Direct Numerical Simulation of boundary-layer transitionunder consideration of chemical and thermal non-equilibrium at a generic capsule geometry with smooth and rough surfaces.

考虑化学和热非平衡的边界层转变的直接数值模拟，具有光滑和粗糙表面的通用胶囊几何形状。

• 批准号: 248982821
• 负责人: Professor Dr.-Ing. Christian Stemmer
• 金额: --
• 依托单位: Lehrstuhl für Aerodynamik und Strömungsmechanik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/248982821?language=en
• 关键词: Direct; Numerical; Simulation; boundary; layer

In the proposed project, direct numerical simulations are used to investigate the laminar-turbulent transition evolution in a high-enthalpy flow under chemical equilibrium and non-equilibrium conditions. A generic geometry of the Apollo-capsule shape is used including high-temperature gas effects. The effect of dissociation and non-equilibrium effects on the disturbance development in the boundary layer subject to instabilities shall be investigated. Especially, roughness induced transition under chemical equilibrium and non-equilibrium conditions as for atmospheric re-entry missions is the main focus of the investigations. These investigations complement the ideal-gas investigations (cold wind-tunnel conditions at HLB) of the other PAK 742 partners. Disturbance amplification through the so-called transient growth mechanism for distributed roughnesses as well as secondary instability mechanisms for the discrete roughness wake flow are examined. Secondary instabilities are driven by local velocity and temperature gradients, which can be more pronounced in chemical (non-)equilibrium flows, leading to earlier transition in these cases. The simulations are then extended to incorporate the disturbance background in the wind tunnel ("wind-tunnel rebuilding") to better predict transition in experiments. Extrapolation of these results to high-enthalpy free-flight conditions are of particular interest.

本文采用直接数值模拟的方法研究了化学平衡和非平衡条件下高焓流动中层流-湍流转捩的演化。阿波罗胶囊形状的通用几何形状，包括高温气体的影响。应研究离解和非平衡效应对受不稳定性影响的边界层中扰动发展的影响。特别是大气层再入任务中化学平衡和非平衡条件下粗糙度诱导的转变是研究的主要重点。这些研究补充了PAK 742其他合作伙伴的理想气体研究（HLB的冷风洞条件）。扰动放大通过所谓的瞬态增长机制分布粗糙度以及二次不稳定机制的离散粗糙度尾流进行检查。二次不稳定性由局部速度和温度梯度驱动，这在化学（非）平衡流中可能更明显，导致在这些情况下更早的转变。然后将模拟扩展到包含风洞中的扰动背景（“风洞重建”），以便在实验中更好地预测转捩。外推这些结果的高焓自由飞行条件是特别感兴趣的。