Search Results

The turbulent boundary layer (TBL) that forms on the outside of a commercial airplane in flight is a significant source of noise. During cruise, the TBL can be the dominant source of noise. Because it is a significant contributor to the interior noise, it is desirable to predict the noise due to the TBL. One modeling approach for the acoustic prediction is statistical energy analysis (SEA). This technique has been adopted by North American commercial airplane manufacturers. The flow over the airplane is so complex that a fully resolved pressure field required for noise predictions is not currently analytically or numerically tractable. The current practice is to idealize the flows as regional and use empirical models for the pressure distribution. Even at this level of idealization, modelers do not agree on appropriate models for the pressure distributions. A description of the wall pressure is insufficient to predict the structural response. A structural model is also required.

Turbulent boundary layers are a significant source of vibration and noise for vehicles moving through a fluid medium. Describing the forcing function for this noise source is an active area of research. Empirical models are commonly used in system noise models. Two common models as discussed by Mellen [1, 2] are separable and non-separable models. The separable models are in a class generally known as Corcos models [3]. The separable models postulate that the wall pressure space time statistics are a function of time times a function of downstream separation times a function of cross stream separation. The non-separable models postulate that the space time statistics are a function of time times a function of space with the downstream and cross stream separation being coupled. Two examples of the non-separable models are Chase [4, 5] and Smol'yakov-Tkachenko [6].