基于代理模型的龙卷风数值模拟参数优化

为实现以实测数据为目标的龙卷风高精度数值模拟,在总结已有研究成果的基础上,基于计算流体力学(CFD)方法建立了ISU型龙卷风数值模型,通过参数灵敏度分析确定拟优化模拟参数;提出了以实测数据为目标的龙卷风模拟参数优化方法,引入代理模型提高计算效率并通过数值模型计算设计样本点响应来训练代理模型,采用最大切向速度、最大切向速度处半径及标准化风剖面线形误差3个指标建立目标函数;通过一组数值算例验证了所提出优化方法的可靠性,采用所提出的优化方法分别以龙卷风物理模拟器试验数据和龙卷风现场实测数据为目标进行模拟参数优化,并基于此进行CFD数值模拟。研究结果表明:入口切向速度U_t、模拟器离地面高度H_g和地面移动速度V_T三个参数对龙卷风场影响较大,因此选作为待优化模拟参数;引入代理模型进行参数优化,避免了数值模型直接参与优化迭代过程,提高了优化效率;以龙卷风物理模拟器试验数据为目标的数值模拟结果,与试验数据的标准化风剖面线形误差V_Mp仅为0.034 4;以龙卷风现场实测数据为目标的数值模拟结果,在h=250 m及h=450 m高度处与实测结果的风剖面综合误差V_M分别为0.024 0、0.035 1,均小于训练样本集中模拟结果的误差,采用优化后的模拟参数进行龙卷风数值模拟很好地改善了模拟精度。

Numerical Simulation Parameter Optimization of Tornado Based on Surrogate Model

To realize numerical simulation of tornado accurately based on measurements,a model of ISU-type tornado was firstly established based on computational fluid dynamics (CFD) after the review of existing researches regarding numerical simulation of tornado.Secondly,a parameters optimization method was formulated which aimed to make results of simulation fit well with measurements.A surrogate model trained with data from numerical simulation was introduced to improve efficiency.The objective function was developed based on the error of the maximum tangential velocity,the radius where the maximum tangential velocity occurs and standardized wind profile.Lastly,a numerical simulation example of tornado was implemented to validate the developed parameters optimization method.Two groups of optimized parameters were achieved to simulate tornadoes of laboratory and field measurements,respectively,and two numerical simulations were implemented based on them.The results show that the tangential velocity at inlet (U_t),the distance between the chamber bottom and ground plane (H_g) and the velocity of ground plane (V_T) have great influence on the tornado,which are selected as the simulation parameters to be optimized.Instead of employing the numerical model in the optimization iteration process,the surrogate model is introduced to improve the optimization efficiency.The error of standardized wind profile is V_Mp=0.034 4 between simulation and tornado of laboratory;The errors between simulation and tornado of field measurements are 0.024 0 and 0.035 1 at the elevations of h=250 m and h=450 m,respectively,both of which are less than the errors of training dataset.Therefore,numerical simulation of tornado based on optimized parameters improve accuracy obviously.