Question

Part I. Indicate whether true or false (T or F).

__When performing flow profile analysis, calculations always proceed in the downstream direction. That is because water flows downhill, i.e., downstream.

__Subcritical flow is controlled by upstream conditions.

__The normal depth of flow, yn, is determined by solving Manning's equation. The critical depth of flow, yc, is determined by solving the Froude number equation set equal to 1.0. Normal depth, yn, varies with flow rate, channel geometry, channel slope, and channel roughness. On the other hand, yc varies only with flow rate, slope, and channel geometry.

__Critical flow (depth) occurs at the point of minimum specific energy, where the Froude number equals 1. The depth of flow at this point is termed the critical depth and is designated as yc. At depths below yc, the flow is classified as subcritical because the depth of flow is below (sub) the critical depth, and at depths greater than yc, the flow is classified as supercritical, because the depth of flow is greater than the critical depth.

__Flows are classified as subcritical, critical, or supercritical by comparing the uniform and critical depths of flow.

__The specific energy curve is obtained by plotting specific energy for a range of depth values (y values) for a given discharge in each channel. The curve falls in the first quadrant, with asymptotes of y=E (45o line) and the abscissa (E axis). The curve has three distinct portions corresponding to subcritical, critical and supercritical flow.

__Weirs and flumes are considered critical flow measurement devices since they force the depth of flow to pass through critical depth. They are indirect measurement devices since they do not directly measure velocity or the volume rate of flow but monitor a form of energy (depth or HGL).

__Subcritical open channel flow is controlled by downstream conditions. In the case of a backwater profile (M1 or S1), the control is some type of downstream constriction (such as an undersized road cross drain) that forces the water to pond to a greater depth.

__The specific energy diagram represents a plot of the sum of the pressure head (depth of flow) and velocity head terms for a range of y-values for a given discharge.

__Given an M2 flow profile, the specific energy increases in the upstream direction (opposite the direction of flow).

__The standard step method of flow profile analysis applies only to non-prismatic channels, while the direct step method applies to prismatic channels. For the standard step method, simply stated, the solution strategy is given y, find x. For the direct step method, the solution strategy is given x, find y.

__When a storm sewer pressurizes, the HGL is indicated by the water level in a manhole, which is above the crown of the downstream pipe. When a culvert pressurizes, the headwater at the inlet is above the crown of the downstream pipe.

__A necessary condition for uniform flow is a prismatic channel, which is a channel with constant cross-sectional geometry, roughness, and slope throughout the reach of interest.

__A control is a channel feature, usually structural, that regulates the state of flow. In the pure sense, a control forces a unique relationship between depth and discharge. The most ideal control is a critical control.

__Flow profile analysis involves determination of the nonuniform flow depth along a channel.

__Culverts operate under inlet or outlet control. Under outlet control, either the condition (e.g., depth of water) at the pipe outlet or the capacity of the pipe barrel regulates the discharge through the culvert. Under inlet control, the inlet capacity, i.e., how much water the inlet can pass subject to headwater depth, regulates the discharge through the culvert. Under inlet control, the pipe barrel can carry whatever discharge passes the inlet.

__Three assumptions underlying Manning's equation are that the flow is steady, uniform, and laminar.

__In the direct step method, the only unknown, given the depths at each end of a sub-reach, is the parameter Δx.

__Steady flow is flow that does not change with time at a point (cross-section) along a channel. Uniform flow is flow that does not change in space along a channel.

__An open channel that is hydraulically mild for one flow can be hydraulically steep for a different flow rate.

__Given an S1 flow profile, the specific energy increases in the downstream direction (direction of flow).

__According to DHEC guidelines, each pump in a duplex station must be designed to pump the average daily flow (ADF).

__One day while walking along Campus Creek (Rocky Branch), President Caslen passed the Catawba Street crossing and noted the depth of flow at a point was 1.50 feet. About 20 minutes later, he reached the Sumter Street crossing and noted the depth of flow there was 1.25 feet. He concluded the flow in the reach between the two crossings was steady and non-uniform. His conclusion was correct and defensible.

__The flow along a backwater curve (M1 or S1) decelerates (slows) in the downstream direction and is subcritical for both hydraulically mild and steep sloped channels. The flow along a drawdown curve (M2 or S2) accelerates (increases velocity) in the downstream direction and is supercritical for both hydraulically mild and steep channels.

__In open channels, flow control may be generated by structures at the upstream and downstream sections (ends of channel reach under consideration), but also may be continuous along the channel. When the control results from a structure at the upstream section, we say the control is upstream, i.e., the resulting profile is controlled by upstream conditions. When the flow control results from a structure at the downstream section, we say the control is downstream. When the flow control occurs continuously along the channel, the flow is under channel, or downstream, control.

Answer 1

1- True because In that direction hydraulic energy decrease and we always do analysis from high energy i.e upstream to low energy level i.e downstream.

2-False, the control section for super critical flow is upstream and for subcritical flow is downstream

3-True, this statement is correct, because at critical flow frouds number is number and also normal depth and critical depths depends only on given factors

4-False, the final conclusion is false because flow is said to be super or sub depending upon the critical velocity(Vc), if v is greater then Vc, flow is super critical and if less then Vc, it is called sub critical.

5-True, if normal depth is equal to critical depth, flow is critical, if it is less then critical depth then flow is super critical and if it is more then critical depth, flow is sub critical.

6-True, the region is divided into 3 zones of critical, sub critical and super critical flow.

7-False, weir and flumes are discharge measurement devices.

8-True, the control section for sub critical flow is downstream.

9-True, specific energy is the total energy with respect to datum and it consist of pressure head and velocity head.

10-True, it increases

11-False, standard step method can be applied to both prismatic and non prismatic channels while direct step method is only applied to prismatic channels

12-True.

13-True, it is said to be uniform flow if flow properties does not change along the length of channel.

14-True

15-False, we always find uniform depth and critical depth for flow profile analysis.

16-False

17-True, we can find using dynamic equation of GVF.

18-True

19-False, a channel is said to be mild steel critical adverse or horizontal depending upon the bed slope and not on discharge flowing through it.

20-True.

21-True, recommended

22-false, as the flow properties depth is changing with time so it is a unsteady flow

23-False

24-True

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