Academic literature on the topic 'Lagrangian sub-variety'

The aim of this study is to compare the CALPUFF and LAMBDA models and evaluate the regulatory model CALPUFF accuracy in situations of line instant source emissions. Line source emissions exist in a variety of situations in the environmental field. Paved and unpaved roads are the most common examples of line sources. For instance, in the mining sector these two types of sources play an important role of anthropogenic influences in the environment. The OLAD experiment is appropriate to evaluate these models and check the accuracy of both. The CALPUFF results show in the simulations for short and long distances a systematic tendency of sub-prediction for the concentration. The LAMBDA model presented better accuracy in the prediction of natural pollutant dispersion even disregarding the spatial variability of meteorological field and topography. When the LAMBDA model is used the flow of pollutants to greater distances is less pronounced, especially because of the time step of one second adopted in the simulation.

Although cataclysmic variables (CVs) come in a wide variety of shapes and sizes, the essential ingredients are a compact primary star and a Roche-lobe-filling secondary. In most cases the cool component is a main sequence dwarf, and the compact component a white dwarf (WD). Material from the cool component flows through the inner Lagrangian point via an accretion disc onto the surface of the WD; the flow near the WD is significantly affected by the strength of the magnetic field the WD may have (see Warner for a review of CVs). CVs are characterised by regular eruptions, ranging in energetics and frequency from ‘dwarf novae’, in which eruptions of amplitude ~3-4 mag in the visual occur every few days to weeks, to classical novae (CNe) in which the eruption is explosive, due to thermonuclear runaway (TNR) in material accreted on the surface of the WD (see Bode & Evans for a review of CNe).

Abstract. In atmospheric tracer experiments, a substance is released into the turbulent atmospheric flow to study the dispersion parameters of the atmosphere. That can be done by observing the substance's concentration distribution downwind of the source. Past experiments have suffered from the fact that observations were only made at a few discrete locations and/or at low time resolution. The Comtessa project (Camera Observation and Modelling of 4-D Tracer Dispersion in the Atmosphere) is the first attempt at using ultraviolet (UV) camera observations to sample the three-dimensional (3-D) concentration distribution in the atmospheric boundary layer at high spatial and temporal resolution. For this, during a three-week campaign in Norway in July 2017, sulfur dioxide (SO2), a nearly passive tracer, was artificially released in continuous plumes and nearly instantaneous puffs from a 9 m high tower. Column-integrated SO2 concentrations were observed with six UV SO2 cameras with sampling rates of several hertz and a spatial resolution of a few centimetres. The atmospheric flow was characterised by eddy covariance measurements of heat and momentum fluxes at the release mast and two additional towers. By measuring simultaneously with six UV cameras positioned in a half circle around the release point, we could collect a data set of spatially and temporally resolved tracer column densities from six different directions, allowing a tomographic reconstruction of the 3-D concentration field. However, due to unfavourable cloudy conditions on all measurement days and their restrictive effect on the SO2 camera technique, the presented data set is limited to case studies. In this paper, we present a feasibility study demonstrating that the turbulent dispersion parameters can be retrieved from images of artificially released puffs, although the presented data set does not allow for an in-depth analysis of the obtained parameters. The 3-D trajectories of the centre of mass of the puffs were reconstructed enabling both a direct determination of the centre of mass meandering and a scaling of the image pixel dimension to the position of the puff. The latter made it possible to retrieve the temporal evolution of the puff spread projected to the image plane. The puff spread is a direct measure of the relative dispersion process. Combining meandering and relative dispersion, the absolute dispersion could be retrieved. The turbulent dispersion in the vertical is then used to estimate the effective source size, source timescale and the Lagrangian integral time. In principle, the Richardson–Obukhov constant of relative dispersion in the inertial subrange could be also obtained, but the observation time was not sufficiently long in comparison to the source timescale to allow an observation of this dispersion range. While the feasibility of the methodology to measure turbulent dispersion could be demonstrated, a larger data set with a larger number of cloud-free puff releases and longer observation times of each puff will be recorded in future studies to give a solid estimate for the turbulent dispersion under a variety of stability conditions.

Dans cette thèse, je présente une nouvelle construction du complexe de Fukaya enroulé d’une lagrangienne ainsi que de l’algèbre de Chekanov d’une legendrienne en utilisant des techniques développées par Cieliebak, Ekholm et Oancea. Ces constructions vérifient des propriétés de fonctorialité par rapport aux cobordismes et sont donc adaptées pour étudier un attachement d’anse symplectique. Ainsi, je démontre que le complexe de Fukaya enroulé de la coâme est isomorphe à l’algèbre de Chekanov de la sphère d’attachement d’anse et je montre que cet isomorphisme se factorise par l’application « Open-Closed » de Abouzaid. Je présente ensuite une stratégie pour déduire de ces résultats deux théorèmes importants annoncés par Bourgeois, Ekholm et Eliashberg concernant le comportement de l’homologie symplectique par attachement d’anse et la génération de la catégorie de Fukaya enroulée. Dans le dernier chapitre, je définis en suivant une idée de A’Campo un flot géodésique sur le squelette des variétés de Brieskorn-Pham et je relie ce dernier au flot de Reeb sur l’entrelacs de contact de la singularité dans l’optique de généraliser le théorème de Viterbo qui relie homologie symplectique du cotangent et homologie d’un espace de lacets
In this PhD thesis, I present a new construction of the wrapped Fukaya complex of a Lagrangian and of the Chekanov algebra of a Legendrian using techniques developed by Cieliebak, Ekholm and Oancea. These constructions behave well under cobordisms and thus are fit to study the symplectic handle attachment procedure. I prove that the wrapped Fukaya complex of the cocore is isomorphic to the Chekanov algebra of the attachment sphere and show that this isomorphism factors through Abouzaid’s Open-Closed map. I then give a strategy in order to deduce from these results two important theorems announced by Bourgeois, Ekholm and Eliashberg concerning the behaviour of symplectic homology under handle attachment and the generation of the Fukaya category. In the last chapter, I define following an idea of A’Campo a geodesic flow on the skeleton of a Brieskorn manifold and relate this flow to the Reeb flow on the link of the singularity in order to try to generalize Viterbo’s isomorphism between the symplectic homology of a cotangent bundle and the homology of a loop space

A continuous random walk (CRW) turbulent diffusion model was developed for Lagrangian particles within flow fields simulated by hybrid RANS/LES methodologies. For RANS flow-fields, the conventional time-scale and length-scale constants were determined by the turbulence intensity and dissipation values computed by the single-phase solver with a k-ω (Menter SST) model and subsequent comparison with turbulent particle diffusion experimental results of Snyder & Lumley (1971). This allowed validation against data for four particle types ranging from hollow glass to copper shot in grid-generated turbulence. The stochastic diffusion model was then extended to utilize the Nichols-Nelson k-ω hybrid RANS-LES turbulence model in a more complex turbulent flow resulting from the unsteady, three dimensional wake of a cylinder at Mach number of 0.1 and Reynolds number (ReD) of 800. The gas flow was computed with a 5th-order upwind-biased scheme. Throughout the wake, the sub-grid random walk model yielded good predictions of particle diffusion as compared with DNS. Also, these results indicate that crossing trajectory effects and inertia-based drift corrections are critical to handling a variety of particle Stokes numbers as well as regions of non-homogeneous turbulence, even when most of the kinetic energy is captured with the resolved-scales of an LES approach.