Fracture mechanics analysis of damaged turbine rotor discs using finite element method

This paper presents evaluation fracture mechanics parameters in low pressure turbine components. Critical locations such as keyway and dovetail area are experiencing stress concentration leading to crack initiation. Stress intensity factors were evaluated using the J-Integral approach available within ANSYS software code. The finite element method allowed the prediction of the point of crack initiation and the crack propagation using the orientations of the maximum principal stresses. Special attention in this investigation is focused to develop analytic expressions for stress intensity factors at critical location of low pres-sure steam turbine disc. [Projekat Ministarstva nauke Republike Srbije, br. I-174001 i br. TR-35045

Assessment Results of Fluid-Structure Interaction Numerical Simulation Using Fuzzy Logic

A fuzzy approximation concept is applied in order to predict results of coupled computational structure mechanics and computational fluid dynamics while solving a problem of steady incompressible gas flow through thermally loaded rectangular thin-walled channel. Channel wall deforms into wave-type shapes depending on thermal load and fluid inlet velocity inducing the changes of fluid flow accordingly. A set of fluid-structure interaction numerical tests have been defined by varying the values of fluid inlet velocity, temperature of inner and outer surface of the channel wall, and numerical grid density. The unsteady Navier-Stokes equations are numerically solved using an element-based finite volume method and second order backward Euler discretization scheme. The structural model is solved by finite element method including geometric and material non-linearities. The implicit two-way iterative code coupling, partitioned solution approach, were used while solving these numerical tests. Results of numerical analysis indicate that gravity and pressure distribution inside the channel contributes to triggering the shape of deformation. In the inverse problem, the results of fluid-structure interaction numerical simulations formed a database of input variables for development fuzzy logic based models considering downstream pressure drop and maximum stresses as the objective functions. Developed fuzzy models predicted targeting results within a reasonable accuracy limit at lower computation cost compared to series of fluid-structure interaction numerical calculations. Smaller relative difference were obtained when calculating the values of pressure drop then maximal stresses indicating that transfer function influence on output values have to be additionally investigated

Unapređenje sistema obrazovanja studenata vazduhoplovstva vojne akademije primenom aviona laboratorije

Abstract This article describes a proposal to improve the educational process for the students of the Military Academy to support the maintenance of the Serbian Army aircraft based on the introduction of the subject called Aircraft Flight Tests. The article particularly emphasizes the importance of establishing aircraft laboratories with the basic characteristics of the test-measuring equipment necessary to be integrated into the aircraft in order to realise practical tests of an aircraft in flight. The formation of aircraft laboratories would form a very strong didactic tool which would provide an optimal synthesis of theory and practice. This concept of improving the educational process would substantially raise the awareness of the necessity of cooperation and involvement of all research capacities of the scientific institutions in the Ministry of Defense of the Republic of Serbia

Two-dimensional numerical analysis of active flow control by steady blowing along foil suction side by different urans turbulence models

The effects of active separation control by steady blowing jets were investigated numerically on three different examples: subsonic flow past Aerospatiale A airfoil at 13º angle-of-attack, transonic flow past NACA 0012 airfoil at 4º angle-ofattack, and transonic flow in linear compressor/turbine cascade. Performed analyses are two-dimensional, flow is turbulent (or transitional) while fluid is viscous and compressible. Jets are positioned along the suction sides of the foils, the first one being located just upstream of the separation point, and modeled by source terms added to flow equations. Several different jet diameters and intensities are investigated. As the choice of turbulence model affects the final solution of Reynolds equations, turbulence is modeled by four different models: Spalart- Allmaras, realizable k-ε, k-ω SST, and γ-Reθ, and a comparison of obtained results is performed. Goals of the study include definition of an adequate numerical setting that enables sufficiently correct simulation of the problems in question as well as evaluation of the possible increase in aerodynamic performances. Lift coefficients, lift-to-drag ratios or relative pressure differences are improved for all controlled cases

Improvement of the military academy education system for aeronautics students using the flying laboratory

Normal 0 false false false MicrosoftInternetExplorer4 This paper describes a proposal to improve the educational process of students of the Military Academy to support the maintenance process of the Serbian Army aircraft based on the introduction of objects in flight test aircraft. It is particularly emphasized the importance of establishing airline laboratories with basic characteristics of the test-measuring equipment that is necessary to integrate the aircraft to perform a practical test of an aircraft in flight. The formation of aircraft laboratories would form a very strong didactic tool, which provides for optimal synthesis of theory and practice. This concept of improving the educational process would be substantially affected the awareness of the necessity of working together and put together all the research capacity of scientific institutions in the Ministry of Defence of the Republic of Serbia.</p

Numerical analysis of a hypersonic turbulent and laminar flow using a commercial CFD solver

Computational fluid dynamics computations for two hypersonic flow cases using the commercial ANSYS FLUENT 16.2 CFD software were done. In this paper, an internal and external hypersonic flow cases were considered and analysis of the hypersonic flow using different turbulence viscosity models available in ANSYS FLUENT 16.2 as well as the laminar viscosity model were done. The obtained results were after compared and commented upon. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 35035

Assessment results of fluid-structure interaction numerical simulation using fuzzy logic

A fuzzy approximation concept is applied in order to predict results of coupled computational structure mechanics and computational fluid dynamics while solving a problem of steady incompressible gas flow through thermally loaded rectangular thin-walled channel. Channel wall deforms into wave - type shapes depending on thermal load and fluid inlet velocity inducing the changes of fluid flow accordingly. A set of fluid - structure interaction (FSI) numerical tests have been defined by varying the values of fluid inlet velocity, temperature of inner and outer surface of the channel wall and numerical grid density. The unsteady Navier-Stokes equations are numerically solved using an element-based finite volume method and second order backward Euler discretization scheme. The structural model is solved by finite element method including geometric and material nonlinearities. The implicit two-way iterative code coupling, partitioned solution approach, were used while solving these numerical tests. Results of numerical analysis indicate that gravity and pressure distribution inside the channel contributes to triggering the shape of deformation. In the inverse problem, the results of FSI numerical simulations formed a database of input variables for development fuzzy logic based models considering downstream pressure drop and maximum stresses as the objective functions. Developed fuzzy models predicted targeting results within a reasonable accuracy limit at lower computation cost compared to series of FSI numerical calculations. Smaller relative difference were obtained when calculating the values of pressure drop then maximal stresses indicating that transfer function influence on output values have to be additionally investigated. [Projekat Ministarstva nauke Republike Srbije, br. III42010, br.TR33050 i br. TR35035