风洞阻塞度对起落架气动噪声测量影响的数值模拟研究

Numerical investigation to wind-tunnel-blockage effects on aerodynamic noise measurements of a landing gear

为了解风洞阻塞效应对起落架气动噪声测量的影响，用基于S-A湍流模式的延迟分离涡模拟（DDES）对四轮基本起落架模型进行了数值模拟。通过不同截面积的滑移壁面计算域模拟模型安装在不同截面积风洞中的效应，并通过将底面和侧面设为远场边界条件模拟了无风洞起落架的流动条件。阻塞度从0变化到8．8％，根据所得到的非定常流场计算了时均表面压力分布和表面声压级分布。计算显示表面声压级总体上随阻塞度增大而减小；存在一个4％～5％的阻塞度阈值范围，在此范围内表面声压级发生突然变化，大于或小于该阈值范围时表面声压级受阻塞度的影响不大；对阻塞度变化最敏感的部件为前轮，而后轮最不敏感。这说明不同阻塞度下模型的气动噪声特性与平均流动特性密切相关。

In order to provide a basis and some references for experimental study on aerody- namic noise of landing gears, a numerical simulation is carried out for a four-wheel rudimentary landing gear （RLG） model using the delayed detached eddy simulation （DDES） based on the S-A turbulent model. Slip wall boundary condition with different section areas are used to mimic wind tunnels with different sizes, and the non-wind-tunnel case is simulated with far field boundary conditions for the side walls and the floor. The blockage ratio fl is varied from 0 to 8.8 %. Time- averaged surface pressure coefficient and surface sound pressure level （SPL） are calculated from the simulated unsteady flow field. The results show that the mean surface SPL decreases with in- creasing/3 in general. There is a threshold/3 ranged of roughly 4% ～5%. The mean surface SPL varies sharply when/3 is within this range, and is insensitive with/3 when it is out of this range. The most fl-sensitive part is the front wheel, while the most insensitive is the back wheel. This demonstrates a close relation between the aeroacoustic properties and mean flow properties at dif- ferent blockage ratios.