V. M. Popov

Using the Approximation of a Generalized Telegraphic Process for Calculation of Thermal Radiation of Turbulent Diffusion Flames

A new method based on stochastic modeling with the use of the approximation of the generalized telegraphic process is suggested to calculate thermal radiation of turbulent high-temperature flows. The computational advantages of this method are discussed in comparison with traditional approaches to stochastic modeling. The considerable effect of fluctuations of temperature and concentrations of radiating components on the formation of fields of brightness and intensity of radiation of a turbulent diffusion flame of a mixture of hydrogen and carbon oxide in air is demonstrated. The results of numerical simulation are compared with experimental data.

OPTIMAL REGRESSIONS TO ESTIMATE AEROSOL PARAMETERS BY DATA OF TWO- AND THREE-WAVELENGTH LASER SOUNDING

A problem on introduction of additional a prior assumptions to construct a closed set of lidar equations at several wavelengths and on their solutions to estimate microphysical parameters of atmospheric aerosols by multi-frequency laser sounding data is discussed. Some regression relations between spectral values of aerosol backscatter and extinction coefficients in the visible and near-IR are used as the assumptions. The regressions are constructed by model considerations. The optical atmospheric aerosol model of the World Meterological Organization is taken as a basic one. The constructed regressions enable one to evaluate the solvability of, generally, ill-conditioned lidar equations and the errors in the solutions as well as to make some estimations with respect to the determination of aerosol microstructural parameters. This work has been directed towards the design of procedures and algorithms to process laser sounding data gathered routinely by lidar setups of the Institute of Physics, Belarus National Academy of Sciences, Minsk, Republic of Belarus within the frame of a number of International and National research and development programs.

Dispersion of the impurity released from an instantaneous source in turbulent atmosphere

The results of comprehensive field experiment are presented. The objective of the experiment is lidar technique development for control of pollutant dispersion from pulse source. Experiment was carried out in steppe region, underlying surface was covered with sparse vegetation. Charge exploded at the altitude of 10 m stand for source of pollutant. Lidar was used to trace the cloud of explosion products. The ratio of backscatter signal from the cloud to aerosol background signal was recorded along with the time and coordinates of sounded points. Ultrasonic meteorological station and sodar 25 - 30 meters distant from explosion location were used to measure air temperature, vertical and horizontal components of wind velocity and its direction, total energy of turbulent motions, tangential turbulent friction stress and vertical turbulent heat flow. Experimental data were compared with the results of numerical modeling of pollutant spatial distribution performed on the basis of Gaussian statistical model. Numerical results were primarily in satisfactory agreement with experimental data.

Effects of uncertainties in atmospheric conditions on the accuracy of concentration measurements by the differential absorption method in the 9- to 11-um and 4.6- to 5.6-um spectral ranges

A potential source of errors at remote measurements of concentration of atmospheric gases by CO2-lasers is the incomplete knowledge of atmospheric composition and temperature during measurements. This paper gives a general expression for errors owing to approximate description of the composition of the base of a statistical atmospheric model and of separate parameters measured during laser sounding. Measurements of additional atmospheric parameters are shown can reduce considerably the uncertainty in the concentration of a gas studied. A special computer code is designed to search pairs of frequencies with minimal error in mean-path horizontal measurements by using a topographic target. The performed calculations showed that a number of referenced experiments on remote measuring of atmospheric gas concentrations by CO2-lasers were conducted at frequencies that did not provide the minimal atmospheric errors.6