Numerical modeling of the early stage of cloud formation in a simulation chamber

<p>"A numerical model has been developed to simulate the growth of cloud droplets by condensation upon a spectrum of hygroscopic nuclei. The model is applicable to cloud simulation chamber conditions as well as to the study of the role of these nuclei on cloud base microstructure.</p> <p>Equations are given for the growth by condensation of water vapor on a population of hygroscopic nuclei in a volume being cooled by expansion. The equations are integrated simultaneously, using Hamming's modified predictor-corrector method for given initial conditions, to obtain the droplet size distribution, temperature, pressure, supersaturation, and liquid water content. Temperature fluctuations, sedimentation of droplets, seeding with hygroscopic nuclei, and the effect of surface films in retarding the growth of nuclei are also considered.</p> <p>By assuming homogeneous thermodynamic parameters and condensation nuclei distribution in the initial volume, the results for adiabatic expansion show a tendency for the droplet spectrum to narrow, similar to the results obtained for closed parcel models. Temperature fluctuations tend to broaden the spectrum. This broadening depends upon the amplitude, frequency of fluctuations, and the expansion rate of the volume. Sedimentation of droplets is shown to be a critical factor in limiting the rate of expansion and the time required to record reliable observations.</p> <p>Calculations on the effect of seeding nuclei after a certain time of spectrum development indicate that the seeding effect depends significantly on the concentration and size of nuclei inserted, and the time of insertion. The passivation of nuclei by surfactant shows that surface films, in general, serve to delay the formation of cloud droplets for a time, depending upon the initial film thickness, condensation coefficient, size spectrum distribution of the nuclei, and the cooling rate"--Abstract, pages iii-iv.</p>

Name thesis:degree_name

Ph. D. in Mechanical Engineering

Grantor

University of Missouri--Rolla

Year dc:date.available

2016

Author dc:creator

• Saad, Adel Nassif

• Mechanical Engineering

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/60

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-1062