Investigations of the origin of turbulent superstructures in a flat-plate boundary layer with pressure gradient

压力梯度平板边界层湍流上层结构的起源研究

• 批准号: 316161270
• 负责人: Professor Dr.-Ing. Ulrich Rist
• 金额: --
• 依托单位: Institut für Aerodynamik und Gasdynamik (IAG)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/316161270?language=en
• 关键词: Investigations; origin; turbulent; superstructures; flat

This contribution is devoted to the numerical study of turbulence in flat-plate boundary layers without and with streamwise pressure gradients using long integration domains in streamwise flow direction. To avoid a possible bias of the development of turbulent superstructures turbulence shall be generated via laminar-turbulent transition within the integration domain, following the successful approach of Schlatter et al. (2009). This has the distinctive advantage that the amount of artificial disturbances which do not comply with the full Navier-Stokes equations is kept to a minimum. The simulations are intended to reach as large as possible Reynolds numbers beyond Re_Theta = 5000, where Theta is the momentum thickness. Under the influence of an adverse streamwise pressure gradient the maximum of turbulence production moves away from the wall similar to the increase of the Reynolds number. Therefore, the pressure gradient shall be used to "speed-up" the flow development in streamwise direction such that formation of large-scale superstructures can be observed easier. Different mechanisms in close-to-the-wall and far-from-the-wall areas can be separated from each other by a suitable choice of pressure gradient, studied separately and conjointly. Appropriate means for the detection and tracking of turbulent superstructures shall be inspected and tested. Thus, detected structures can then be compared with eigenfunctions of linear stability theory and results of linearized Navier-Stokes equations for Re_Theta=const which are obtained for the Reynolds-averaged local flow or filtered flow fields. This comparison is intended to investigate whether turbulent superstructures can be explained, modeled and predicted by local instability. The hypothesis, according to which turbulent superstructures might be generated further upstream and then convected downstream by the flow, shall be evaluated using data from feature tracking. The present direct numerical simulations complement experimental investigations within the priority programme 1881 "Turbulent Superstructures". They yield additional data and understanding for examination of hypotheses, despite their limitations to smaller Reynolds numbers than in most experiments. This allows additional insight into the flow and theoretical studies of existing as well as new hypotheses that may appear in the course of the priority programme. Cooperation with all partners who work on boundary layers is possible and intended as soon as the structure of the programme is finalized. An exchange of material during preparation of the proposals has already occurred. Already identified cooperations are described in the work programme.

该贡献专门用于使用流向流动方向上的长积分域的平板边界层中湍流的数值研究。为了避免湍流上层建筑的发展的可能偏见，应在Schlatter等人的成功方法中通过整合域内的层流扰动过渡产生湍流。 （2009）。这具有独特的优势，即不符合完整的Navier-Stokes方程的人工干扰量保持在最低限度。模拟旨在达到雷诺的尽可能大的雷诺数，而theta是动量厚度。在不利的流动压力梯度的影响下，湍流产生的最大生产从壁上移动，类似于雷诺数的增加。因此，压力梯度应用于“加速”流方向上的流动发展，以便可以更容易地观察到大规模上层建筑的形成。几乎墙壁和远面区域中的不同机制可以通过适当的压力梯度选择，分别研究和共同研究。应检查和测试适当的检测和跟踪湍流上层建筑。因此，可以将检测到的结构与线性稳定性理论的本征函数进行比较，并为re_theta = const的线性化navier-stokes方程的结果进行比较，这是雷诺平均局部流或过滤的流场获得的。该比较旨在研究是否可以通过局部不稳定来解释，建模和预测湍流的上层建筑。该假设根据该假设，可以使用功能跟踪中的数据来评估湍流上游的湍流上层建筑，然后通过流量下游进行对流。目前的直接数值模拟补充了1881年优先级计划中的实验研究。尽管与大多数实验相比，它们对较小的雷诺数字的局限性局限性产生了更多的数据和理解，以检查假设。这样可以进一步了解对优先计划过程中可能出现的现有假设的流量和理论研究。与所有在边界层工作的合作伙伴的合作是可能的，并且一旦该计划的结构完成，就打算立即。在准备提案期间的材料交换已经发生。在工作计划中描述了已经确定的合作。