Computational Simulation On Human Thermal Regulation Based On A Multi-scale Model

Human body is a complicated system that is able to control thermal responses to different thermal environments. An image-based finite element model of human hand was first developed in this thesis to analyzethe relationship between vasomotion of microcirculation and fingertip temperature oscillations.Wavelet analysis was further employed to extract the temperature oscillations in the frequency of microvessel endothelium and compared with the experimental temperature data.On this basis, an integrated model including blood circulation, heat transfer and clothing system was developed to analyze skin blood variation and thermal regulation in different conditions.The main contents are as follows:1. Skin temperature oscillation modeling for assessing vasomotion of microcirculationBased on the developed porous media model of heat transfer,a mathematical relation was formulated to evaluate micro-vasomotion through the skin temperature,where the porosity which represents the density of microvessels was assumed to vary periodically and was a function of the skin temperature. Finite element analysis of skin temperature for a contra lateral hand under a cooling test was conducted. Subsequently, wavelet analysis was carried out to extract the temperature oscillations of the data through the numerical analysis. Furthermore, the oscillations extracted from the numerical analysis were statistically analyzed to compare the amplitude. The simulation results show that for the subjects in cardiovascular health, skin temperature fluctuations in endothelial frequency decrease during the cooling test and increase gradually after cooling, implying that the assumed porosity variation can represent the vasomotion in the endothelial frequency band.2. Integrated thermal modeling for blood circulation-heat transfer-clothing system6elliptic cylinders were adopted to construct a3-D human body model, including head, trunk, arms and legs. This geometrical model can be modulated in size to various objects and can be directly constructed from medical images. Then the3-D heat transfer model was coupled with the1-D blood circulation and thermal regulation model. Blood flow, temperature distribution and heat generation by shivering and evaporation were calculated by this comprehensive model. The integrated model was validated by comparing other simulation and experimental results under cold and heat stress.The results show how human heat-regulating center maintain the stabilization of core temperature, especially on the condition of extreme environment. Compared with nude model, a rise of5℃in the skin temperature was found for clothing model (lclo), which revealed that right clothes played an important role in keeping temperature of human skin.The integrated model is helpful in studying the thermoregulation behaviors of blood flow and body temperature and can be applied in evaluation of safety driving, prediction of heat-illness symptoms and thermal therapy, and design of special clothing.