@article { author = {Mehrjou, H. and Farshchi, Mohammad}, title = {Analysis of Radial Baffle Effects on Acoustic Characteristics of a Combustion Chamber}, journal = {Journal of Aerospace Science and Technology}, volume = {6}, number = {1}, pages = {1-12}, year = {2009}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {An efficient finite volume approach has been used to develop a three dimensional Helmholtz acoustic solver for complex geometries. This acoustic solver was utilized to obtain characteristic mode shapes and frequencies of a baffled combustion chamber. An experimental setup, including stationary and moving sensors, has also been used to measure these quantities for the same model combustion chamber. Although each of these methods has certain limitations, combination of the numerical results and the experimental data provide a capability to identify complicated acoustical fields created by the combustor complex geometry. Using this approach the effects of the nozzle convergent section and the number of radial baffles on the chamber’s dominant acoustic modes were investigated. It has been shown that acoustic solver is capable of capturing major effects caused by the presence of radial baffles and combustor nozzle geometry; however radial baffles may produce nonlinear effects that cannot be captured by a Helmholtz acoustic solver.}, keywords = {}, url = {https://jast.ias.ir/article_51570.html}, eprint = {https://jast.ias.ir/article_51570_aef58a1a39fb1f825c5775f96c296804.pdf} } @article { author = {S. Forouzan-sepehr, and Dr. Mohammadi, Soheil}, title = {A FAST MESH-FREE GALERKIN METHOD FOR THE ANALYSIS OF STEADY-STATE HEAT TRANSFER}, journal = {Journal of Aerospace Science and Technology}, volume = {6}, number = {1}, pages = {13-23}, year = {2009}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {The element-free Galerkin method is employed for two-dimensional analysis of steady-state heat transfer. The unknown response of the system, i.e. temperature is approximated using the moving least squares technique. Numerical integration of governing simultaneous system of equations is performed by Gauss quadrature and new modified nodal integration techniques. Numerical examples and tests have proved that the new methods remain in an acceptable level of accuracy while providing less expensive and much faster approaches.}, keywords = {Element Free Galerkin,EFG,Meshless,Nodal Integration,heat transfer}, url = {https://jast.ias.ir/article_51571.html}, eprint = {https://jast.ias.ir/article_51571_19c108f4b41844a507e9421d6e1e3344.pdf} } @article { author = {Davari, A. and Hadi Dulabi, M. and Dr. Soltani, Mohammad Reza and asakari, F.}, title = {Impact of Body on the Tail Surface Flowfield at High Incidences}, journal = {Journal of Aerospace Science and Technology}, volume = {6}, number = {1}, pages = {25-35}, year = {2009}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {An experimental study was performed to investigate the effects of the body angle of attack on the tail surface pressure distribution for a half body-tail combination in subsonic flow. The results show, in small deflection angle regions, that the tail deflection has the same effect on the surface pressure as the body angle of attack. However at moderate to high deflections, the flowfiled caused by the tail deflection angle is completely different from that of the body angle of attack, which is an indication of the nose and body vortex shedding effects on the tail at high angle of attack regime.}, keywords = {}, url = {https://jast.ias.ir/article_51572.html}, eprint = {https://jast.ias.ir/article_51572_2fce0ecf289004dfe6222b03688101c0.pdf} } @article { author = {Heydari, P. and Khaloozadeh, H. and Heydari, A.P.}, title = {Gyroscope Random Drift Modeling, using Neural Networks, Fuzzy Neural and Traditional Time- series Methods}, journal = {Journal of Aerospace Science and Technology}, volume = {6}, number = {1}, pages = {35-44}, year = {2009}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {In this paper statistical and time series models are used for determining the random drift of a dynamically Tuned Gyroscope (DTG). This drift is compensated with optimal predictive transfer function. Also nonlinear neural-network and fuzzy-neural models are investigated for prediction and compensation of the random drift. Finally the different models are compared together and their advantages are discussed}, keywords = {Dynamically Tuned Gyroscope,Random Drift,Time series methods,Neural-Networks,Fuzzy logic,Error compensation}, url = {https://jast.ias.ir/article_51573.html}, eprint = {https://jast.ias.ir/article_51573_429d9d4e1b16bff349b16aa971be8b7b.pdf} } @article { author = {bazazzadeh, Mehrdad and Badihi, Hamed and Shahriari, Ali}, title = {Improved Turbine Engine Hierarchical Modeling and Simulation Based on Engine Fuel Control System}, journal = {Journal of Aerospace Science and Technology}, volume = {6}, number = {1}, pages = {45-53}, year = {2009}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {Aircraft engines constitute a comp‌lex system, requiring adequate mon-itoring to ensure flight safety and timely maintenance. The best way to achieve this, is modeling the engine. Therefore, in this paper, a suitable mathematical model from engine controller design point of view, for a specific aero turbine engine is proposed by the aid of MATLAB/Simulink software. The model is capable of reducing costs of actual engine tests and predicting some of important controlled variables, which can usually not be measured directly (e.g. compressor surge margin, the turbine inlet temperature or the engine net thrust). The model has maximum accuracy for maximal variance of the fuel flow input command consistent with the engine control system specifications. So the model is strongly adaptable to the engine control systems and real time applications. Simulation results which proved logical and well founded are obtained from applying an acquired fuel flow function to the engine model.}, keywords = {}, url = {https://jast.ias.ir/article_51574.html}, eprint = {https://jast.ias.ir/article_51574_f7e16c29a403a2a2bcc1bad047098bab.pdf} }