The flow field around a hemispherical/cylindrical structure at Mach number of Ma=0.4 is calculated, and the distributions of temporal root mean square value of velocity and density in the wake are presented. Further more, the optical path difference and aero-optical phase are calculated according to density field, and then the impact of the wake on adaptive optics systems with a point source and a plane-wave source beacon is studied respectively. It is found that there are plentiful turbulent structures in the wake, and the maximum values of the temporal root mean square of density and velocity both decrease 84% when the distance from the calculated position to the center of the structure varies from 0.43 m to 1.5 m. The spatial root mean square of optical path difference varies dramatically over time, and its time average gain two times while the angle of projection varies from 120°to 148°. The hemispherical/cylindrical wake has little impact on the adaptive optics system when the beacon is point source. While the wake has great impact when the beacon is plane-wave source, and the impact gets worse when the angle of projection gets larger. The Strehl ratio of the main laser decreases from 0.72 to 0.33 when the angle of projection increases from 120°to 148°.
A mesoscopic method is developed to analyze the temperature field of composite materials under laser radiation based on their meso-structures. Laser energy coupling to fibers and matrix are characterized by different absorption coefficients, and multi-phase heat transfer process in composites is solved by the lattice Boltzmann method (LBM). The temperature field of carbon fiber reinforced polymer(CFRP) composites with laser intensities ranging from 100 W/cm2 to 500 W/cm2 is calculated, and the results reveal that the temperature distribution of composites is closely related to their meso-structures.
A numerical study is conducted to determine which model could be used to compute temperature fields of polymer matrix composites under laser irradiating. By using the local thermal non-equilibrium model, solid and gas temperature on surfaces of materials with different volume convection coefficients have been computed and compared under different heat flux. The results show that the assumption of local thermal equilibrium is not reasonable until the heat flux applied to composites is low enough and the volume convection coefficient is big enough. And the gas may be not important for solid temperature when the volume convection coefficient is small.
In order to investigate the similarity on thermo-mechanical effects by different pulsed beams, this paper
conducts a comparison study on the blow-off impulse of aluminum target by pulsed ultraviolet laser and
X-ray irradiation. Especially, this paper focuses on the thermo-mechanical effects by pulsed ultraviolet laser
and X-ray (blow-off impulse), and build up the scaling relations of impulse coupling with aluminum target
by the two pulsed beams within a certain range of energy flux. The study shows that, within the energy flux
range of 100~400J/cm2, although the mechanisms of blow-off impulse generation of the two pulsed beams
are different, the impulse coupling with aluminum target or impulse coupling coefficients of both X-ray and
laser have similar scaling relations. Among others, the impulse coupling coefficient of X-ray is larger than
that of laser. Based on the comparison of scaling relations, this paper provides the similarity between the
two pulsed beams.