experimental study of the hydraulic performance of d-type triangular piano key weirs

Piano key weirs are a new type of weir designed to enhance the discharge capacity of dams. the present study is aimed at experimentally evaluating the hydraulic characteristics of a d-type triangular piano key weir. the purpose of these experiments was to study the flow regime, the stage-discharge relationship, and the effect of h/p ratio on the discharge coefficient. the results indicated that the discharge coefficient in d-type triangular piano key weirs was higher than that of rectangular ones, and it varied in the range of 0.48 < cd< 1.6 and 0.6 < (with and without a downstream ramp, respectively). moreover, under similar laboratory conditions, the results showed that the discharge coefficient of the piano key weir is higher than that of the linear weir. the increase in the discharge coefficient of the piano key weirs, compared to linear weirs, can be up to three times in low heads. finally, to predict the discharge coefficient of the piano key weirs, an equation was proposed for two cases, i.e., with a downstream ramp and without a downstream ramp