The research described in this thesis has been focused on the detailed investigation of horizontaludco-current liquid-liquid two-phase flows. The experiments were carried out in channels ofudsquare and circular cross section and involved the use of two immiscible liquids of matchedudrefractive index; namely an oil (Exxol™D80) and a 81.7 wt% glycerol-water solution. Theudexperiments were carried out in a refurbished liquid-liquid flow facility (TOWER) and the focusudwas on examining the flows using high-speed laser-based visualisation methods which allowedudboth qualitative evaluation of the nature of the flows (i.e. the flow patterns) and quantitativeudmeasurements of parameters such as drop size and velocity distribution. The laser-basedudtechniques used included Planar Laser Induced Fluorescence (PLIF), Particle TrackingudVelocimetry (PTV) and Particle Image Velocimetry (PIV). Using these techniques, it wasudpossible to obtain high spatial and temporal resolution measurements of velocity and phaseuddistribution of liquid-liquid flows which enabled the detailed diagnostic inspection to an extentudthat has not been previously possible. 144 experiments were carried out in three experimentaludcampaigns. In the first campaign, a square cross section channel was used in order to avoidudimage distortion by the channel walls. In the second and third campaigns, a circular tube wasudemployed and a graticule correction method was used to correct the distortion to the PLIF andudPTV/PIV images which occurs when the circular cross-section visualisation cell is used. In theudtwo circular tube experiments, two methods of injection of the phases were used: (1) the heavierud(glycerol solution) phase was injected in its natural location at the bottom of the channel, andud(2) in the second case the heavier phase was injected at the top of the channel.udThe PLIF images gave a clear indication of the distribution of the phases at the channel centreudline and have been used qualitatively in obtaining information about the flow patterns occurring. The PLIF images have also been used quantitatively in generating data on phase distribution, insituudphase fraction, interface level and drop size distribution. Much of the data on in-situ phaseudfraction and interface level fits well with a simple laminar-laminar stratified flow model. TheudPTV/PIV method provided extensive data on velocity profiles; in the lower (aqueous glyceroludsolution) phase, the profile usually showed the curved shape characteristic of laminar flow andudin the upper (Exxol™D80) phase, the velocity profile often showed the flattened formudcharacteristic of turbulent flow.
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