نشریه مهندسی هوانوردی
سال بیست و پنجم شماره 1 (بهار و تابستان 1402)

This research explores and compares the AUSM scheme family based on compressible, steady, viscous, and inviscid axisymmetric flows in a finite-volume method-based and unstructured data storage grids code. When the effects of side-velocity are taken into account, axisymmetric flows can be considered a three-dimensional problem in the longitudinal plane; as a result, there is a considerably decreased number of computations required compared to computations in three dimensions. The most important and latest modifications of the AUSM-family were developed to identify more efficient methods in the AUSM- family in terms of accurate prediction of the axisymmetric flow field in internal and external axisymmetric flows, viscous (inviscid), and high-speed flows with shock waves characteristics. The novelty of this investigation is the assessment and comparison done on the AUSM-family in resolving the compressible axisymmetric flow field, which has received less attention in prior studies. The studies determined that the AUSM+M method performs better against a strong shock wave than other methods investigated in this research. According to the modifications made in this scheme, unlike other methods, there are no wiggles in the regions mentioned earlier. Furthermore, it is discovered that the AUSM+M method had a higher rate of convergence than the AUSM+ and SLAU approaches. In addition, the AUSM+M scheme is distinctive from other techniques in viscous flows because it produces the minimum kinetic energy dissipation rate and fewer shock anomalies in the shock wave region.

In recent years, with the development of Unmanned aerial vehicle (UAV) technology in various fields such as military industry, telecommunications, meteorological research and espionage and etc. studies on the mass movement of UAVs have attracted the attention of various scientists. This article pursues objectives such as ensuring the information security of UAV groups, maximizing the UAV group detection range, and minimizing the communication range by improving the Olfati Saber’s flocking algorithm. An improved control algorithm can help track the speed of virtual leaders by each agent. Then we introduce a concept called virtual communication circle to control the communication power of each UAV to ensure no collisions and stable communication. Multiple UAVs can track the virtual leader for batch flight, and a distributed participatory control strategy can be achieved. The simulation results at the end of this paper show the effectiveness of this algorithm for the group system of UAVs.

Regarding the importance and critical effect of human factors and anthropometric characteristics on pilot's performance, especially in military area, the purpose of this research is identifying and detecting priority of critical anthropometrics’ factors affecting performance of pilots in aircraft cockpit. Research method is based on comprehensive literature review in first step, then identified factors will be evaluated based on recommendations of flight experts. Analyzing of gathered data has been done using descriptive and inferential statistics using EXCEL and SPSS software. As collected data aren't normal, non-Para metric’s statistical tests were used for analyzing data. The results will be clarified more critical factors that can be used for evaluating flight military and civil candidates in educational centers of flight and Shahid Sattari Aeronautical university of science and Technology. Also, research and development centers which work in design of cockpit of military and civil aircrafts can used from the result of this research for more effective design.

Shape of the jet hole highly affects the film cooling effectiveness of the gas turbine blades, which must be designed in such a way that creates proper distribution of the coolant over the surface to remove the hot spots. The present study investigates the cooling performance of the novel Bean-shaped hole geometry design for the jet hole experimentally using an infrared thermography method. The tests are performed at the main flow Reynolds number of 10,000 (based on the hole equivalent diameter) over a test plate at injection angle of 30 degrees relative to the surface. The measurements were carried out at the mainstream speed of 27 m/s and four blowing ratios of, 0.4, 0.5, 0.7 and 0.8. The obtained results show that the geometry of the Bean-shaped holes lead to an increase in the film cooling effectiveness in comparison to the cylindrical holes. The highest cooling effectiveness is obtained at blowing ratio of 0.5 and the lowest effectiveness is obtained over the surface at blowing ratio of 0.4. In the case of Bean-shaped hole geometry, the full area averaged cooling effectiveness increases by 45.4% to 207.4%.

Operational sensitivities of military air craft, deterrent measures in aircraft design to prevent the accumulation of static charge on the surface of the aircraft or Electrostatic Discharge, is very necessary and important. These include antistatic coatings, flame spraying, the use of carbon fiber composites and nanocomposites in aircraft fuselage design, and electrostatic dischargers. The aim of this study was to investigate, simulate and compare the effect of electrostatic discharge (ESD) in military aircraft with all-metal, all-composite body and the combined state of several structures. In this paper, by selecting the military Aircraft body of composite, metal and combined mode, the effects and surface of induced electric field, surface currents due to electrostatic flux and Radiation electromagnetic fields from the transient state of surface current will be compared and examined in different parts of the military air craft, including: radar system, cabin and electronic telecommunication systems, internal and external fuel tank.

Due to industrial advances and the application of more dynamic loads, it is necessary to pay more attention to the fatigue issue. Among non-destructive methods, the acoustic emission method has become a standard and reliable method in recent years.With the aim of online structural monitoring of the aircraft propeller that undergoes cracks in the hub part, this article investigates and determines the characteristics of acoustic emission in the growth of aluminum 2025 fatigue crack. Referable research on the loading frequency considered in this research has not been conducted for this alloy. In this project, the characteristics of acoustic emission in the fatigue crack growth of aluminum alloy 2025 for online structural monitoring have been investigated and determined. Acoustic emission tests have been performed in two parts: bending fatigue test with the aim of initiation of fatigue cracks in aluminum alloy 2025 specimens and following tensile tests with the aim of growth of fatigue cracks. According to the received acoustic emission information, various diagrams are plotted. Analyzing the results from online acoustic emission monitoring showed, the acoustic emission method can be considered as a suitable and reliable technique for detecting crack initiation and crack growth in aluminum alloy 2025.

In this paper, mathematical modeling and sliding mode control of a roll-pitch seeker is provided. First, the dynamic model of the roll and pitch frames is obtained by the Newton-Euler equations of motion. The effect of mass asymmetry and the asymmetry of the moment of inertia matrix on the dynamics of the seeker is also considered. The dynamics of the roll-pitch seeker are hardly nonlinear. Also, the presence of unmodified uncertainties and perturbations causes uncertainty in the model. To control the nonlinear dynamics of the seeker and to deal with the uncertainties, a two-input two-output integrated sliding mode controller is designed. The motor transfer functions of the inner and outer frames and the input voltage and output current saturation limits are also considered in the simulation. Numerical simulation results show that the stabilization loop has good performance in both roll and pitch channels. Also, by examining the performance of the designed controller in the presence of mass uncertainty of the frames, it is shown that the controller has good robustness.

The aim of the current research is to investigate the effective factors on the implementation of the announced policies of the aviation and air transportation sectors based on the law of the 6th five-year development plan of the country. The research method is practical in terms of purpose, descriptive-survey in terms of data collection method and quantitative in terms of data type. The intended statistical population in this research includes 250 staff and operational experts of the Civil Aviation Organization and the Airports and the Iran Airports Company, and based on simple random sampling and Cochran's sampling formula, 152 of them were selected as a sample. Based on the review of theoretical foundations, literature, 19 indicators in the form of 6 variables as effective factors on the implementation of the desired statistical policies and a researcher-made questionnaire for collecting the required data were distributed among the population. The content validity of the questionnaire was confirmed by experts and its reliability using Cronbach's alpha coefficient and a coefficient above 0.7 for all variables. The data was analyzed using SPSS, SMART PLS and EXPERT CHOICE software’s. The findings have shown that the effective factors, in order of priority, are the organization implementing the policies, the policy executors, the types of actions in the execution of the policies, the nature of the policies, the implementation environment of the policies, the codification of the aviation policies and air transport. These results are significant at the alpha level of 0.05.

Currently, complex megaprojects in the country facing many problems such as failure to achieve goals. This issue is more noticeable in the megaprojects of aircraft design and construction, Regarding the effective factors in the management of megaprojects, such as: complex design and engineering activities, complex interactions, strategic management and technology management, which have not been comprehensively investigated, this research has identified and ranked the factors effective in the management of complex megaprojects in the aircraft industry. For this purpose, by reviewing the research literature and obtaining the opinions of aviation industry experts, especially Iran 140 plane and 150 plane, the components of aviation megaprojects were identified by primary coding, dimensions and categories using MAXQDA2020 software. Then, the variables identified through the questionnaire from the experts related to air projects were categorized and validated using SMARTPLS3 software. The components were ranked by the multi-criteria decision-making approach of network analysis (ANP) with SuperDecision software. The main dimensions in the management of megaprojects are the two dimensions of system engineering and management factors, and 10 main components and 40 indicators were identified for the factors affecting the management of complex megaprojects of aviation industry. Finally, according to the results, strategic management with a weight of 0.144172 ranked first among the components and the infrastructure index of testing and testing parts and products with a weight of 0.02235 was identified as the first among the indicators. At the end, solutions were presented for the best possible management of complex megaprojects in the aviation industry.

UAVs are used in the armies of the world with variety of missions. Considering the merits of using drones, these systems are used in missions such as; Identification, target, air surveillance, communication, electronic warfare, training, combat, support, suicide, meteorology and deception are used in the armies of the Islamic Republic of Iran. In this research, using SPSS statistical software, the main question titled; "What are the solutions to improve surveillance and identification of drones in future battles?" has been analyzed. The results in form of Friedman's test showed that the average of the examined sample is significantly greater than the hypothetical and expected average of the society. Also, detection and identification solutions to improve the monitoring and identification of UAVs in the future battle and the process of aerial surveillance of combat reconnaissance UAVs in the scene of future battles have been examined. In this research, these results have been obtained that the use of UAV operations networking and the possibility of implementing network-oriented operations and as a result, the concentration of UAV flights in the areas of enemy activity and timely detection at any time is the most important strategy to improve the care and identification of UAVs in battles. the use of UAV with high endurance, safe and stable telecommunication link at different altitudes and in different flight areas for cruise and searching flight for the desired targets is the most important solution for achieving the desired air surveillance process of combat and reconnaissance drones in future battles.

In the last two decades, the use of plasma actuators has emerged as a new technology in the aerospace field. An example of plasma actuator is corona plasma actuators, in which corona discharge is created by a high-voltage electrode with a small radius of curvature as an emitter and another electrode as a collector, which are located at a certain distance from each other and leads to the production of ion wind. In this research, the effect of two optimized arrangements for measuring the driving force in positive and negative corona has been investigated experimentally. The results of the research show that the corona actuator can create thrust and the amount of thrust is directly related to the amount of voltage. The relationship between voltage changes and thrust is almost linear and the increase in voltage causes more growth in thrust, electric power and electric current. In both arrangements, the amount of thrust and electrical power in the negative corona is more than the positive corona. Finally, it can be concluded that as the number of plasma actuators in the first arrangement is more than the second arrangement, this leads to an increase in the thrust and the amount of electric power in the first arrangement compared to the second arrangement.

Since humans have begun to fly and construct various aircraft, the occurred accidents and incidents ‎have always resulted in irreparable injuries and damages. Therefore, today, aviators especially airlines ‎continuously trying to maintain the maximum level of safety and reduce the rate of accidents by ‎spending resources. In this research, by analyzing the available reports and information for 46 accidents ‎and serious incidents in Iran's civil aviation between 1979 and 2021, first, a statistical-analytical ‎evaluation is performed, then influential factors like failures and errors in these occurrences are analyzed ‎by using failure mode and effects analysis and multi-attribute decision making. The statistical population of this research includes a panel of experts and experts in the field of aviation and air accidents, and a questionnaire was used to collect the required information. According to findings, ‎human is the most important factor, Fokker100 is the most engaged aircraft and pilots with low ages and ‎experiences are the most vulnerable factors in mentioned occurrences; in addition, failures in landing ‎system and engines and also the pilot error in not following the structures were the most important ‎factors.‎