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SECTION 2: TRAPEZOIDAL AND CIRCULAR CHANNEL ANALYSIS PROGRAMS <br /> 2.3 PURPOSE OF THE PROGRAMS <br /> The Trapezoidal Channel Analysis (TRAP) program quickly computes the Normal <br /> Depth, Critical Depth, Rating Curve, or Standard Step Water Surface Profile <br /> for flow in a trapezoidal channel. The Circular Channel Analysis (CIRC) <br /> program provides the same information for circular channels. <br /> Using the Trapezoidal Channel Analysis program, you can quickly and easily <br /> analyze the hydraulic characteristics of almost any trapezoidal channel, <br /> including those with a different side slope for each bank. Triangular and <br /> rectangular channels can also be easily analyzed by the program, because they <br /> are both special kinds of trapezoidal channels. A triangular channel is a <br /> trapezoidal channel with a channel bottom width of zero. A rectangular <br /> channel is a trapezoidal channel with side slopes of zero (vertical sides) . <br /> The Trapezoidal Channel Analysis and Circular Channel Analysis programs are <br /> appropriate for open-channel flow only. Pressure flow in pipe and box culverts <br /> should be analyzed using the Pipe Culvert Analysis and Box Culvert Analysis <br /> programs which are included in the DODSON HYDRAULICS LIBRARY. <br /> 2.4 NORMAL DEPTH FOR TRAPEZOIDAL OR CIRCULAR CHANNELS <br /> 2.4.1 Purpose of Normal Depth Procedure <br /> Normal Depth is the depth at which uniform flow will occur in an open channel. <br /> In other words, if you had a uniform channel of infinite length, carrying a <br /> constant flow rate, then flow in the channel would be at a constant depth at <br /> all points along the channel, and this depth would be the Normal Depth. <br /> It is often useful to determine Normal Depth, because it may represent a good <br /> approximation of the actual depth of flow within a channel segment. It is <br /> common practice to use Normal Depth computations to prepare a preliminary <br /> design for channel improvements, and then to check or refine the design by <br /> computing the water surface profile in the channel using the Standard Step or <br /> Direct Step Methods. The Standard Step procedure of the TRAP and CIRC <br /> programs, for example, can be used for further analysis of a preliminary <br /> channel design identified using the Normal Depth procedure. <br /> 2.4.2 Required Input Data for Normal Depth Procedure <br /> 2.4.2.1 Getting Help During Data Entry <br /> Instant help is available at all times during data entry, as described in <br /> Section 1.5 of this manual. Pressing the <F1> key on the upper left corner of <br /> your keyboard will cause each of the HYDRAULICS LIBRARY programs to display a <br /> box containing guidance on entering the required data. <br /> 2.4.2.2 Flow Rate <br /> The user must supply the flow rate which the channel is to convey, in cubic <br /> feet per second (cfs) . Sometimes, the flow rate may vary through the length of <br /> DODSON & ASSOCIATES, INC. THE DODSON HYDRAULICS LIBRARY, PAGE 14 <br />