Water Resources: Hydraulics and Hydrology
A:
Let's take a simple case, an ogee spillway. Water flows over the ogee. The criteria
needed to calculate the discharge under different heads is the coefficient of discharge for
an ogee spillway of this type. This depends on the height of the spillway and the
maximum discharge head.
The coefficients are originally obtained from model tests. Frank Campbell computed the
coefficients of different kinds of spillways from available model test data. Then he either
plotted a curve of coefficients with respect to head, or produced a table of coefficients.
That information and the discharge formula were all placed on one x 10 chart. It was
named "Hydraulic Design Criteria for Ogee Spillway Discharge."
I have a large three-ring binder of hydraulic design criteria charts. I'd like to show you
its contents. [Pause and then he reads] "Corps of Engineers, Hydraulic Design Criteria.
Preface that tells how it's done. Classification Index. General Spillways. Concrete
Overflow Spillways. Spillway Crest. Spillway Energy Dissipation. Erosion Below
Spillways. Chute Spillways. Approach Channel. Ogee Crests. Spillway Chutes.
Spillway at Basins. Spillway Exit Channel. Side Channel Spillways. Morning Glory
Spillways.
Let's look at this chart for length of hydraulic jump, which is used to design the stilling
basin for a chute spillway. Some text is given about where the information was obtained
and defmes the length of jump and the height of tail water, or depth.
depth is the
depth at the start of the jump, which occurs on the chute slope entering the horizontal
stilling basin. L is the length of the jump from its beginning to where it reaches full
depth. The length of the jump is determined by using the curve shown on the design
criteria chart. Generally, the length may be taken as 3 times
so both the length and
depth can be determined by using the chart. Knowing the length and depth of the
jump, the wall height can be designed.
This is the hydraulic design criteria chart for Morning Glory Spillways. By applying the
information on the chart, the discharge can be calculated for any head of water over the
spillway. Other design criteria charts are used in a similar manner.
So that becomes the book that they use to design.
A:
Designers have this book.
Q:
Once those design criteria are done and approved, they don't change very much then?
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