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Öğe A CFD Study On the Hydrodynamic Characteristics of the Antifouling Paints(Galenos Publ House, 2019) Karabulut, Utku Cem; Ozdemir, Yavuz Hakan; Barlas, BarisThis paper presents a computational fluid dynamics (CFD) approach which can be used to investigate the hydrodynamic performances of various antifouling paints. Steady Reynolds - Averaged - Navier - Stokes (RANS) equations were solved for the flows around a flat plate at Reynolds number of 2,8x10(6) and 5,5x10(6). The surface roughness effects were modelled as downward shift of the velocity profile at the log - law region of the boundary layer. Granville's similarity law was used to extrapolate the results for a full scale ship. Results are in good agreement with the previous experimental and numerical studies.Öğe FREE SURFACE FLOW SIMULATION AROUND AN APPENDED SHIP HULL(Univ Zagreb Fac Mechanical Engineering & Naval Architecture, 2018) Ozdemir, Yavuz Hakan; Barlas, BarisThis study brings forward the results of previously published work of free surface flow simulation around a fast ship model. Experimental measurements and numerical simulations of a fast bare-hull ship model form are now extended to the same ship form with appendices for a wide range of Froude numbers. The governing equations are discretized by means of an unstructured finite volume mesh. The standard k-epsilon turbulence model and Volume of Fluid Method to capture the two phase media are used. The total resistance, due to wave and wake fields of the ship model with appendages and the resistance of the appendages alone are calculated numerically, and compared with the experiments. The experiments and computations were performed for 11 different Froude numbers between 0.103 and 0.322. For Froude numbers up to 0.25, numerical simulations found to be quite in agreement with the experiments. It has been found that appendages increase the total drag mainly by increasing the pressure resistance, and the effect of the appendages becomes more important as the flow speed gets higher.Öğe Numerical Investigation of the Effect of Surface Roughness on the Viscous Resistance Components of Surface Ships(Springernature, 2022) Karabulut, Utku Cem; Ozdemir, Yavuz Hakan; Barlas, BarisRecently, computational fluid dynamics (CFD) approaches have been effectively used by researchers to calculate the resistance characteristics of ships that have rough outer surfaces. These approaches are mainly based on modifying wall functions using experimentally pre-determined roughness functions. Although several recent studies have shown that CFD can be an effective tool to calculate resistance components of ships for different roughness conditions, most of these studies were performed using the same ship geometry (KRISO Container Ship). Thus, the effect of ship geometry on the resistance characteristics of rough hull surfaces is worth investigating. In this study, viscous resistance components of four different ships are calculated for different roughness conditions. First, flat plate simulations are performed using a previous experimental study for comparison purposes. Then, the viscous resistance components of three-dimensional hulls are calculated. All simulations are performed using two different turbulence models to investigate the effect of the turbulence model on the results. An examination of the distributions of the local skin friction coefficients of the DTMB 5415 and Series 60 showed that the plumpness of the bow form has a significant effect on the increase in frictional resistance with increasing roughness. Another significant finding of the study is that viscous pressure resistance is directly affected by the surface roughness. For all geometries, viscous pressure resistances showed a significant increase for highly rough surfaces.Öğe Numerical Study on the Hydrodynamic Performance of Antifouling Paints(Springernature, 2020) Karabulut, Utku Cem; Ozdemir, Yavuz Hakan; Barlas, BarisThis study presents a simple numerical method that can be used to evaluate the hydrodynamic performances of antifouling paints. Steady Reynolds-averaged Navier-Stokes equations were solved through a finite volume technique, whereas roughness was modeled with experimentally determined roughness functions. First, the methodology was validated with previous experimental studies with a flat plate. Second, flow around the Kriso Container Ship was examined. Lastly, full-scale results were predicted using Granville's similarity law. Results indicated that roughness has a similar effect on the viscous pressure resistance and frictional resistance around a Reynolds number of 10(7). Moreover, the increase in frictional resistance due to roughness was calculated to be approximately 3%-5% at the ship scale depending on the paint.Öğe
