Michael J. Labowsky

The effects of nearest neighbor interactions on the evaporation rate of cloud particles

Abstract A modified images method is presented and used to determine the vapor density field in arrays of up to nine “quasi-stationary” evaporating particles. The evaporation rate of each particle in an array is calculated as a function of the particle separation. Correction factors to Maxwells evaporation rate expression to account for nearest neighbor interactions are proposed. The “R 2 -law” is assessed and found to be only approximately correct when applied to interacting particles.

Inertial deposition of particles from potential flows past cylinder arrays

Abstract We exploit the computationally efficient method of images (MOI) to create steady potential flows past finite and infinite circular cylinder arrays, in order to study inertial impaction of particles on them. Although such flows are often encountered in practice (e.g. high Reynolds number “dusty gas” flows past heat exchanger tube banks and filter screens), little is yet known about the proximity effects of adjacent collectors on the capture efficiency of any particular collector in the array. Our results for linear, symmetric arrays in steady cross-flow, containing an odd number of collectors (from three to infinity), over a wide range of array spacings, support the conjecture that an appropriately defined effective Stokes number based on the stagnation region fluid deceleration rate (computed and reported here as a function of the number of collectors and their spacing) can adequately correlate, for practical purposes, the capture efficiency of a representative collector in the array. This scheme, combined with well-known correlations for an isolated collector, simplifies significantly the task of estimating inertial impaction rates on aerodynamically interacting collectors.

A model for solvated ion emission from electrospray droplets

A model is presented which shows that the energy required to emit small singly charged and large multiply charged (protein) solvated ions from electrospray droplets can be considerably lower than those predicted by earlier models. By allowing the droplet surface to distort in reaction to the emerging ion, a more nuanced picture of the ion emission mechanism appears, one that covers the range from pure ion evaporation (PIE) for small ions to what may be termed activated pseudo-Rayleigh ion release (PRIR), a mechanism that yields charge states nearly indistinguishable from the charge residue model (CRM), for large ions. Predictions based on this model are qualitatively consistent with many experimentally observed trends.

Transfer rate calculations for compositionally dissimilar interactiong particles

Abstract The method of images is shown to be applicable to the problem of calculating the transfer rates of interacting spherical particles, which differ in size and chemical composition. The method can be applied to any transfer problem in which the governing transport equations can be reduced to the Laplace equation and the particles have iso-potential surfaces. From a sample calculation it is found that, while particle interactions do not affect particle temperatures, they may severly affect the particle transfer rates. The effect of interactions on these transfer rates may be either positive (enhance transfer) or negative (retard transfer). Negative interaction effects may be sufficiently strong as to cause transfer reversal.