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Accurate prediction of secondary flows and associated heat transfer phenomena in a cascade of turbine blades or vanes remains to be a challenging task, despite the great effort made in this area for several past decades. In a revi...
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Accurate prediction of secondary flows and associated heat transfer phenomena in a cascade of turbine blades or vanes remains to be a challenging task, despite the great effort made in this area for several past decades. In a review of secondary flow literature, covering up to 2000, Langston [1] has stated also achievements and shortcomings of secondary flow CFD predictions at that moment. The present contribution objective is to reveal the progress achieved for the last decade. The main focus is on prediction of the horseshoe vortex system and endwall heat transfer.
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Results of direct numerical simulations for time-developing air natural-convection boundary layer are presented. Computations have been performed assuming periodicity conditions in both the directions parallel to the vertical isot...
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Results of direct numerical simulations for time-developing air natural-convection boundary layer are presented. Computations have been performed assuming periodicity conditions in both the directions parallel to the vertical isothermal hot plate. The contribution is mainly focused on understanding of laminar-turbulent transition peculiarities in the case of perturbation action of external turbulence that is modeled by isotropic disturbances initially introduced into the computational domain. Special attention is paid to identification and analysis of evolving three-dimensional vortices that clearly manifest themselves through the whole stages of laminar-turbulent transition in the boundary layer. A comparison of computed profiles of mean velocity, mean temperature and fluctuation characteristics for turbulent regimes of convection with experimental data is performed as well.
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The obtained results of direct numerical simulation of the free mercury convection in a rotating cylindrical container heated from below are presented. Setting the Prandtl number equal to 0.025 and the height-to-diameter ratio equ...
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The obtained results of direct numerical simulation of the free mercury convection in a rotating cylindrical container heated from below are presented. Setting the Prandtl number equal to 0.025 and the height-to-diameter ratio equal to 1.0, effects of container rotation and heat transfer in horizontal solid walls have been studied. The effective Rayleigh number was close to 106. The Navier–Stokes equations, written with the Boussinesq approximation, were solved using the fractional-step method. The instant and time-averaged flow fields, the pulsation spectra and the integral heat transfer data were analyzed. The in-house code SINF/Flag-S results were compared with the available experimental data, and with the data obtained using the commercial software ANSYS Fluent 15.0.
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Ventilation characteristics of the Columbus module are numerically predicted on the basis of the Reynolds- Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) approaches. The steady-state RANS computations were performed...
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Ventilation characteristics of the Columbus module are numerically predicted on the basis of the Reynolds- Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) approaches. The steady-state RANS computations were performed using the high-Reynolds-number kappa-epsilon turbulence model, and the Smagorinsky- Lilly subgrid-scale model was used for LES. The computed results were compared with experimental data available for spatial distributions of the time-averaged absolute velocity magnitude. On the basis of LES data, distinctions in the fields of this quantity and the whole mean velocity were analysed. A procedure for evaluation of the time-averaged absolute velocity spatial distributions using RANS data on the mean velocity and the turbulent kinetic energy is suggested and examined.
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Results of the numerical simulation of turbulent flow field and heat transfer of liquid metal in cross-flow over inline tube bundles consisting of smooth round tubes are presented. Computations have been performed with CFD-code AN...
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Results of the numerical simulation of turbulent flow field and heat transfer of liquid metal in cross-flow over inline tube bundles consisting of smooth round tubes are presented. Computations have been performed with CFD-code ANSYS Fluent on the base of a two-dimensional unsteady RANS formulation using the SST turbulence model by Menter and assuming constant physical properties of a fluid with the Prandtl number equal to 0.023. The Reynolds number ranged from 26,200 to 52,400. Instantaneous and time-averaged velocity and temperature fields obtained for bundles of different intertube spacing with a variation of the bundle width (number of tube rows in the cross direction) were analyzed. Integral characteristics of heat transfer were compared with the experimental data.
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Investigation of weakly swirling flow in a model of a blood vessel with asymmetrical stenosis has been performed using both experimental flow measurement techniques (ultrasound Doppler) and computational fluid dynamics methods. A ...
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Investigation of weakly swirling flow in a model of a blood vessel with asymmetrical stenosis has been performed using both experimental flow measurement techniques (ultrasound Doppler) and computational fluid dynamics methods. A special attention is paid to getting data for the length of the reverse-flow zone occurring past the stenosis. It has been established that the laminar steady-state flow model is acceptable for numerical analysis of flow past the given-geometry stenosis at Reynolds number values less than 300. At higher values of this parameter, application of the semi-empirical k-ω SST turbulence model is preferable. It has been shown that flow swirl can lead to an increase of the reverse-flow zone.
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A numerical study of the secondary flow in two geometrically different models of a common carotid artery has been carried out. One of the models (Model 1) is characterized by a statistically averaged curvature, and the second one ...
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A numerical study of the secondary flow in two geometrically different models of a common carotid artery has been carried out. One of the models (Model 1) is characterized by a statistically averaged curvature, and the second one (Model 2) is attributed to the maximal curvature of the artery. It was shown that the most intensive swirl occurred at the phase of flow rate decreasing, the maximum values of the swirl parameters were observed at the interface of the cervical and thoracic segments of the artery. This interface is the place where the Dean vortices are transformed into a single vortex forming a swirling flow. The swirl intensity averaged over the systole and characterized by the ratio of the maximal values of the axial and circumferential velocities was evaluated as 0.20 for Model 1 and 0.25 for Model 2. Generally, it was in accordance with the data of clinical measurements.
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The objective of this study is to evaluate ventilation efficiency regarding to the International Space Station (ISS) cabin ventilation during the ISS assembly mission 1J. The focus is on carbon dioxide spatial/temporal variations ...
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The objective of this study is to evaluate ventilation efficiency regarding to the International Space Station (ISS) cabin ventilation during the ISS assembly mission 1J. The focus is on carbon dioxide spatial/temporal variations within the Node 2 and attached modules. An integrated model for CO_2 transport analysis that combines 3D CFD modeling with the lumped parameter approach has been implemented. CO_2 scrubbing from the air by means of two ISS removal systems is taken into account. It has been established that the ventilation scheme with an ISS Node 2 bypass duct reduces short-circuiting effects and provides less CO_2 gradients when the Space Shuttle Orbiter is docked to the ISS. This configuration results in reduced CO_2 level within the ISS cabin.
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The paper presents the results of a CFD study for predictions of ventilation characteristics and convective heat transfer within the Shuttle Orbiter middeck cabin in the presence of seven suited crewmember simulation and Individua...
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The paper presents the results of a CFD study for predictions of ventilation characteristics and convective heat transfer within the Shuttle Orbiter middeck cabin in the presence of seven suited crewmember simulation and Individual Cooling Units (ICU). For two ICU arrangements considered, the thermal environmental conditions directly affecting the ICU performance have been defined for landing operation. These data would allow for validation of the ICU arrangement optimization.
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