Mean free path

About: Mean free path is a research topic. Over the lifetime, 4412 publications have been published within this topic receiving 114418 citations.

Multidimensional quasiballistic thermal transport in transient grating spectroscopy

Abstract: Transient grating spectroscopy has emerged as a useful technique to study thermal phonon transport because of its ability to perform thermal measurements over length scales comparable to phonon mean free path (MFPs). Although several prior works have performed theoretical studies of quasiballistic heat conduction in transient grating, the analysis methods are either restricted to one spatial dimension or require phenomenological fitting parameters. Here, we analyze quasiballistic transport in a two-dimensional transient grating experiment in which heat conduction can occur both in and cross plane using an analytic Green's function of the Boltzmann equation we recently reported that is free of fitting parameters. We demonstrate a method by which phonon MFPs can be extracted from these measurements, thereby extending the MFP spectroscopy technique using transient grating to opaque bulk materials.

Resistance of a gaseous medium to the motion of a spherical particle of a size comparable to the mean free path of the gas molecules

Abstract: An assumption is made that inside the “ limiting sphere ” surrounding the particle the transfer of momentum to the latter proceeds according to the laws of the gas kinetic theory, and on the outside of the sphere according to the laws of the hydrodynamics of a viscous fluid. The distance between the particle and the limiting sphere is of the same order of magnitude as the mean free path of gas molecules A. From this assumption an approximate expression for the mobility of spherical particles is deduced which agrees satisfactorily with the results of Millikan’s measurements in the whole range of Air-values covered by these measurements. All the coefficients in this expression can be computed theoretically.