Experimental Study On Simultaneous Measurement Of Temperature And Velocity Fields In Thermal Convection Process

With the increasing demand for Marine resource exploration and underwater target identification,it is particularly important to monitor the heat convection and analyze and discuss its evolution law,so as to realize the identification from "field" to "source".In order to achieve this goal,it is necessary to simultaneously measure its multi-physical fields,and analyze and study its evolution law from its momentum and heat transfer perspectives,so as to enhance the ability of underwater target recognition.In this paper,based on Laser Induced Fluorescence(LIF)and Particle Image Velocimetry(PIV),an experimental system for simultaneous measurement of underwater temperature field and velocity field was established.Under the condition of ensuring the measurement reliability of the system,the 2D temperature field and the 2D3 C velocity field in the thermal wake were measured simultaneously,and the flow and heat transfer characteristics were analyzed,and then the relevant conclusions were drawn.This paper has mainly completed the following work:1.Synchronous measurement system construction.The simultaneous measurement system of temperature field and velocity field was established,and the experimental process of the system was improved.The corresponding auxiliary experimental devices were designed for different experimental objects,and the relevant codes were written to realize the space-time matching of temperature field measurement and temperature field with velocity field.2.Study on the characteristics of fluorescein dye in temperature measurement experiment.Aiming at the laser-induced fluorescence technology,the temperature sensitivity and photo-bleaching characteristics of each dye and its combination in KR/FL27 and RHB /FL27 were studied experimentally.The relative characteristics were determined and the advantages and disadvantages of each dye combination were summarized.3.Study on flow and heat transfer characteristics of natural convection based on synchronous measurement:simultaneous measurement of natural convection between plates was realized and verified by numerical simulation.The measurement of synergistic Angle is realized and the heat transfer performance of different regions is discussed.Through further analysis of the second-order statistics,the spatial distribution characteristics of momentum and heat transfer are determined.It is found that the heat and momentum transfer outside the large-scale circulation have obvious directionality,and the influence range of momentum and heat transfer shows obvious evolution law with the change of spatial location.4.Study on flow and heat transfer characteristics of hot jet based on synchronous measurement.In this study,the 2D temperature field and the 2D3 C velocity field in the hot jet were measured simultaneously.The flow and heat transfer laws of the tube are analyzed,and the effects of different parameters on the tube are discussed.The results show that in terms of heat transfer,the spiral tube can enhance the migration of energy from low mode to high mode.The increase of temperature difference makes the heat transfer structure merger intensely in the process of moving downstream.In terms of momentum transfer,the spiral tube further strengthens the migration of energy from low-order mode to high-order mode,and the increase of temperature difference can promote the merger of momentum transfer structures and make them more orderly.