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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenFri, 08 Dec 2023 12:21:26 +0000Kinetic‐Theory Description of Conductive Heat Transfer from a Fine Wire
https://resolver.caltech.edu/CaltechAUTHORS:20131120-135449172
Authors: Lees, Lester; Liu, Chung-Yen
Year: 1962
DOI: 10.1063/1.1706498
The Maxwell moment method utilizing the two‐sided Maxwellian distribution function is applied to the problem of conductive heat transfer between two concentric cylinders at rest. Analytical solutions are obtained for small temperature differences between the cylinders. The predicted heat transfer agrees very well with experiments performed on the heat loss from a fine wire by Bomelburg and Schäfer, Rating, and Eucken. Comparison with results given by Grad's thirteen‐moment equations, and with those given by Fourier's "law'' plus the Maxwell—Smoluchowski temperature‐jump boundary condition, shows that the two‐sided character of the distribution function is a crucial factor in problems involving surface curvature.https://authors.library.caltech.edu/records/0cazg-9fg16Reply by Authors to A. Goldburg
https://resolver.caltech.edu/CaltechAUTHORS:20170807-144358436
Authors: Behrens, Wilhelm; Lees, Lester
Year: 1965
DOI: 10.2514/3.55155
Goldburg has apparently misunderstood the significance of the local minimum critical Reynolds number (Re_f, d)min, er. When the effective turbulent diffusivity ε_T is smaller than the kinematic viscosity, v_i, the work done by the Reynolds stresses is more than counterbalanced by the rate of viscous dissipation. Thus, turbulence in the wake cannot exist when (ε_T/u_fd) < (v_f/u_jd), or when Re_f, d < (Re_f, d)min, er, any more than turbulent flow in a pipe can exist below a critical Reynolds number of 2000. If one chooses to call this "quenching," that is a problem in semantics and not in fluid mechanics.https://authors.library.caltech.edu/records/hpgrg-3pn34Finite disturbance effect on the stability of a laminar incompressible wake behind a flat plate
https://resolver.caltech.edu/CaltechAUTHORS:20120806-104808057
Authors: Ko, D. Ru-Sue; Kubota, T.; Lees, L.
Year: 1970
DOI: 10.1017/S0022112070000198
An integral method is used to investigate the interaction between a two-dimensional, single frequency finite amplitude disturbance in a laminar, incompressible wake behind a flat plate at zero incidence. The mean flow is assumed to be a non-parallel flow characterized by a few shape parameters. Distribution of the fluctuation across the wake is obtained as functions of those mean flow parameters by solving the inviscid Rayleigh equation using the local mean flow. The variations of the fluctuation amplitude and of the shape parameters for the mean flow are then obtained by solving a set of ordinary differential equations derived from the momentum and energy integral equations. The interaction between the mean flow and the fluctuation through Reynolds stresses plays an important role in the present formulation, and the theoretical results show good agreement with the measurements of Sato & Kuriki (1961).https://authors.library.caltech.edu/records/dz7g8-5mz59Near wake of a hypersonic blunt body with mass addition
https://resolver.caltech.edu/CaltechAUTHORS:20141201-162815216
Authors: Collins, Donald J.; Lees, Lester; Roshko, Anatol
Year: 1970
DOI: 10.2514/3.5775
An experimental investigation of the steady, laminar near-wake flowfield of a two-dimensional, adiabatic, circular cylinder ·with surface mass transfer has been made at a freestream Mach number of 6.0. The pressure and mass- concentration fields associated with the transfer of argon, nitrogen, or helium into the near wake were studied for mass transfer from the forward stagnation region, and from the base. For sufficiently low mass transfer rates from the base, for which a recirculating zone exists, the entire near-wake flowfield correlates with the momentum flux, not the mass flux, of the injectant, and the mass-concentration field is determined by counter-current diffusion into the reversed flow. For mass addition from the forward stagnation region, the pressure field is undisturbed and the mass- concentration field is nearly uniform in the region of reversed flow. The axial decay of argon mass concentration in the intermediate wake, downstream of the neck, is explained with the aid of an integral solution in the incompressible plane, from which the location of the virtual origin for the asymptotic far-wake solution has been derived as one result.https://authors.library.caltech.edu/records/k9t1y-dnm29Finite-Amplitude Instability of the Compressible Laminar
Wake. Strongly Amplified Disturbances
https://resolver.caltech.edu/CaltechAUTHORS:20120810-112829770
Authors: Liu, J. T. C.; Lees, Lester
Year: 1970
DOI: 10.1063/1.1692884
The interaction between mean flow and finite‐amplitude disturbances in certain experimentally observed unstable, compressible laminar wakes is considered theoretically without explicitly assuming small amplification rates. Boundary‐layer form of the two‐dimensional mean‐flow momentum, kinetic energy and thermal energy equations and the time‐averaged kinetic energy equation of spatially growing disturbances are recast into their respective von Kármán integral form which show the over‐all physical coupling. The Reynolds shear stresses couple the mean flow and disturbance kinetic energies through the conversion mechanism familiar in low‐speed flows. Both the mean flow and disturbance kinetic energies are coupled to the mean‐flow thermal energy through their respective viscous dissipation. The work done by the disturbance pressure gradients gives rise to an additional coupling between the disturbance kinetic energy and the mean‐flow thermal energy. The compressibility transformation suggested by work on turbulent shear flows is not applicable to this problem because of the accompanying ad hoc assumptions about the disturbance behavior. The disturbances of a discrete frequency which corresponds to the most unstable fundamental component, are first evaluated locally. Subsequent mean‐flow and disturbance profile‐shape assumptions are made in terms of a mean‐flow‐density Howarth variable. The compressibility transformation, which cannot convert this problem into a form identical to the low‐speed problem of Ko, Kubota, and Lees because of the compressible disturbance quantities, nevertheless, yields a much simplified description of the mean flow.https://authors.library.caltech.edu/records/x7hqb-87j77Oxidant and precursor trends in the metropolitan Los Angeles region
https://resolver.caltech.edu/CaltechAUTHORS:20140625-131747244
Authors: Trijonis, John; Peng, Ted; McRae, Gregory; Lees, Lester
Year: 1978
DOI: 10.1016/0004-6981(78)90083-5
This paper describes recent historical trends in oxidant and precursors in the Los Angeles region. Control strategies and basinwide emission trends for nitrogen oxides and reactive hydrocarbons are documented year by year from 1965 to 1974. Trends in the geographic distribution of emissions are illustrated by computing net percentage emission changes over the decade for individual counties. The changes in emissions are compared with changes in ambient precursor concentrations and oxidant concentrations. We find that many of the changes in monitored air quality can be explained by trends in both total emissions and the spatial distribution of emissions.https://authors.library.caltech.edu/records/bqedx-0hz09Theory of evaporation and condensation
https://resolver.caltech.edu/CaltechAUTHORS:KOFpof84
Authors: Koffman, L. D.; Plesset, M. S.; Lees, Lester
Year: 1984
DOI: 10.1063/1.864716
The theory of evaporation and condensation is considered from a kinetic theory approach with a particular interest in the continuum limit. The moment method of Lees is used to solve the problem of the steady flow of vapor between a hot liquid surface and a cold liquid surface. By incorporating the singular nature of the problem, the forms of the continuum flow profiles found by Plesset are recovered. The expression for mass flux has the form of the Hertz–Knudsen formula but is larger by a factor of 1.665. A result of the theory is that the temperature profile in the vapor for the continuum problem is inverted from what would seem physically reasonable. This paradox is significant in that it casts a shadow of doubt on the fundamental theory.https://authors.library.caltech.edu/records/15nd6-wp673