توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Prediction of Aerodynamic Coefficients of a Plunging Airfoil Using Neural Networks
نویسنده(ها): ، ،
اطلاعات انتشار: هفتمین همایش انجمن هوافضای ایران، سال
تعداد صفحات: ۶
Neural networks were used to minimize the amount of data required to predict the aerodynamic coefficients of an airfoil oscillating in plunging motion. For this purpose, series of experimental tests have been conducted on a section of a 660kw wind turbine blade. Two MLP (multi layer perceptron) and GRNN (general regression neural network) were trained using experimental data of the airfoil at various conditions. Results showed that with using only 50% of the acquired data, the trained neural networks were able to predict accurate results with minimal errors when compared with the corresponding measured values. Moreover, these methods can predict the aerodynamic coefficients of the plunging airfoil at different oscillation frequencies, amplitudes, and incidence angles. Therefore with employing this trained networks, the aerodynamic coefficients are predicted accurately with minimum experimental data; hence reducing the cost of tests while achieving acceptable accuracy.<\div>

۲Effects of sulfite waste fibers incorporating silica nano–particles on mechanical and microstructural properties of cementitious composite
اطلاعات انتشار: دومین کنفرانس بین المللی کامپوزیت، سال
تعداد صفحات: ۶
Natural fibers are one of the most appropriate alternatives for designation and production of structural panels due to low final production cost. However a principal point is the strength loss caused by usage of these fibers in the matrix of cement based composites. Hence, a simple and cheap method should be applied to develop the properties of these fibers. Therefore, in this study by application of sulfite waste (along with waste management in the wood and paper industries) and usage of low–dosage silica nanoparticles (in order to enhance the interfacial transition zone of the cement–fiber paste), production of cement based sheets reinforced with natural fibers and silica nano–particles are investigated. Alongside, flexural strength and microstructure of sheets are examined by calculating the Modulus of Rupture (MOR) and Modulus of Elasticity (MOE), and applying the Scanning Electron Microscopy (SEM), respectively. Results show that mechanical performance and microstructure of cement based composites containing waste natural fibers and silica nano–particles can be improved<\div>

۳Experimental Investigation of the Leading–edge Roughness on the Crossflow Instability of a Swept Wing
نویسنده(ها): ، ،
اطلاعات انتشار: دهمین همایش انجمن هوافضای ایران، سال
تعداد صفحات: ۶
An Experimental investigation is conducted to evaluate surface pressure distribution over a semi span swept wing with sweep angle of 33 degrees. The wing section has a laminar flow airfoil similar to that of NACA 6–series airfoils. The tests were conducted at speeds ranging from 50 to 70m\s with and without surface roughness. The differences between pressure distributions on three sections of the wing were are analyzed and the Experimental results showed that addition of surface roughness does not influence the pressure distribution significantly. The spectral analyses were then performed to realize the instability frequencies at each chordwise section<\div>

۴Linear and Nonlinear PSE for Stability Analysis of the Boundary Layer over an Airfoil
نویسنده(ها): ، ، ،
اطلاعات انتشار: دهمین همایش انجمن هوافضای ایران، سال
تعداد صفحات: ۸
An accurate PSE code has been developed to study the stability of incompressible boundary layer over the surface of an arbitrary airfoil. The primitive variable form of the PSE are derived in the body–fitted natural coordinate system and solved by a highly accurate finite–difference method. In the present study, both effects of the basic flow nonparallelism and nonlinear mode interaction are taken into account. Comparisons show good agreement between the results of the present study and those of pervious investigators. To investigate the stability of the boundary layer over an airfoil, the linear propagation of the TS waves and the nonlinear three–dimensional subharmonic instability are analysis for the NACA 0012 airfoil. The nonlinear analysis gives the skin friction rise in the transition region.<\div>

۵Spectral Analysis of Vortex Growth and Breakdown over a Delta Wing
نویسنده(ها): ، ،
اطلاعات انتشار: دهمین همایش انجمن هوافضای ایران، سال
تعداد صفحات: ۶
A series of subsonic wind tunnel tests was carried out on a coplanar wing–canard configuration at an angle of attack range from 10 to 30 degrees. In this experiment, a 60° swept canard was placed in front of a 60° swept main delta wing. The results of surface pressure distribution show that the presence of canard, delays the vortex formation and growth on the wing to some higher angles of attack comparing to the canard–off case. Due to the downwash of the canard, the wing operates at lower effective angles of attack and therefore, the vortex breakdown is delayed. Spectral Analysis is also applied to the time histories of the unsteady wing surface pressure distribution. The power spectrum Results show the existence of narrow, dominant frequency band containing the majority of the fluctuation energy.<\div>
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