Sürdürülebilir Kalkınma Amaçları

• 2

• MakaleYalnız künye2025Scopus SJRQ1/r/munzur/900
  Reduction of fluid forces on a circular cylinder in the laminar flow regime using a pair of airfoils

  Fırat, Erhan; Oruç, Vedat; You, Rui; Biçer, Uğur; Devecioğlu, Atilla G.

  Flow around the cylinder, with/without a pair of airfoils symmetrical to the cylinder's horizontal axis, was simulated for a diameter-based Reynolds number (Re) of 100. The objective of this numerical study is to simultaneously reduce the values of the time-averaged and fluctuating forces acting on a system consisting of a pair of airfoils and a cylinder below those of a single cylinder by using different combinations of the parameters chord (c), angle of rotation (β), angle of attack (α), and the shortest distance between the aerodynamic center of the airfoil and the surface of the cylinder (g). The values of these key parameters are determined primarily through two approaches. The first approach involves emulating the flow pattern surrounding the system to match the potential flow pattern. The second approach involves disrupting the interaction between the shear layers from the cylinder by stretching them in the mean flow direction. The second approach has been demonstrated to exhibit superior performance in terms of reducing both time-averaged and fluctuating forces concurrently. The second approach has been demonstrated to exhibit superior performance in terms of reducing both time-averaged and fluctuating forces concurrently. The optimal geometrical parameters that yield the desired end results are determined to be c = 0.5D, α = 0°, β = 60°, and g = 0.2D. Utilizing these parameters has been demonstrated to result in a substantial reduction in the time-averaged drag, fluctuating drag, and fluctuating lift coefficients of the system, with the respective percentage reductions reaching 14.4 %, 92.1 %, and 73 %, respectively, when compared to the values obtained for a single cylinder.

  AtıfScopus4·OpenAlex3

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• MakaleYalnız künye2018Scopus SJRQ1/r/munzur/3151
  An interval type-2 fuzzy AHP and TOPSIS methods for decision-making problems in maritime transportation engineering: The case of ship loader

  Celik, Erkan; Akyuz, Emre

  Duration of cargo operation (loading or discharging) is of paramount importance for ship owners and port managers since idle time at terminal significantly boost to the cost of providing shipping service. Hence, it is important to choose the appropriate shiploader type for handling bulk materials. This paper aims to present a comprehensive multi-criteria decision making (MCDM) method extended by interval type-2 fuzzy sets (IT2FSs) for selecting appropriate shiploader type in maritime transportation. The proposed approach incorporates Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) under IT2FSs environment to overcome more of the uncertainty of experts’ judgement and expression in decision-making. The proposed approach adopts a sensitivity analysis to investigate the impact of key performance indicator (KPI) under numerous conditions. Besides its robust theoretical background, this paper prompts practical benefits to decision-makers (port owners or port managers) who make investment decision for appropriate shiploader type in dry bulk cargo shipment.

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  AtıfScopus165·WoS148·OpenAlex172

  İncele
• MakaleAçık Erişim2017Scopus SJRQ1/r/munzur/3928
  Application of AHP and VIKOR methods under interval type 2 fuzzy environment in maritime transportation

  Soner, Omer; Celik, Erkan; Akyuz, Emre

  The aim of this paper is to provide not only a hybrid theoretical methodology in multiple-attribute decision making problems but also a practical application in maritime transportation industry. The proposed hybrid approach integrates Analytic Hierarchy Process (AHP) method into VlseKriterijumska Optimizacijia I Kompromisno Resenje, (VIKOR) technique under interval type-2 fuzzy (IT2F) environment. While AHP and VIKOR provides a comprehensive framework to solve multiple-attribute decision making (MADM) problems in maritime transportation industry, the IT2F enables to deal with much uncertainty during linguistic assessment of decision-makers. The proposed approach is demonstrated with a hatch cover design selection problem since it has utmost importance in structure of bulk carrier ships to prevent water ingress and protect cargo form the external damages. Besides its robust theoretical insight, the paper has practical contribution to the naval engineers, classification societies and ship owners who have difficulty in deciding appropriate hatch cover type during construction of the ship.

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  AtıfScopus117·WoS103·OpenAlex122

  İncele
• MakaleYalnız künye2017Scopus SJRQ1/r/munzur/3858
  Passive flow control in the near wake of a circular cylinder using attached permeable and inclined short plates

  Ozkan, Gokturk M.; Firat, Erhan; Akilli, Huseyin

  The main objective of this study is to assess the effectiveness of attached permeable plates in suppressing nominally two-dimensional vortex shedding from a fixed cylinder. The permeable plate along the entire span of the cylinder was made of a chrome-nickel screen and was attached normal to the cylinder surface. The main parameters of the study are porosity of the permeable plate, β, and the plate angle of the cylinder-plate arrangement, θ, with respect to the freestream. Experiments were performed using Particle Image Velocimetry (PIV) and Flow Visualization Techniques. Additionally, drag force measurements were carried out in a wind tunnel to analyze the effects of permeable plates on drag coefficient of the circular cylinder. The results revealed that the use of a permeable plate successfully suppresses the vortex shedding downstream of the circular cylinder by reducing the velocity fluctuations in the wake, elongating the vortex formation region further downstream and attenuating the vortex shedding frequency. The porosity values of β=0.4 and 0.5 with plate angles in the range of 35°≤θ≤90° were found to be effective on suppressing the vortex shedding. Furthermore, both the drag coefficients of the cylinder-plate arrangement and the <TKE>maxwere reduced almost for all porosity ratios for θ<30°.

  AtıfScopus63·WoS55·OpenAlex59

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