Solenoidal linear forcing for compressible, statistically steady, homogeneous isotropic turbulence with reduced turbulent Mach number oscillation

2021 ◽  
Vol 33 (9) ◽  
pp. 095108
Author(s):  
T. Watanabe ◽  
K. Tanaka ◽  
K. Nagata
Keyword(s):  
Mach Number ◽  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence

scholarly journals Turbulence decay in the density-stratified intracluster medium

2019 ◽  
Vol 487 (1) ◽  
pp. 1072-1081 ◽  
Author(s):  
Xun Shi ◽  
Congyao Zhang
Keyword(s):  
Mach Number ◽  
Gravitational Potential ◽  
Energy Flow ◽  
Density Fluctuation ◽  
Isotropic Turbulence ◽  
Density Stratification ◽  
Intracluster Medium ◽  
Energy Evolution ◽  
Homogeneous Isotropic Turbulence ◽  
Number Relation

Abstract Turbulence evolution in a density-stratified medium differs from that of homogeneous isotropic turbulence described by the Kolmogorov picture. We evaluate the degree of this effect in the intracluster medium (ICM) with hydrodynamical simulations. We find that the buoyancy effect induced by ICM density stratification introduces qualitative changes to the turbulence energy evolution, morphology, and the density fluctuation–turbulence Mach number relation, and likely explains the radial dependence of the ICM turbulence amplitude as found previously in cosmological simulations. A new channel of energy flow between the kinetic and the potential energy is opened up by buoyancy. When the gravitational potential is kept constant with time, this energy flow leaves oscillations to the energy evolution, and leads to a balanced state of the two energies where both asymptote to power-law time evolution with slopes shallower than that for the turbulence kinetic energy of homogeneous isotropic turbulence. We discuss that the energy evolution can differ more significantly from that of homogeneous isotropic turbulence when there is a time variation of the gravitational potential. Morphologically, ICM turbulence can show a layered vertical structure and large horizontal vortical eddies in the central regions with the greatest density stratification. In addition, we find that the coefficient in the linear density fluctuation–turbulence Mach number relation caused by density stratification is in general a variable with position and time.

Direct numerical simulation of decaying homogeneous isotropic turbulence — numerical experiments on stability, consistency and accuracy of distinct lattice Boltzmann methods

2019 ◽  
Vol 30 (09) ◽  
pp. 1950074 ◽  
Author(s):  
Marc Haussmann ◽  
Stephan Simonis ◽  
Hermann Nirschl ◽  
Mathias J. Krause
Keyword(s):  
Relaxation Time ◽  
Mach Number ◽  
Lattice Boltzmann ◽  
Numerical Experiments ◽  
Isotropic Turbulence ◽  
Reynolds Numbers ◽  
Homogeneous Isotropic Turbulence ◽  
Energy Contribution ◽  
Stability And Accuracy ◽  
The Impact

Stability, consistency and accuracy of various lattice Boltzmann schemes are investigated by means of numerical experiments on decaying homogeneous isotropic turbulence (DHIT). Therefore, the Bhatnagar–Gross–Krook (BGK), the entropic lattice Boltzmann (ELB), the two-relaxation-time (TRT), the regularized lattice Boltzann (RLB) and the multiple-relaxation-time (MRT) collision schemes are applied to the three-dimensional Taylor–Green vortex, which represents a benchmark case for DHIT. The obtained turbulent kinetic energy, the energy dissipation rate and the energy spectrum are compared to reference data. Acoustic and diffusive scaling is taken into account to determine the impact of the lattice Mach number. Furthermore, three different Reynolds numbers [Formula: see text], [Formula: see text] and [Formula: see text] are considered. BGK shows instabilities, when the mesh is highly underresolved. The diverging simulations for MRT are ascribed to a strong lattice Mach number dependency. Despite the fact that the ELB modifies the bulk viscosity, it does not mimic a turbulence model. Therefore, no significant increase of stability in comparison to BGK is observed. The TRT “magic parameter” for DHIT at moderate Reynolds numbers is estimated with respect to the energy contribution. Stability and accuracy of the TRT scheme is found to be similar to BGK. For small lattice Mach numbers, the RLB scheme exhibits lowered energy contribution in the dissipation range compared to an analytical model spectrum. Overall, to enhance stability and accuracy, the lattice Mach number should be chosen with respect to the applied collision scheme.

Small-scale energy cascade in homogeneous isotropic turbulence

2019 ◽  
Vol 4 (10) ◽  
Author(s):  
Mohamad Ibrahim Cheikh ◽  
James Chen ◽  
Mingjun Wei
Keyword(s):  
Isotropic Turbulence ◽  
Energy Cascade ◽  
Small Scale ◽  
Homogeneous Isotropic Turbulence

Deterministic forcing of homogeneous, isotropic turbulence

1994 ◽  
Vol 6 (4) ◽  
pp. 1612-1614 ◽  
Author(s):  
Neal P. Sullivan ◽  
Shankar Mahalingam ◽  
Robert M. Kerr
Keyword(s):  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence
Sign in / Sign up

Export Citation Format

Share Document