DNS and Modelling of Turbulent Heat Transfer for Low to Medium-High Prandtl Number Fluids

借助超级计算机和并行计算机的最新发展，湍流的直接数值模拟(DNS)越来越多地被用于各种构型和边界条件。数值模拟为我们提供了湍流量的详细分布，如平均速度、温度、湍流热通量和输运方程的收支等。另一方面，湍流的模拟仍然是湍流热和流体流动工程分析中的重要工具，因为目前该程序的应用仅限于具有相对简单几何形状的低雷诺数湍流。本文对具有标量输运的充分发展的槽道流动进行了数值模拟，考察了不同普朗特数流体在不同热条件下的流动情况。建立了标量输运模型，并与已有的数值模拟结果进行了比较。

With an aid of recent development in the super and parallel computers, the deirect numerical simulation (DNS) of turbulence is now performed increasingly for various configulations and boudary conditions. The DNS provides us with the detailed distributions of the turbulent quantities, such as the averaged velocity, temperature, turbulent heat flux and the budgets of transport equations. The modelling of the turbulence, on the other hand, is still an important tool in the engineering analysis of the turbulent heat and fluid flow, because the application of the DNS is now limited only to low Reynolds number turbulence with relatively simple geometries. The information obtained from the DNS contributessignificantly to the refinement of the turbulence modelling.In the present study, DNS of the fully developed channel flow with the scalar transport were performed, where various Prandtl number fluids were examined with several kinds of thermal conditions imposed. A scalar transport model was developed and examined in comparison with the obtained DNS results.