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Subject: fractionation ×

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    Scheme for calculation of multi-layer cloudiness and precipitation for climate models of intermediate complexity
    (München : European Geopyhsical Union, 2013) Eliseev, A.V.; Coumou, D.; Chernokulsky, A.V.; Petoukhov, V.; Petri, S.
    In this study we present a scheme for calculating the characteristics of multi-layer cloudiness and precipitation for Earth system models of intermediate complexity (EMICs). This scheme considers three-layer stratiform cloudiness and single-column convective clouds. It distinguishes between ice and droplet clouds as well. Precipitation is calculated by using cloud lifetime, which depends on cloud type and phase as well as on statistics of synoptic and convective disturbances. The scheme is tuned to observations by using an ensemble simulation forced by the ERA-40-derived climatology for 1979–2001. Upon calibration, the scheme realistically reproduces basic features of fields of cloud fractions, cloud water path, and precipitation. The simulated globally and annually averaged total cloud fraction is 0.59, and the simulated globally averaged annual precipitation is 100 cm yr−1. Both values agree with empirically derived values. The simulated cloud water path is too small, probably because the simulated vertical extent of stratiform clouds is too small. Geographical distribution and seasonal changes of calculated cloud fraction and precipitation are broadly realistic as well. However, some important regional biases still remain in the scheme, e.g. too little precipitation in the tropics. We discuss possibilities for future improvements in the scheme.
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    Continuous electroosmotic sorting of particles in grooved microchannels
    (London : Royal Soc. of Chemistry, 2017) Dubov, Alexander L.; Molotilin, Taras Y.; Vinogradova, Olga I.
    We propose a novel microfluidic fractionation concept suitable for neutrally buoyant micron-sized particles. This approach takes advantage of the ability of grooved channel walls oriented at an angle to the direction of an external electric field to generate a transverse electroosmotic flow. Using computer simulations, we first demonstrate that the velocity of this secondary transverse flow depends on the distance from the wall, so neutrally buoyant particles, depending on their size and initial location, will experience different lateral displacements. We then optimize the geometry and orientation of the surface texture of the channel walls to maximize the efficiency of particle fractionation. Our method is illustrated in a full scale computer experiment where we mimic the typical microchannel with a bottom grooved wall and a source of polydisperse particles that are carried along the channel by the forward electroosmotic flow. Our simulations show that the particle dispersion can be efficiently separated by size even in a channel that is only a few texture periods long. These results can guide the design of novel microfluidic devices for efficient sorting of microparticles.