Roughness Effect of Submerged Groyne Fields with Varying Length, Groyne Distance, and Groyne Types

Abstract

Design guidelines were developed for a number of in-stream structures; however, the knowledge about their morphological and hydraulic function is still incomplete. A variant is submerged groynes, which aim to be applicable for bank protection especially in areas with restricted flood water levels due to their shallow height. Laboratory experiments were conducted to investigate the backwater effect and the flow resistance of submerged groyne fields with varying and constant field length and groyne distance. The effect of the shape of a groyne model was investigated using two types of groynes. The validity of different flow types, from “isolated roughness” to “quasi smooth”, was analyzed in relation to the roughness density of the groyne fields. The results show a higher backwater effect for simplified groynes made of multiplex plates, compared to groynes made of gravel. The relative increase of the upstream water level was lower at high initial water levels, for short length of the groyne field, and for larger distance between the single groynes. The highest roughness of the groyne fields was found at roughness densities, which indicated wake interference flow. Considering a mobile bed, the flow resistance was reduced significantly.

Quantifying Hydraulic Roughness From Field Data: Can Dune Morphology Tell the Whole Story?

“…Those undulations are fixed and do not interact with bedforms (Ouillon & Dartus, 1997; Wilbers, 1999), but may statically influence bedform geometry (de Ruijsscher et al., 2020). The influence of groynes changes with high discharge conditions, especially when groynes are submerged and become part of the conducting section of the bed (Möws & Koll, 2019; Yossef, 2004). The low flow conditions studied minimize the impact of groynes, but the ubiquitous presence of groynes along the opposite banks complicates quantifying groyne roughness.…”

Investigation of Local Scour around L-Shape Submerged Groynes in Clearwater Conditions

“…While; (20) cm projection length (Lg) (approximately not less than one-third of the flume width [11], and (10) cm is the projection length of the Groyne which parallel to the flow direction (I) as appeared in Fig. 2 and 3.…”

Colebrook’s Flow Friction Explicit Approximations Based on Fixed-Point Iterative Cycles and Symbolic Regression

“…As the Colebrook equation is empirical [1,16], its accuracy can be disputed [17,18] (e.g., the new Oregon and Princeton experiment related to pipe friction [18]); nevertheless, the equation is widely accepted as a standard and is in common use in the design of water and gas pipe networks [19]. It can be also adapted for special cases such as air flow through fuel cells [20], water flow in rivers [21,22] and blood flow in blood vessels [23].…”