Numerical simulation and analysis of the transition to turbulence

2007 ◽  
pp. 1-13
Author(s):  
Ch.-H. Bruneau
Keyword(s):  
Numerical Simulation ◽  
Transition To Turbulence

High Rayleigh Number Flows in a Cubical Enclosure

2005 ◽  
Author(s):  
Lucas Vargas ◽  
Ikram Ahmed ◽  
David N. Koert
Keyword(s):  
Numerical Simulation ◽  
Rayleigh Number ◽  
Prandtl Number ◽  
Turbulent Flows ◽  
State Of The Art ◽  
Transition To Turbulence ◽  
Computing Technology ◽  
Chaotic Flows ◽  
Convective Flows ◽  
Cubical Enclosure

High Rayleigh number (Ra) natural convective flows in cubical enclosures were investigated using Direct Numerical Simulation (DNS). Here the bottom of the cavity was heated while the top was cooled, each maintained at a different constant temperature, with the sidewalls insulated. The Prandtl number was maintained at 2.5 and the Ra varied between 106 and 108. In order to observe the transition to turbulence with increasing Ra, power spectrum slopes were compared with Kolmogorov’s −5/3 rule for turbulent flows. At the higher Ra studied, the flows showed characteristics typically attributed to “chaotic” flows. However, the transition to full turbulence was not observed, which is expected around Ra ∼ 109 and may not be predicted using DNS with the state-of-the-art computing technology.

Direct numerical simulation of the flow over a sphere at Re = 3700

2011 ◽  
Vol 679 ◽  
pp. 263-287 ◽  
Author(s):  
IVETTE RODRIGUEZ ◽  
RICARD BORELL ◽  
ORIOL LEHMKUHL ◽  
CARLOS D. PEREZ SEGARRA ◽  
ASSENSI OLIVA
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Shear Layer ◽  
Large Scale ◽  
Power Spectra ◽  
Numerical Data ◽  
Transition To Turbulence ◽  
Stream Velocity ◽  
Sphere Diameter ◽  
Mean Flow

The direct numerical simulation of the flow over a sphere is performed. The computations are carried out in the sub-critical regime at Re = 3700 (based on the free-stream velocity and the sphere diameter). A parallel unstructured symmetry-preserving formulation is used for simulating the flow. At this Reynolds number, flow separates laminarly near the equator of the sphere and transition to turbulence occurs in the separated shear layer. The vortices formed are shed at a large-scale frequency, St = 0.215, and at random azimuthal locations in the shear layer, giving a helical-like appearance to the wake. The main features of the flow including the power spectra of a set of selected monitoring probes at different positions in the wake of the sphere are described and discussed in detail. In addition, a large number of turbulence statistics are computed and compared with previous experimental and numerical data at comparable Reynolds numbers. Particular attention is devoted to assessing the prediction of the mean flow parameters, such as wall-pressure distribution, skin friction, drag coefficient, among others, in order to provide reliable data for testing and developing statistical turbulence models. In addition to the presented results, the capability of the methodology used on unstructured grids for accurately solving flows in complex geometries is also pointed out.

Modeling Transition to Turbulence in Eccentric Stenotic Flows

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Sonu S. Varghese ◽  
Steven H. Frankel ◽  
Paul F. Fischer
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Turbulence Models ◽  
Transition To Turbulence ◽  
Mean Flow ◽  
Poor Agreement ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Simulation Results

Mean flow predictions obtained from a host of turbulence models were found to be in poor agreement with recent direct numerical simulation results for turbulent flow distal to an idealized eccentric stenosis. Many of the widely used turbulence models, including a large eddy simulation model, were unable to accurately capture the poststenotic transition to turbulence. The results suggest that efforts toward developing more accurate turbulence models for low-Reynolds number, separated transitional flows are necessary before such models can be used confidently under hemodynamic conditions where turbulence may develop.

G0700-3-4 Numerical simulation of the transition to turbulence in an engine

2010 ◽  
Vol 2010.3 (0) ◽  
pp. 97-98
Author(s):  
Satoshi TANAKA ◽  
Shou KIMURA ◽  
Ken NAITOH
Keyword(s):  
Numerical Simulation ◽  
Transition To Turbulence
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