SIMULATANEOUS MEASUREMENT OF TEMPERATURE AND VELOCITY IN THRR-DIMENSIONAL SPACE BY LIQUID CRYSTALS AND APPLICATION TO STUDY OF TURBULENCE STRUCTURE OF THERMAL CONVECTION

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The research was carried out for investigating the simultaneous measurement technique of temperature and velocity field of three components with a liquid crystal visualization and PIV technique. This method was further extended to three-dimensional measuring technique by scanning a light sheet, which was used for the study of thermal convection. The results obtained here are summarized as follows.(1) Evaluation of uncertainty in temperature and velocity by artificial color imageA method for generating artificial color image was studied to simulate the color change by liquid crystal visualization. This color image was used for evaluating the temperature and two-components of velocity in a light sheet plane. This method was extended to three-components of velocity as well by using a stereoscopic configuration of the observation. The results indicate that the accuracy of velocity measurement was improved by adding a certain amount of tracer particles, but the addition of too many particle … More s is not suitable for the temperature measurement because of the reduction of measurable temperature area. Temperature calibration by three color parameters HIS produces a better accuracy than the others in temperature measurement. It is found from the stereo observation that there is an optimum off-axis observation angle for improving the accuracy of simultaneous measurement.(2) Application of stereo system to thermal convection studySimultaneous measurement of temperature and velocity in a thermal convection phenomenon was carried out in a three-dimensional volume of test section. The experiments are made for a fluid layer heated from below and cooled at the top boundary in a turbulent Rayleigh-Bernard convection. The results indicate that the hot plumes are generated from the heated boundary and cold plumes are created from the cooled boundary, and they interact with each other in the middle of the fluid layer. It is found that these generation of the plumes are random in space and three-dimensional in structure. However, the vertical velocity of the plumes and the temperature fluctuations are well correlated and varied with the distance from the wall. It is also found from the three-dimensional measurement that the structure of the plumes near the heated surface has a form of spoke structure. Less