Abstract:
The application of fractals to the analysis of fluid flow is well established. Mandelbrot considered the fractal characteristics of iso-scalars in turbulent flows and intermittency in turbulence, while Meneveau and Sreenivasan attempted to describe the multi-fractal nature of turbulence dissipation. By contrast, the use of fractal geometry grids to generate bespoke multi-scale turbulence is comparatively recent. Hurst and Vassilicos conducted parametric studies using different types of fractal grids and showed that higher turbulence intensities, as compared to classical grids with higher blockage ratios, can be generated. Fractal theories have also been applied to analyse the wrinkling of premixed turbulent flame surfaces. Lindstedt and Sakthitharan used a fractal dimension of 7/3 combined with inner and outer cutoff scales equivalent to the Kolmogorov and integral length scales to show that turbulent burning velocities are dependent on the ratio between the laminar burning and Kolmogorov velocities. Despite the use of fractal based analysis techniques, the potential advantages of using fractal grids to generate turbulence in geometries suitable for systematic investigations of turbulent flames is comparatively recent and progress is reviewed.  An analysis is presented in the context of a multi-fluid formalism that extends the customary bimodal approach to include multiple fluid states. The approach is quantified via simultaneous OH-PLIF and PIV, permitting the identification of five separate states.

Brief Biography:

Peter Lindstedt studied at Chalmers Tekniska Högskola, Göteborg, Sweden, where he received a MEng in Chemical Engineering in 1980. At Imperial College London, he received a PhD from the Department of Chemical Engineering 1984. Peter then moved to Mechanical Engineering, where he was awarded the title Professor of Thermofluids in 1999, served as head of the Thermofluids Division from 2000 to 2010 and as Director of Research from 2003 to 2013. In 2013, he was elected Consul for the Faculty of Engineering and Business School. Peter has published over 100 peer reviewed archival journal and conference contributions and has received the Gaydon Prize and the Sugden Awards from the Combustion Institute. Invited lectures include a plenary on the Chemical Complexities of Flames at the 27th International Symposium on Combustion. He is a Director on the International Board of the Combustion Institute (2006 to 2018) and served as associate editor for Combustion and Flame from 2000 - 2010. He is an editorial board member of Combustion Theory and Modelling and Progress in Energy and Combustion Science. Peter served as the Technical Program Co-Chair (with Ron Hanson, Stanford University) for the 30th International Symposium on Combustion that also celebrated the 50th Anniversary of the Combustion Institute. Peter also serves on the program committee for the International Workshop on Turbulent Non-Premixed flames.