Discussion of “Discharge Capacity of Labyrinth Side Weir Located on a Straight Channel” by M. Emin Emiroglu, Nihat Kaya, and Hayrullah Agaccioglu

Abstract

The declining trend of discharge coefficient in the labyrinth side weir with an increase of flow depth is well-depicted in Fig. 2. In some cases, the effect of flow-depth increase on the decrease of the discharge coefficient of the labyrinth side weir can be so significant after reaching a certain depth that the discharge coefficient of these types of side weirs would be almost equal to that of the corresponding normal rectangular weirs (Fig. 2). In other words, the flow magnification (QL=QN, where QL ¼ discharge over labyrinth side weir and QN ¼ discharge over corresponding linear weir) of the labyrinth side weir proposed by Hay and Taylor (1970) decreases notably with an increase of the nondimensional parameter h=p (where h = main channel depth and p ¼ height of weir crest). This is illustrated in Fig. 3 for a labyrinth side weir with height, span length, and included angle of 10 cm, 60 cm, and 60°, respectively. Moreover, the decrease rate of the discharge coefficient (with an increase of the depth) increases by the decrease of the included angle in a constant height of the side weir. This is evident for labyrinth side weirs with a length of 60 cm and height of 5 cm in Fig. 4. This feature of the labyrinth side weir clearly reveals that in weirs with low included angles (such as 60°), low flow depth results in an increase in the discharge coefficient; however, they are highly vulnerable to the flow depth increase over the weir, and their discharge coefficient decreases notably with an increase of depth flow. This important point should be considered in the design of such weirs.