A laser-induced surface flow visualization technique using liquid crystal thermography

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Title: A laser-induced surface flow visualization technique using liquid crystal thermography
Author: Hunt, Emily McFather
Abstract: Observation of flow field characteristics such as flow separation and reattachment are important in many industries . Current methods for flow visualization can be difficult to implement , expensive , and highly intrusive . The objective of this project is to develop an inexpensive , user -friendly , non -intrusive measurement technique useful to engineers interested in surface flow visualization . This is accomplished using liquid crystals in conjunction with a laser heat source to generate a thermal tuft . The shape and size of the thermal tuft is used to characterize the flow field . Wind tunnel experiments are conducted to validate this concept and examine flow behavior over a flat plate in a low Reynolds number environment . The plate is coated with liquid crystals of one -degree and fivedegree bandwidths . A 150 -mW infrared , diode laser provides a constant heat source and generates a high temperature thermal spot on the model . The results obtained during the wind tunnel experimentation show that an irradiated spot on a liquid crystal coated surface will produce a tuft . The shape and size of the thermal tuft is indicative of the direction and magnitude of the flow conditions . As the wind speed increases from 2 to 10 m /s , it was shown that the length of the thermal tuft increases linearly . The tail of the tuft was also found to follow the direction of flow . Turbulent and laminar flow conditions can be distinguished ; however , the angle of attack could not be realized with this technique . Developing a technique for generating a matrix of heated spots on the model indicates that the results of using this method can be viewed over a large area . Overall , it was shown that this is an easy , inexpensive , and non -intrusive technique for visualizing flow on the surface of an object .
URI: http : / /hdl .handle .net /2346 /11912
Date: 2002-12

Citation

Hunt, Emily McFather A laser-induced surface flow visualization technique using liquid crystal thermography. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /11912 .

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