Journal of Aerospace Science and Technology
Volume:9 Issue: 1, Winter and Spring 2012

The 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.

A 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.

Based on the idea of Continuous Fuzzy Guidance Law (CFGL), a “three-phase fuzzy guidance” (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.

An 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 Roe''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.

This 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.

The 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.