No abstract

A lattice Boltzmann formulation for relativistic fluids is presented and numerically validated through quantitative comparison with recent hydrodynamic simulations of relativistic fluids. In order to illustrate its capability to handle complex geometries, the scheme is also applied to the case of a three-dimensional relativistic shock wave, generated by a supernova explosion, impacting on a massive interstellar cloud. This formulation opens up the possibility of exporting the proven advantages of lattice Boltzmann methods, namely, computational efficiency and easy handling of complex geometries, to the context of (mildly) relativistic fluid dynamics at large, from quark-gluon plasmas up to supernovae with relativistic outflows.

A. Adare, 13 S. Afanasiev, 31 C. Aidala, 40, 44, 45

We provide numerical evidence that electronic preturbulent phenomena in graphene could be observed, under current experimental conditions, through current fluctuations, echoing the detachment of vortices past localized micron-sized impurities. Vortex generation, due to micron-sized constriction, is also explored with special focus on the effects of relativistic corrections to the normal Navier-Stokes equations. These corrections are found to cause a delay in the stability breakout of the fluid as well as a small shift in the vortex shedding frequency.

Measurements of midrapidity charged particle multiplicity distributions, dN ch /dη, and midrapidity transverse-energy distributions, dET /dη, are presented for a variety of collision systems and energies. Included are distributions for Au+Au collisions at For all A+A collisions down to √ s N N = 7.7 GeV, it is observed that the midrapidity data are better described by scaling withNqp than scaling with Npart. Also presented are estimates of the Bjorken energy density, εBJ, and the ratio of dET /dη to dN ch /dη, the latter of which is seen to be constant as a function of centrality for all systems.

No abstract

Starting from the Maxwell-Jüttner equilibrium distribution, we develop a relativistic lattice Boltzmann (LB) algorithm capable of handling ultrarelativistic systems with flat, but expanding, spacetimes. The algorithm is validated through simulations of quark-gluon plasma, yielding excellent agreement with hydrodynamic simulations. The present scheme opens the possibility of transferring the recognized computational advantages of lattice kinetic theory to the context of both weakly and ultra-relativistic systems.PACS numbers: 47.75.+f, 47.11.-j Keywords: Relativistic fluid dynamics, Quark-gluon plasmas, Lattice Boltzmann I. MOTIVATIONThe great success of the Relativistic Heavy-Ion Collider (RHIC) experimental program [1][2][3][4] has provided the motivation to come up with realistic and quantitative simulations of heavy-ion collisions.Since the bulk of particles produced in relativistic heavy-ion collisions is described by fluid dynamics [5], the center-piece of any complete simulation attempt will involve a viscous fluid dynamics algorithm. The majority of presently available fluid dynamics codes is able to handle smooth initial conditions in 2+1 dimensions in the presence of shear viscosity [6][7][8][9][10]. However, it has by now been understood that the presence of event-by-event fluctuations in the initial state can lead to significantly different quantitative results with respect to smooth initial conditions [11], and may in some cases even explain qualitatively new phenomena. To be more specific, the presence of event-by-event fluctuations is the source of the non-vanishing elliptic flow found in RHIC experiments at central collisions, the source of hydrodynamic flow-fluctuations, and may (through the presence of socalled triangular flow v 3 ) naturally explain the presence of the 'ridge phenomenon' found in experiments [12][13][14][15]. Thus, it is probably fair to say that without including the effect of event-by-event fluctuations, a description of the medium created in heavy-ion collisions cannot be regarded as realistic. This provides the motivation to develop a fully relativistic and computationally efficient viscous fluid dynamics algorithm that can handle initial state fluctuations. Also, such an algorithm can be used Further motivation is provided by other systems where relativistic viscous fluid flows are of interest, such as astrophysical systems and condensed matter systems such as graphene [17]. One particular question that arises in all this different systems is when relativistic fluid flow becomes turbulent, which involves a determination of the critical Reynolds number and the turbulent spectrum [18,19]. II. LATTICE KINETIC APPROACH TO HYDRODYNAMICSFluid turbulence, both classical and relativistic, sets one of the most compelling challenges in modern computational physics. This motivates a relentless search for new and ever more efficient methods for solving the hydrodynamic equations of motion in the high-Reynolds turbulent regimes. In the last two decades, a new computational paradigm has...

A study with synchrotron radiation X-ray tomographic microscopy (SRXTM) of PUR, PVAC, and UF adhesive bond lines in beech wood, bonded under various growth ring angles is presented. After determining the hardening characteristics of the adhesives, we evaluate the bond line morphologies, and the adhesive penetration into the wood structure. We find distinct bond line imperfections for the different adhesive systems. To describe the adhesive distribution inside the bond line we propose the saturation of the pore space instead of the commonly used maximum penetration depth. The results are the basis for a penetration model of hardening fluids into hardwood (part II).