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Convective Flows Under Conditions Applicable to Fires in High Rise Buildings


Cannon, Johnnie B., Jr. (1975) Convective Flows Under Conditions Applicable to Fires in High Rise Buildings. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/DXY0-9G71.


This study was an attempt to analyze convective flow patterns under conditions applicable to fires in high rise buildings when natural convection alone is the most important driving force. The primary aim of this investigation was to consider the turbulent flow in vertical shafts caused by hot gases entering the bottom of the shaft which is already filled with a cooler (denser) gas, and hence creating an unstable density field.

The small scale model used to study this problem consisted of a vertical tube of dense fluid placed in an infinite (less dense) fluid environment. General scaling laws were developed for the variation of density with time for the flow set up in the model. Also, an analytical model was developed to account for the observed mixing rates in this simple configuration.

In the analysis, the diffusion equation was solved and found to be in agreement with the small scale model. The mixing coefficient for this unstable system is

See abstract for formula

where the constant, 0.28, was determined empirically, and the fundamental time scale that characterizes the mixing in the vertical column is

See abstract for formula

Later, the above techniques were used to investigate in a more superficial way the effects on the mixing rates of geometric variations, limited external environments, changes in the internal geometry of the shafts, gas density ration, and heat transfer.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Mechanical Engineering
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Zukoski, Edward E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:20 September 1974
Funding AgencyGrant Number
NSFGI 31892X
Record Number:CaltechTHESIS:02282018-094023116
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10736
Deposited By: Benjamin Perez
Deposited On:28 Feb 2018 18:38
Last Modified:20 Dec 2019 19:56

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