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Numerical experiments for turbulent flows
Trefilík, Jiří ; Kozel, Karel ; Příhoda, J.
The aim of the work is to explorethe possibilities of modelling transonic flowsin the internal and external aerodynamics. Several konfigurationswere analyzed and calculations were performed using both inviscid and viscous models of flow. Viscous turbulent flows have been simulated using either zero equation algebraic Baldwin-Lomax model and two equation k - w model in its basic version and improved TNT variant. The numerical solution was obtained using Lax-Wendroff scheme in the MAcCormack from on structured non-ortogonal grids. Artificial dissipation was added to improve the numerical stability. Achieved results are compared with experimental data.
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Oscillation pattern decomposition
Uruba, Václav
A new method for analysis spatio-temporal data is to be presented. The Oscillation Pattern Decomposition method is applicable on the dynamical velocity vector fields of turbulent flow coming from either mathematical simulation (DNS) or from experiment using an appropriate technique (time-resolved PIV). The OPD method is based on idea of identification of patterns rated according to their stability of appearance.
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Numerical Simulation of Turbulent Flow Affected by Vortex Generators in Straight Channel
Součková, Natálie ; Šimurda, David ; Uruba, Václav
The presented work is the next step after several experimental examinations of the vortex generator (VG) influence on flow separation occurring on a model of the NACA 63A421 airfoil with a deflected simple flap. The other purpose of this simulation is to obtain beneficial information that can be utilized for the preparation of the experimental investigation of the same configuration using Particle Image Velocimetry method (PIV) in the future. The numerical simulation was performed for one single pair and two pairs of low-profile VGs of the same size, whose heights were smaller than the boundary layer thickness. The rectangular vane type VGs in such configuration, which generates counter-rotating vortices, was examined. The behaviour of vortices produced by VG pair or pairs in several positions downstream the VGs is investigated and will be used as a background of the measurement.
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Srovnávací studie měřících technik ADV a LDA
Chára, Zdeněk ; Matoušek, V.
The contribution compares measurements of local velocities for water flows of different configurations carried out with the help of the ADV (Acoustic Doppler Velocimeter) and LDA (Laser Doppler Anemometry) measuring techniques. Three different geometrical configurations were tested – open channel flow, flow behind a rectangular cylinder and flow behind a hole in a plate.
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Turbulent flow near the wall
Jaňour, Zbyněk
Models of turbulent flow are derived under assuption that the turbulent Reynolds number is high. This assumption is fulfilled far from the wall. Because of non-slip condition on the wall it is necessary to take into account the molecular viscosity near the surface. Following solution of this problem are described by: wall function method, equation of motion modification and simple model of coherent structure near the wall introduction
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Numerické řešení sdílení tepla v proudu dopadajícím na stěnu
Kozel, K. ; Louda, Petr ; Příhoda, Jaromír
The paper deals with the numerical solution of 3D impinging turbulent jet cooling a weakly heated wall. The solution was carried out using the SST model and/or an explicit algebraic Reynolds stress model and completed by a generalized gradient-diffusion hypothesis for modelling of turbulent heat flux. While the EARSM model gives good results for the velocity field, all used models overestimate heat transfer in the impingement region.
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Measurement of the velocity field in a ribbed channel
Chára, Zdeněk
The contribution deals with an experimental investigation of the turbulent along a ribbed channel bottom. The main goal is an application of ultrasound velocity profile technique for measurement of the turbulent flow characteristics in complex geometries. Four configurations of the ribbed surfaces were tested with fixed ribs of square cross section and variable groove widths. The experiments were performed in a water channel.
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