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Wyszukujesz frazę "transonic" wg kryterium: Temat


Tytuł:
The effects of lean and sweep on transonic fan performance a computational study
Autorzy:
Denton, J. D.
Tematy:
transonic fan
transonic compressor
three-dimensional flow
shock waves
CFD
Pokaż więcej
Wydawca:
Politechnika Gdańska
Powiązania:
https://bibliotekanauki.pl/articles/1986819.pdf  Link otwiera się w nowym oknie
Opis:
The aerodynamics of transonic fans is discussed with emphasis on the use of three-dimensional design techniques, such as blade sweep and lean, to improve their performance. In order to study the interaction of these 3D features with the shock pattern a series of five different designs is produced and analysed by CFD. It is found that the 3D features have remarkably little effect on the shock pattern near the tip where the shock must remain perpendicular to the casing. Lower down the blade significant shock sweep, and hence reduced shock loss, can be induced by 3D design but this is usually at the expense of reduced stall margin and increased loss elsewhere along the blade span. Overall, very little change in efficiency is produced by blade sweep or lean. However, forwards lean of the rotor does produce a small increase in mass flow. Radial migration of the boundary fluid on the suction surface behind the shock is shown to play a large part in the aerodynamics near the blade tip.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Condensation wave identification in moist air transonic flows through nozzles
Autorzy:
Dykas, S.
Smołka, K.
Majkut, M.
Strozik, M.
Tematy:
air
transonic flows
condensation
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Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/175576.pdf  Link otwiera się w nowym oknie
Opis:
This paper identifies the location of water vapour spontaneous condensation during air expansion in convergent-divergent nozzles. The comprehensive analysis proposed herein includes an analytical solution together with experimental and numerical investigations. Numerical calculations are performed using an in-house computational fluid dynamics code based on the solution of Reynolds averaged Navier-Stokes equations supplemented with additional partial differential equations modelling the condensation process of water vapour contained in atmospheric air. Experiments were carried out using an in-house facility adapted for measurements of atmospheric air transonic flows.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of model helicopter rotor in hover
Autorzy:
Doerffer, P.
Szulc, O.
Tematy:
transonic
hover
helicopter rotor
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Wydawca:
Politechnika Gdańska
Powiązania:
https://bibliotekanauki.pl/articles/1943245.pdf  Link otwiera się w nowym oknie
Opis:
The article presents details of a URANS simulation of the flow field near a hovering model of the Caradonna and Tung (1981) helicopter rotor [1]. The CFD code SPARC [2] proves to be capable of capturing the aerodynamics of a two-bladed rotor in high-speed transonic hover conditions. A comparison of the simulation results with the experimental data is acceptable, hence the described methodology might be used with confidence in future numerical studies of application of noise-reducing devices on helicopter blades.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Aerodynamic Research on the Midsection of a Long Turbine Blade
Autorzy:
Šimurda, D.
Luxa, M.
Šafařík, P.
Synáč, J.
Tematy:
transonic flow
turbine blade cascade
experimental research
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Wydawca:
Politechnika Gdańska
Powiązania:
https://bibliotekanauki.pl/articles/1943255.pdf  Link otwiera się w nowym oknie
Opis:
The paper is concerned with experimental aerodynamic research on the midsection of a 1220mm long turbine rotor blade. Optical as well as pneumatic measurements of the midsection blade cascade have been performed in a suction type high-speed wind tunnel. The results of measurements are analyzed and discussed. Interferograms and schlieren pictures taken in a wide range of isentropic exit Mach numbers and incidence angles exhibit the existence of several phenomena occurring in the transonic flow field at certain conditions concerning the exit Mach number and the angle of incidence. A flow separation taking place at an extreme negative incidence has been found to produce an additional loss of 6%. The presence of the reflection of an exit shock wave on the suction side of the neighbouring profile has been found to have a substantial influence on the losses, since the loss coefficient value has increased about 10% in cases without the reflection, i.e. the cases at a high exit Mach number and a high positive angle of incidence. Several reflection types have been observed and described.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of hybrid CFD/CAA technique for modeling pressure fluctuations in transonic flows
Autorzy:
Dykas, S.
Wróblewski, W.
Rulik, S.
Tematy:
transonic flow
aeroacoustic noise
hybrid technique
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Wydawca:
Politechnika Gdańska
Powiązania:
https://bibliotekanauki.pl/articles/1955297.pdf  Link otwiera się w nowym oknie
Opis:
Solving AeroAcoustics (CAA) problems by means of the Direct Numerical Simulation (DNS) or even the Large Eddy Simulation (LES) for a large computational domain is very time consuming and cannot be applied widely for engineering purposes. In this paper in-house CFD and CAA codes are presented. The in-house CFD code is based on the LES approach whereas the CAA code is an acoustic postprocessor solving non-linearized Euler equations for fluctuating (acoustic) variables. These codes are used to solve the pressure waves generated aerodynamically by a flow over a rectangular cavity and by the vortex street behind a turbine blade. The obtained results are discussed with respect to the application of the presented numerical techniques to pressure waves modeling in steam turbine stages.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Flow simulation at shock wave triple point
Autorzy:
Doerffer, P.
Namieśnik, K.
Magagnato, F.
Tematy:
transonic flow
shock waves
lambda-foot
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Wydawca:
Politechnika Gdańska
Powiązania:
https://bibliotekanauki.pl/articles/1967643.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents supersonic flow simulation results concerning the lambda-foot formation in the divergent nozzle. The SPARC code was used and the vicinity of the triple point was analysed. Special boundary conditions have been used in order to obtain supersonic inlet velocity with shock wave in the divergent nozzle. It was proved that the condition of pressure equality on both sides of shear layer following the triple point for flow parameter of interest, does not hold.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of limiting walls on shock wave structure in single passage test section with compressor profile
Autorzy:
Piotrowicz, M.
Flaszyński, P.
Szwaba, R.
Tematy:
shock wave
laminar-turbulent transition
transonic compressor
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Wydawca:
Politechnika Gdańska
Powiązania:
https://bibliotekanauki.pl/articles/1938636.pdf  Link otwiera się w nowym oknie
Opis:
The shock wave boundary layer interaction on the suction side of a transonic compressor blade is one of the main objectives of the TFAST project (Transition Location Effect on Shock Wave Boundary Layer Interaction). In order to look more closely into the flow structure on the suction side of the blade, a design of a turbine passage model in a rectilinear transonic wind tunnel was proposed. The model which could reproduce the flow structure, the shock wave location, the pressure distribution and the boundary layer development similar to the obtained in a reference cascade profile is the main objective of the design presented here. The design of the proposed test section is very challenging, because of the existence of a shock wave, its interaction with the boundary layer and its influence on the 3-D flow structure in the test section. The paper presents the influence of the test section geometry configuration on the flow structure as an effect of the shock wave boundary layer interaction.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unsteady Shock Wave: Turbulent boundary layer interaction in the Laval Nozzle
Autorzy:
Doerffer, P.
Szulc, O.
Magagnato, F.
Tematy:
unsteady transonic flow
shock waves
nozzle flow
Pokaż więcej
Wydawca:
Politechnika Gdańska
Powiązania:
https://bibliotekanauki.pl/articles/1965143.pdf  Link otwiera się w nowym oknie
Opis:
The flow in transonic diffusers and supersonic air intakes often becomes unsteady due to shock wave-boundary layer interaction. Oscillations may be induced by natural separation unsteadiness or forced by boundary conditions. Significant improvements of CFD tools, increased computer resources and the development of experimental methods have again drawn the attention of researchers to this topic. Forced oscillations of a transonic turbulent flow in an asymmetric two-dimensional Laval nozzle have been considered to investigate the problem. A viscous, perfect gas flow was numerically simulated using SPARC, a Reynolds-averaged compressible Navier-Stokes solver, employing a two-equation, eddy viscosity, turbulence closure in the URANS approach. For time-dependent and stationary flow simulations, Mach numbers upstream of the shock between 1.2 and 1.4 were considered. Comparison of computed and experimental data for steady states generally gave acceptable agreement. In the case of forced oscillations, a harmonic pressure variation was prescribed at the exit plane resulting in shock wave motion. Excitation frequencies between 0Hz and 1024Hz were investigated at a constant pressure amplitude. The main result of the work is the relation between the amplitude of shock wave motion and the excitation frequency in the investigated range. Increasing excitation frequency resulted in decreasing amplitude of the shock movement. At high frequencies, a natural mode of shock oscillation (of small amplitude) was observed, which was insensitive to forced excitement.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Turbulent triggers and the model quality influence on aerodynamic characteristics of the laminar aerofoil in transonic flow regime
Autorzy:
Placek, Robert
Ruchała, Paweł
Tematy:
transonic flow
aerofoil
model quality
aerodynamic characteristics
shock wave
Pokaż więcej
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/245279.pdf  Link otwiera się w nowym oknie
Opis:
The test with a roughness application on the laminar aerofoil has been conducted in the N-3 trisonic wind tunnel of the Institute of Aviation in Warsaw. The main goal of tests was to investigate the influence of the boundary layer transition triggers on a laminar profile aerodynamic characteristic. For baseline configuration, the natural transition was applied. As a local roughness on the upper model surface, the carborundum strips with different heights were applied. These were positioned on the upper model surface in the front of the shock position occurrence. The Mach number during test was equal Ma = 0.7 and Reynolds number was about 2.85·106 . Tests have been conducted for different model incidence in range 0º-7º. Current article refers partially to the previous study, where aerofoil model with lower quality of surface had been tested. Investigation results from previous work indicated that some of transition positions improved an aerodynamic characteristic by reducing the drag coefficient value and decreasing shock wave unsteadiness in the transonic regime. However, current article indicates that beneficial effects in respect to the baseline configuration are also strictly dependent on the model quality and turbulent triggers size. Improved surface quality of the laminar aerofoil model affected on aerodynamic characteristics with and without turbulent triggers. Resultant aerodynamic coefficients of all tested cases i.e. drag, lift and lift to drag ratio were compared.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PIV measurements of flow separation over laminar airfoil at transonic speeds
Autorzy:
Stryczniewicz, W.
Placek, R.
Szczepaniak, R.
Tematy:
shock wave
transonic flow
boundary layer separation
Particle Image Velocimetry
Pokaż więcej
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/247542.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents results of transonic flow field visualization over a laminar airfoil in high-speed wind tunnel. Quite recently, considerable attention has been paid to experimental investigations of an interaction between the shock and the boundary layer for aerodynamics applications. The purpose of the paper is to investigate development of the flow separation over laminar airfoil at transonic speeds. In a course of presented studies, the Particle Image Velocimetry (PIV) method was used for instantaneous velocity measurements of flow field in the test section of N-3 Institute of Aviation transonic wind tunnel. The object of the research was a laminar airfoil inclined at various angles. The effect of the varying angle of incidence on the flow filed was investigated. The freestream Mach number was 0.7. The results of the PIV measurements were analysed in order to identify the type of the separation from the measured velocity fields. Three forms of separation for low, medium and high angle of incidence was distinguished. The results are in good agreement with theoretical models reported in the literature. The study showed that application of quantitative flow visualisation technique allowed gaining new insights on the complex phenomenon of transonic flow over airfoil. The results of the presented research can be used for better understanding of the mechanism of the flow separation process in transonic flow over airfoils and fluid structure interactions.
Dostawca treści:
Biblioteka Nauki
Artykuł

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