Laser-Doppler Analysis of the Separation Zone of the Ground Vortex Flow

• Autor(a) principal: Silva, André
• Data de Publicação: 2009
• Outros Autores: Durão, Diamantino, Barata, Jorge M M, Santos, Pedro José da Costa Teixeira, Ribeiro, Samuel
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/11544
• topic: VSTOL; Ground effect; Highly curved flow

Laser Doppler measurements are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The experiments were performed for a wall jet-to-boundary layer velocity ratio of 2, and include mean and turbulent velocity characteristics along the two normal directions contained in planes parallel to the nozzle axis. The results, which have relevance to flows encountered by powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow resulting from the collision of a wall jet with a boundary layer. The results revealed the existence of a very low-frequency instability. The source of this low frequency unsteadiness is probably associated with a small vortex located near the separation point. In the central zone of the upwash flow where the maximum values of the vertical velocity component occurs, additional distinct high frequency peaks were also identified.