ZIB

1

Digitale Medien

Asymptotic solution and numerical simulation of homogeneous condensation in expansion cloud chambers (1996)

Delale, C. F. ; Muitjens, M. J. E. H. ; van Dongen, M. E. H.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 105 (1996), S. 8804-8821

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: Asymptotic solution of homogeneous condensation in expansion cloud chambers in different droplet growth regimes is presented. In particular an exactly solvable droplet growth model ranging between the Hertz–Knudsen and continuum droplet growth laws is introduced. The distinct condensation zones in each droplet growth regime are identified by the asymptotic solution of the condensation rate equation and the results are compared with those of direct numerical simulations using the classical nucleation theory. Excellent qualitative agreement is reached despite some minor quantitative differences in some of the condensation zones arising from the nature of the asymptotic solution in these zones. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.472631

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2

Digitale Medien

On the stability of stationary shock waves in nozzle flows with homogeneous condensation (2001)

Delale, C. F.

[S.l.] : American Institute of Physics (AIP)

Physics of Fluids 13 (2001), S. 2706-2719

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ISSN: 1089-7666

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The stability limit of stationary normal shock waves in supercritical nozzle flows with homogeneous condensation is investigated by the singularity theory of the quasi-one-dimensional steady-state differential equations of motion. In this case it is shown that a catastrophic change in the phase portraits of the flow variables, where the spiral point turns into a nodal point, occurs when the initial relative humidity exceeds a critical value, resulting in the alteration of the quasi-one-dimensional steady-state condensation structures. In particular, a criterion for the limit of stability, based on the break-up of structural stability of the steady equations of motion in the quasi-one-dimensional approximation, is established by variational analysis and a correlation for the critical initial relative humidity is derived for fixed nozzle geometry keeping appropriate reservoir conditions fixed in the same approximation. A comparison of the values of the critical initial relative humidity, calculated by this correlation, shows excellent agreement with those of experiments and/or numerical simulations for moist air expansions in various slender nozzles under different reservoir conditions. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1388206

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3

Digitale Medien

A comparison of nucleation theories by the asymptotic solution of condensing nozzle flows (1996)

Delale, C. F. ; Meier, G. E. A.

Springer

Acta mechanica 117 (1996), S. 23-32

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ISSN: 1619-6937

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau , Physik

Notizen: Summary The classical and Dillmann-Meier nucleation rates are compared in transonic nozzle flows of moist air under atmospheric supply conditions using the asymptotic solution of Delale, Schnerr and Zierep. The comparison is made in slender nozzles using two distinct expressions for the poorly known surface tension, one fitted to the experiments of Peters and Paikert by the classical theory and the other extrapolated from room temperatures to the range of temperatures investigated. The droplet growth law is fixed by the Hertz-Knudsen formula. It is shown that the Dillmann-Meier theory predicts higher nucleation rates than the classical theory together with a delay of the onset of condensation when either of the surface tension expressions is employed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01181034

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4

Digitale Medien

Thermal choking in two-dimensional expansion flows (1998)

Delale, C. F. ; van Dongen, M. E. H.

Springer

Zeitschrift für angewandte Mathematik und Physik 49 (1998), S. 515-537

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ISSN: 0044-2275

Schlagwort(e): Key words. Heat addition, two-dimensional expansion flows, critical heat, thermal choking.

Quelle: Springer Online Journal Archives 1860-2000

Thema: Mathematik , Physik

Notizen: Abstract. Two-dimensional supersonic flows with heat addition from given internal sources and/or nonequilibrium condensation are considered. The critical amount of heat necessary to thermally choke the flow is defined at any point in the flow field, and the necessary and sufficient conditions for thermal choking are identified from the singularities of the equations of motion along streamlines. In particular, for any practical purposes, it is shown that the flow Mach number reaches unity at any point where the heat added to the flow along the streamline passing through that point reaches the critical value. Thermally choked flows are then identified as those flows where the critical heat along streamlines is exceeded leading to embedded oblique shock waves with a local subsonic flow field downstream.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s000000050106

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