中文摘要：

利用对流水槽模拟分析了均匀下垫面自由对流边界层的水平温度场结构特征.根据几何相似、运动相似和动力相似等要求设置初始条件和边界条件实施模拟.对流水槽的尺度为1.5 m×1.5 m×0.6 m,先加入具有一定温度层结的去离子水,然后底部加热形成对流,模拟对流边界层的发生和发展.利用快速响应的温度传感器测量温度廓线和不同高度上的温度起伏;利用准直光闪烁原理获得光学湍流场.根据温度廓线和光学湍流场的结果得到对流边界层厚度和稳定度等参数.根据不同高度的水平脉动温度,利用AR谱方法分析水平温度谱峰值频率所对应的尺度,该尺度对应于对流边界层的准二维对流热泡的水平尺度.统计分析结果表明,自由对流边界层大涡的水平尺度在边界层的下部随高度的增加而增加,约在0.65倍边界层厚度处达到最大,然后随高度的增加又逐渐减小.物理模拟与数值模拟和野外观测结果符合一致.根据对流热泡的这种特征,提出了一个自由对流边界层的热泡模型.

英文摘要：

The characteristics of horizontal temperature of the convective boundary layer（CBL） were analyzed using water tank simulation.Based on the geometric similarity,kinematic similarity and dynamic similarity,the initial and boundary conditions can be set for simulation.The dimension of the water tank is 1.5 m×1.5 m×0.6 m.The degassed water was first filled with inversion stratification,then the bottom was heated and the convection was generated.The generation and evolution of the CBL were simulated.Temperature profiles and fluctuations at several heights were measured using fast response temperature sensors;optical turbulence was retrieved from the record using scintillation effect.Several parameters,such as the CBL depth,can be calculated.The AR power spectrum estimate was used to obtain the peak frequency of temperature fluctuations at those heights,which corresponds to the scale of quasi two-dimensional structure.The results show that scales of quasi two-dimensional structure at the low part of CBL increase with the height,reaching the maximum scale at about 0.65 Zi,and then decrease with the height at the upper part of the CBL.The results show good agreement with the fields and the numerical simulation.At the upper part of CBL,the normalized scales decrease with stabilizations.Based on the results,a thermal pattern for the free CBL was proposed.