In this publication a Doctrine for the Conditional Extremization of the Hybrid-Optional Effectiveness Functions Entropy is discussed as a tool for the Reliability Assessments of Engineering Systems. Traditionally, most of the problems having been dealt with in this area relate with the probabilistic problem settings. Regularly, the optimal solutions are obtained through the probability extremizations. It is shown a possibility of the optimal solutions “derivation”, with the help of a model implementing a variational principle which takes into account objectively existing parameters and components of the Markovian process. The presence of an extremum of the objective state probability is observed and determined on the basis of the proposed Doctrine with taking into account the measure of uncertainty of the hybrid-optional effectiveness functions in the view of their entropy. Such approach resembles the well known Jaynes’ Entropy Maximum Principle from theoretical statistical physics adopted in subjective analysis of active systems as the subjective entropy maximum principle postulating the subjective entropy conditional optimization. The developed herewith Doctrine implies objective characteristics of the process rather than subjective individual’s preferences or choices, as well as the states probabilities maximums are being found without solving a system of ordinary linear differential equations of the first order by Erlang corresponding to the graph of the process. Conducted numerical simulation for the proposed mathematical models is illustrated with the plotted diagrams.
As the rotor configuration has the most impact on helicopter properties, the process of determination the assumptions for rotor design is a very important factor in the early stage of rotorcraft development. The following paper presents a mechanical analysis process used at the Institute of Aviation to quickly develop a coaxial rotor prototype applicable in ultra-light unmanned helicopter which has the potential for further improvement of its flight parameters. The article describes the rotor analysis process due to its feasibility based on commercially available solutions, the process of formulating assumptions for the entire structure, MES analysis of the rotor parts all leading to creation of the rotor prototype.
Ruben Di Battista, Maria Teresa Scelzo and Maria Rosaria Vetrano
Slushes are two-phase solid-liquid single-species cryogenic fluids that exhibit an increased density and a greater heat capacity with respect to the corresponding normal boiling point liquids. These promising features are of large interest for applications that exploit slush as a thermal fluid, like super magnets refrigeration, cryogenic cooling of bio-materials or air conditioning, and for aerospace systems that use slush fluids as fuel or oxidizer. Several programs in the frame of the research on Slush Hydrogen (SLH2) as a new-generation fuel for aerospace propulsion have been started in the past. This work was carried out in the framework of a VKI research activity promoted by the Predict ESA Technology Research Programme, to investigate experimentally and numerically the behavior of slush flows in a representative upper stage feeding line. In this paper, we present a simulation based on a granular two-fluid model on an isothermal solid liquid mixture (slurry) and a Nitrogen slush (SLN2) fluid flowing in a horizontal pipe. A finite-volumes discretization using the software library OpenFOAM was benchmarked against experimental and numerical literature data, to assess the accuracy of the code in predicting pressure drops along the pipe axis and solid particle distribution across the pipe diameter. Moreover, the effects of concentration and inlet velocity are investigated. We show that the numerical model fairly reproduces the literature data in terms of important aspects as the solid volume fraction distribution and the pressure drops, especially for high flow rates.
This article presents adhesive shearing test methods, focusing especially on the ASTM D5656 method. These methods will be briefly characterized and compared. The most important concerns about the D5656 method are described. With the use of ASTM D1002 and D5656 methods, the influence of adherend surface preparation on shearing properties of the bond is evaluated. Compared to sandblasting only, sandblasting followed by the FPL process (sulfochromate etching of aluminum) increased shear strength of joints by 35 % for ASTM D1002 tests and by 48% for D5656 tests. Comparing these two methods, shear strength obtained in D5656 tests is about two times higher than in D1002 tests. The cause for this phenomena is much larger adherend thickness in the D5656 method, which provides the coupons with increased stiffness. Shear modulus, calculated with 3 different calculation methods, showed differences in obtained results, which points to necessary actualization of D5656 standard.
Publication contains a description of the preparation and the implementation of a test flight of a stratospheric balloon with a mounted camera GoPro Hero3. Description includes: used equipment, its parameters, role in the success of the mission and the difficulties and limitations that the project team encountered during the preparation and implementation of the flight. The mission was attended by a team of six engineers and scientists from the Remote Sensing Division, who were also involved in the implementation of the HESOFF project. One of the main goals of the HESOFF project was to obtain aerial images on the Krotoszyńska Plate (woj. wielkopolskie) using the Unmanned Aerial Vehicle (UAV) and to carry out remote monitoring of oak stands. The primary goal of an experimental balloon flight was to check the technical operational capability and gain experience in planning and implementing this type of project. During the balloon raising, the video material was acquired in the form of a recording, which later was analyzed. On the basis of the collected information, the conclusions regarding the possibility of implementing a long endurance flight in the stratosphere, illustrating (using a multisensor platform) research surfaces of the HESOFF project were presented. The stages of implementation of the presented mission were divided into following parts: preparation of the flight with the completion of equipment and necessary documents (flight permission), proper flight realization, understood as the release of the balloon and identification of the place where the equipment landed, as well as analysis and presentation of the results.
This paper is a review of testing methods dedicated for sandwich type composite structures with honeycomb core. First, information about the composition of sandwich materials structures, their properties, types of core materials and applications in the industry is presented. Mechanical properties were compared in the case of different types of the core material. Later, tests methods needed to describe properties of those materials and normalization organizations which create them were mentioned. The testing methods were divided into two groups: mechanical and physicochemical tests. Mechanical properties are: compressive strength (two types of test), edge compressive strength, shear strength (in two directions) and tension strength (two types of test). Physicochemical properties are: material density, water migration, water absorption and thermal conductivity. Testing methods were described according to American Society for Testing and Materials (ASTM) standards. This article is based on professional literature and the author’s experience.
The paper presents simulation method and results of calculations determining behavior of helicopter and landing site loads which are generated during phase of the helicopter take-off and landing. For helicopter with whirling rotor standing on ground or touching it, the loads of landing gear depend on the parameters of helicopter movement, occurrence of wind gusts and control of pitch angle of the rotor blades. The considered model of helicopter consists of the fuselage and main transmission treated as rigid bodies connected with elastic elements. The fuselage is supported by landing gear modeled by units of spring and damping elements. The rotor blades are modeled as elastic axes with sets of lumped masses of blade segments distributed along them. The Runge-Kutta method was used to solve the equations of motion of the helicopter model. According to the Galerkin method, it was assumed that the parameters of the elastic blade motion can be treated as a combination of its bending and torsion eigen modes. For calculations, data of a hypothetical light helicopter were applied. Simulation results were presented for the cases of landing helicopter touching ground with different vertical speed and for phase of take-off including influence of rotor speed changes, wind gust and control of blade pitch. The simulation method may help to define the limits of helicopter safe operation on the landing surfaces.
The article describes 10 known programmes of practical flight training in military aviation – specialization: Multi-Mission Tactical Jet Pilot, which is the highest level of military pilot training in all types of military and civil aviation – comparable only to the level of training and experience of the pilot-instructor of the Military Aviation School. The presented comparison was developed on the basis of literature research from the point of view of, among others, an aircraft operation engineer and a pilot-instructor.
The paper presents application of Particle Image Velocimetry for determination of an airfoil’s drag coefficient in wind tunnel tests. The purpose of the study was to investigate the feasibility of using PIV as an alternative to pressure rake measurements, especially at high angles of attack. The integral momentum concept was applied for determination of fluid drag from experimental low speed wind tunnel data. The drag coefficient was calculated from velocity and pressure rake data for intermediate angles of attack from 5° to 10°. Additionally, the experimental results were compared to panel method results. After validating the procedures at low angles of attack, the drag coefficient was calculated at close to critical angles of attack. The presented study proved that PIV technique can be considered as an attractive alternative for drag coefficient determination of an airfoil.