It is well known that on long time scales the behaviour of tracer particles diffusing in a cellular flow is effectively that of a Brownian motion. This paper studies the behaviour on “intermediate” time scales before diffusion sets in. Various heuristics suggest that an anomalous diffusive behaviour should be observed. We prove that the variance on intermediate time scales grows like O( √ t). H...

In this paper we further explore and apply our recent anti-diffusive flux corrected high order finite difference WENO schemes for conservation laws [18] to compute the Saint-Venant system of shallow water equations with pollutant propagation, which is described by a transport equation. The motivation is that the high order anti-diffusive WENO scheme for conservation laws produces sharp resoluti...

In this paper we construct numerical schemes to approximate linear transport equations with slab geometry by one-dimensional diffusion equations. We treat both the case of pure diffusive scaling and the case where kinetic and diffusive scalings coexist. The diffusion equations and their data are derived from asymptotic and layer analysis which allows general scattering kernels and general data....

The decomposition of the local motion a fluid into straining, shearing, and rigid-body rotation is examined in this work for compressible isotropic turbulence by means direct numerical simulations. triple closely associated with basic reference frame (BRF), which extraction biasing effect shear maximized. In study, new computational inexpensive procedure proposed to identify BRF three-dimension...

Angular momentum transport must have occurred in the Sun’s radiative zone to explain its current solid body rotation. We survey the stability of the early Sun’s radiative zone with respect to diffusive rotational instabilities, for a variety of plausible past configurations. We find that the (faster rotating) early Sun was prone to rotational instabilities even if only weak levels of radial dif...

Continental freshwater systems have now been shown to be globally significant sources of methane, but there are still large uncertainties associated with freshwater methane fluxes. Studies to date have mainly focused on either ebullition of bubbles originating from sediments or on diffusive fluxes of dissolved methane across the air–water interface. We examined the potential influence of a new ...

In the presence of gratuitous inducers, the lac operon of Escherichia coli exhibits bistability. Most models in the literature assume that the inducer enters the cell via the carrier (permease), and exits by a diffusion-like process. The diffusive influx and carrier efflux are neglected. However, analysis of the data shows that in non-induced cells, the diffusive influx is comparable to the car...

This paper focuses on the robustness problem of full implication triple implication inference method for fuzzy reasoning. First of all, based on strong regular implication, the weighted logic metric for measuring distance between two fuzzy sets is proposed. Besides, under this metric, some robustness results of the triple implication method are obtained, which demonstrates that the triple impli...

The benthic O2 uptake and the O2 microdistribution in a coastal sediment of Aarhus Bay, Denmark, were investigated during a seasonal study. Measurements were performed in situ by a profiling lander and a flux chamber lander, as well as on recovered sediment cores. The O2 penetration depth, the diffusive O2 uptake, and the volumespecific O2 consumption rate strongly depended on the seasonal chan...

The study of convective motions produced by unstable density distributions in a fluid is now highly developed. Most attention has been given to the case of a thin horizontal layer of fluid, heated below and cooled above, and results obtained using a combination of Boussinesq theory and laboratory experiments have been success­ fully applied in many contexts (Chandrasekhar 1961, Spiegel 1971). T...