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Stability of supersonic boundary layer on permeable surface

100%

Gaponov S. A. , Ermolaev Y. G. , Kosinov A. D. , Lysenko V. I. , Semionov N. V. , Smorodsky B. V.

tom Vol. 66, nr 6

453--466

In the present study we have performed combined theoretical and experimental investigation of the surface permeability influence on the linear stability of the supersonic flat-plate boundary layer at free-stream Mach number M = 2. Good quantitative agreement was obtained between the data calculated by the linear theory of stability and the data obtained in experiments with artificially generated disturbances performed on models with various porous inserts.

Modelling of Influence of Turbulent Transition on Heat Transfer Conditions

100%

Bochon K. , Wróblewski W. , Dykas S.

tom Vol. 12, No 3-4

173-184

This article deals with the turbulent transition phenomenon modelling and its influence on heat transfer. The purpose of the analyses was to verify the transition modelling implemented in the ANSYS CFX 11 commercial code for popular test cases (low flow speed) described in literature, and then use it for verification of the in-house CFD code (created for compressible flows). The inhouse CFD code has been extended lately for the Conjugate Heat Transfer modelling (CHT) as well, taking into account important flow effects, especially the turbulent transition. A Wilcox k-omega turbulence model with the Low-Reynolds modification was used in the in-house code. The calculations in ANSYS CFX were made using an SST turbulence model and a gamma-theta transition model. A fully turbulent flow was modelled by means of both codes, and the results were compared with the available experimental data. Then, the turbulent transition for several test cases was analysed with ANSYS CFX. Afterwards, the in-house CFD code was verified by means of ANSYS CFX for a higher flow speed (Mach numbers). The CHT modelling was analysed by means of both codes and the results were compared and discussed. The conducted analyses show that the results obtained by means of both codes are comparable, but the turbulence model used in the in-house CFD code is simpler and requires less computation time. A modification of two equations turbulence models can be an alternative for design problems in more developed laminar/turbulent flows.

Numerical Investigations of Taylor-Couette Flow Using DNS/SVV Method

88%

Tuliszka-Sznitko E. , Kiełczewski K.

tom Vol. 21, No. 4

211--219

In the paper the authors present the results obtained during a numerical investigation (Direct Numerical Simulation/ Spectral Vanishing Viscosity method – DNS/SVV) of a Taylor-Couette flow, i.e. the flow between two concentric disks and two concentric cylinders. The Taylor-Couette flow is one of paradigmatical systems in hydrodynamics, widely used for studying the primary instability, pattern formation, transitional flows and fully turbulent flows. Simultaneously, the flows in rotating cavities appear in numerous machines in the field of mechanics and chemistry, e.g., in cooling systems of gas turbines and axial compressors. In the paper, attention is focused on the laminar-turbulent transition region of the Taylor-Couette flow. The main purpose of the computations is to investigate the influence of different parameters (the aspect ratio, the end-wall boundary conditions, temperature gradient) on the flow structure and on flow characteristics.