Wszystkie pola: Sznajder, J. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Simulation of rime icing and its effects on aerodynamic characteristics of an airfoil
Autorzy:: Sznajder, J.
Powiązania:: https://bibliotekanauki.pl/articles/243475.pdf
Data publikacji:: 2018
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: computational fluid dynamics
aerodynamics
two-phase flow
simulation of ice accretion
heat exchange
aircraft engineering
transport
vehicle
Opis:: A mathematical model for simulation of icing dedicated to simulation of ice accretion and its effects on aircraft aerodynamic characteristics in conditions of rime icing is presented. Pure rime icing occurs at lower temperatures than glaze icing and results in higher roughness of the surface of deposited ice. The model accounts for increased surface roughness, in terms of equivalent sand grain roughness, caused by deposited rime ice, which influences generation and dispersion of heat in the boundary layer. Increase of surface roughness is determined by analytical models created upon experimental data obtained in icing wind tunnels. Increased generation of heat is a result of increased tangential stress on the surface and is quantified in the temperature recovery factor determined numerically by a CFD solver. Effects of surface roughness on the intensity of forced convection are quantified by application of Colburn analogy between heat and momentum transfer in the boundary layer, which allows assessment of heat transfer coefficient for known friction coefficient, determined by CFD. The computational method includes determination of the surface distribution of mass of captured water in icing conditions. The model of freezing of captured water accounts for generation of heat due to latent heat of captured water droplets, temperature recovery in boundary layer and kinetic energy of captured droplets. The sinks of heat include forced convection, heating of super cooled droplets, conduction of heat through the ice layer and sublimation. The mathematical model is implemented as user-defined function module in ANSYS Fluent solver. The results include effects of deposited ice, including increased surface roughness on aerodynamic characteristics of an airfoil.
Źródło:: Journal of KONES; 2018, 25, 3; 437-443
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Modeling of selected phenomena governing surface icing
Autorzy:: Sznajder, J.
Powiązania:: https://bibliotekanauki.pl/articles/248155.pdf
Data publikacji:: 2013
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: icing
transport
air transport
simulation
two-phase flow
Opis:: Atmospheric icing poses a threat for safety in many areas of transport, especially in air transport and exerts harmful impact on operation of external sensors and mechanisms of aircraft, ships and land vehicles. In order to investigate phenomena leading to ice accretion on sensitive parts of objects exposed to icing conditions numerical simulation models are in use. These models are typically composed of submodels dealing with a fragment of the complex phenomenon of ice accretion and its interaction with external flow. A practical approach to simulation of icing process is to divide it into three problems being solved interactively: 1) simulation of two-phase flow of air and dispersed supercooled water and determination of distribution of mass of water hitting the object’s surface, 2) determination of conditions on the surface collecting supercooled water from the external flow and simulation of freezing and water film flow, and 3) modification of computational grid as a consequence of change of shape of the surface with deposits of ice. A simulation system directed at investigation of atmospheric icing on moving object is being developed as an extension of capabilities of a commercial CFD code ANSYS FLUENT. Solutions of two-phase flow of air and dispersed water with specific boundary conditions enabling the determination of distribution of water hitting the surface, as well as results of modelling of water film flow on the surface will be presented. The system of equations describing the transport of the dispersed water consists of the continuity and momentum equations. It is assumed, that interactions between the phases are onedirectional, i.e. the air flow influences the water droplet flow and not vice-versa. It is also assumed that the water film velocity distribution is linear in direction normal to surface. This way, both phenomena are being described with first order partial differential equations with respect to space and time and the solution approaches may be similar.
Źródło:: Journal of KONES; 2013, 20, 2; 377-384
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Modification of aerodynamic wing loads by fluidic devices
Autorzy:: Stalewski, W.
Sznajder, J.
Powiązania:: https://bibliotekanauki.pl/articles/243884.pdf
Data publikacji:: 2014
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: transport
aircraft engineering
mechanical engineering
Opis:: Airplane wing load control systems are designed for modification/redistribution of aerodynamic loads in order to decrease risk of structural damage in conditions of excessive loads, to improve passenger comfort in turbulent atmosphere or to act as flight control systems. Classical examples include systems involving symmetric deflections of ailerons reducing wing root bending moments (Lockheed C-5 Galaxy) or deflections of spoilers stabilizing landing approach path (Lockheed TriStar). The fast development of Micro Electromechanical Systems and their application in Flow Control System opens the perspectives of designing practical wing load control systems based on fluidic actuators, modifying local aerodynamic loads by inducing changes to flow, for example, by inducing flow separation in the boundary layer or modifying Kutta condition on the trailing edge. This is the principle of operation of novel concepts of flow control actuators proposed by Institute of Aviation and discussed in the paper. The systems include actuators in the central part of the wing section, reducing local lift similarly to classical spoilers and actuators on the modified trailing edge, acting similarly to ailerons. The potential advantages in comparison to classical devices include potentially shorter reaction time because of avoiding the necessity of moving large surfaces against high dynamic pressure, which is important in conditions of fast-changing loads in turbulent atmosphere.
Źródło:: Journal of KONES; 2014, 21, 3; 271-278
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Analysis of effects of shape and location of micro-turbulators on unsteady shockwave-boundary layer interactions in transonic flow
Autorzy:: Sznajder, J.
Kwiatkowski, T.
Powiązania:: https://bibliotekanauki.pl/articles/242878.pdf
Data publikacji:: 2016
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: transonic flow control
laminar-turbulent transition
flow simulations
aircraft engineering
transport
vehicles
Opis:: Solutions for turbulisation of a part of laminar boundary layer upstream of shockwave on laminar airfoil in transonic flow were investigated by means of solution of Unsteady Reynolds-Averagd Navier-Stokes equations using as a closure the four-variable Transition SST turbulence model of ANSYS FLUENT solver. This turbulence model has the capability of resolving laminar-turbulent transition occurring in undisturbed flow as well as under the influence of flow-control devices. The aim of the work was to investigate possibilities of improvement of aerodynamic characteristics of laminar wing of a prospective transport aircraft in adverse conditions characterised by occurrence of a shockwave over a laminar-turbulent transition region with separation of laminar flow under the shockwave. The subject is important for application of laminar flow technology, offering economic and environmental advantages due to decreased friction drag, into civil transport aviation. Natural laminar-turbulent transition in the investigated conditions takes place with occurrence of “laminar separation bubble” under the foot of a shockwave and the resulting shockwave is intensive and prone to unsteady oscillations, the “buffet” phenomenon, limiting operational range of flight parameters. In order to counteract the harmful effects of natural laminar-turbulent transition in transonic flow two types of turbulators, placed upstream of the shockwave, were investigated. One of them consisted of delta-shaped vortex generators, producing chordwise-oriented vortices. The other consisted of rectangular micro-vanes, perpendicular to flow and to airfoil surface producing vortices of rotation axes oriented spanwise. Effectiveness of both types of turbulators was investigated for varying height and their location on airfoil chord. Both types of turbulators have proved their effectiveness in tripping laminar boundary layer. The specific effects of the tutbulators, different for each type occurred in the region where laminar separation takes place on clean airfoil. As a result, the changes of lift and drag were different for each type of turbulators.
Źródło:: Journal of KONES; 2016, 23, 2; 373-380
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Determination of ice deposit shape and ice accretion rate on airfoil in atmospheric icing conditions and its effects on airfoil characteristics
Autorzy:: Sznajder, J.
Sieradzki, A.
Stalewski, W.
Powiązania:: https://bibliotekanauki.pl/articles/242499.pdf
Data publikacji:: 2017
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: aerodynamics
two-phase flow
simulation of ice accretion
aircraft engineering
transport
vehicle
Opis:: Simulations of ice accretion on airfoil in icing conditions were conducted using ice accretion model implemented by authors in ANSYS FLUENT CFD solver. The computational model includes several sub-models intended for simulations of two-phase flow, determination of zones of water droplets impinging on the investigated surface, flow of water in a thin film on airfoil surface and heat balance in air-water-ice contact zone. The method operates in an iterative loop, which enables determination of effects of gradual deformation of aircraft surface on airflow over the surface, which has impact on distribution of collected water, flow of water film over the surface and local freezing rates. The implementation of the method in CFD solver made it necessary to complement the mathematical model of determination of local rates of deformation of aircraft surface with modification of computational mesh around the surface, which must conform, to the deformed surface. Results of simulated ice accretion on NACA 0012 airfoil were compared with results of experiment conducted in icing wind tunnel for a 420 s long process of ice accretion in steady-flow, steady angle-of-attack conditions. Close agreement of values and location of maximum ice thickness obtained in experiment and in the flow, simulations can be observed. For the airfoil deformed with ice, contour determination of its aerodynamic characteristics at several other angles of attack was conducted proving dramatic degradation of its aerodynamic characteristics due to ice deformation.
Źródło:: Journal of KONES; 2017, 24, 2; 271-278
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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