- Author
-
Klote, J. H.
- Title
- Pulsatile Infiltration.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Sponsor
- George Washington Univ., Washington, DC
- Report
-
PHD THESIS,
December 1985,
187 p.
- Keywords
-
smoke
|
vortex pairs
- Abstract
- Conventional steady flow methods are inappropriate for analysis of infiltration when the average pressure difference across a leakage path is small compared to the fluctuating component. The direction of such flow reverses or pulsates. The objective of this project is to study pulsatile infiltration in the laboratory to gain an understanding of the process and to relate these experimental findings to the practical concerns of air infiltration in buildings and of smoke infiltration due to building fires. The experimental apparatus that was constructed for this project was limited to sinusoidal motion for ease of analysis. Quasi-steady analysis of air flow at room temperature through straight slots was shown to be appropriate provided that the square of the slot thickness divided by the period of pulsation is less than 1.5 x 10(-6) m(2)/s (1.6 x 10(-5) ft(2)/sec.). From visualization photographs of flow outside the slot, two distinct types of mixing were observed. The first was characterized by a free vortex pair moving away from the slot. The second consisted of slow motion in the vicinity of the slot. The transition between these two types of mixing was at a Reynolds number of 16 (where the length is the hydraulic diameter of the slot and the velocity is at the maximum flow through the slot). Two methods of mass transfer analysis were developed, both of which were in very good agreement with the results of tracer gas experiments. The method called effective steady flow does not provide the insight of the other method but lends itself to calculation. An approach for computer simulation of pulsatile infiltration based on the effective steady flow concept is presented. An example calculation is presented which illustrates that for specific fire situations pulsatile smoke infiltration can pose a real threat to life.