Search results for "Fluid flow"
showing 10 items of 405 documents
Condensation nuclei measurements at theGeorg von Neumayer-Station (F.R.G.), Coastal Antarctica
1991
The analysis of nearly continuous records of surface-based atmospheric condensation nucleiconcentration (CNC) since 1984 up to the present at the Georg von Neumayer-Station (GvN) shows clearly: u - an annual cycle of CNC with low values in winter time; - a significantly increasing frequency of CNC of more than 1000 particles per cm3 over the years.
Activation radius of aerosol particles in cloud events - ground based and aircraft field measurements
1997
CHARACTERIZATION OF IRON COMPOUNDS FROM URBAN AND RURAL AEROSOL SOURCES
2000
Abstract Iron plays an important role in the chemistry and physics (by varying the hygroscopicity) of the atmosphere. Bulk samples were taken from an air-conditioning device, from the electrofilter of a gas–oil power station of the Technical University of and from rural sites near Darmstadt, situated between medium-altitude mountains and with a climate dominated by air masses from the west. Samples were collected in urban and rural (meadow) air, from different waste incineration power stations, from the exhausts of a gasoline and from a diesel motor car, and from a private gas fired heating system. The samples were characterized for elemental composition by total reflection X-ray fluorescen…
Analysis of microsphere oblique impact with planar surfaces based on the independent friction-restitution approach
2020
The independent friction restitution closure (IFR) previously applied to describe planar oblique impact of a homogeneous sphere on an infinitely massive rough plane is applied here to microsphere collisions and is extended to describe horizontal launch experiments. The model provides analytical solutions of the motion equations based on a unique set of values of the coefficients of normal and tangential restitution and friction. Comparison with experimental data in literature for the impact of microspheres of diameter <100 mu m yields a satisfactory agreement between experimentation and theory.
On the influence of the physico-chemical properties of aerosols on the life cycle of radiation fogs
1991
A one-dimensional model of radiation fog with detailed microphysics is presented. Aerosols and cloud droplets are treated in a joint two-dimensional size distribution. Radiative fluxes are calculated as functions of the radiative properties of the time-dependent particle spectra. The droplet growth equation is solved by considering radiative effects. Turbulence is treated by means of a higher order closure model. The interaction between the atmosphere and the earth's surface is explicitly simulated. Three numerical sensitivity studies are performed to investigate the impact of the different physico-chemical properties of urban, rural and maritime aerosols on fog formation. Numerical results…
Atmospheric aerosol changes in the vertical followed by sunphotomteres and telephotometers during VELETA 2002
2004
Collection efficiency of the Mainz-rotating-arm-collector
1990
Perspectives on aerosol deposition to natural surfaces: interactions between aerosol residence times, removal processes, the biosphere and global env…
1990
Abstract This paper summarizes the state-of-the-art and the research needs in the areas of aerosol residence-time assessments, deposition modelling, and understanding of aerosols in biogeochemistry. Research needs are emphasized from a systems perspective of global environmental change. Although fundamental quantitative knowledge is lacking, some qualitative linkages between source strengths, residence times, removal processes and the biosphere can be identified. It turns out that not only are the respective areas as such challenged by new problems, superimposed on the fairly well established conventional ones, but these areas also face mutually operating sets of feedbacks between residence…
Measurements of atmospheric condensation nuclei size distributions in Siberia
1992
Abstract The least investigated atmospheric aerosol is the one in remote continental areas. In this study, measurements of condensation nuclei size distributions near Lake Baikal, Siberia, were performed. Data for total aerosol number concentration and aerosol size distribution were obtained. The measurement equipment consisted of a TSI screen diffusion battery (SDB) Model 3040 and a TSI condensational nuclei counter (CNC) Model 3020. The average aerosol number concentration was about 104 cm−3. The evolution of aerosol number concentration during the day is correlated with the solar radiation. The inversion problem was solved using Tihonov's regularisation procedure. The possibility of appl…
A method to identify biological aerosol particles with radius > 0.3μmfor the determination of their size distribution
1991
Abstract The relevance of biological aerosol will be demonstrated. A method to determine the sizedistribution of the biological aerosols is shown, which gives the opportunity to determine a lower limit of the biological particles. For evaluation a light microscope and a scanning electron microscope equipped with an energy dispersive x-ray spectrometer are used.