Nikolay N. Kurochkin

Coherent CO 2 lidars for measuring wind velocity and atmospheric turbulence

We have developed two coherent lidar systems based on cw and TEA CO 2 lasers. The lidars have been tested and applied for the atmospheric wind velocity measurements. We have elaborated and experimentally verified a new method of nondestructive long-range measurement of the parameters of the atmospheric turbulence with a cw Doppler lidar (DL). The method is based on certain processing of the heterodyne Doppler spectra. In addition to the wind velocity magnitude, the method yields the value of the velocity structure constant. The method has been experimentally verified. Some results of applications of the DL for detecting artificially generated vortexes (aircraft traveling vortexes) and distinguishing them from natural winds and turbulence based on a comparison of the magnitudes of the velocity structure constant are presented.

New method for the measurement of the structure function constant in turbulent atmosphere with a cw Doppler lidar

We have elaborated and experimentally verified a new method of non-destructive long-range measurement of the parameters of the atmospheric turbulence with a cw Doppler lidar. The method is based on certain processing of the heterodyne Doppler spectra. In addition to the wind direction and magnitude the method yields the value of the velocity structure coefficient. The method has been experimentally verified. The measurements of structure function constant were carried out in parallel with the Doppler lidar and with the equipment (rumbo- anemometers) of the High Meteorological Mast in Obninsk (Russia). The results are in good agreement.

Infrared coherent lidar systems for wind velocity measurements

Doppler lidars are prospective means for long-range measurements of wind velocity in the atmosphere, based on the registration of Doppler frequency shifts in the radiation backscattered by moving aerosol particles. The development of coherent lidar systems based on CW and TEA CO2 and on Nd:YAG lasers is presented. Test results from the application of these lidars to atmospheric wind velocity measurements are discussed.

Heterodyne diagnostics by Doppler signal of backscattering of near-surface flows induced by intense laser radiation

A procedure of operational inspection of laser technological processes has been suggested that is based on measuring spectral properties of Doppler signal of backscattering from the interaction region by optical heterodyne technique. The technique enables us to obtain the qualitative and quantitative information on hydrodynamic flows in reactor. The measurements have been performed with about 1 kW/cm2 beam intensity of continuous-wave carbon- dioxide laser at the surface of a number of condensed substances by monostatic scheme of interaction.

Backscattered heterodyne Doppler diagnostics of laser-induced near-surface transport phenomena

Laser processing has become a powerful tool for surface or bulk modifications and is applied successfully in many areas. The use of laser in technology depends on the knowledge of the physics of the processes that occur on interaction between laser radiation and matter. To optimize laser material processing an effective diagnostic method should be developed. Strong light scattering is very typical for laser processing, so measured parameters of scattered light bring information of the process, including velocity field. That opens the way to developing laser physic methods for non-destructive diagnostics and on-line control. The main idea of our measurements is by irradiating the surface of strongly absorbing condensed matter with the intense coherent radiation one can on the one hand induce such phase transitions as thermocapillary convection and evaporation and on the other hand form and observe the Doppler shift in the frequency of radiation backscattered from scatterers within the irradiated volume and consequently measure the velocity of laser induced near-surface hydrodynamic processes.

Study of laser-induced thermocapillary convection using backscattered Doppler signal

As the result of free surface deformation during laser-induced thermocapillary convection process near-surface flow velocity vector has a non-zero projection on direction laser beam spreads. This property of liquid flow allows to measure the velocity of near-surface mass flow using the backscatter signal from surface particle inclusions and rippling induced by surface tension gradient. Similar to coherent Doppler wind lidar scheme measurements can be formed by high intensity irradiating a target surface (with consequent phase transition in the boundary layer zone) and observing the Doppler shift in the frequency of the radiation backscattered from scatters within interaction region. We have proposed the monostatic interaction scheme. In this case interaction and probe regions are equivalent precisely. Our paper is devoted in investigation of laser-induced-near-surface thermocapillary convection flow in such target materials as water, paraffin, naphthalene, ehyl alcohol and oil using Doppler backscattered signal detected by heterodyne method.

Study of artificial and natural turbulence in atmospheric boundary layer with a cw Doppler CO2 lidar

An examination is conducted of the feasibility of using a Doppler lidar (DL) to detect artificially generated vortices, such as those due to aircraft drag-due-to-lift, and clearly distinguish them from natural gusts and turbulence on the basis of the C(V)-squared constants magnitude. Both experimental and theoretical results are presented for DL performance; the intersection of the probing DL beam with the aircraft vortex generated a satisfactory Doppler signal whose S/N decreased with increasing distance to the passing aircraft.

Detection and parameter estimation of atmospheric turbulence by ground-based and airborne CO2 Doppler lidars

Potentials of ground-based and of airborne CO2 Doppler lidars are discussed in relation to the problems of long range detection and parameters estimation of atmospheric turbulence. Our experience to use such systems working in CW and quasipulsed regimes is reviewed. A new method for the measurement of the C sub V-sq constant in turbulent atmosphere with a CW CO2 Doppler lidar is presented.