Home – Home – Jornals – Atmospheric and Oceanic Optics 2017 number 8

Results of the analysis of the mean intensity, intensity fluctuations, and regular and random wandering of optical beams propagating through the high-density area, which is formed due to subsonic airflow about a turret, in a turbulent atmosphere, are described. It is shown that the presence of perturbations around the turret caused by aircraft subsonic movements has a little impact on beam parameter. Quantitative data, which illustrate changes in the beam parameters along paths of different geometry versus turbulent conditions of light propagation, are presented and discussed.

Results of the analysis of microphysical characteristics obtained from the data of nighttime Raman lidar measurements in Tomsk (56N, 85E) in 2013 within the CIS-LiNet project (lidar networks in CIS countries) are presented. Theoretical aspects of the retrieval of the particle size distribution function at the preset refractive index are considered. It is shown that the coarse fraction is retrieved ambiguously. Parabolic approximation of the mean size of coarse particles, R_coarse, is suggested, which allows calculation of the size distribution function determine for particles of up to 3 mm in size. It is shown that when estimating the parameters under study together, the retrieved refractive index is non-linearly related with the optical coefficients and the distribution function, which leads to appearance of different, including false values of the_{refractive index. The parameters are assessed for the boundary air layer and middle troposphere.}

Application of bionic methods, such as neural networks and genetic algorithms, to solution of the inverse problem of CO₂ relative concentration determination from stratospheric airship signals is considered. The backscattered and reflected from the surface signals at wavelengths near 1572 nm are used for the measurements. The errors of the standard DIAL approach and DIAL-IDPA technology are compared. For the lidar with specification described, the mean error of algorithms developed is lower than 1 ppm. The genetic algorithm used is based on the minimization of the difference between the model signal and the signal received. Application of neural networks is based on their training on the examples of the simulated signals (reflected and scattered) and the altitude distribution of the gas concentration.

An OPO-based laser system is presented, which is a part of a differential absorption lidar and provides for tunable generation of nanosecond pulses in the 3-4 mm spectral range. The DIAL-DOAS technique for lidar measurements of atmospheric gases is developed and tested in numerical simulation with the aim of estimating the lidar capabilities of sensing atmospheric trace gases. The simulation results of lidar measurements of atmospheric trace gases in the 3-4 mm range are described.

Data on the variability of vertical and temporal aerosol structures in the stratosphere over Tomsk received during experiments at the lidar station for high-altitude atmosphere sounding of Institute of Atmospheric Optics SB RAS carried out in 2011-2015 are described. As in the previous studies, the emphasis is placed on disturbances of the aerosol components in the stratosphere due to volcanic eruptions and on identification of peculiarities in the intra-annual variability of the stratospheric aerosol content. A feature of that period, except for the second half of 2011 (the appearance of eruptive layers from the Grimsvotn volcano eruption over Tomsk), was near absence of volcanic activity, which leads to the formation of stratospheric aerosol and its transfer toward Tomsk; this allows the study of the behavior of the vertical structure of the background aerosol in the stratosphere during the five years. The analysis of the lidar data shows a steady trend of aerosol filling of the lower stratosphere during cold seasons, with the aerosol content maximum in December-January, and near absence in warm seasons throughout the stratosphere.

The high-resolution analysis of the ro-vibrational IR spectrum of the absorption bending bands n₂ + n₄ (F₁) and n₂ + n₄ (F₂) of the ²⁸SiH₄ molecule is performed with the SPHETOM software package. About 618 experimental transitions are assigned to n₂ + n₄ (F₁) and n₂ + n₄ (F₂) bands with J^max = 8. Rotational, centrifugal distortion, tetrahedral splitting, and resonance interaction parameters for these vibrational bands are determined from the weighted fit of experimental line positions. The obtained set of parameters reproduces the initial experimental data with the accuracy closed to experimental uncertainties, d_rms = 8 × 10^-4 cm^-1.

A method for parameterizations of the absorption of UV radiation by atmospheric ozone is described. Parameterizations are proposed for computer modeling of tropospheric fluxes of UV-A and UV-B radiation and modified fluxes of biologically active UV radiation in medical applications (for the analysis of vitamin D formation and risk of erythema, cancer, and cataracts). The parameterizations allow solution of the UV radiation transfer equations at the only effective spectral point to obtain integral fluxes in the 280-400 nm range (taking into account the spectral factors characterizing biological effects). When using the parameterizations, the characteristic errors in the calculations of the fluxes in the clear and cloudy troposphere are ~ 3-5%. The use of these parameterizations is relevant for fast radiation models, for example for on-line modeling of UV radiation fluxes for medical purposes. This method can be used to improve the accuracy of radiation codes in general atmospheric circulation models, radiation-chemical models, etc.

The results of numerical study of accuracy of the method of azimuthal structure function for estimation of the dissipation rate of kinetic energy of turbulence from measurements by low energy coherent Doppler lidars are presented. Conical scanning of probing beam of a lidar around the vertical axis is considered. Applicability of the azimuthal structure function method depending on turbulence strength and signal-to-noise ratio is analyzed.

The results of lidar study of wind turbulence in the atmospheric boundary layer in the littoral zone of Lake Baikal are presented. 2D spatiotemporal distributions of the turbulent energy dissipation rate in the presence of atmospheric internal waves and low level jet streams are obtained for the first time.

The results of retrieval of wind speed and direction from measurements of radial velocity by a Stream Line pulsed coherent Doppler lidar using the duo-beam method and conical scanning are presented. These results are compared with data of a sonic anemometer (point sensor).

A passive optical method for measurement of the crosswind velocity averaged over an atmospheric path is developed. The crosswind velocity estimation is based on the correlation algorithm operating with the shifts of energy centroids of images of topographic objects under natural daylight. Testing results of a measurer prototype based on this algorithm are discribed. The wind velocity estimates recorded by passive optical measurer and acoustic weather station are compared. The optimal duration for averaging the mutual correlation function providing the stability of real-time wind measurements is estimated.

The results of comparative experiments on measurement of the crosswind velocity by the passive correlation optical method and with a coherent Doppler wind lidar are analyzed. A crosswind velocity meter, developed at Institute of Atmospheric Optics SB RAS, was used in the passive correlation optical measurements.

The paper presents the results of measurements of parameters of aircraft wake vortices by a Stream Line coherent Doppler lidar during the three-day experiment on the airfield of Tolmachevo Airport. We have analyzed spatial dynamics and evolution of the wake vortices generated by aircrafts of various types: from Airbus A319 passenger aircraft to heavy Boeing 747-8 cargo aircraft entering the landing at Tolmachevo airport. It is shown that Stream Line lidars may well be used to obtain reliable information about the presence and intensity of aircraft wake vortices in the vicinity of а runway.

Coherent properties of vortex Bessel-Gaussian beams propagating in the turbulent atmosphere are theoretically studied. The approach to the analysis of this problem is based on the analytical solution of the equation for the transverse second-order mutual coherence function of the optical radiation field. The behavior of coherence degree, coherence length and integral scale of coherence degree of vortex Bessel-Gaussian beams depending on parameters of a beam and characteristics of the turbulent atmosphere is particularly considered. It is shown that the coherence length, and integral scale of coherence degree of a vortex Bessel-Gaussian beam essentially inversely depend on the topological charge of a vortex beam. Thus, in process of increase in a topological charge of a vortex beam the increase in reduction of values of coherence radius and integral scale of coherence degree of a vortex Bessel-Gaussian beam becomes less. The value of the given effect also essentially depends on characteristics of the turbulent atmosphere: at weak and strong fluctuations of optical radiation the given effect is not great, it reaches a maximum in the transition region from weak to strong fluctuations of optical radiation.

Possibilities of the crosswind profiling along an observation path of a distant object from the analysis of distortions of atmospheric object images are studied in this work by numerical simulation. The proposed method for wind velocity determination is based on the analysis of two adjacent incoherent images and exhibit higher performance in comparison with counterparts, which is explained by the absence of accumulation of analyzed statistical characteristics. A new method for filtration of turbulent distortions of an image by their characteristic sizes is suggested with the aim of determining the wind velocity at different segments of an observation path. The work shows a possibility of determining the motion velocity under certain turbulent conditions for several (no less than three) layers of turbulent atmosphere, which are located at different positions between observed object and optical system.

We present experimental results on the remote detection of surface traces of some high energetic materials using a Raman lidar designed on the basis of an excimer KrF laser with a narrow generation line and a multi-channel spectrum analyzer based on diffraction spectrograph and time gated CCD camera. Sensitivity of the system is evaluated for the detection range 10 m. A detection limit of 0.5 μg/cm² is reached for the surface density of traces of nitrogen-containing chemical materials at the signal accumulation over 1000 laser pulses.

Possibilities of estimating the microstructure parameters of atmospheric aerosol from regression equations that describe their relationships with spectral measurements of the aerosol optical depth (AOD) are considered. Special attention is given to the volume concentration, total cross section, and average radius of coarse aerosol particles. The urgency of this problem is stipulated by large errors in the retrieval of the above-indicated parameters in the case of direct АОD retrieval from measurements in an insufficiently wide spectral range. The coefficients of simple and multiple linear regressions are estimated and the results of retrieval on their basis of coarse aerosol parameters from data of solar photometry in Tomsk are presented.

Results of investigations of the time variability of aerosol microstructure parameters retrieved by inversion of spectral measurements of the aerosol optical depth (АОD) are presented. The input data were obtained at the IAO SB RAS using solar photometers of SP type in the observation periods 2003-2006 and 2011-2014. During the first period of measurement, the АОD was measured at 13 wavelengths in the range 0.37-4 mm. In the second observation period, the upper limit of the spectral range of measurements was 2.14 mm. The total volume of the data processed included over 7000 hourly average spectra. The geometric aerosol cross section, volume concentration, and average particle radius are analyzed.

The concentrations of normal hydrocarbons are studied on the basis of measurements in the surface air layer in different Siberian regions and in the free atmosphere over the Kara Sea water area. The total content of normal hydrocarbons in the aerosol composition is found to change from 244.56 ng/m³ in the surface air layer to 0.08 ng/m³ in the free atmosphere over the Kara Sea. Most organic compounds are from the C₁₅H₃₂-C₂₂H₄₆ range independently of the season; lighter compounds beginning from C₉H₂₀ are detected in the mid-seasons (spring and autumn); C₁₈H₃₈ concentration is maximal in autumn; C₁₉H₄₀, in spring and summer, and C₂₀H₄₂, in winter.

A method of generation of electromagnetic energy and magnetic flux in a magnetic cumulation generator is proposed. The method is based on dynamic variation of the circuit coupling coefficient. This circuit is compared with other available circuits of magnetic energy generation with the help of magnetic cumulation (classical magnetic cumulation generator, generator with transformer coupling, and generator with a dynamic transformer). It is demonstrated that the proposed method allows obtaining high values of magnetic energy. The proposed circuit is found to be more effective than the known transformer circuit. Experiments on electromagnetic energy generation are performed, which demonstrate the efficiency of the proposed method.

This paper describes the results of measurement of the temperatures of gaseous and liquid reacting media, carried out by the thermocouple method with the use of a battery (copper-constantan-copper) of planar thermocouples, placed in the medium under study. It is shown that convective heat transfer lasting for 0.5-1.5 μs equalizes the temperatures of “hot” thermocouple junctions and environment. The relationship between the voltage on the thermobattery and time, which occurred in this type of heating, was determined by a pulse oscilloscope. The measured maximum voltage was used to determine the temperature of the medium. A series of experiments was carried out on measuring the temperature of water and emulsion explosive matrix, which were compressed by a shock wave, as well as the detonation products of ammonite with sodium hydrogencarbonate at various mass ratios. The estimates of heat fluxes from the detonation products to the metallic surfaces of the thermobattery contacting with them are obtained.

The group analysis method is applied to a system of integrodifferential equations corresponding to a linear thermoviscoelastic model. A recently developed approach for calculating the symmetry groups of such equations is used. The general solution of the governing equations for the system is obtained. Using subalgebras of the admissible Lie algebra, two classes of partially invariant solutions of the considered system of integrodifferential equations are studied.

The evolution of small perturbations of the kinematic and dynamic characteristics of the radial flow of a flat ring filled with a homogeneous Newtonian fluid or an ideal incompressible fluid is studied. When the flow rate is specified as a function of time, the basic motion is completely defined by the incompressibility condition regardless of the properties of the medium. For the streamfunction, we obtained a biparabolic equation with four homogeneous boundary conditions, which simulate adherence to the expanding (narrowing) walls of the ring. Upper-bound estimates of the perturbation are obtained using the method of integral relations for quadratic functionals. The case of exponential decay of initial perturbations is considered on a finite or infinite time interval. Justified The admissibility of the inviscid limit in the given problem is substantiated, and and both upper- and lower-bound estimates for this limit are obtained.

This paper derives a new system of equations for the simulation of the dynamics of long-wave perturbations on the surface of a thin horizontal layer of heavy viscous fluid moving under the action of turbulent gas flow. In the case of small Reynolds numbers of the fluid, this system of equations is used to derive an evolution equation for the value of deviation of the film thickness from the unperturbed level. Some solutions of this equation are given.

A steady boundary layer flow of a non-Newtonian Casson fluid over a power-law stretching sheet is investigated. A self-similar form of the governing equation is obtained, and numerical solutions are found for various values of the governing parameters. The solutions depend on the fluid material parameter. Dual solutions are obtained for some particular range of these parameters. The fluid velocity is found to decrease as the power-law stretching parameter  in the rheological Casson equation increases. At large values of  , the skin friction coefficient and the velocity profile across the boundary layer for the Casson fluid tend to those for the Newtonian fluid.

Electrokinetic processes in the vicinity of inhomogeneous ion-selective surfaces (electrodes, membranes, microchannels, and nanochannels) consisting of alternating conducting and non-conducting regions in the presence of normal-to-surface electric current are numerically studied. An increase in the electric current density is observed in the case of some particular alternation of conducting and nonconducting regions of the surface. The voltage-current characteristics of homogeneous and inhomogeneous electric membranes are found to be in qualitative agreement. Various physical phenomena leading to the emergence of supercritical current in homogeneous and inhomogeneous membranes are detected.

Oscillations of semi-infinite ice cover in an ideal incompressible fluid of finite depth under local time-periodic axisymmetric load type are considered. Ice cover is simulated by a thin elastic plate of constant thickness. An analytical solution of the problem is obtained using the Wiener-Hopf method. The asymptotic behavior of the amplitudes of oscillations of the plate and the liquid in the far field is studied. It is shown that the propagation of waves in the far field is uneven: in some directions the waves propagate at significantly greater amplitude.

This paper presents a mathematical model for carbon dioxide injection into a natural gas reservoir saturated with methane and water accompanied by formation of carbon dioxide hydrate in an extended region. The dependence of the coordinates of the boundaries of the region of phase transitions on the pressure of the injected gas and the initial parameters of the formation are investigated. It is established that the velocity of the near boundary of the region of hydrate formation decreases with increasing water saturation and initial temperature of the reservoir and the velocity of the far boundary of the region of phase transitions increases with increasing pressure of the injected gas and reservoir permeability. It is shown that at large initial temperatures of the reservoir, a regime is possible in which replacement of methane by carbon dioxide without hydrate formation occurs at the far interface, and at the near interface, water is completely transformed into a hydrated state.

This paper describes the results of an experimental study of heat transfer in the case of the flow of a helium-xenon mixture with a Prandtl number approximately equal to 0.23 and the flows of pure helium and air in heated tubes of circular or triangular cross sections with a constant density of the heat flux. The region of thermal stability is studied. The law of heat transfer on the stabilized region is compared with known relationships. The approach that helps to obtain an expression for calculating the heat transfer in heat transfers with circular and triangular cross sections, which operate in a mixture heating mode on the initial region is developed.

The effect of thermal radiation on an unsteady boundary layer flow and heat transfer in a Cu-water nanofluid over an exponentially shrinking porous sheet is investigated. With the use of suitable transformations, the governing equations are transformed into ordinary differential equations. Dual non-similarity solutions are obtained for certain values of some parameters. Owing to the presence of thermal radiation, the heat transfer rate is greatly enhanced, and the thermal boundary layer thickness decreases.

The problems of experimental studies of the boiling of superfluid helium (He-II) on a cylindrical heater placed in a porous body are considered. A diagram of the setup, a description of the experimental cell, control and measurement means, and video recording and data processing techniques are presented. The technique of the experiment and the results are described.

This paper studies the stability of steady convective flow in an inclined plane liquid layer bounded by ideally thermally conductive solid planes in the presence of a homogeneous longitudinal temperature gradient under stable stratification when the layer is inclined so that the temperature in its lower part is smaller than in the upper part.

Based on the thermal conduction equation that takes into account phase changes and the evolution of thermophysical parameters with temperature, laser-induced heating and melting of monocrystalline silicon are studied. The changes in the behavior of silicon temperature at different places within the irradiation spot and at different time instants are investigated by the finite element and finite difference methods for a wide range of energy and duration of millisecond laser pulses with the Gaussian spatial and temporal shapes. The numerical results are compared with the experimental measurements.

The temperature distribution in a reservoir with hydraulic fracture is studied by numerical modeling of transient temperature fields taking into account the Joule-Thomson effect and the adiabatic effect. It is shown that the presence of hydraulic fracture in the reservoir leads to a nonmonotonic temperature variation in the reservoir temperature: as the well pressure decreases, the temperature first decreases due to the adiabatic expansion of the fluid and then increases due to the Joule-Thomson effect. As the water-oil displacement front approaches the wellbore, the temperature decreases slightly due to the heat exchange processes in the fracture-reservoir system.

The dynamic equation of a viscoelastic floating ice plate under a triangular pulse load is solved analytically through the Hankel transformation and the Laplace transformation. The effects of physical and geometrical parameters of the problem on the displacement response as a function of time and spatial coordinate are discussed.

The elastic buckling analysis and the static postbuckling response of the Euler-Bernoulli microbeams containing an open edge crack are studied based on a modified couple stress theory. The cracked section is modeled by a massless elastic rotational spring. This model contains a material length scale parameter and can capture the size effect. The von Karman nonlinearity is applied to display the postbuckling behavior. Analytical solutions of a critical buckling load and the postbuckling response are presented for simply supported cracked microbeams. This parametric study indicates the effects of the crack location, crack severity, and length scale parameter on the buckling and postbuckling behaviors of cracked microbeams.

The problem of dynamic buckling of a bar under the influence of a compressive force is solved with inclusion of inertial and elastic forces in different stages of the process. The duration of the inertial phase is determined. It is shown that in solids and gas-liquid media, the duration of the inertial stage for real parameters of structural members can be longer than the duration of impact loading.

The inverse problem of determining the inhomogeneity laws of a coating of an elastic cylinder that provide the smallest reflection of a plane acoustic wave in a certain angular sector and in a given frequency range. A functional that expresses the reflection intensity is constructed by direct solution of the direct problem, and an algorithm for minimizing it is proposed. Analytical expressions describing the mechanical parameters of the inhomogeneous coating.

The problem of stability of fluid-conveying carbon nanotubes embedded in an elastic medium is investigated in this paper. A nonlocal continuum mechanics formulation, which takes the small length scale effects into consideration, is utilized to derive the governing fourth-order partial differential equations. The Fourier series method is used for the case of the pinned-pinned boundary condition of the tube. The Galerkin technique is utilized to find a solution of the governing equation for the case of the clamped-clamped boundary. Closed-form expressions for the critical flow velocity are obtained for different values of the Winkler and Pasternak foundation stiffness parameters. Moreover, new and interesting results are also reported for varying values of the nonlocal length parameter. It is observed that the nonlocal length parameter along with the Winkler and Pasternak foundation stiffness parameters exert considerable effects on the critical velocities of the fluid flow in nanotubes.

The dynamic response of a clamped L-connected plate and an actively controlled vibratory power flow are studied. The vibratory power flow is suppressed by a piezoelectric patch, which is bonded on the L-connected plate. The electric patch is considered as an actuator. The feedforward least mean square algorithm is used to deduce the optimal piezoelectric patch control moment. Actuator operation with close-to-optimal moments is studied with allowance for the presence of in-plane waves.