Turbulence behind a passive grid in a wind tunnel has been the paradigm of experimental investigation since the beginning of turbulence research. Flows in modest-sized traditional wind tunnels, however, suffer from the limitation of relatively low Reynolds numbers. At the Max Planck Institute for Dynamics and Self-Orgaization (MPIDS) in Göttingen, Germany, we surpass the usual limitations by using pressurized Sulfur-hexafluoride (SF₆) gas as the working fluid. At the pressure of 15 bar, the kinematic viscosity of the SF₆ gas is only one hundredth of air viscosity, which dramatically increases the Reynolds number achievable in a wind tunnel with a 2 m² cross-sectional area. With a traditional cross-bar passive grid, the Taylor-microscale Reynolds number, R_l, reaches 1700 at the mean flow velocity of 5 m/s, and the Kolmogorov scale is still resolvable with hot-wire probes. I will present velocity spectra and structure functions measured with hot-wire probes in the tunnel over the range of 150 < R_l < 1700 by varying the density (kinematic viscosity) of the working fluid alone. This is an order of magnitude higher in Reynolds number than previously reported grid turbulence studies in the literature.

Prof. Bodenschatz received his doctorate in theoretical physics from the University of Bayreuth in 1989. In 1991, during his postdoctoral research at the University of California at Santa Barbara, he received a faculty position in experimental physics at Cornell University. From 1992 until 2005, during his tenure at Cornell he was a visiting professor at the University of California at San Diego (1999-2000). In 2003 he became Director and Scientific Member at the Max Planck Institute for Dynamics and Self-Organization. He continues to have close ties to Cornell University, where he is Adjunct Professor of Physics and of Mechanical and Aerospace Engineering (since 2005).

 

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