a b s t r a c tIn micromixers, fluids deform through convection generated by variations in the shape of a channel, e.g., channel confluence and bend. This deformation enhances the mixing performance of the micromixer. In this study, we consider the effect of deformation on mixing performance in terms of a reduction in diffusion length, which is equivalent to the size of the fluid segments formed through fluid deformation. Based on improvements in the mixing rate through convection, we establish a design method that enables a micromixer to achieve a desired rapid mixing rate. For this purpose, we correlate the mixing performance of micromixers having various channel shapes and fluid velocities with the diffusion length; the equivalent mixing rate is obtained using computational fluid dynamics (CFD) simulations. The results of the CFD simulations reveal that the combination of fluid collision and channel bend after the development of the velocity profile of confluent flow is effective at enhancing the mixing rate. To establish a design method for a micromixer, we define and employ the energy dissipation rate based on the pressure drop profile in microchannels. The relationship between the segment size and the energy dissipation rate based on channel shape has been derived and integrated into the design method.

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In a recent paper a variational form of the continuum distorted wave approximation was used to calculate a variational expression for the cross section for resonant ground state capture at very high velocities in proton-hydrogen atom collisions. In this paper the previous work is extended in that the cross section is calculated by first calculating a variational expression for the transition amplitude. The resulting cross section is found to have the form o = 26n.yt'-"(na;), where the velocity U is in atomic units, y = 4 exp(20)E2(2.0), and where EZ(z) is the exponential function. This cross section differs from the high velocity limit of the cross section obtained in the second Born approximation, and in any other second order approximation. However, the present approximation is thought to be poor at large impact parameters so that the above result should probably not be taken too seriously.