Journal of Fluid Mechanics

Experiments in a boundary layer subjected to free stream turbulence. Part 1. Boundary layer structure and receptivity

K. J. A.  Westin a1, A. V.  Boiko a2, B. G. B.  Klingmann a1p1, V. V.  Kozlov a2 and P. H.  Alfredsson a1
a1 Department of Mechanics/Fluid Physics, Royal Institute of Technology, S-10044 Stockholm, Sweden
a2 Department of Theoretical and Applied Mechanics, Russian Academy of Sciences, Siberian Branch, 630090 Novosibirsk, Russia

Article author query
westin kj   [Google Scholar] 
boiko av   [Google Scholar] 
klingmann bg   [Google Scholar] 
kozlov vv   [Google Scholar] 
alfredsson ph   [Google Scholar] 


The modification of the mean and fluctuating characteristics of a flat-plate boundary layer subjected to nearly isotropic free stream turbulence (FST) is studied experimentally using hot-wire anemometry. The study is focussed on the region upstream of the transition onset, where the fluctuations inside the boundary layer are dominated by elongated flow structures which grow downstream both in amplitude and length. Their downstream development and scaling are investigated and the results are compared with those obtained by previous authors. This allows some conclusions about the parameters which are relevant for the modelling of the transition process. The mechanisms underlying the transition process and the relative importance of the Tollmien–Schlichting wave instability in this flow are treated in an accompanying paper (part 2 of the present report).

(Published Online April 26 2006)
(Received November 17 1993)
(Revised July 8 1994)

p1 Present address: Volvo Aerospace Corp., Space Propulsion Division, S-461 81 Trollhättan, Sweden.