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RISS 인기검색어
- 검색키워드
- 저자 : Abou-Rayan, Ashraf M. (검색결과 5 건)
- 무료
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Dynamic behavior of TLP's supporting 5-MW wind turbines under multi-directional waves
Abou-Rayan, Ashraf M.,Khalil, Nader N.,Afify, Mohamed S. Techno-Press 2016 Ocean systems engineering Vol.6 No.2
Over recent years the offshore wind turbines are becoming more feasible solution to the energy problem, which is crucial for Egypt. In this article a three floating support structure, tension leg platform types (TLP), for 5-MW wind turbine have been considered. The dynamic behavior of a triangular, square, and pentagon TLP configurations under multi-directional regular and random waves have been investigated. The environmental loads have been considered according to the Egyptian Metrological Authority records in northern Red sea zone. The dynamic analysis were carried out using ANSYS-AQWA a finite element analysis software, FAST a wind turbine dynamic software, and MATLAB software. Investigation results give a better understanding of dynamical behavior and stability of the floating wind turbines. Results include time history, Power Spectrum densities (PSD's), and plan stability for all configurations.
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Response of square tension leg platforms to hydrodynamic forces
Abou-Rayan, A.M.,Seleemah, Ayman A.,El-Gamal, Amr R. Techno-Press 2012 Ocean systems engineering Vol.2 No.2
The very low natural frequencies of tension leg platforms (TLP's) have raised the concern about the significance of the action of hydrodynamic wave forces on the response of such platforms. In this paper, a numerical study using modified Morison equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between surge, sway, heave, roll, pitch and yaw degrees of freedom on the dynamic behavior of TLP's. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of wave characteristics such as wave period and wave height on the response of TLP's was evaluated. Only uni-directional waves in the surge direction was considered in the analysis. It was found that coupling between various degrees of freedom has insignificant effect on the displacement responses. Moreover, for short wave periods (i.e., less than 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on the wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations about its original position. Also, for short wave periods, a higher mode contribution to the pitch response accompanied by period doubling appeared to take place. For long wave periods, (12.5 and 15 sec.), this higher mode contribution vanished after very few cycles.
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Wave induced motion of a triangular tension leg platforms in deep waters
Abou-Rayan, A.M.,El-Gamal, Amr R. Techno-Press 2013 Ocean systems engineering Vol.3 No.2
Tension leg platforms (TLP's) are highly nonlinear due to large structural displacements and fluid motion-structure interaction. Therefore, the nonlinear dynamic response of TLP's under hydrodynamic wave loading is necessary to determine their deformations and dynamic characteristics. In this paper, a numerical study using modified Morison Equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between all degrees of freedom on the dynamic behavior of a TLP. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of wave characteristics was considered.
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Flexural Behavior of Encased Beam Flat or Perforated steel Cold Formed Sections
Abou-Rayan Ashraf,Nader Khalil,Ahmed Youssef,Mohamed Eldeib 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4
This paper presents an experimental study on the fl exural behavior of encased fl at cold formed steel sections FCFS and perforated cold formed steel sections PCFS. A full scale eleven specimens were prepared and tested till failure. One specimen without steel cold formed section tested as a control beam. Six specimens with fl at steel cold formed section were tested to fi gure out the enhancement eff ect of section area and position. Finally, four specimens with a new shape of perforated steel cold formed sections were tested with diff erent positions. Cold formed steel section height, fl ange width, and position are the main parameters studied and investigated. The ultimate load and vertical defl ections were recorded and investigated. Also, modes of failure of the control and composite concrete beams were studied. From the experimental investigations, it has been observed that there is signifi cant increase in ultimate load of composite beams with a perforated steel cold formed section. A signifi cant increasing in the ultimate load was observed for specimens with perforated steel cold formed section
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Moataz Fathi,Magdy Abdelsalam,Ibrahim Al-Homidan,Osama Abou-Emera,Gamal Rayan Asian Australasian Association of Animal Productio 2023 Animal Bioscience Vol.36 No.7
Objective: Better feed efficiency can be achieved by selecting rabbit genotypes with lower residual feed intake (RFI) under high ambient temperatures. Methods: Two genotypes of rabbits (Jabali, Saudi local breed and imported, Spanish V-line) were used to derive RFI and to investigate the relationship between RFI and productive traits. In total, 250 animals (125 each) were housed in individual wire mesh cages in a semi-closed rabbitry. Growth performance, feed criteria, carcass evaluation, biochemical blood analysis, and immune responses were determined. Results: Superiority in growth performance, feed efficiency, carcass characteristics, and cellular immunity was recorded in the Jabali breed compared to the V-line genotype. According to regression analysis, a significant effect of daily body weight gain was found, upon computing the expected feed intake in both genotypes. Moreover, mid-body weight<sup>0.75</sup> had a significant effect only in the Jabali breed. Positive correlation coefficients between RFI and dry matter feed intake or feed conversion ratio were found. The same trend in this relationship between RFI and productive traits was observed in some cases for both genotypes. An opposite trend in correlations was observed in the studied genotypes for some traits. Conclusion: The results suggest that the relationship between RFI and productive traits must be taken into consideration in rabbit breeding programs under the prevailing environment. However, further studies are required to investigate the effect of rabbit genotype and environmental factors on computing RFI.
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