### Straight Channel

The straight channel is characterized by a trapezoid cross section, the bottom width of which can be defined to vary linearly. This is illustrated in Figure . The following constants have to be specified on the line beneath the *FLUID SECTION,TYPE=CHANNEL STRAIGHT card:

• the width b
• the slope S_0= \sin \phi (if S_0<-1 the slope is calculated from the coordinates of the end nodes belonging to the element)
• the length L
• the trapezoid angle \theta
• the grain diameter k_s for the White-Colebrook law or the Manning constant n for the Manning law (in the latter case the user has to specify the parameter MANNING on the *FLUID SECTION card)
• the number of the upstream reference element

Example files: channel1, chanson1.