Mack (1977) criticized methods referring to a single frequency perturbation for correlation of transition prediction because the external disturbance source (like free stream turbulence) should have a broadband spectrum. Delta-correlated perturbations are characterized by the mean square of physical amplitude, which is expressed as a double integral of the power spectral density in frequency and the spanwise wave number. It is suggested to evaluate this integral asymptotically. The results obtained using the asymptotic method and direct numerical integration are compared with ad hoc approaches for high speed and moderate supersonic boundary layers. This allows us to suggest recommendations on rational usage of the amplitude method with avoiding unconfirmed simplifications while reducing the computational effort to the level affordable for engineering practice.

Mack (1977) 批评了将单频扰动用于过渡预测相关性的方法，因为外部扰动源（如自由流湍流）应该具有宽带频谱。Delta 相关扰动的特征是物理幅度的均方，它表示为频率功率谱密度和展向波数的二重积分。建议渐近地评估这个积分。使用渐近方法和直接数值积分获得的结果与高速和中等超音速边界层的临时方法进行了比较。