Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2019
Thesis Language: Turkish
Student: ZÜLFİKAR ERKAY KEMALOĞLU
Supervisor: MÜSTEYDE BADUNA KOÇYİĞİT
Open Archive Collection: AVESIS Open Access Collection
Abstract:In this study, three dimensional numerical modelling of local scour around abutments with various lengths and contraction scour beneath a bridge deck without a pier was performed by using Flow-3D under different flow conditions. At first, experimental data from literature was used to calibrate the computational grid size and the parameters of sediment model and determine the turbulence model to be employed in the simulations. Then, the predictions of the calibrated numerical model were verified by different sets of data. It was noted that entrainment coefficient, bed load coefficient, angle of repose, maximum packing fraction and turbulence mixing length had an insignificant effect in prediction of maximum scour hole depth, while smaller values of critical Shields and higher ratios of Nikuradse bed surface roughness / local median grain diameter increased the maximum scour hole depth. Results of mesh size sensivity analysis conducted by using four different mesh sizes showed that the maximum scour hole depth depends on the mesh size and it is not appropriate to use mesh sizes smaller than ten times of the sediment mean grain size for numerical modelling. To decide the turbulence model to be employed in the model simulations showed that LES turbulence model underpredicted the maximum scour hole depth while the RNG model overestimated and computational time of LES model was longer than RNG model. Then, calibrated 3-D model was employed to simulate local scour around abutment with two different lengths under free surface flow condition and scouring beneath a bridge deck without a pier under pressurized and weir flow conditions. Furthermore, the model predictions were compared with experimental data. The results of the study showed that there was a good agreement between the calibrated model predictions of the maximum scour depth and the experimental data under different flow conditions