The use of a submerged inlet is advantageous in modern aircrafts because of its low drag resistance, small radar cross section and ease of maintenance. Although it is well known that the forebody boundary layer deteriorates the aerodynamic performance of a submerged inlet, the level of impact has not yet been fully quantified. To quantify the forebody boundary-layer effect, a submerged diverter was designed to remove a portion of the low-energy boundary flow. The flow pattern and aerodynamic performance of a submerged inlet, with and without the diverter, were investigated by wind-tunnel experimentation and numerical simulations. The effects of mass flow, free stream speed, angle-of-attack and sideslip angle on the aerodynamic characteristics of the inlet with and without the submerged diverter were studied, over an operating envelope of M0 = 0.3 ∼ 0.6, $\alpha$ = –6$^{\circ}$ ∼ 8$^{\circ}$ and $\beta$ = 0$^{\circ}$ ∼ 4$^{\circ}$. The results indicate that both the total pressure loss and the circumferential distortion can be significantly reduced with the removal of the forebody boundary-layer low-energy flow. Meanwhile, the main mechanisms for losses in the submerged inlet were also analysed.

中文翻译：

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前体边界层对水下进气道性能的影响

在现代飞机中使用水下进气道是有利的，因为它阻力低、雷达横截面小并且易于维护。虽然众所周知，前体边界层会降低水下进气道的气动性能，但影响程度尚未完全量化。为了量化前体边界层效应，设计了一个浸没式分流器以去除一部分低能边界流。通过风洞试验和数值模拟研究了带和不带分流器的淹没式入口的流动模式和气动性能。研究了质量流量、自由流速度、迎角和侧滑角对带有和不带有浸没式分流器的进气道气动特性的影响，其运行范围为米0= 0.3 ∼ 0.6,$\阿尔法$= –6$^{\circ}$～ 8$^{\circ}$和$\beta$= 0$^{\circ}$～ 4$^{\circ}$. 结果表明，去除前体边界层低能流可以显着降低总压力损失和周向变形。同时，还分析了淹没进水口损失的主要机理。