@article { author = {Shokrollahi, S.}, title = {Flutter Analysis of a Low Aspect Ratio Swept- Back Trapezoidal Wing at Low Subsonic Flow}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {2}, pages = {61-66}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {A linear, aeroelastic analysis of a low aspect ratio swept back trapezoidal wing modeled as a cantilever plate is presented. An analytical and numerical formulation for both the aerodynamic forcing and structural response of the wing was developed. The analytical model uses a three dimensional time domain vortex lattice aerodynamic method. A Rayleigh-Ritz approach has been used to transfer equations into a modal domain in order to solve equations of motion. The theoretical results are consistent with numerical results for low aspect ratio rectangular wings and experimental data reported by other investigators for delta wings.}, keywords = {Flutter,Swept Back,Trapezoid,Low Aspect Ratio,Subsonic}, url = {https://jast.ias.ir/article_51511.html}, eprint = {https://jast.ias.ir/article_51511_dc7711ca05a48a7c8fa3b7269b56d873.pdf} } @article { author = {Shams, Mehrzad and Ebrahimi, Reza}, title = {Numerical Simulation of Scaling Effect on Bubble Dynamics in a Turbulent Flow around a Hydrofoil}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {2}, pages = {67-75}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {A Lagrangian-Eulerian numerical scheme for the investigation of bubble motion in turbulent flow is developed. The flow is analyzed in the Eulerian reference frame while the bubble motion is simulated in the Lagrangian one. Finite volume scheme is used, and SIMPLEC algorithm is utilized for the pressure and velocity linkage. The Reynolds stresses are modeled by the RSTM model of Launder. Upwind scheme is used to model convective fluxes. The Guassian Filter White Noise is incorporated to simulate the turbulent fluctuation velocities. The bubble diameter is found by the use of Rayleigh-Plesset equation. Various forces in the equation of motion of the bubble are considered. The Buoyancy, Saffman lift, drag, pressure, and change of volume forces are carefully applied. The effects of all of these forces on bubble path are also examined. The bubbles are created in the low pressure zones, and then traced in the flow field. It is observed that the bubble diameter is highly dependent on the mean stream pressure, and its location. The results are compared with the other published works, and have an acceptable accuracy.}, keywords = {}, url = {https://jast.ias.ir/article_51512.html}, eprint = {https://jast.ias.ir/article_51512_0b5ee0d5ec3a5e57d494fb792f4ceb09.pdf} } @article { author = {Esfahanian, Vahid and Ghader, S.}, title = {Numerical Solution of Parabolized Stability Equations Using Super Compact Scheme}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {2}, pages = {77-85}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {}, keywords = {}, url = {https://jast.ias.ir/article_51513.html}, eprint = {https://jast.ias.ir/article_51513_facf7f529b89f733c44ec1ddf695c72e.pdf} } @article { author = {}, title = {Study of Clear Air Turbulence over Iranian Plato}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {2}, pages = {87-95}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {This study was carried out using two sets of numerical weather forecast data and flight reports for Clear Air Turbulence (CAT) over Iranian Plato to find atmospheric flow patterns favorable to the formation of CAT. The numerical data include five months of AVN analysis with horizontal resolution of 1 degree(about 100 km) and four months forecast data of MM5 model with resolution of 50 km. Important indices associated with conditions favorable for CAT formation include wind shear, flow deformation fields and atmospheric static stability (or joint effects such as Richardson number). These indices were estimated and also some algorithms such as Dutton to find their threshold values for CAT occurrence. The best selected algorithms are determined in the 5 months period using AVN outputs. In another 4 months period the MM5 outputs were used for the forecast of CAT using the POD method. The results for there periods indicated that severe CAT rarely occurred over Iran and condition for moderate CAT are often in upstream of troughs ridges, near straight jet stream with cold advection and upper region of ridges. The POD method shows Dutton and Ellrod-2 are the best selected algorithms for CAT forecasting and have good consistency with observations. Their typical threshold values (associated with wind shears) are about 3 and 20 for moderated CAT respectively.}, keywords = {Clear air turbulence,CAT algorithms,Iran}, url = {https://jast.ias.ir/article_51514.html}, eprint = {https://jast.ias.ir/article_51514_335d32c12c90fdfec8720710a1ed5dd6.pdf} } @article { author = {Bazdidi-Tehrani, Farzad}, title = {Numerical Simulation of a Confined Swirling Flow in a Model Gas Turbine Combustor}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {2}, pages = {97-103}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {}, keywords = {}, url = {https://jast.ias.ir/article_51515.html}, eprint = {} } @article { author = {Haddad Pour, Hassan}, title = {The Comparison of Direct and Indirect Optimization Techniques in Equilibrium Analysis of Multibody Dynamic Systems}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {2}, pages = {105-111}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {The present paper describes a set of procedures for the solution of nonlinear static-equilibrium problems in the complex multibody mechanical systems. To find the equilibrium position of the system, five optimization techniques are used to minimize the total potential energy of the system. Comparisons are made between these techniques. A computer program is developed to evaluate the equality constraints and objective function of a general multi-body dynamic system in order to find the equilibrium condition. The obtained results from different approaches are compared together and finally some conclusions are made considering the existing results of the artificial damping method. It is seen that the indirect methods may produce more accurate results with faster convergence.}, keywords = {static-equilibrium,multibody mechanical systems,constrained optimization,Dynamic}, url = {https://jast.ias.ir/article_51516.html}, eprint = {https://jast.ias.ir/article_51516_b90be75d9fe158dcd1331d1528cea591.pdf} }