Effect of compressibility on the local flow topology in homogeneous shear turbulence

2020 ◽  
Vol 32 (1) ◽  
pp. 015118
Keyword(s):  
Flow Topology ◽  
Local Flow ◽  
Homogeneous Shear ◽  
Shear Turbulence

Effect of heat source on statistics and scaling in compressible homogeneous shear turbulence

2021 ◽  
Vol 33 (12) ◽  
pp. 125128
Author(s):  
Yuandong Chen ◽  
Xiaoning Wang ◽  
Zhou Jiang ◽  
Jianchun Wang
Keyword(s):  
Heat Source ◽  
Homogeneous Shear ◽  
Shear Turbulence

scholarly journals Flow topologies in bubble-induced turbulence: a direct numerical simulation analysis

2018 ◽  
Vol 857 ◽  
pp. 270-290 ◽  
Author(s):  
Josef Hasslberger ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Small Scale ◽  
Flow Topology ◽  
Two Phase ◽  
Local Flow ◽  
Interface Curvature

This paper presents a detailed investigation of flow topologies in bubble-induced two-phase turbulence. Two freely moving and deforming air bubbles that have been suspended in liquid water under counterflow conditions have been considered for this analysis. The direct numerical simulation data considered here are based on the one-fluid formulation of the two-phase flow governing equations. To study the development of coherent structures, a local flow topology analysis is performed. Using the invariants of the velocity gradient tensor, all possible small-scale flow structures can be categorized into two nodal and two focal topologies for incompressible turbulent flows. The volume fraction of focal topologies in the gaseous phase is consistently higher than in the surrounding liquid phase. This observation has been argued to be linked to a strong vorticity production at the regions of simultaneous high fluid velocity and high interface curvature. Depending on the regime (steady/laminar or unsteady/turbulent), additional effects related to the density and viscosity jump at the interface influence the behaviour. The analysis also points to a specific term of the vorticity transport equation as being responsible for the induction of vortical motion at the interface. Besides the known mechanisms, this term, related to surface tension and gradients of interface curvature, represents another potential source of turbulence production that lends itself to further investigation.

scholarly journals Flow topologies in primary atomization of liquid jets: a direct numerical simulation analysis

2018 ◽  
Vol 859 ◽  
pp. 819-838 ◽  
Author(s):  
Josef Hasslberger ◽  
Sebastian Ketterl ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Incompressible Flows ◽  
Flow Structures ◽  
Liquid Jets ◽  
Small Scale ◽  
Flow Topology ◽  
Local Flow ◽  
Turbulent Length Scale

The local flow topology analysis of the primary atomization of liquid jets has been conducted using the invariants of the velocity-gradient tensor. All possible small-scale flow structures are categorized into two focal and two nodal topologies for incompressible flows in both liquid and gaseous phases. The underlying direct numerical simulation database was generated by the one-fluid formulation of the two-phase flow governing equations including a high-fidelity volume-of-fluid method for accurate interface propagation. The ratio of liquid-to-gas fluid properties corresponds to a diesel jet exhausting into air. Variation of the inflow-based Reynolds number as well as Weber number showed that both these non-dimensional numbers play a pivotal role in determining the nature of the jet break-up, but the flow topology behaviour appears to be dominated by the Reynolds number. Furthermore, the flow dynamics in the gaseous phase is generally less homogeneous than in the liquid phase because some flow regions resemble a laminar-to-turbulent transition state rather than fully developed turbulence. Two theoretical models are proposed to estimate the topology volume fractions and to describe the size distribution of the flow structures, respectively. In the latter case, a simple power law seems to be a reasonable approximation of the measured topology spectrum. According to that observation, only the integral turbulent length scale would be required as an input for the a priori prediction of the topology size spectrum.

scholarly journals Decay and growth laws in homogeneous shear turbulence

2016 ◽  
Vol 17 (7) ◽  
pp. 699-726 ◽  
Author(s):  
Antoine Briard ◽  
Thomas Gomez ◽  
Vincent Mons ◽  
Pierre Sagaut
Keyword(s):  
Homogeneous Shear ◽  
Growth Laws ◽  
Shear Turbulence

Topological evolution in compressible turbulent boundary layers

2013 ◽  
Vol 733 ◽  
pp. 414-438 ◽  
Author(s):  
You-Biao Chu ◽  
Xi-Yun Lu
Keyword(s):  
Boundary Layers ◽  
Evolution Equations ◽  
Turbulent Boundary Layers ◽  
Rate Of Change ◽  
Power Law Distribution ◽  
Flow Topology ◽  
Local Flow ◽  
Compressibility Effect ◽  
Topological Evolution ◽  
The Mean

AbstractTopological evolution of compressible turbulent boundary layers at Mach 2 is investigated by means of statistical analysis of the invariants of the velocity gradient tensor based on the direct numerical simulation database. The probability density functions of the rate of change of the invariants exhibit the $- 3$ power-law distribution in the region of large Lagrangian derivative of the invariants in the inner and outer layers. The topological evolution is studied by conditional mean trajectories for the evolution of the invariants. The trajectories illustrate inward-spiralling orbits around and converging to the origin of the space of invariants in the outer layer, while they are repelled by the vicinity of the origin and converge towards a limit cycle in the inner layer. The compressibility effect on the mean topological evolution is studied in terms of the ‘incompressible’, compressed and expanding regions. It is found that the mean evolution of flow topologies is altered by the compressibility. The evolution equations of the invariants are derived and the relevant dynamics of the mean topological evolution are analysed. The compressibility effect is mainly related to the pressure effect. The mutual-interaction terms among the invariants are the root of the clockwise spiral behaviour of the local flow topology in the space of invariants.

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