Iranian Aerospace SocietyJournal of Aerospace Science and Technology1735-21349120120301Effect of Wing Sweep Angle on the Vortex Interaction of a Tail-Wing ConfigurationEffect of Wing Sweep Angle on the Vortex Interaction of a Tail-Wing Configuration51610ENBahman Jahromiدانشگاه صنعتی شریفM.R. Soltaniدانشگاه صنعتی شریفM. Masdariدانشگاه صنعتی شریفJournal Article20130928The goal of this investigation is to study the effect of wing sweep angle on the horizontal wing-body- tail configurations in subsonic flow. For this purpose, a series of wind tunnel tests were conducted on a model having a moveable horizontal tail and a wing planform with different sweep angles. Tests were performed at different tail deflection angles. Static surface pressure distribution over the suction side of wing was measured for both static and dynamic changes of the tail angles of attack. The strength of the vortices over different wings was compared and the effect of tail deflection on the wing flow field was investigated. It is seen that the wing sweep angle is a dominant factor for the strength of the vortices over the wing and hence the maneuverability of the vehicle.https://jast.ias.ir/article_51610_4282644e04905f6b2d3a0c3bb34c8d41.pdfIranian Aerospace SocietyJournal of Aerospace Science and Technology1735-21349120120301An Innovation in Film Cooling of the Gas Turbine Blades Applying an Upstream JetAn Innovation in Film Cooling of the Gas Turbine Blades Applying an Upstream Jet51611ENM.R. Salimiدانشگاه صنعتی شریفM. Taeibi Rahniدانشگاه صنعتی شریف0000-0002-7875-5601Mahdi Ramezanizadehدانشگاه هوایی شهید ستاریJournal Article20130928A new design concept is introduced to control the near-wall integration between the hot-gas boundary layer and the cooling jets in order to enhance the adiabatic film cooling effectiveness of the gas turbine blades. In this new approach, another film cooling port, having a very low blowing ratio, which prevents formation of the counter-rotating vortex pare, is applied just upstream of the main film cooling jet. The fluid injected from the small upstream port changes the flow pattern, resultsinwider horseshoe vortices in the span-wise direction, and generates a more uniform distribution of the coolant film. Also, this coolant fluid flows towards the low pressure region located just behind the main film-cooling hole. Therefore, by producing a cold layer of gas beneath the coolant jet and diverting the hot cross-flow gases into this area, it significantly improves the film cooling effectiveness, especially in the near field of the main jet. The obtained results show lower stream-wise velocity gradients near the wall, which considerably decreases the wall shear stresses, comparing to the regular film cooling holes.https://jast.ias.ir/article_51611_0f8d918feb53bad88adf5c3b4de5d044.pdfIranian Aerospace SocietyJournal of Aerospace Science and Technology1735-21349120120301A Comprehensive Approach to Develop a Continuous Fuzzy Guidance Law for Maneuvering TargetsA Comprehensive Approach to Develop a Continuous Fuzzy Guidance Law for Maneuvering Targets51612ENLabid HassanM.B. Malaekدانشگاه صنعتی شریفJournal Article20130929Based on the idea of Continuous Fuzzy Guidance Law (CFGL), a andldquo;three-phase fuzzy guidanceandrdquo; (TFG) law is proposed for the class of surface to air homing missiles. The current approach enables the guidance law to track a maneuvering target from the beginning of the launch phase up to the terminal one while itdynamically attempts to keep miss-distance, flight time and control effort at a minimum acceptable level. The guidance law developed heredepends on four factors:line-of-sight (LOS) angle, LOS rate, LOS angular acceleration, and relative distance to the target. To show the relative superiority of the approach, the performance of the new guidance law has been compared with that of proportional navigation guidance. The results confirm the validity of the idea; as for a TFG,we get quite comparable results. The current approach also shows a relatively good robustness for a wide variety of flight conditions.https://jast.ias.ir/article_51612_793d31da698ae0573afe1a9be839c3ae.pdfIranian Aerospace SocietyJournal of Aerospace Science and Technology1735-21349120120301Helicopter Rotor Airloads Prediction Using CFD and Flight Test Measurement in Hover FlightHelicopter Rotor Airloads Prediction Using CFD and Flight Test Measurement in Hover Flight51613ENDavoud HassanzadehJournal Article20130929An implicit unsteady upwind solver including a mesh motion approach was applied to simulate a helicopter including body, main rotor and tail rotor in hover flight. The discretization was based on a second order finite volume approach with fluxes given by the Roeand#39;s scheme. Discretization of Geometric Conservation Laws (GCL) was devised in such a way that the three-dimensional flows on arbitrary moving grids could be solved. The accurate geometric representation together with the flexibility required for grid displacement was achieved by using a tetrahedral grid. First, the numerical methodology was validated through experimental test data; then, our supposed helicopter configuration was utilized. At the same time, the main rotor loading measurements were done through flight tests. Two methods of moving reference frame (MRF) and viscous/inviscid Dynamic Mesh were compared resulting in robustness of Dynamic Mesh approach. Ultimately, our calculationsyieldedvalid solutions to the blade loading and wake structure.https://jast.ias.ir/article_51613_5873dfc87653d2a70828bdb7907898e7.pdfIranian Aerospace SocietyJournal of Aerospace Science and Technology1735-21349120120301Practical Evaluation of EKF1 and UKF2 Filters for Terrain Aided NavigationPractical Evaluation of EKF1 and UKF2 Filters for Terrain Aided Navigation51614ENA. Moghtadaei RadIslamic Azad University0000-0001-9299-2067Journal Article20130929This article would study batch and recursive methods that used in terrain navigation systems. Terrain navigation has a lot ofdisadvantages and so researchers have been studied on different method of aided navigation for many years. Therefore, more types of aided navigation systems were introduced with advantages and disadvantages in terms of practical and theoretical. One of the main ideas for aided navigation is integration of extended kalman filter and INS[1]. But this integration method has significant weakness in practice that caused to benonsignificant among the aided navigation methods. So in this article, the author introduces more accurate filter (UKF) for integration byINS and other sensors as barometer and radar system. In continue,the use of Aided EKF and UKF navigation schemes would be justified anddeveloping and performing algorithms written for the needed application and simulation results will be presented and compared.Finally, benefit of the proposed methods in this article will be compared with other batch and recursive methods. The most significant of this article is related to its practical application on UAV that was tested in 2010.https://jast.ias.ir/article_51614_88d2fa476caa7c73cbb387bc7af881b4.pdfIranian Aerospace SocietyJournal of Aerospace Science and Technology1735-21349120120301Performance Modeling and Examination of Losses in the Axial -Flow Compressor and Comparisonwith Experimental ResultsPerformance Modeling and Examination of Losses in the Axial -Flow Compressor and Comparisonwith Experimental Results51615ENM. EftariJournal Article20130929The performance prediction of axial flow compressors at different speeds and under various pressure ratio conditions are still being developed because of costly empirical experiments. One-dimensional modeling is a simple, fast and accurate method for performance prediction in any type of compressor with different geometries. In this approach, inlet flow conditions and compressor geometry are known and by considering various losses of the compressor, velocity triangles at rotor, stator inlets and outlets are determined and, then, compressor performance characteristics are predicted.
Numerous models have been developed theoretically and experimentally for estimating various types of compressor losses. In the present study, the performance characteristics of the axial-flow compressor are predicted based on a one-dimensional modeling approach. Models of Lieblein, Koch-Smith, Aungier, Hawell are implemented to consider the compressor losses. To validate the model, the modeling results are compared with experimental data. This model can be used for various types of axial-flow compressors with different geometries.https://jast.ias.ir/article_51615_46567525fc6e548bdb501ef058e1b107.pdfIranian Aerospace SocietyJournal of Aerospace Science and Technology1735-21349120120301Crack Analysis, Using a New Coupled FE-EFG MethodCrack Analysis, Using a New Coupled FE-EFG Method51616ENS. Mohamadnejadدانشگاه گیلانJournal Article20130929To solve crack problems, some coupled methods have been developed in recent years. Most of these methods have some shortcomings such as the need for a transition region. The finite element and enriched element free Galerkin methods are widely used for this class of problems. In order to take the advantages of these methods while avoiding the disadvantages, it is essential to follow solution approaches based on a combination of them. Prompted by this idea, in this article, the authors mainly aim at finding a simple way to solve the problem of a cracked plate by using a novel coupled finite element-element free Galerkin (FE-EFG) method. In this procedure, the usage of transition region is bypassed by employing the concept of andldquo;virtual particlesandrdquo;. The enriched element free Galerkin method is applied to approximate regions near a crack tip and the finite element method is put to use in the areas far from the crack tip. Static analysis of two-dimensional crack problems, according to the plane stress condition under mode-I loading, has been done. The results from the present method are indicated to be in excellent agreement with those from the existing analytical solutions.https://jast.ias.ir/article_51616_9776dae474fc2374de8fb1a79c48e38b.pdf