Recirculating Coherent Structures Inside the Cove of a Bulb Sealed Slat

The current aircraft noise has a large contribution provenient from the airframe in which the most relevant sources are the landing gear, the flap and the slat. The leading edge slat is a distributed noise source since it spans almost the whole wing extension. The presence of excrescences inside the slat cove can change significantly the recirculating flow and the characteristics of noise generated. Previous experiments showed substantial increasing in the narrow band peaks for the MD30P30N high-lift model in which the slat geometry included a bulb seal attached at some positions of its cove. We present simulations performed with the same sealed slat geometry. Mean flow shows the presence of an additional recirculation bubble for some positions of the seal. For these cases, Proper Orthogonal Decomposition was used to identify the most significant coherent structures which could be related to the slat cavity modes. These structures are confined inside the most external and narrow recirculation which enhances their interaction with the mixing layer creating a more complex scenario than that observed for slat geometries without any excrescences