Luis Gustavo Nogueira Martins

Monitoring the micrometeorology of a coastal site next to a thermal power plant from the surface to 140 m

AbstractA 140-m micrometeorological tower has been operating since August 2016 at 4 km from the coastline and 250 m from a thermal power plant that releases heat from its 20-m stacks in southeaster...

Quasi-Experimental Determination of Turbulent Dispersion Parameters for Different Stability Conditions from a Tall Micrometeorological Tower

AbstractTurbulent wind data measured by sonic anemometers installed at various heights on a 140-m-tall micrometeorological tower located at a coastal site are used to obtain vertical profiles of th...

APPLICATION OF THE HILBERT-HUANG TRANSFORM IN VELOCITY DATA MEASURED IN WIND TUNNEL

In this study, the Hilbert-Huang transform was applied to experimental measurements performed in a wind tunnel to determine the frequency of occurrence of the spectral maximum. These maximum frequencies are associated with the time scale of the most energetic eddies and represent an important input parameter in the pollutants dispersion models. The values of the maximum frequencies obtained by the Hilbert-Huang marginal spectrum are compared with the vaues obtained by the traditionally used Fourier transform. The results show that the energy distribution calculated by both methods are very similar in the region of occurence of the spectral maximum, and for this reason, the maximum frequency values obtained by each method do not presente significant differences. Under determined hypothesis, the Hilbert-Huang transform provided physically more realistic maximum frequency values that those obtained using the Fourier transform.

The Influence of the Intermittent Behavior of the Nocturnal Atmospheric Flow on the Prediction of the Diurnal Temperature Range: A Simplified Model Analysis

The variation of the atmospheric temperature near the surface associated with anthropogenic effects is analyzed using a simplified atmospheric model. Local changes in cloud cover and four different scenarios of atmospheric concentration of carbon dioxide are considered. The results show that the highest temperature variability occurs in the weak wind and decoupled state and in the transition between flow regimes. In agreement with previous efforts, the results indicate that the reduction of diurnal temperature range is related to the existence of two distinct flow regimes in the stable boundary layer. However, in the decoupled state, the occurrence of intermittent bursts of turbulence may cause temperature variations among the different scenarios to become unpredictable. It implies that it is difficult to predict the diurnal temperature range in places where low winds are common.

Identification and Estimation of the Period of Non-Turbulent Oscillatory Processes in the Stable Boundary layer Through Autocorrelation Functions

The autocorrelation function of the flow speed components, measures the relationship that the speed in a certain instant, has with the speed at an earlier instant. In some conditions, in the atmospheric flow, this autocorrelation presents a low frequency oscillatory shape, presenting negative lobes. This behavior is known as meandering phenomenon and becomes prevalent in low wind conditions. The objective of this study is to compare the adjustments of autocorrelation functions, present in the literature, with trial of the experimental data of FLOOSS II experiment, for determining the meandering oscillation period. Initially, three selection criteria were used to select the windows of analysis. Among the criteria the magnitude of the wind showed the most satisfactory. The fitting curves showed that both autocorrelation functions performed well, even with a large variability of oscillation periods that were found. The great variability in the oscillation period of the meandering phenomena can be associated with the nature of the physical phenomenon that is responsible for its origin. However, this hypothesis needs confirmation.

ANALYSIS OF THE PROPAGATION AND MAINTENANCE OF VORTICES GENERATED BY A STATIC AND ISOLATED MICROBURST

The Southern Brazilian region is specially affected by extreme weather events, very often intense wind gusts coming from deep convection may develop itself as a microburst producing winds higher than 100 km/h. In order to understand the physical and dynamical process evolved in this phenomena, a static and isolated microburst is produced through a Large Eddy Simulation. A quantitative analysis of propagation an maintenance of the microburst vortex ring is performed in order to understand its evolution.

DEPENDÊNCIA DA TAXA DE DISSIPAÇÃO VISCOSA COM A ESTABILIDADE ATMOSFÉRICA EM CONDIÇÕES MUITO ESTÁVEIS

A descricao prognostica do escoamento turbulento na camada limite muito estavel e um desafio para modelos numericos, pois os mecanismos que mantem a atividade turbulenta sao desconhecidos. Neste trabalho, sao analisadas as implicacoes das hipoteses de Kolmogorov na parametrizacao da taxa de dissipacao viscosa. Os resultados indicam que esta deve depender do regime de escoamento atmosferico.