Lateral Outflow Over Side Weirs

The lateral outflow mechanism of side weirs is investigated using a one‐dimensional approach. In particular, the effects of flow depth, approaching velocity, lateral outflow direction and side weir channel shape are included, resulting in expressions for the lateral outflow angle and the lateral discharge intensity. For vanishing channel velocity, the conventional weir formula for plane flow conditions is reproduced. However, for increasing local Froude number, the lateral outflow intensity decreases under otherwise fixed flow parameters. A comparison of the theoretically determined solution with observations indicates a fair agreement. The results are then applied to open channel bifurcations by considering a side‐weir of zero weir height. Distinction between sub‐ and supercritical flow conditions is made. Again, the computed results compare well with the observations and allow a simple prediction of all pertinent flow characteristics.