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The outer region of a turbulent boundary layer along a flat plate was photographed and analysed; in addition, limited observations of the wall area were also made. The technique involved suspending very small solid particles in water and photographing their motion with a high-speed camera moving with the flow.The single most important event observed in the outer region was fluid motion which in the convected view of the travelling camera appeared as a transverse vortex. This was a large-scale motion transported downstream almost parallel to the wall with an average velocity slightly smaller than the local mean. It appeared to be the result of an instability interaction between accelerated and decelerated fluid, and it is believed to be closely associated with the wall-region ejections. The transverse vortex was part of a deterministic sequence of events; although these events occurred randomly in space and time. The first of these events was a decelerated flow exhibiting velocities considerably smaller than the local mean. It was immediately followed by an accelerated flow. Both these events extended from near the wall to the far outer region. Their interaction resulted in the formation of one or more transverse vortices. While the transverse vortex was transported downstream, small-scale fluid elements, originating in the wall area of the decelerated flow, were ejected outwards (ejection event). After travelling some distance outwards the ejected elements interacted with the oncoming accelerated fluid in the wall region and were subsequently swept downstream (sweep event). The sequence of events closed with two large-scale motions.Estimated positive and negative contributions to the instantaneous Reynolds stress during the events were many times higher than the local mean values.

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It is my pleasure to acknowledge my teachers and friends who contributed to this work. I wish to express my special thanks and appreciation to my adviser, Dr. Robert S. Brodkey, who suggested the subject of this dissertation, enthusiastically followed its progress, and was never tired to work with his student in the lab until the early hours in the morning. My special thanks are also extended to Dr. Harry C. Hershey for his continuous advice during the course of this investigation.

SynopsisLength-temperature measurements on a seri-of polymer blends over the whole range of composition from pure polyethylene to pure polypropylene and one set of determinations on a 50:50 copolymer and on polystyrene are evaluated. The total crystallinity of the samples did not exceed 54%. The experimental procedure utilized a linear variable differential transformer without the use of a confining fluid, and the temperature ranged from about +20 to -185°C. A least-square numerical differentiation procedure based on moving arc9 is applied to yield directly the coefficients of thermal expansion as a function of temperature. The linear voltage differential transformer (LVDT) technique can detect transitions in which the change in thermal expansion coefficients is less than 10-6OC.-*. In polypropylene as well as the blends, the principal glass transition is clearly seen in the range observed by others, namely at about -9 to -14°C.Its location varies only slightly with composition at polyethylene contents less than 88 mole-%. For polyethylene the transition region broadens noticeably.The results are suggestive of two transitions for 0 > T > -40°C. A second transition region is observed for either pure component around -126OC. Its location varies somewhat with composition. However, our results do not indicate the appearance of an additional transition region characteristic of the mixture. The copolymer exhibits a major transition at -61°C. in good agreement with earlier workers. The thermal expansion decreases again around -150OC. In general our observations concerning transitions below T, are consistent with dynamic results.