approach conditions alter only concrete self-weight and cannot affect flow B Because they always make the discharge coefficient exactly unity C Because they eliminate the velocity head regardless of approach speed D Because approach velocity, flow distribution, separation and contractions can influence the effective head and discharge coefficient

Question 5 ప్రశ్న 5

For the same effective crest length and discharge coefficient, an uncontrolled spillway follows Q proportional to H^(3/2). If the head increases from 2.0 m to 2.5 m, by approximately what factor does the discharge increase?

A 1.25 B 1.40 C 1.56 D 1.95

Question 6 ప్రశ్న 6

Why does spillway flow commonly require substantial downstream protection after descending through a large elevation difference?

A Because potential-energy loss is converted largely into static pressure only B Because gravity stops acting once water passes the crest C Because a large part of the available head can appear as high flow velocity capable of causing severe bed and bank erosion D Because the discharge necessarily becomes zero at the spillway toe

Question 7 ప్రశ్న 7

At a section of spillway flow, the depth is 1.2 m and the average velocity is 12 m/s. Neglecting elevation datum effects at that section, what is the specific energy E = y + V²/(2g), taking g = 9.81 m/s²?

A Approximately 8.54 m B Approximately 6.14 m C Approximately 13.20 m D Approximately 15.88 m

Question 8 ప్రశ్న 8

A rectangular spillway channel carries water 1.0 m deep at a velocity of 10 m/s. Using Fr = V/sqrt(g y) with g = 9.81 m/s², what is the Froude number and flow regime?

A Fr ≈ 0.31, subcritical B Fr ≈ 1.00, critical C Fr ≈ 9.81, always critical D Fr ≈ 3.19, supercritical

Question 9 ప్రశ్న 9

Which description best characterizes a hydraulic jump used for spillway energy dissipation?

A An abrupt transition from supercritical to subcritical flow accompanied by strong turbulence and substantial loss of mechanical energy B A transition from subcritical to supercritical flow without energy loss C A pressure surge occurring only inside a closed pipe D A phenomenon in which flow velocity increases while turbulence disappears

Question 10 ప్రశ్న 10

For a hydraulic jump in a horizontal rectangular channel, use y2/y1 = 0.5[sqrt(1 + 8Fr1²) - 1]. If y1 = 1.0 m and Fr1 = 4.0, what is the sequent depth y2?

A 2.50 m B 4.00 m C Approximately 5.18 m D 8.00 m

Question 11 ప్రశ్న 11

For an ideal hydraulic jump in a horizontal rectangular channel, use ΔE = (y2 - y1)^3/(4 y1 y2). If y1 = 1.0 m and y2 = 4.0 m, what is the specific-energy loss?

A Approximately 1.69 m B 0.75 m C 3.00 m D 4.25 m

Question 12 ప్రశ్న 12

For a conventional hydraulic-jump stilling basin, which tail-water condition is generally most favorable for forming the intended jump near the basin location?

A Tail-water depth must always be zero B Tail-water depth should be much smaller than the incoming supercritical depth C Tail-water depth must be independent of the sequent depth D Available tail-water should approximately match the required conjugate or sequent depth for the design condition

Question 13 ప్రశ్న 13

What is a likely consequence if the available tail-water depth is substantially lower than the conjugate depth required for a hydraulic jump at the spillway toe?

A The jump may sweep downstream beyond the intended basin, leaving high-velocity flow capable of causing scour B The jump necessarily moves upstream into the reservoir C The incoming supercritical flow automatically becomes subcritical without turbulence D The discharge becomes independent of spillway head

Question 14 ప్రశ్న 14

What is the most appropriate interpretation when tail-water is substantially greater than the depth required for a free hydraulic jump?

A The hydraulic jump must always disappear without any turbulence B The jump can become submerged or drowned, and basin performance should be checked for the resulting flow condition C The spillway discharge must immediately become zero D The tail-water has no effect on energy dissipation

Question 15 ప్రశ్న 15

What is the purpose of chute blocks, baffle blocks and end sills when they are appropriately incorporated into a hydraulic-jump stilling basin?

A To assist jump formation and stabilization, increase turbulence or resistance, and help reduce the basin length or downstream velocity where the adopted design permits B To eliminate all hydraulic forces acting on the basin floor C To convert the basin into an uncontrolled reservoir D To prevent any air from entering the hydraulic jump

Question 16 ప్రశ్న 16

Which site condition most strongly favors consideration of a hydraulic-jump stilling basin rather than projecting the spillway jet far downstream?

A Very low tail-water and sound exposed rock far downstream B No downstream bed requiring protection C Adequate tail-water close to the required sequent depth and a need to dissipate energy on a protected apron before flow reaches an erodible channel D A requirement that all energy remain in the flow downstream

Question 17 ప్రశ్న 17

Under IS 7365 terminology, which two broad classes of bucket-type energy dissipators are recognized?

A Hydraulic-jump basin and stilling well B Roller-bucket type and trajectory or flip-bucket type C Ogee crest and side-channel spillway D Shaft spillway and siphon spillway

Question 18 ప్రశ్న 18

Which hydraulic condition is particularly associated with a solid roller bucket?

A Tail-water depth much lower than the sequent depth with no downstream water B Operation only when downstream rock is completely dry C Tail-water sufficiently high, commonly substantially above the sequent-depth condition, so that strong roller action develops around the bucket D A requirement that the jet remain entirely airborne until it leaves the project area

Question 19 ప్రశ్న 19

Which combination of conditions most strongly favors a trajectory or flip-bucket dissipator?

A Tail-water too low to form the desired hydraulic jump, sound downstream rock, and sufficient distance for the projected jet to land safely away from the structure B Deep erodible alluvium immediately downstream with no acceptable scour zone C A requirement that all kinetic energy be dissipated inside the bucket itself D A flat site where no jet trajectory can be accommodated

Question 20 ప్రశ్న 20

Which statement most accurately describes the energy-dissipation mechanism of a flip or ski-jump bucket?

A Nearly all energy is dissipated by friction within the short bucket itself B The bucket reduces discharge to zero before the jet leaves the lip C The bucket functions by producing a conventional hydraulic jump inside its curved surface D The bucket mainly redirects and projects the jet so that much of the remaining energy is dissipated during jet breakup and in the downstream plunge or impact region

Question 21 ప్రశ్న 21

A spillway discharges 360 m³/s through a 24 m wide rectangular chute. What is the discharge intensity, or unit discharge q = Q/b?

A 8 m²/s B 15 m²/s C 24 m²/s D 360 m²/s

Question 22 ప్రశ్న 22

The unit discharge entering a stilling basin is 15 m²/s and the incoming flow depth is 1.5 m. Assuming a rectangular section and uniform velocity, what is the average velocity?

A 5 m/s B 7.5 m/s C 10 m/s D 22.5 m/s

Question 23 ప్రశ్న 23

A high-velocity spillway flow enters an energy dissipator at 10 m/s. Taking g = 9.81 m/s², what is its velocity head V²/(2g)?

A Approximately 5.10 m B Approximately 2.55 m C Approximately 9.81 m D Approximately 19.62 m

Question 24 ప్రశ్న 24

A hydraulic jump carries Q = 100 m³/s and dissipates 4.0 m of specific energy. Using water density 1000 kg/m³ and g = 9.81 m/s², what is the approximate rate of mechanical-energy dissipation, P = rho g Q ΔE?

A 0.392 MW B 0.981 MW C 39.24 MW D 3.924 MW

Question 25 ప్రశ్న 25

Consider the following statements about spillway energy dissipation: I. A hydraulic-jump basin is strongly influenced by the relation between available tail-water and required sequent depth. II. A flip bucket principally projects the jet away from the structure rather than dissipating all energy within the bucket. III. High residual velocities downstream can require bed or bank protection even after an energy dissipator. IV. Geology, tail-water, discharge intensity and scour risk are important when selecting an energy-dissipation arrangement. Which option is correct?

A I and II only B I, II, III and IV C II and III only D I, III and IV only

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