New expression-based models to estimate scour depth at clear water conditions in rectangular channels. Issue 2 (17th February 2018)

• Record Type: Journal Article
• Authors: Najafzadeh, Mohammad; Shiri, Jalal; Rezaie-Balf, Mohammad
• Is Part Of: Marine georesources & geotechnology. Volume 36:Issue 2(2018)
• Page Start: 227
• Page End: 235
• Publication Date: 2018-02-17
• Subjects: Evolutionary polynomial regression -- gene-expression programming -- long contraction -- model tree -- scouring process; Marine mineral resources -- Periodicals; 551.46
• DOI: 10.1080/1064119X.2017.1303009
• Languages: English
• ISSNs: 1064-119X

Abstract

ABSTRACT: Scouring in the channel contractions occurs due to the flow concentration within them inducing excessive bed shear stress. This is a complex process, so it is difficult to describe it through a general empirical model, the present research work describes contemporary conceptual relationships to estimate the local scour depth under equilibrium and clear water conditions in rectangular channels. Incidentally, gene-expression programming (GEP), evolutionary polynomial regression (EPR), and model tree (MT)-based formulations were utilized to predict the scour depth at long contractions. The input variables comprising average flow velocity, critical threshold velocity of sediment movement, flow depth, median particle diameter, geometric standard deviation, and uncontracted and contracted channel widths were used to feed the applied models. The performances of the developed approach were compared with those calculated using existing scour prediction equations. The results showed that the developed MT approach in terms of linear relationships could predict the scour depth more precisely than GEP, EPR, and the traditional equations. What is more, dimensionless parameter of h 1 / b 1 (ratio of upstream flow depth to uncontracted channel width) was determined as the most influential variable in predicting the scour depth in long contractions.