Crossflow instability (CFI) is crucial for triggering boundary-layer flow transition over a transonic natural laminar flow (NLF) wing, whose leading edge is swept for reducing wave drag. This paper proposes a new flow parameter called the nondimensionalized crossflow pressure gradient (CFPG) to combine the effects of both wing sweep and pressure distribution on crossflow, which enables an alternative interpretation of the mechanism for CFI suppression. At first, a self-contained derivation of nondimensional form of CFPG is presented, and the Falkner–Skan–Cooke boundary layers are employed to theoretically show that the nondimensionalized CFPG does relate to wing sweep and pressure gradients. Besides, infinite obliquely placed NLF wings with different sweep angles or pressure distributions are used to numerically validate our hypothesis. Second, examples of nontapered finite-span wings are used to demonstrate the advantage of using nondimensionalized CFPG. Finally, nondimensionalized CFPG is applied to analyze the crossflow on tapered NLF forward-swept wing (FSW) and backward-swept wing (BSW) configured with the same airfoil, and the underlying flow mechanism is exposed from a new perspective. It is observed by this paper that nondimensionalized CFPG can take into account the effects of both wing sweep and pressure distribution, which leads to a different perspective to analyze the crossflow on FSW as well as BSW.

横流不稳定性 (CFI) 对于触发跨音速自然层流 (NLF) 机翼上的边界层流动过渡至关重要，其前缘被扫掠以减少波阻。本文提出了一种称为无量纲横流压力梯度 (CFPG) 的新流动参数，以结合机翼后掠和压力分布对横流的影响，从而对 CFI 抑制机制进行另一种解释。首先，提出了 CFPG 无量纲形式的独立推导，并采用 Falkner-Skan-Cooke 边界层从理论上表明无量纲 CFPG 确实与机翼后掠和压力梯度有关。此外，具有不同后掠角或压力分布的无限倾斜放置的 NLF 机翼用于在数值上验证我们的假设。第二，非锥形有限跨翼的例子被用来证明使用无量纲化 CFPG 的优势。最后，应用无量纲化CFPG分析了相同翼型的锥形NLF前掠翼（FSW）和后掠翼（BSW）的横流，从新的角度揭示了潜在的流动机制。本文观察到，无量纲化 CFPG 可以同时考虑机翼后掠和压力分布的影响，这导致从不同的角度分析 FSW 和 BSW 上的横流。应用无量纲化CFPG分析相同翼型配置的锥形NLF前掠翼（FSW）和后掠翼（BSW）的横流，从新的角度揭示了潜在的流动机制。本文观察到，无量纲化 CFPG 可以同时考虑机翼后掠和压力分布的影响，这导致从不同的角度分析 FSW 和 BSW 上的横流。应用无量纲化CFPG分析相同翼型配置的锥形NLF前掠翼（FSW）和后掠翼（BSW）的横流，从新的角度揭示了潜在的流动机制。本文观察到，无量纲化 CFPG 可以同时考虑机翼后掠和压力分布的影响，这导致从不同的角度分析 FSW 和 BSW 上的横流。