Exact asymptotic expressions for eddy diffusivity and eddy viscosity are ob tained as the lead ing terms of in finite-series representations of integral equations which express the act ion of turbulence on an infinitesimal mean field. The series are transformed term by te rm from Euler ian to Lagrangian form. The latter is more suitable for constructing approximations to the exact asymptotic ex...

After removing annual variability, power spectral analyses of local atmospheric temperature from hundreds of stations and ice core records have been carried out from timescales of 1 day to 200 kyr. A clear sequence of power-law behaviors is found as follows: 1) from 40 kyr to 200 kyr a flat spectrum is observed, 2) from 2 kyr to 40 kyr the spectrum is proportional to f22 where f is the frequenc...

In this paper the results of material investigations of sodium nitrate (NaNO3) with a melting temperature of 306 °C as a phase change material (PCM) are presented. The thermal stability was examined by long duration oven tests. In these experiments the nitrite formation was monitored. Although some nitrite formation in the melt was detected, results show that the thermal stability of NaNO3 is s...

In order to increase the rate of gas absorption, chemical reaction in the liquid phase is considered. The purpose of this paper was to simulate gas absorption process by a liquid film over a spherical packing incorporating eddy viscosity and diffusivity. Second order chemical reaction for two different cases (fast and slow) were considered. The system partial differential equations obtained...

Cross-magnetic-field heat transport in a quiescent pure ion plasma is found to be diffusive and to be dominated by long-range ‘‘guiding center’’ collisions. In these long-range collisions, which occur in plasmas with Debye length lD greater than cyclotron radius rc , particles with impact parameters rc,r<lD exchange parallel kinetic energy only. The resulting thermal diffusivity xL is independe...

In this thesis, we introduce random differential equations in an abstract framework and study their well-posedness. We study average controllability properties of a random heat equation when the diffusivity is a random variable. We show that the solutions of such random heat equations are both null and approximately controllable in average from an arbitrary open set of the domain and in an arbi...

It has been hypothesized that radial electron heat transport in low collisionality, current-carrying magnetically-confined toroidal plasmas results from paleoclassical Coulomb collision processes (parallel electron heat conduction and magnetic field diffusion). In such plasmas the electron temperature equilibrates along magnetic field lines a long length L, which is the minimum of the electron ...

It is hypothesized that radial electron heat transport in magnetically confined toroidal plasmas results from paleoclassical Coulomb collision processes (parallel electron heat conduction and magnetic field diffusion). In such plasmas the electron temperature is equilibrated along magnetic field lines a long length L (>> poloidal periodicity length piR0q), which is the minimum of the electron c...

Subgrid-scale models for large-eddy simulation that are based on exact series expansions for ltered products are considered. In particular, if the rst two terms are retained, the result is a di usive subgrid term with a tensor di usivity. This tensor is proportional to the rate-of-strain tensor of the large-scale velocity eld. This leads to negative di usion in the stretching directions. Implic...