In order to explore the laser propagation influence of thermal blooming effect of pipe flow and to analysis the influencing factors, scaling law theoretical analysis of the thermal blooming effects in pipe flow are carry out in detail based on the optical path difference caused by thermal blooming effects in pipe flow. Firstly, by solving the energy coupling equation of laser beam propagation, the temperature of the flow is obtained, and then the optical path difference caused by the thermal blooming is deduced. Through the analysis of the influence of pipe size, flow field and laser parameters on the optical path difference, energy scaling parameters Ne=nTαLPR2/(ρεCpπR02) and geometric scaling parameters Nc=νR2/(εL) of thermal blooming for the pipe flow are derived. Secondly, for the direct solution method, the energy coupled equations have analytic solutions only for the straight tube with Gauss beam. Considering the limitation of directly solving the coupled equations, the dimensionless analysis method is adopted, the analysis is also based on the change of optical path difference, same scaling parameters for the pipe flow thermal blooming are derived, which makes energy scaling parameters Ne and geometric scaling parameters Nc have good universality. The research results indicate that when the laser power and the laser beam diameter are changed, thermal blooming effects of the pipeline axial flow caused by optical path difference will not change, as long as you keep energy scaling parameters constant. When diameter or length of the pipe changes, just keep the geometric scaling parameters constant, the pipeline axial flow gas thermal blooming effects caused by optical path difference distribution will not change. That is to say, when the pipe size and laser parameters change, if keeping two scaling parameters with constant, the pipeline axial flow thermal blooming effects caused by the optical path difference will not change. Therefore, the energy scaling parameters and the geometric scaling parameters can really describe the gas thermal blooming effect in the axial pipe flow. These conclusions can give a good reference for the construction of the thermal blooming test system of laser system. Contrasted with the thermal blooming scaling parameters of the Bradley-Hermann distortion number ND and Fresnel number NF, which were derived based on the change of far field beam intensity distortion, the scaling parameters of pipe flow thermal blooming deduced from the optical path deference variation are very suitable for the optical system with short laser propagation distance, large Fresnel number and obviously changed optical path deference.
In order to weaken the chemical laser exhaust gas influence of the optical transmission, a vent pipe is advised to emissions gas to the outside of the optical transmission area. Based on a variety of exhaust pipe design, a flow field characteristic of the pipe is carried out by numerical simulation and analysis in detail. The research results show that for uniform deflating exhaust pipe, although the pipeline structure is cyclical and convenient for engineering implementation, but there is a phenomenon of air reflows at the pipeline entrance slit which can be deduced from the numerical simulation results. So, this type of pipeline structure does not guarantee seal. For the design scheme of putting the pipeline contract part at the end of the exhaust pipe, or using the method of local area or tail contraction, numerical simulation results show that backflow phenomenon still exists at the pipeline entrance slit. Preliminary analysis indicates that the contraction of pipe would result in higher static pressure near the wall for the low speed flow field, so as to produce counter pressure gradient at the entrance slit. In order to eliminate backflow phenomenon at the pipe entrance slit, concerned with the pipeline type of radial size increase gradually along the flow, flow field property in the pipe is analyzed in detail by numerical simulation methods. Numerical simulation results indicate that there is not reflow phenomenon at entrance slit of the dilated duct. However the cold air inhaled in the slit which makes the temperature of the channel wall is lower than the center temperature. Therefore, this kind of pipeline structure can not only prevent the leak of the gas, but also reduce the wall temperature. In addition, compared with the straight pipe connection way, dilated pipe structure also has periodic structure, which can facilitate system integration installation.
For the thermal blooming of the beam path indoor, solving the coupling equations of optical field and fluid field
completely is a meaningful and important subject. In this paper a numerical emulation platform for solving the coupling
equations was established. The laser beam coupled with the fluid field by the method of User Defined Function which
was offered by the CFD software. Thermal blooming effects in the beam path indoor of the line pipe are modeled by the
established numerical emulation platform. In order to testify the rightness of the numerical emulation results, steady-state
thermal blooming effects in the axial pipe flow are calculated by the theoretical methods, and corresponding experiments
are also carried out. The results indicate that the numerical emulation platform is creditable in simulating the thermal
blooming of axial pipe flow.
The effect of beacon Anisoplanatism needs to be considered in analyzing the error of the adaptive optical system.
Therefore, thermal blooming anisoplanatic effect of the Gaussian beam is analyzed numerically and theoretically. Wavefront
distortion of the Gaussian beam caused by thermal blooming anisoplanatic effect is expanded by the Zernike
polynomials. The Zernike coefficient and the fitting error are obtained by numerical calculations. The comparisons
between the Zernike coefficients indicate that the defocus item is the most important to the angular anisoplanatic error.
Based on the Wave-front distortion caused by the thermal blooming angular anisoplanatic effect, the defocus coefficient
of the Zernike polynomials is obtained theoretically. The result of the angular anisoplanatic error calculated by
theoretical formula is consistent with the outcome of the numerical calculation, and the result also indicates that the
angular anisoplanatic error is the function of the caliber size and varies as the square of the anisoplanatic angle. The
square relation of angle anisoplanatism is consistent with the result obtained by the turbulence angular anisoplanatic