Numerical Investigations on the Use of Roughness Patterns for Boundary-Layer Flow Control

使用粗糙度模式进行边界层流动控制的数值研究

• 批准号: 322405353
• 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: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/322405353?language=en
• 关键词: Numerical; Investigations; Use; Roughness; Patterns

In the present proposal investigations of new means for boundary-layer flow control are intended, based on small bristle-like hair structures attached to a wall in specific patterns. The main purpose of this proposal consists of obtaining knowledge about those wall patterns which are most usefully for technical applications.As already shown in preliminary work performed in DFG grant "Investigation of grid effects on surfaces covered with sensor hairs for selective detection of characteristic flow-field patterns (coincidence sensor)" thin hairs may significantly influence the local flow field. Despite this, we were able to show that the signal of an individual sensor is not inadmissibly falsified by this. Only if a second sensor is placed in the vicinity of another one, position-dependent variations of the second sensor's signal output appear which bear new and exciting application aspects. Results of our previous work on the flow around wall-mounted finite-length cylinders in single and tandem configuration will be used for validation of a new-to-implement modeling of bristle-like structures using body forces in the Navier-Stokes equations. After an additional validation for unsteady flow conditions, the numerical method will be used to perform direct numerical simulations based on the complete Navier-Stokes equations with modeled roughness elements. The distances between individual elements will be modified in such that their individual contributions intensify in the most appropriate way.An easily imaginable realization of this idea is an arrangement in rows parallel to the main flow direction with a certain distance between the rows and a certain length or height of the structures such that these hair structures exert a similar effect on the flow as already-known "riblets" in a turbulent boundary layer. Related questions will be studied in the present project using numerical investigations. However, the present approach is not restricted to riblets in turbulent flow, as other patterns for control of a boundary layer over a wall exist as well, like, e.g., so-called "zig-zag or pimple stripes" for provoking laminar-turbulent transition or delaying flow separation. For investigations of this problem, the impact of relevant roughness-element patterns on laminar-turbulent transition in a flat-plate boundary layer will be studied via numerical simulation. Results will be compared with data for critical Reynolds numbers found in literature. Additionally, the influence of roughness patterns on disturbance growth in a laminar boundary layer and hence on the transitions position will be quantified as well.

在本提案中，打算研究边界层流动控制的新方法，其基础是以特定图案附着在壁面上的小刚毛状毛发结构。 该建议的主要目的包括获得有关这些壁图案的知识，这是最有用的技术application.As已经显示在DFG赠款进行的初步工作“调查网格效应的表面覆盖传感器头发选择性检测的特征流场图案（符合传感器）”薄的头发可能会显着影响局部流场。 尽管如此，我们能够证明，单个传感器的信号并不是不可接受的伪造。 只有当第二传感器被放置在另一个传感器的附近时，第二传感器的信号输出的位置相关变化才会出现，这具有新的和令人兴奋的应用方面。 我们以前的工作的结果，在单个和串联配置的壁装有限长圆柱体周围的流动将用于验证一个新的实施建模的刚毛状结构使用体积力的Navier-Stokes方程。 在对非定常流条件进行额外验证后，将使用数值方法根据完整的Navier-Stokes方程和建模粗糙度元素进行直接数值模拟。 单个元件之间的距离将被修改，使得它们的单个贡献以最适当的方式增强。这个想法的一个容易想象的实现是平行于主流动方向的排布置，其中排之间具有一定的距离并且结构具有一定的长度或高度，使得这些毛发结构对流动施加与已知的“肋”类似的效果。在湍流边界层中。 相关问题将在本项目中使用数值调查进行研究。 然而，本方法不限于湍流中的沟槽，因为还存在用于控制壁上方的边界层的其他图案，例如，所谓的“锯齿或疙瘩条纹”，用于引起层流-湍流过渡或延迟流动分离。 为了研究这一问题，将通过数值模拟研究相关粗糙元模式对平板边界层中层流-湍流转捩的影响。 结果将与文献中的临界雷诺数数据进行比较。 此外，粗糙度模式对层流边界层中的扰动增长的影响，从而对过渡位置也将被量化。