In this work, a study involving the fully coupled Euler and Navier-Stokes reactive equations is performed. These equations, in conservative and finite volume contexts, employing structured spatial discretization, on a...In this work, a study involving the fully coupled Euler and Navier-Stokes reactive equations is performed. These equations, in conservative and finite volume contexts, employing structured spatial discretization, on a condition of thermochemical non-equilibrium, are analyzed. High-order studies are accomplished using the Spectral method of Streett, Zang, and Hussaini. The high enthalpy hypersonic flows around a circumference, around a reentry capsule, along a blunt body, and along a double ellipse in two-dimensions are simulated. The Van Leer, Liou and Steffen Jr., and Steger and Warming flux vector splitting algorithms are applied to execute the numerical experiments. Three temperatures, which are the translational-rotational temperature, the vibrational temperature, and the electron temperature, are used to accomplish the numerical comparisons. Excellent results were obtained with minimum errors inferior to 6.0%. The key contribution of this work is the correct implementation of a three temperature model coupled with the implementation of three algorithms to perform the numerical simulations, as well the description of energy exchange mechanisms to perform more realistic simulations.展开更多
This paper extends the previous work[1]for the three-temperature gray radiative transfer equations to the frequency-dependent case.Since the additional frequency variable is considered,the equations are more complicat...This paper extends the previous work[1]for the three-temperature gray radiative transfer equations to the frequency-dependent case.Since the additional frequency variable is considered,the equations are more complicated than those in the gray case.Moreover,opacity may be typically a decreasing function of the frequency variable in applications.At the same spatial location,the equations can be in the optically thick case for low frequency photons,while in the optically thin case for high frequency ones.Thus,the resulting discrete equations can significantly increase the computational cost for opacity having the multi-scale property in multiple frequency radiation.Due to the presence of the radiation-electron coupling,electronion coupling,and electron-ion diffusion terms,the model under consideration exhibits strong nonlinearity and strong coupling properties.In this paper,the multigroup method is used to discretize the frequency variable and the H_(N)^(T)method to discretize the angular variable first.Then,within the framework of a unified gas kinetic scheme(UGKS),a multigroup H_(N)^(T)-UGKS method is constructed to solve this complex model iteratively.Furthermore,it can be shown that as the Knudsen number tends to zero,with variations in the electron-ion coupling,absorption,and scattering coefficients,the multigroup H_(N)^(T)-UGKS scheme can converge to numerical schemes for the single-temperature,two-temperature,and the frequency-dependent three-temperature,two-temperature diffusion limit equations,respectively.Finally,several numerical examples are provided to validate the effectiveness and stability of the proposed scheme.展开更多
The evapotranspiration(ET)from urban vegetation is recognized as an effective way to improve the urban thermal environment.However,the traditional ET measurement approaches,such as the sap flow method,are limited in p...The evapotranspiration(ET)from urban vegetation is recognized as an effective way to improve the urban thermal environment.However,the traditional ET measurement approaches,such as the sap flow method,are limited in providing urban ET for specific areas.Consequently,establishing quantitative relationship between cooling effects and ET becomes challenging,which is crucial for understanding the role of urban greenery in mitigating urban heat.To overcome this challenge,an estimation model based on the three-temperature(3T)model was developed for accurately estimating urban ET by employing a reference tree with accurate ET data.In contrast to the 3T model,this study proposed a new method(modified 3T model)that considers the influence of the three-dimensional crown structure on the energy balance.Additionally,it retains the advantage over traditional ET models by not requiring the calculation of resistance parameters.This reduces the impact of uncertainty in the estimated resistance parameters on the ET results.The modified 3T model was validated based on the sap flow method and Bowen ratio system,where the results indicated good agreement between the modified 3T model and measured ET data,with root mean square errors of 22.2 W·m^(−2)and 26.4 W·m^(−2),respectively.Furthermore,the absolute relative error of ET estimation was affected by energy-related factors,such as solar radiation,air temperature,and relative humidity.The modified 3T model exhibited low sensitivity to surface temperatures,where the average sensitivity coefficients were below±0.15 from 0600 local time(LT)to 1700 LT.Considering the low accuracy of surface temperatures measured by infrared cameras(±2℃),it would be beneficial to combine the modified 3T model with unmanned aerial vehicles and infrared remote sensing to measure urban ET.展开更多
Population of the rare and endangered species Ammopiptanthus mongolicus （Maxim.） Cheng f. declined rapidly in China＇s add region and Central Asia. There is an urgent need to protect this species, which is particula...Population of the rare and endangered species Ammopiptanthus mongolicus （Maxim.） Cheng f. declined rapidly in China＇s add region and Central Asia. There is an urgent need to protect this species, which is particularly important in maintaining biodiversity throughout the arid region of northwestern China. By analyzing the infrared thermal images based on plant-transpiration transfer coef- ficient （hat） and photosynthetic parameters, we made quantitative and accurate diagnoses of the plant growth and health status of A. mongolicus. Using an LI-COR6400 photosynthesis system, we measured the net photosynthetic rate （Pn）, stomatal conductance （Gs）, and transpiration rate （Tr）. Infrared thermal images obtained in the field were processed by ENVI4.8 software to calculate surface tem- peratures of the plant subjects. We found that the plant transpiration transfer coefficient of A. mongolicus was inthe order of old plants 〉young plants 〉intermediate-aged plants. Declining health levels of young, intermediate, and old plants were divided into three categories： 〈0.4, 0.4-0.7, and 〉0.7. The coefficient showed a significant negative correlation with Tr, Gs, and Pn, indicating that they can simultaneously reflect the state of plant growth. By estab- lishing hat and photosynthetic parameters in regression model Y = a-blnx, we can accurately diagnose plant growth and decline of plant health conditions.展开更多
The main aim of this paper is to propose a new memory dependent derivative(MDD)theory which called threetemperature nonlinear generalized anisotropic micropolar-thermoelasticity.The system of governing equations of th...The main aim of this paper is to propose a new memory dependent derivative(MDD)theory which called threetemperature nonlinear generalized anisotropic micropolar-thermoelasticity.The system of governing equations of the problems associated with the proposed theory is extremely difficult or impossible to solve analytically due to nonlinearity,MDD diffusion,multi-variable nature,multi-stage processing and anisotropic properties of the considered material.Therefore,we propose a novel boundary element method(BEM)formulation for modeling and simulation of such system.The computational performance of the proposed technique has been investigated.The numerical results illustrate the effects of time delays and kernel functions on the nonlinear three-temperature and nonlinear displacement components.The numerical results also demonstrate the validity,efficiency and accuracy of the proposed methodology.The findings and solutions of this study contribute to the further development of industrial applications and devices typically include micropolar-thermoelastic materials.展开更多
Based on the two-dimensional three-temperature （2D3T） radiation diffusion equations and its discrete system, using the block diagonal structure of the three-temperature matrix, the reordering and symbolic decomposit...Based on the two-dimensional three-temperature （2D3T） radiation diffusion equations and its discrete system, using the block diagonal structure of the three-temperature matrix, the reordering and symbolic decomposition parts of the RSMF method are replaced with corresponding block operation in order to improve the solution efficiency. We call this block form method block RSMF （in brief, BRSMF） method. The new BRSMF method not only makes the reordering and symbolic decomposition become more effective, but also keeps the cost of numerical factorization from increasing and ensures the precision of solution very well. The theoretical analysis of the computation complexity about the new BRSMF method shows that the solution efficiency about the BRSMF method is higher than the original RSMF method. The numerical experiments also show that the new BRSMF method is more effective than the original RSMF method.展开更多
文摘In this work, a study involving the fully coupled Euler and Navier-Stokes reactive equations is performed. These equations, in conservative and finite volume contexts, employing structured spatial discretization, on a condition of thermochemical non-equilibrium, are analyzed. High-order studies are accomplished using the Spectral method of Streett, Zang, and Hussaini. The high enthalpy hypersonic flows around a circumference, around a reentry capsule, along a blunt body, and along a double ellipse in two-dimensions are simulated. The Van Leer, Liou and Steffen Jr., and Steger and Warming flux vector splitting algorithms are applied to execute the numerical experiments. Three temperatures, which are the translational-rotational temperature, the vibrational temperature, and the electron temperature, are used to accomplish the numerical comparisons. Excellent results were obtained with minimum errors inferior to 6.0%. The key contribution of this work is the correct implementation of a three temperature model coupled with the implementation of three algorithms to perform the numerical simulations, as well the description of energy exchange mechanisms to perform more realistic simulations.
基金supported by the Beijing Natural Science Foundation(Z230003)for Sunby the National Key R&D Program(2020YFA0712200)+1 种基金the National Key Project(GJXM92579)the Sino-German Science Center(GZ 1465)for Jiang。
文摘This paper extends the previous work[1]for the three-temperature gray radiative transfer equations to the frequency-dependent case.Since the additional frequency variable is considered,the equations are more complicated than those in the gray case.Moreover,opacity may be typically a decreasing function of the frequency variable in applications.At the same spatial location,the equations can be in the optically thick case for low frequency photons,while in the optically thin case for high frequency ones.Thus,the resulting discrete equations can significantly increase the computational cost for opacity having the multi-scale property in multiple frequency radiation.Due to the presence of the radiation-electron coupling,electronion coupling,and electron-ion diffusion terms,the model under consideration exhibits strong nonlinearity and strong coupling properties.In this paper,the multigroup method is used to discretize the frequency variable and the H_(N)^(T)method to discretize the angular variable first.Then,within the framework of a unified gas kinetic scheme(UGKS),a multigroup H_(N)^(T)-UGKS method is constructed to solve this complex model iteratively.Furthermore,it can be shown that as the Knudsen number tends to zero,with variations in the electron-ion coupling,absorption,and scattering coefficients,the multigroup H_(N)^(T)-UGKS scheme can converge to numerical schemes for the single-temperature,two-temperature,and the frequency-dependent three-temperature,two-temperature diffusion limit equations,respectively.Finally,several numerical examples are provided to validate the effectiveness and stability of the proposed scheme.
基金funded by the National Natural Science Foundation of China(NSFC)(Grant No.52178076)the Guangdong Science and Technology Plan Project(Grant No.2023A0505050125)+1 种基金the State Key Laboratory of Subtropical Building and Urban Science(Grant No.2023ZB03)supported by the Fundamental Research Funds for the Central Universities(Grant No.x2jz/D2240030).
文摘The evapotranspiration(ET)from urban vegetation is recognized as an effective way to improve the urban thermal environment.However,the traditional ET measurement approaches,such as the sap flow method,are limited in providing urban ET for specific areas.Consequently,establishing quantitative relationship between cooling effects and ET becomes challenging,which is crucial for understanding the role of urban greenery in mitigating urban heat.To overcome this challenge,an estimation model based on the three-temperature(3T)model was developed for accurately estimating urban ET by employing a reference tree with accurate ET data.In contrast to the 3T model,this study proposed a new method(modified 3T model)that considers the influence of the three-dimensional crown structure on the energy balance.Additionally,it retains the advantage over traditional ET models by not requiring the calculation of resistance parameters.This reduces the impact of uncertainty in the estimated resistance parameters on the ET results.The modified 3T model was validated based on the sap flow method and Bowen ratio system,where the results indicated good agreement between the modified 3T model and measured ET data,with root mean square errors of 22.2 W·m^(−2)and 26.4 W·m^(−2),respectively.Furthermore,the absolute relative error of ET estimation was affected by energy-related factors,such as solar radiation,air temperature,and relative humidity.The modified 3T model exhibited low sensitivity to surface temperatures,where the average sensitivity coefficients were below±0.15 from 0600 local time(LT)to 1700 LT.Considering the low accuracy of surface temperatures measured by infrared cameras(±2℃),it would be beneficial to combine the modified 3T model with unmanned aerial vehicles and infrared remote sensing to measure urban ET.
基金supported by the national forestry nonprofit industry research projects of China,‘‘Diagnosis of rare and endangered plants Ammopiptanthus mongolicus degradation and research of conservation technology’’(No.201304305)
文摘Population of the rare and endangered species Ammopiptanthus mongolicus （Maxim.） Cheng f. declined rapidly in China＇s add region and Central Asia. There is an urgent need to protect this species, which is particularly important in maintaining biodiversity throughout the arid region of northwestern China. By analyzing the infrared thermal images based on plant-transpiration transfer coef- ficient （hat） and photosynthetic parameters, we made quantitative and accurate diagnoses of the plant growth and health status of A. mongolicus. Using an LI-COR6400 photosynthesis system, we measured the net photosynthetic rate （Pn）, stomatal conductance （Gs）, and transpiration rate （Tr）. Infrared thermal images obtained in the field were processed by ENVI4.8 software to calculate surface tem- peratures of the plant subjects. We found that the plant transpiration transfer coefficient of A. mongolicus was inthe order of old plants 〉young plants 〉intermediate-aged plants. Declining health levels of young, intermediate, and old plants were divided into three categories： 〈0.4, 0.4-0.7, and 〉0.7. The coefficient showed a significant negative correlation with Tr, Gs, and Pn, indicating that they can simultaneously reflect the state of plant growth. By estab- lishing hat and photosynthetic parameters in regression model Y = a-blnx, we can accurately diagnose plant growth and decline of plant health conditions.
文摘The main aim of this paper is to propose a new memory dependent derivative(MDD)theory which called threetemperature nonlinear generalized anisotropic micropolar-thermoelasticity.The system of governing equations of the problems associated with the proposed theory is extremely difficult or impossible to solve analytically due to nonlinearity,MDD diffusion,multi-variable nature,multi-stage processing and anisotropic properties of the considered material.Therefore,we propose a novel boundary element method(BEM)formulation for modeling and simulation of such system.The computational performance of the proposed technique has been investigated.The numerical results illustrate the effects of time delays and kernel functions on the nonlinear three-temperature and nonlinear displacement components.The numerical results also demonstrate the validity,efficiency and accuracy of the proposed methodology.The findings and solutions of this study contribute to the further development of industrial applications and devices typically include micropolar-thermoelastic materials.
基金supported by the National Natural Science Foundation of China(GrantNos.61202098,61033009,61170309,91130024,and 11171039)the China Tianyuan Mathematics Youth Fund(GrantNo.11226337)
文摘Based on the two-dimensional three-temperature （2D3T） radiation diffusion equations and its discrete system, using the block diagonal structure of the three-temperature matrix, the reordering and symbolic decomposition parts of the RSMF method are replaced with corresponding block operation in order to improve the solution efficiency. We call this block form method block RSMF （in brief, BRSMF） method. The new BRSMF method not only makes the reordering and symbolic decomposition become more effective, but also keeps the cost of numerical factorization from increasing and ensures the precision of solution very well. The theoretical analysis of the computation complexity about the new BRSMF method shows that the solution efficiency about the BRSMF method is higher than the original RSMF method. The numerical experiments also show that the new BRSMF method is more effective than the original RSMF method.
