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SUMMARY:Interfacial Studies on a Charged Surface in Oil by Contact Angle M
 easurements / Natural ventilation of an enclosed space driven by periodic 
 gusting of wind - Seung Yeon Lee / Richard Mott\, BP Institute
DTSTART:20101202T113000Z
DTEND:20101202T123000Z
UID:TALK31876@talks.cam.ac.uk
CONTACT:Helen Mawdsley
DESCRIPTION:Interfacial Studies on a Charged Surface in Oil by Contact Ang
 le Measurements (Seung Yeon Lee)\nContact angles are dependent upon three 
 interfacial energies: γ_solid/liquid \, γ_solid/vapour \, and γ_liquid/
 vapour  according to Young’s relation. Solid\, liquid and vapour phases 
 in this work are respectively amorphous silicates\, water droplets and oil
  media. Due to the three variables\, contact angles could be insufficient 
 but necessary to study the surface modification and water adsorption on th
 e surfaces /in situ/. Surfactants\, Ca(AOT)_2  added in the oil phase can 
 modify the surface via a cation bridging and hence the surface tension\, 
 γ_solid/liquid . Added electrolytes in water droplets can vary the water 
 adsorption on the modified surfaces.\nNatural ventilation of an enclosed s
 pace driven by periodic gusting of wind (Richard Mott)\nWe investigate the
  mixing of a warm enclosed space by a series of discrete gusts of cold air
  from a high level opening. Initially we examine the case of a series of g
 usts of identical size each modelled as a turbulent buoyant thermal and de
 velop a model of the filling box like flow which develops in the space.  W
 e successfully test the predictions of the model with a series of new labo
 ratory experiments. The experiments combined with the model also provide a
  new independent estimate for the entrainment coefficient of a thermal\, b
 ased on the propagation speed of a filling box front. We then examine the 
 mixing produced by a series of thermals of non identical size which we cha
 racterise in terms of a mean size and coefficient of variation. We find th
 at as the coefficient of variation increases\, the density profile becomes
  progressively more stratified owing to the asymmetry of dilution through 
 entrainment of large and small thermals. 
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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