Question 5.1: Sketch the water-surface profile in the channels connecting ......
Sketch the water-surface profile in the channels connecting the reservoirs, as shown in Fig. 5-5a. The bottom slope of channel 1 is steep and that of channel 2 is mild.
Compute the critical and normal depths for each channel. Then plot the critical-depth line and the normal-depth line (marked as CDL and NDL, respectively in Fig. 5-5b).
\quad\quadThe water depth at the channel entrance is equal to the critical depth, since the water level in the upstream reservoir is above the CDL of channel 1. Let us mark this water level at the channel entrance by a dot (5-5b). The water level at the downstream end of channel 2 is lower than the CDL. Therefore, the water surface passes through the CDL approximately three to four times the critical depth upstream of the entrance to the downstream reservoir. Let us again mark this water level at the downstream end by a dot, as shown in Fig. 5-5b.
In channel 1, the water surface at the entrance, after passing through the critical depth, tends to the normal depth. Thus, we have an S2 profile in channel 1. The flow decelerates downstream of the junction of channels 1 and 2 because of mild slope. Hence, the flow depth increases until a hydraulic jump is formed. The water surface follows the M2 profile downstream of the jump and the exact location of the jump is determined by detailed calculations as discussed in Chapter 8.
\quad\quadIn the following example, a control gate is located at an intermediate location and depending upon the gate opening and the location of the other controls, several different profiles are possible.