Vortex formation on a pitching aerofoil at high surging amplitudes
Vortex formation on a pitching aerofoil at high surging amplitudes
复制标题
高波动幅度下俯仰翼型上的涡流形成
DOI：
10.1017/jfm.2020.741
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发表时间：
2020
影响因子：
3.7
通讯作者：
Anya R. Jones
中科院分区：
文献类型：
--
作者：
Luke R. Smith;Anya R. Jones
摘要在许多应用中，常规翼型受到许多同时运动的影响，这使得流动分离的预测变得复杂。本工作的目的是评估大振幅自由流振荡对同时喘振和俯仰机翼的涡形成时间的影响。在NACA 0012翼型上获得了宽范围喘振振幅（$1.50 \leq \lambda \leq 2.25$）和折合频率（$0.1 \leq k \leq 0.3$）的实验流场测量结果。特别注意的是，各种流动分离机制，特别是尾流引起的速度和边界层中的非定常效应，如何受到波动运动特性变化的影响。在该制度中，$k \leq 0.3$，浪涌运动学的变化主要表现为尾流的相对强度的变化。边界层非定常被发现有一个可以忽略不计的影响，在相同的流动制度的旋涡形成的时间。因此，结合非定常无粘流解算器和边界层准定常处理，可以很好地预测前缘涡流形成的时间，这是非定常翼型流中涡流行为低阶预测的一个有希望的结果。
Abstract In many applications, conventional aerofoils are subject to a number of simultaneous motions that complicate the prediction of flow separation. The purpose of this work is to evaluate the impact of a large-amplitude free-stream oscillation on the timing of vortex formation for a simultaneously surging and pitching wing. Experimental flow field measurements were obtained on a NACA 0012 aerofoil over a wide range of surge amplitudes ($1.50 \leq \lambda \leq 2.25$) and reduced frequencies ($0.1 \leq k \leq 0.3$). Particular attention was paid to how various mechanisms of flow separation, specifically the velocity induced by the trailing wake and unsteady effects in the boundary layer, were impacted by a change in the properties of the surge motion. In the regime where $k \leq 0.3$, a change in the surge kinematics primarily manifested as a change in the relative strength of the trailing wake. Boundary layer unsteadiness was found to have a negligible influence on the timing of vortex formation in the same flow regime. Thus, the timing of leading-edge vortex formation was well predicted by a combination of an unsteady inviscid flow solver and a quasi-steady treatment of the boundary layer, a promising result for low-order predictions of vortex behaviour in unsteady aerofoil flows.