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- 저자 : Shahrokh Shams (검색결과 2 건)
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풍차날개의 공력 성능 향상과 유동 박리 감소를 위한 수동 유동 제어에 대한 DES 해석
Mohammad Moshfeghi,Shahrokh Shams,Morteza Ramezani,허남건 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.4
Power generation of a horizontal axis wind turbine is severely dependent upon aerodynamic phenomena over the blade, especially the flow separation. Since, usually the local AoA (Angle of Attack) in the inner and middle parts of a blade is much greater than the separation onset, the blade section encounters a highly separated flow or even stall condition. Hence, flow control methods can be employed in order to reduce or weaken the negative effects of the separation. This paper investigates the effects of a recently verified passive flow control method for HAWTs via a validated three dimensional DES(Detached Eddy Simulation) of split versions of the S809 airfoil. In this research, two different airfoil families with four various split width values of 0.5, 1, 2 and 4 percent of chord length are simulated at a range of angle of attack from 0 to 25 degrees. As a result of existence of the split, flow from the high-pressure zone at the lower surfaces gets injected into the separated area over the suction surfaces. The positive or negative effect of this method is mainly dependent upon split end location on the suction surface. Direction of the jet flow with respect to the free stream and also the width of split are the other important parameters. Also, the findings reveal that in each family there exists one optimal split width for which the airfoil aerodynamic performance is enhanced remarkably.
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Ali Reza Torabi,Shahrokh Shams,Mahdi Fatehi-Narab 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.5
In this study free vibration analysis of a cracked Goland composite wing is investigated. The wing is modelled as a cantilevered beam based on Euler- Bernoulli equations. Also, composite material is modelled based on lamina fiber-reinforced. Edge crack is modelled by additional boundary conditions and local flexibility matrix in crack location, Castigliano’s theorem and energy release rate formulation. Governing differential equations are extracted by Hamilton’s principle. Using the separation of variables method, general solution in the normalized form for bending and torsion deflection is achieved then expressions for the cross-sectional rotation, the bending moment, the shear force and the torsional moment for the cantilevered beam are obtained. The cracked beam is modelled by separation of beam into two interconnected intact beams. Free vibration analysis of the beam is performed by applying boundary conditions at the fixed end, the free end, continuity conditions in the crack location of the beam and dynamic stiffness matrix determinant. Also, the effects of various parameters such as length and location of crack and fiber angle on natural frequencies and mode shapes are studied. Modal analysis results illustrate that natural frequencies and mode shapes are affected by depth and location of edge crack and coupling parameter.
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