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In this paper, a sequence of passive micromixers with spiral patterns on the side wall of cylindrical chambers are designed, optimized, prepared and tested. The simulation studies show that the vortex magnitude and continuity in the mixing chamber are the most important factors to determine mixing performance, while the inlet position and structural parameters are secondary influences on their performance. According to the above principles, the performance of a micromixer with a continuous sidewall spiral finally wins out. The total mixing length is only 14 mm, but when Re = 5, the mixing index can reach 99.81%. The multi-view visual tests of these mixer chips prepared by 3D printing are consistent with the simulation results. This paper provides a new idea for optimizing the micromixer with spiral patterns on the side wall and the problems of floor area and pressure loss are significantly improved compared to the conventional spiral structure.

The improved discrete ordinates method (IDOM) developed in our previous paper is extended to solve radiative transfer in three-dimensional radiative systems with anisotropic scattering medium. In IDOM, radiative intensities in a large number of new discrete directions are calculated by direct integration of the conventional discrete ordinates method (DOM) results, and radiative heat flux is obtained by integrating radiative intensities in these new discrete directions. Ray effects and false scattering, which tend to compensate each other, are investigated together in IDOM. Results show that IDOM can mitigate both of them effectively with high computation efficiency. Finally, the effect of scattering phase function on radiative transfer is studied. Results of radiative heat flux at boundaries containing media with different scattering phase functions are compared and analyzed. This paper indicates that the IDOM can overcome the shortages of the conventional DOM well while inheriting its advantages such as high computation efficiency and easy implementation.