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Compressive isothermal turbulence is known to have a near lognormal density probability distribution function (PDF) with a width that scales with the sonic Mach number and nature of the turbulent driving (solenoidal vs compressive).…

Astrophysics of Galaxies · Physics 2019-11-06 Philip Mocz , Blakesley Burkhart

Based on recent developments in physics-informed deep learning and deep hidden physics models, we put forth a framework for discovering turbulence models from scattered and potentially noisy spatio-temporal measurements of the probability…

Fluid Dynamics · Physics 2018-11-20 Maziar Raissi , Hessam Babaee , Peyman Givi

There has been overwhelming evidence that coherent structures play a critical role in determining the overall transport in a variety of systems. We compute the probability distribution function (PDF) tails of momentum flux and heat flux in…

Plasma Physics · Physics 2009-11-13 Johan Anderson , Eun-jin Kim

We study turbulent flows in planar channels with unstable thermal stratification, using direct numerical simulations in a wide range of Reynolds and Rayleigh numbers and reaching flow conditions which are representative of asymptotic…

Fluid Dynamics · Physics 2017-06-28 Sergio Pirozzoli , Matteo Bernardini , Roberto Verzicco , Paolo Orlandi

The joint probability density function (PDF) of turbulent velocity and concentration of a passive scalar in an urban street canyon is computed using a newly developed particle-in-cell Monte Carlo method. Compared to moment closures, the PDF…

Geophysics · Physics 2010-03-25 J. Bakosi , P. Franzese , Z. Boybeyi

In probability density function (PDF) methods of turbulent flows, the joint PDF of several flow variables is computed by numerically integrating a system of stochastic differential equations for Lagrangian particles. A set of parallel…

Fluid Dynamics · Physics 2010-06-04 J. Bakosi , P. Franzese , Z. Boybeyi

The evolution of probability distribution functions (PDFs) of continuous density, velocity and velocity derivatives ( deformation tensor) fields in the theory of cosmological gravitational instability are considered. We show that in the…

Astrophysics · Physics 2007-05-23 Lev Kofman

Turbulent flows preferentially concentrate inertial particles depending on their stopping time or Stokes number, which can lead to significant spatial variations in the particle concentration. Cascade models are one way to describe this…

Fluid Dynamics · Physics 2017-04-26 Thomas Hartlep , Jeffrey N. Cuzzi , Brian Weston

A partial differential equation governing the global evolution of the joint probability distribution of an arbitrary number of local flow observations, drawn randomly from a control volume, is derived and applied to examples involving…

Fluid Dynamics · Physics 2026-01-14 John Craske , Paul Mannix

We introduce a method for calculating the probability density function (PDF) of a turbulent density field in three dimensions using only information contained in the projected two-dimensional column density field. We test the method by…

Astrophysics of Galaxies · Physics 2015-05-18 Christopher M. Brunt , Christoph Federrath , Daniel J. Price

Turbulence is a complex phenomenon that plays a critical role in the interstellar medium (ISM). Previous simulations and observations show that the probability density function (PDF) of gas density in isothermal and compressible systems…

Astrophysics of Galaxies · Physics 2025-03-26 Xunchuan Liu

The probability density function (PDF) of the logarithmic density contrast, $s=\ln (\rho/\rho_0)$, with gas density $\rho$ and mean density $\rho_0$, for hydrodynamical supersonic turbulence is well-known to have significant non-Gaussian…

Astrophysics of Galaxies · Physics 2022-11-16 James R. Beattie , Philip Mocz , Christoph Federrath , Ralf S. Klessen

Turbulence is a mysterious phenomenon in physical systems and plays a critical role in the interstellar medium (ISM). Previous simulations and observations have shown that the probability density functions (PDFs) of gas densities in…

Astrophysics of Galaxies · Physics 2025-03-26 Xunchuan Liu

An impact of particles' roughness on the self-diffusion coefficient in granular gases is investigated. For a simplified collision model where the normal and tangential restitution coefficients are assumed to be constant we develop an…

Statistical Mechanics · Physics 2012-01-19 Anna Bodrova , Nikolai Brilliantov

Small-scale turbulence can be comprehensively described in terms of velocity gradients, which makes them an appealing starting point for low-dimensional modeling. Typical models consist of stochastic equations based on closures for…

Fluid Dynamics · Physics 2024-03-01 Maurizio Carbone , Vincent J. Peterhans , Alexander S. Ecker , Michael Wilczek

We present experimental results on statistics of polymer orientation angles relatively to shear plane and tumbling times in shear flow with thermal noise. Strong deviation of probability distribution functions (PDF) of these parameters from…

Chaotic Dynamics · Physics 2009-11-11 Sergiy Gerashchenko , Victor Steinberg

We investigate the statistics of turbulence in emulsions of two-immiscible fluids of same density. We compute for the first time velocity increments between points conditioned to be located in the same phase or in different phases and…

The structure of molecular clouds can be characterized with the probability distribution function (PDF) of the mass surface density. In particular, the properties of the distribution can reveal the nature of the turbulence and star…

Astrophysics of Galaxies · Physics 2015-06-22 Rachel L. Ward , James Wadsley , Alison Sills

We use the spherical evolution approximation to investigate nonlinear evolution from the non-Gaussian initial conditions characteristic of the local f_nl model. We provide an analytic formula for the nonlinearly evolved probability…

Astrophysics · Physics 2009-11-13 Tsz Yan Lam , Ravi K. Sheth

The probability density functions (PDFs) for energy dissipation rates, created from time-series data of grid turbulence in a wind tunnel, are analyzed in a high precision by the theoretical formulae for PDFs within multifractal PDF theory…

Fluid Dynamics · Physics 2015-06-03 Toshihico Arimitsu , Naoko Arimitsu , Hideaki Mouri