Spectral energy transfer in a viscoelastic homogeneous isotropic turbulence

2019 ◽  
Vol 31 (9) ◽  
pp. 095105
Author(s):  
Mani Fathali ◽  
Saber Khoei
Keyword(s):  
Energy Transfer ◽  
Isotropic Turbulence ◽  
Spectral Energy ◽  
Homogeneous Isotropic Turbulence

Measurements of spectral energy transfer in grid turbulence

1969 ◽  
Vol 38 (4) ◽  
pp. 743-763 ◽  
Author(s):  
C. W. Van Atta ◽  
W. Y. Chen
Keyword(s):  
Energy Transfer ◽  
Dynamical Equation ◽  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Direct Interaction ◽  
Spectral Energy ◽  
Grid Turbulence ◽  
Local Isotropy ◽  
Isotropic Energy ◽  
Direct Interaction Approximation

Direct measurements of the energy transfer spectrum in locally isotropic grid turbulence have been used to determine the extent of validity for grid turbulence of the dynamical equation for the three-dimensional energy spectrum in isotropic turbulence. The extent of applicability of the isotropic energy balance is consistent with the usual local isotropy criterion based on energy spectra alone.The present results are in general agreement with some previous measurements by Uberoi, who determined the transfer spectrum assuming the strict validity of the isotropic dynamical equation. The measured energy transfer spectra are quantitatively similar to those calculated by Kraichnan using the direct-interaction approximation.

The role of bulk viscosity on the decay of compressible, homogeneous, isotropic turbulence

2017 ◽  
Vol 833 ◽  
pp. 717-744 ◽  
Author(s):  
Shaowu Pan ◽  
Eric Johnsen
Keyword(s):  
Energy Transfer ◽  
Turbulent Flows ◽  
Bulk Viscosity ◽  
Shear Viscosity ◽  
Isotropic Turbulence ◽  
Stokes Equations ◽  
Compressible Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Viscous Effects ◽  
Bulk Viscous

While Stokes’ hypothesis of neglecting bulk viscous effects is exact for monatomic gases and unlikely to strongly affect the dynamics of fluids whose bulk-to-shear viscosity ratio is small and/or of weakly compressible turbulence, it is unclear to what extent this assumption holds for compressible, turbulent flows of gases whose bulk viscosity is orders of magnitude larger than their shear viscosities (e.g. $\text{CO}_{2}$). Our objective is to understand the mechanisms by which bulk viscosity and the associated phenomena affect moderately compressible turbulence, in particular energy transfer and dissipation. Using direct numerical simulations of the compressible Navier–Stokes equations, we study the decay of compressible, homogeneous, isotropic turbulence for ratios of bulk-to-shear viscosity ranging from 0 to 1000. Our simulations demonstrate that bulk viscosity increases the decay rate of turbulent kinetic energy; whereas enstrophy exhibits little sensitivity to bulk viscosity, dilatation is reduced by over two orders of magnitude within the first two eddy-turnover times. Via a Helmholtz decomposition of the flow, we determine that the primary action of bulk viscosity is to damp the dilatational velocity fluctuations and reduce dilatational–solenoidal exchanges, as well as pressure–dilatation coupling. In short, bulk viscosity renders compressible turbulence incompressible by reducing energy transfer between translational and internal degrees of freedom. Our results indicate that for gases whose bulk viscosity is of the order of their shear viscosity (e.g. hydrogen) the turbulence is not significantly affected by bulk viscous dissipation, in which case neglecting bulk viscosity is acceptable in practice. However, in problems involving compressible, turbulent flows of gases like $\text{CO}_{2}$ whose bulk viscosities are thousands of times greater than their shear viscosities, bulk viscosity cannot be ignored.

scholarly journals Third-order structure functions for isotropic turbulence with bidirectional energy transfer

2019 ◽  
Vol 877 ◽  
Author(s):  
Jin-Han Xie ◽  
Oliver Bühler
Keyword(s):  
Energy Transfer ◽  
Isotropic Turbulence ◽  
Full Range ◽  
Structure Functions ◽  
Spectral Energy ◽  
Order Structure ◽  
Stratified Turbulence ◽  
Mhd Turbulence ◽  
Third Order ◽  
Transfer Rates

We derive and test a new heuristic theory for third-order structure functions that resolves the forcing scale in the scenario of simultaneous spectral energy transfer to both small and large scales, which can occur naturally, for example, in rotating stratified turbulence or magnetohydrodynamical (MHD) turbulence. The theory has three parameters – namely the upscale/downscale energy transfer rates and the forcing scale – and it includes the classic inertial-range theories as local limits. When applied to measured data, our global-in-scale theory can deduce the energy transfer rates using the full range of data, therefore it has broader applications compared with the local theories, especially in situations where the data is imperfect. In addition, because of the resolution of forcing scales, the new theory can detect the scales of energy input, which was impossible before. We test our new theory with a two-dimensional simulation of MHD turbulence.

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
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