Turbulence revealed by wavelet transform: power spectrum and intermittency for the velocity field of the cosmic baryonic fluid
Abstract
We use continuous wavelet transform techniques to construct the global and environmentdependent wavelet statistics, such as energy spectrum and kurtosis, to study the fluctuation and intermittency of the turbulent motion in the cosmic fluid velocity field with the IllustrisTNG simulation data. We find that the peak scales of the energy spectrum and the spectral ratio define two characteristic scales, which can be regarded as the integral scale and the dissipation scale of turbulence, respectively, so that the energy spectrum can be divided into the energycontaining range, the inertial range and the dissipation range of turbulence. The wavelet kurtosis is an increasing function of the wavenumber $k$, first grows rapidly then slowly with $k$, indicating that the cosmic fluid becomes increasingly intermittent with $k$. In the energycontaining range, the energy spectrum increases significantly from $z = 2$ to $1$, but remains almost unchanged from $z = 1$ to $0$. We find that both the environmentdependent spectrum and kurtosis are similar to the global ones, and the magnitude of the spectrum is smallest in the lowestdensity and largest in the highestdensity environment, suggesting that the cosmic fluid is more turbulent in a highdensity than in a lowdensity environment. In the inertial range, the exponent of the energy spectrum is steeper than not only the Kolmogorov but also the Burgers exponent, suggesting that there may be more complex mechanisms for energy transfer than Kolmogorov and Burgers turbulence.
 Publication:

arXiv eprints
 Pub Date:
 April 2024
 DOI:
 10.48550/arXiv.2404.11255
 arXiv:
 arXiv:2404.11255
 Bibcode:
 2024arXiv240411255W
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Instrumentation and Methods for Astrophysics;
 Physics  Fluid Dynamics
 EPrint:
 15 pages, 9 figures, 1 table, comments welcome