Piano Key Weir Hydraulics and Labyrinth Weir Comparison

• Published in: Journal of irrigation and drainage engineering Vol. 139; no. 3; pp. 246 - 253
• Main Authors: Anderson, R. M, Tullis, B. P
• Format: Journal Article
• Language: English
• Published: Reston, VA American Society of Civil Engineers 01.03.2013
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Irrigation. Drainage; Technical Papers; Piano key weir; Discharge coefficient; Hydraulics; Nonlinear weir; Weirs; Water discharge; Nonlinearity; Labyrinth weir; Weir
• ISSN: 0733-9437; 1943-4774
• DOI: 10.1061/(ASCE)IR.1943-4774.0000530

AbstractA piano key (PK) weir is a type of nonlinear (labyrinth-type) control structure with a relatively small spillway footprint. No standard PK weir design procedure is available, and the amount of published information on PK weirs is limited. PK weirs have a large number of geometric parameters that can affect head-discharge performance. A PK weir geometric design has, however, been recommended in the literature, along with a head-discharge relationship specific to that PK weir geometry. To develop a better understanding of the effects of PK weir geometry on discharge efficiency, nine laboratory-scale four-cycle PK weir configurations were tested (including the recommended design). The effects of the following PK weir geometry or modifications on weir performance were partially isolated: varying the inlet-to-outlet key ratio, raising the crest via a parapet wall, rounding the upstream apex walls, and varying the crest type. The appropriateness of the recommended head-discharge equation specific to the recommended design was evaluated, and the relative head-discharge efficiency of trapezoidal labyrinth and PK weirs with respect to footprint restrictions and crest length were compared.