Convection in the vicinity of linear extended optical sources. Numerical solutions of the Navier-Stokes equations. I. Horizontal configuration
E.V. Nosov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: convection, inclined optical beam, thermal trace
Abstract
Optical radiation propagating in the atmosphere is partially absorbed by air, thus heating it; at the same time, an optical radiation beam acts as a linear extended heat source. The resulting convective phenomena contribute to atmospheric turbulence. Indoors, this convective turbulence has features related to spatial limitations and the presence of other heat sources. In this paper, convective air motions in a vicinity of a group of linear extended optical sources in a horizontal configuration of an open-side room under external wind influence are studied by numerically solving three-dimensional Navier-Stokes equations. To parallelize the calculations, a computing cluster with MPI interface was used. Convective cells arising along inclined optical beams and the corresponding velocity and temperature fields are described. It was found that the shape and location of the cells are determined by the inclination of beams optical axis and the configuration of the room. The evolution of temperature and velocity fields is shown. Spatial spectra of temperature fluctuations in various directions, including in the vicinity of optical paths, are constructed. The causes are described and the mutual effects of the beams are estimated upon changes in the structural characteristic of air refractive index fluctuations in the vicinity of inclined optical paths. The influence of the external wind on the thermal traces of optical radiation beams inside and outside the room is considered. Upon completion of the numerical experiment, there is a turbulence inside the room with spectrum of temperature fluctuations similar to Kolmogorov spectrum. The considered situations can be observed in specialized rooms of optical systems when air is heated by optical radiation of varying intensity. The resulting turbulence fields of convective and dynamic nature significantly impact the operation of recording devices. The results are important for predicting the correct operation of such devices and for evaluating the mutual influence of optical beams.
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