FBE- İnşaat Mühendisliği Lisansüstü Programı - Doktora
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Yazar "Altunkaynak, Abdüsselam" ile FBE- İnşaat Mühendisliği Lisansüstü Programı - Doktora'a göz atma
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ÖgeA novel approach for the incipience of sediment entrainment in a wide range of flow conditions via experimentally driven geno-fuzzy inference system model( 2020) Bizimana, Hussein ; Altunkaynak, Abdüsselam ; 635861 ; Hidrolik ve Su Kaynakları Mühendisliği Bilim DalıIn Civil Engineering works, the beginning of sediment particle motion and the design of stable and economical channels are of the utmost importance. The beginning of sediment motion often called incipience of sediment motion is a very important physical aspect of the investigation of sediment transport phenomena. The incipience of sediment motion is very significant for water resources and hydraulic engineering for the proper design of dams, reservoirs, sewers, drainage channels, etc. Consequently, many experimental and mathematical studies have been conducted previously to generate more explicit solutions that define the best the beginning of particle motion, yet subjectivity resulting from different experimental conditions has resulted in considerable dissimilarities in developed solutions. Therefore, an engineer dealing with the choice of the best solution meets a serious challenge. Moreover, many of the available methodologies in the literature have been generated from hydraulically rough flow conditions. In this study, novel approaches are introduced for accurate prediction of the incipient motion of uniform non-cohesive grain particles in sand and gravel-bedded open channels under unidirectional flows. Two different types of modeling were used. The first type of models generated in the present study are novel Fuzzy Logic (FL) based models and the second type of models are experimentally generated mathematical and analytical models. In the first step of modeling, novel FL-based models were applied to predict the critical condition that governs the initiation of sediment motion in a wide range of flow conditions from hydraulically smooth to rough flow conditions. Under the FL-based models, novel and improved Sugeno Fuzzy Inference (Sugeno FI) and Mamdani Fuzzy Inference (Mamdani FI) Systems are calibrated using the evolutionary Genetic Algorithms (GAs); further evaluated and applied. Furthermore, the Adaptive Neural Fuzzy Inference System (ANFIS) tool is based on Sugeno FIS. The consequent part of the ANFIS tool is limited to either a constant or a linear function. This means that not only a non-linear function is available for the consequent part of the model but also it cannot be represented by a constant and linear functions, at the same time. Moreover, the ANFIS tool optimizes antecedent parameters (fuzzy sets) and consequent parameters (constant or linear functions) by utilizing neural and least square methods, respectively. In the present study, a novel hybrid model named as novel Geno-Fuzzy Inference System (GENOFIS) is introduced by integrating improved Sugeno FIS and Genetic Algorithms (GAs) that refer to where, the antecedent (fuzzy sets) and consequent (constant, linear and non-linear functions) parameters are optimized by using Genetic Algorithms (GAs) tools. Additionally, the novel GENOFIS offers the possibility to represent the consequent part of the Sugeno FIS model by a constant or any defining function at the same time. Furthermore, during the second FL-based modeling, the Mamdani FIS is improved by training the membership functions using GAs instead of the conventionally used trial and error method which is not accurate and is extremely time-consuming. Consequently, a novel improved Geno-Mamdani FIS named as GMFIS is calibrated using independent data, evaluated and proposed as well. Quantitative and qualitative comparisons with theoretical considerations are implemented between the calculated results generated using ANFIS, GENOFIS and GMFIS models and observed experimental results by applying root mean square error (RMSE), the Nash-Sutcliffe coefficient of efficiency (CE) as evaluation criteria. The observed experimental data are collected from three different types of incipient motion techniques that are the most utilized and cited in the literature as reference, visual, and development of competence functions. The results generated from the FL-based methodologies demonstrated that the novel GENOFIS model provided more accurate prediction results in comparisons with the ANFIS model results for three different types of incipient motion of sediment approaches by comparing their respective results with observed experimental data. Furthermore, the novel GMFIS model had provided results in close agreement with the experimental data collected from the aforementioned three different types of incipient motion of sediment techniques. Additionally, using the GMFIS model, upper and lower curves that define the critical conditions of sediment motion were generated and these curves are proposed after calibration and validation using experimental data made off uniform and non-cohesive sand and gravel sediment particles. The results show that the upper curve corresponds to the incipient motion of uniform non-cohesive sand particles in loose boundary channels while the lower curve represents the incipient motion of uniform non-cohesive gravel particles in rigid boundary channels as well. Moreover, the FL-based Shields curves generated can be used to represent the incipient motion of uniform non-cohesive sediment particles in rigid boundary channels with a smooth bed floor and loose boundary channels, for the lower and upper limit, respectively. This physical finding was concluded after a comparison between the GMFIS results and experimental data collected in loose and rigid boundary channels in researchers performed previously. In the second stage of this study, an attempt to feel the gap that is found in the literature on the best channel design in terms of sediment carrying capacity when the channel bed is smooth and when it is rough has been experimentally investigated. The effects of the cross-sectional shape, flow depth, hydraulic radius, and channel slope on the incipience of sediment entrainment in rigid boundary channels with a smooth bed floor and a rough bed floor are investigated. Experiments were performed to investigate the incipient motion under hydraulically smooth, laminar, and rough flow conditions in a rectangular cross-sectional channel and under hydraulically smooth and transitional flow conditions in a circular cross-sectional channel. The experiments were carried out on both smooth and rough bed floor. Experiments conducted on a smooth bed floor generated one hundred twenty-four and ninety-seven experimental data in a rigid rectangular and a rigid circular cross-sectional channel, respectively. Furthermore, experiments conducted on a rough bed floor with a specific bed roughness factor (λ) generated more data. One hundred, and seventy-five experimental data were generated in a rigid rectangular and a rigid circular cross-sectional channel, respectively. Based on the shear stress approach as the theoretical consideration, new experimental and analytical equations that represent the critical condition for the initiation of sediment motion for rigid rectangular and circular cross-sectional channels are proposed using experimental data collected for smooth and rough channel floor. The results of the new proposed experimental and analytical equations are compared to those obtained from the existing incipient motion equations proposed by other researchers for rigid boundary channels. It is found that the cross-sectional shape, flow depth, hydraulic radius, channel slope, and most importantly the bed roughness are crucial in defining the critical shear velocity and bed shear stress for the incipience of sediment entrainment. The results found in this study show that weaker bed shear stresses are required to initiate sediment motion in a rigid boundary channel with a smooth channel bed floor than the same rigid boundary channel but with a rough channel bed floor. Moreover, weaker bed shear stresses are need in a circular cross-sectional channel than in a rectangular cross-sectional channel to initiate sediment particle motion. Therefore, in this study, a circular cross-sectional channel is found to be more efficient in terms of self-cleansing purposes than a rigid rectangular cross-sectional channel. Furthermore, compatibility of the generated explicit formula and previously proposed threshold approaches is depicted in terms of the similar trendline in which in all incipient motion models it is realized that higher bed shear stress values are required under hydraulically smooth flow conditions and decreases towards the hydraulically rough flow conditions whether the channel bed floor is smooth or rough. Moreover, by using experimental data generated in hydraulically rough flow conditions in a rigid rectangular cross-sectional channel with a smooth channel bed floor, a new formula is developed to determine the average diameter (D) of a sediment particle that would not be subjected to the motion under rough flow conditions. The formula is derived and proposed for bed regulation, stability purposes in rigid boundary rectangular channels.