New results on grid-generated turbulence

Författare: Kurian, T., Fransson, J. H. M.
Dokumenttyp: Konferens
Tillstånd: Publicerad
Tidskrift: Advances in Turbulence XII, Proc. 12th EUROMECH ETC, Sept. 7-10, 2009, Marburg, Germany
År: 2009


To experimentally study the receptivity of laminar boundary layers to free stream turbulence, the use of grids is the simplest and most effective way to generate turbulence. To investigate the receptivity it is essential to be able to vary the parameters of the free stream turbulence such as turbulence level and length scales. By altering the distance of different grids from the receptivity region, these parameters can be adjusted independently. In the current experimental setup seven grids with mesh widths (M ) in the range of 0.95 ? 50 mm were studied with two X-probes. The grids were characterized in terms of kinetic energy decay, integral turbulent length scale (both streamwise and transverse), Kolmogorov and Taylor scales, power spec- tra, dissipation and level of anisotropy. The downstream evolution of turbulent length scales and kinetic energy will be presented and compared with relations based on the assumption of isotropic turbulence. A new method for evaluating the coefficients in the power-law decay will be introduced. It will be shown that the levels of anisotropy and the power-law coefficients asymptotically approach the theoretical values based on the assumption of isotropy for large ReM