积雪覆盖条件下土壤水热迁移规律分析

发布时间：2018-05-08 18:44

  本文选题：粒子群算法 + 土壤水分运动参参数　； 参考：《东北农业大学》2016年硕士论文

【摘要】：黑龙江省冬季寒冷,历史上最低的气温达到过零下50℃,白天和夜晚的温差较大。冬季降雪,积雪覆盖在广袤农田上的时间能够持续整个冬季,并为春季作物生长提供了一定的水源。由于积雪具有高导热性弱、反射率高、热容量等特性影响土壤温度和含水率的变化。研究积雪覆盖条件下土壤水分的传递规律以及土壤水分运动参数和含水率的关系对于水分在自然界中的循环转移有重要意义。在冻结期由于室外温度低,土壤中的水分基本不转移同时土壤的深层基本保持恒定,所以雪的存在为春季农业生产提供了一定的水资源保证,土壤温度的变化也为工程力学和工程冻胀研究提供了相应的研究思路。应用优化算法通过计算机编程确定土壤的水分运动参数的方法能够克服土壤空间变异的特性使研究模型精度得到保证。本研究即有在土壤水分运动模型和优化算法求解土壤水分运动参数模型上具有较高的理论意义,对于农业生产和土壤特性分析等方面又有将强的实践意义。因此本文的研究主要内容、材料方法、主要结论归纳总结如下:(1)表层土壤剖面温度有积雪覆盖的土壤度高于无积雪覆盖土壤,无积雪覆盖的土壤由于可以直接吸收太阳辐射进行能量交换所以随着时间的推移温度变化明显。温度保持不变时土壤温度随之恒定不变。自然降雪、积雪压密、积雪加厚的表层土壤剖面温度基本保持不变。自然降雪、积雪覆盖、积雪压密能够保持土壤温度,保持的深度范围为100 cm,超过100cm后各个小区的剖面温度基本保持一致不发生变化。(2)将粒子群算法引入到季节性冻土水分迁移规律研究中,提出了一种新的季节性冻土水分运动参数识别方法。建立了基于粒子群算法的参数识别模型,实现了季节性冻土水分运动参数的优化。通过优化模型计算的土壤导水率和扩展率与实测值总体变化趋势一致,通过分析发现实测值忽略了土壤容重随空间的变化,所以优化模型更适合田间土壤实际应用。采用优化后的参数模型模拟土壤体积含水率具有较高的精度,模拟值和真实值各点的最大绝对误差仅为2.57%,最大相对误差仅为5.53%,平均相对误差仅为2.51%,表明建立的季节性冻土水分迁移模型可以很好的模拟水分的迁移规律[1],同时可以反映粒子群算法可以较好的优化季节性冻土的水分运动参数。研究成果对于指导农田的灌溉与排水、土壤的蒸发、地下水补给和植物根区土壤水分运动具有重要的理论和实践意义。(3)推导了柱坐标和球坐标中的土壤水分运动的基本方程,并且推导了零通量面与通量面、表面通量法、定位通量法的运算过程。梳理了一维土壤水分运动方程的差分求解的三种方程。对积雪覆盖条件下的土壤水分运动方程进行差分求解,将相应方程转化为追赶法求解的形式,利用MATLAB编程求解该方程,计算结果表明:所建的水分迁移模型可以很好的模拟有积雪覆盖边界条件下的土壤水分状况。
[Abstract]:Heilongjiang province is cold in winter, the lowest temperature in history reaches 50 degrees below zero, and the temperature difference between day and night is greater. Winter snowfall, snow cover on vast farmland can continue throughout the winter, and provide a certain water source for spring crop growth. The snow has the characteristics of high thermal conductivity, high reflectance, heat capacity and so on. The change of soil temperature and water content. The study of the law of soil moisture transfer under the condition of snow cover and the relationship between soil moisture movement parameters and water content is of great significance to the circulation and transfer of water in nature. In the freezing period, the water base in the soil is not transferred and the soil is basically preserved because of the low outdoor temperature. The existence of snow provides a certain water resource for the agricultural production in spring, and the change of soil temperature also provides the corresponding research ideas for the research of Engineering Mechanics and engineering frost heave. The application of the optimization algorithm to determine the soil moisture movement parameters through computer programming can overcome the characteristics of soil spatial variation. The accuracy of the model is guaranteed. This study has a high theoretical significance on soil moisture movement model and optimization algorithm for soil moisture movement parameter model. It is of great practical significance for agricultural production and soil characteristics analysis. Therefore, the main contents, material methods and main conclusions of this paper are summarized and summarized in this paper. The following are as follows: (1) the surface soil profile with snow covered soil is higher than that of no snow covered soil. The soil without snow covered soil can exchange energy because of the direct absorption of solar radiation, so the temperature changes with time. The soil temperature keeps constant when the temperature is kept constant. The temperature of the thickened surface soil section remains unchanged. The natural snow, snow cover, and snow cover can keep the soil temperature, the depth of the depth is 100 cm, and the temperature of the section of each plot after more than 100cm does not change basically. (2) the particle swarm optimization algorithm is introduced to the study of the water migration law of seasonal frozen soil. A new method for identifying water movement parameters of seasonal frozen soil is developed. A parameter identification model based on particle swarm optimization is established to optimize the water movement parameters of seasonal frozen soil. The soil water conductivity and expansion rate calculated by the optimized model are in accordance with the overall change trend of the measured values. The soil bulk density varies with space, so the optimization model is more suitable for the practical application of soil in the field. The maximum absolute error is only 2.57%, the maximum relative error is only 5.53%, the average relative error is only 2.51%, which indicates the established season. The water migration model of the segmental frozen soil can well simulate the migration law of water [1], and it can also reflect the particle swarm optimization to optimize the water movement parameters of the seasonal frozen soil. The research results are important to guide the irrigation and drainage of the farmland, the evaporation of soil, the recharge of groundwater and the soil water movement in the plant root zone. (3) the basic equations of soil moisture movement in cylindrical coordinates and spherical coordinates are derived, and the operation process of zero flux surface and flux surface, surface flux method and location flux method are derived. The three formulas for the difference solution of one dimension soil moisture movement equation are combed. The soil moisture movement under the condition of snow cover is given. The difference solution is carried out, and the corresponding equation is transformed into the form of the pursuit method, and the MATLAB programming is used to solve the equation. The calculation results show that the water migration model can well simulate the soil moisture condition under the condition of snow covered boundary conditions.

【学位授予单位】：东北农业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S152
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本文编号：1862588