Author(s): Robert Feurich; Nils Reidar B. Olsen
Keywords: No Keywords
Abstract: Supercritical flows often appear in spillway channels, chutes and other man-made structures. One way for assessing the effects of supercritical flows on water levels is by conducting physical model tests, but those results are often influenced by scale effects, especially in cases where air entrainment is involved. Another possibility, which became more and more important and reliable over the last years, is using numerical models to obtain data from flow fields. Two commercial, three dimensional codes, both using the Volume of Fluid method for tracking the free surface, have been tested, simulating the supercritical flow in a channel junction. The main purpose was to see how they can be applied to predict extreme wave values. The calculated free surface elevations have been compared with measurement data from literature. In the chosen test case two rectangular channels are joining together. The combining angle is 22. 5°and the total length is app 0. 6 m with a channel width of 0. 1 m. In each of the two inflow branches the Froude number is app. 4. 5 which results in a flow rate of 6. 2 l/s. The results showed clearly that numerical simulations can provide reliable data for supercritical flow situations in channel junctions. Using numerical tools can help finding optimized technical solutions fast for channel construction, either by demanding additional freeboard or other measures to reduce crosswaves.