To determine the water surface profile for supercritical flow, where should flow calculations begin?

To determine the water surface profile for supercritical flow, calculations should indeed begin from upstream. In supercritical flow conditions, the flow is characterized by high velocities and low depths, which leads to significant changes in flow properties as one moves downstream. Supercritical flow does not have the capacity to backwater because it is faster and shallower than subcritical flow, meaning that disturbances do not propagate upstream.

By starting the calculations from upstream, you can accurately assess the influences of boundary conditions and flow structures, ensuring that the critical depth and energy levels are appropriately considered. This allows for an understanding of how the supercritical flow transitions and evolves as it moves downstream, as well as providing insights into flow behavior in various channel configurations.

In summary, beginning calculations from the upstream allows for a correct representation of the flow regime and ensures that all changes in energy state are captured effectively, reflecting accurately the characteristics of supercritical flow.