ABSTRACT

The objective of this paper is to propose a new intermittency transport equation that is naturally capable of capturing the effects of free-stream turbulence and pressure gradient on bypass and natural transition without need for any extra parameters/terms to take into account the free-stream turbulence and the pressure gradient. This new intermittency transport equation is obtained by derivation and, in it, only its production term is modeled via two empirical functions in order to detect the onset location of transition and to control the growth rate of transition process. Only one sensing parameter is used to detect the transition onset for both natural and bypass transition. For the purpose of not altering the original form of the base turbulence model, the effective intermittency factor is used to describe the separation-induced transition. The base turbulence model remains unmodified in conjunction with the effective intermittency factor as a regulator to control the net turbulent generation rate. For the evaluation of model performance, the modeled intermittency equation is tested against (1) the transitional boundary layer on a flat plate with zero and non-zero pressure gradients, (2) the transitional flow over a compressor blade with a laminar separation bubble, and (3) the transitional flow over a wind turbine airfoil at various angles of attack. The present results are also compared to those of the $\gamma$ transition model of Menter et al. [1] and those of the $\gamma -R{e}_{\theta }$ transition model of Langtry and Menter [2]. The evaluation results reveal that the new intermittency transport equation is capable of predicting the bypass, natural and separation-induced transition.

摘要

本文的目的是提出一个新的间歇输运方程，它自然能够捕捉自由流湍流和压力梯度对旁路和自然过渡的影响，而无需任何额外的参数/项来考虑自由流湍流和压力梯度。这个新的间歇传输方程是通过推导得到的，其中只有它的生产项通过两个经验函数建模，以检测过渡的开始位置并控制过渡过程的增长速度。仅使用一个传感参数来检测自然过渡和旁路过渡的过渡开始。为了不改变基础湍流模型的原始形式，使用有效间歇因子来描述分离引起的转变。基本湍流模型与有效间歇因子结合作为控制净湍流生成率的调节器保持不变。为了评估模型性能，模拟的间歇方程针对 (1) 具有零和非零压力梯度的平板上的过渡边界层，(2) 具有层流分离气泡的压缩机叶片上的过渡流进行测试， (3) 不同攻角下风轮机翼型上的过渡流。目前的结果也与 模拟的间歇方程针对 (1) 具有零和非零压力梯度的平板上的过渡边界层，(2) 具有层流分离气泡的压缩机叶片上的过渡流，以及 (3) 过渡流进行测试在不同攻角的风力涡轮机翼型上。目前的结果也与 模拟的间歇方程针对 (1) 具有零和非零压力梯度的平板上的过渡边界层，(2) 具有层流分离气泡的压缩机叶片上的过渡流，以及 (3) 过渡流进行测试在不同攻角的风力涡轮机翼型上。目前的结果也与$\gamma$Menter 等人的转换模型。[1] 和那些$\gamma -\mathrm{电阻}{\mathrm{电子}}_{\theta }$Langtry 和 Menter [2] 的转换模型。评估结果表明，新的间歇传输方程能够预测旁路、自然和分离诱导的转变。