Turbulence without pressure in d dimensions

The randomly driven Navier-Stokes equation without pressure in d-dimensional space is considered as a model of strong turbulence in a compressible fluid. We derive a closed equation for the velocity-gradient probability density function. We find the asymptotics of this function for the case of the gradient velocity field (Burgers turbulence), and provide a numerical solution for the two-dimensional case. Application of these results to the velocity-difference probability density function is discussed.Comment: latex, 5 pages, revised and enlarge

Dynamical Anomalies and Intermittency in Burgers Turbulence

We analyze the field theory of fully developed Burgers turbulence. Its key elements are shock fields, which characterize the singularity statistics of the velocity field. The shock fields enter an operator product expansion describing intermittency. The latter is found to be constrained by dynamical anomalies expressing finite dissipation in the inviscid limit. The link between dynamical anomalies and intermittency is argued to be important in a wider context of turbulence.Comment: revised version, 4 pp., 1 fig., to appear in PR

Thermal Process Integration in the AVDU A12/2 Crude Distillation Unit during Winter Operation

A pinch analysis of the AVDU A12/2 crude distillation unit processing 2 million tons of crude oil per year is made. A pinch retrofit of the recuperative heat-exchange system of the unit is performed. It is shown that the implementation of the proposed project will reduce the arbitrary energy consumption by 60 %, which corresponds to a reduction in specific fuel consumption from 36 to 13 kg per ton of refined oil

Extreme Plasma Astrophysics

This is a science white paper submitted to the Astro-2020 and Plasma-2020 Decadal Surveys. The paper describes the present status and emerging opportunities in Extreme Plasma Astrophysics -- a study of astrophysically-relevant plasma processes taking place under extreme conditions that necessitate taking into account relativistic, radiation, and QED effects.Comment: A science white paper submitted to the Astro-2020 and Plasma-2020 Decadal Surveys. 7 pages including cover page and references. Paper updated in late March 2019 to include a several additional co-authors and references, and a few small change

A Turbulent Origin for Flocculent Spiral Structure in Galaxies

The flocculent structure of star formation in 7 galaxies has a Fourier transform power spectrum for azimuthal intensity scans with a power law slope that increases systematically from -1 at large scales to -1.7 at small scales. This is the same pattern as in the power spectra for azimuthal scans of HI emission in the Large Magellanic Clouds and for flocculent dust clouds in galactic nuclei. The steep part also corresponds to the slope of -3 for two-dimensional power spectra that have been observed in atomic and molecular gas surveys of the Milky Way and the Large and Small Magellanic Clouds. The same power law structure for star formation arises in both flocculent and grand design galaxies, which implies that the star formation process is the same in each. Fractal Brownian motion models that include discrete stars and an underlying continuum of starlight match the observations if all of the emission is organized into a global fractal pattern with an intrinsic 1D power spectrum having a slope between 1.3 and 1.8. We suggest that the power spectrum of optical light in galaxies is the result of turbulence, and that large-scale turbulent motions are generated by sheared gravitational instabilities which make flocculent spiral arms first and then cascade to form clouds and clusters on smaller scales.Comment: accepted for ApJ, 31 pg, 9 figure

Radio-Frequency Measurements of Coherent Transition and Cherenkov Radiation: Implications for High-Energy Neutrino Detection

We report on measurements of 11-18 cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultra high-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultra high-energy neutrinos.Comment: updated figure 10; fixed typo in equation 2.2; accepted by PR

Yield, plasticity, stability and homeostasis of spring barley cultivars in the Non-Black Earth Region

Background. The expansion of agrometeorological factors negatively affecting the productivity of spring barley has oriented plant breeders towards developing adaptable forms capable of realizing their genetic potential for higher yield under unfavorable conditions. Applying several methods of statistical data analysis helps to perform a more accurate assessment of the material differentiated according to its adaptability indicators. The objective of this study was to assess the adaptability of spring barley cultivars on the basis of their yield, plasticity, stability and homeostasis.Materials and methods. The resulting data were obtained for ten spring barley cultivars developed at Nemchinovka FRC.Results. High yield potential of more than 8.5 t/ha was disclosed in barley cultivars ‘Yaromir’, ‘Nur’, ‘Nadezhny’, ‘Sudar’, ‘Zlatoyar’ and ‘Znatny’. Cvs. ‘Luboyar’, ‘Nadezhny’ and ‘Rafael’ showed the highest adaptability to the worst growing conditions (4.65–5.04 t/ha) as well as high adaptive and compensatory ability. Cvs. ‘Sudar’, ‘Nur’ and ‘Zlatoyar’ were identified for high environmental plasticity (Cvi = 24.1–25.9%; bi = 1.02–1.16; σ = 1.52–1.59), while ‘Lyuboyar’, ‘Znatny’ and ‘Vladimir’ for their stability parameters (S2di = 0.05–0.19; σ2CACi = 1.60–1.78; σ2(G×E)gi = 0.05–0.15). The highest values of homeostasis (BVGi = 3.45– 3.53; CSLi = 138.7–139.4; Homi = 9.02–9.85) were registered for cvs. ‘Rafael’ and ‘Lyuboyar’. The calculated rating of the tested cultivars identified ‘Nadezhny’ as the best in productivity, while ‘Zlatoyar’ was the best in environmental plasticity. The highest levels of stability and homeostasis were recorded for cvs. ‘Rafael’ and ‘Lyuboyar’.Conclusion. Comprehensive assessment of productivity and adaptability indicators in the tested spring barley cultivars showed that ‘Lyuboyar’, ‘Nadezhny’, ‘Zlatoyar’ and ‘Rafael’ were the best under the conditions of the Non-Black Earth Region

Simulating Supersonic Turbulence in Magnetized Molecular Clouds

We present results of large-scale three-dimensional simulations of weakly magnetized supersonic turbulence at grid resolutions up to 1024^3 cells. Our numerical experiments are carried out with the Piecewise Parabolic Method on a Local Stencil and assume an isothermal equation of state. The turbulence is driven by a large-scale isotropic solenoidal force in a periodic computational domain and fully develops in a few flow crossing times. We then evolve the flow for a number of flow crossing times and analyze various statistical properties of the saturated turbulent state. We show that the energy transfer rate in the inertial range of scales is surprisingly close to a constant, indicating that Kolmogorov's phenomenology for incompressible turbulence can be extended to magnetized supersonic flows. We also discuss numerical dissipation effects and convergence of different turbulence diagnostics as grid resolution refines from 256^3 to 1024^3 cells.Comment: 10 pages, 3 figures, to appear in the proceedings of the DOE/SciDAC 2009 conferenc