Laserfiche WebLink
<br />downstream by supercritical surface velocities even though the cal- <br /> <br /> <br />culated Froude number is less than 1. <br /> <br /> <br />In calculating water surface profiles, calculations should begin <br /> <br /> <br />at the downstream end and proceed in the upstream direction when flow <br /> <br /> <br />is subcritical. When supercritical flow exists, calculations are <br /> <br /> <br />made in the downstream direction. If the direction of profile com- <br /> <br /> <br />putation is not correct for the prevailing flow condition, the cal- <br /> <br /> <br />culated profile diverges from the true profile unless the starting <br /> <br /> <br />water surface elevation is precisely correct. If the calculations <br /> <br /> <br />proceed in the proper direction for prevailing flow conditions, the <br /> <br /> <br />calculated water surface profile converges to the true profile even <br /> <br /> <br />if the starting water surface is in error. <br /> <br />Section 3.03. Types of Flow <br /> <br />Possible types of open channel flow are shown in fig. 3.02. <br /> <br />Steady Versus Unsteady Flow <br />If the change in velocity with respect to time at a given location <br />is zero, the flow is steady. Otherwise, the flow is classified as <br />unsteady in which case the additional variable, time, must be included <br />as discussed in Chapter 7 of this volume. <br /> <br />Uniform Versus Varied Flow <br />If dV/dx, the change in velocity with respect to distance (where <br />V is velocity and x is distance along the channel) is zero for any <br /> <br />3.06 <br />