Numerical simulation and analysis of the transition to turbelence in boundary layer flows

Abstract

The transition from laminar to turbulent flow has always been a complicated and intractable process which can hardly be explained completely so far. Although a series of models were built to study the transition, no manageable one could exhibit its entire characteristics and make an accurate prediction when the transition would occur. In this context, Assoc. Prof. Vladimir V. Kulish has come up with a new model that views the velocity fluctuations during a transition from laminar to turbulent flow as a fractal time series. Hence, the author would conduct two types of experiments, i.e. Open Channel Flow Experiment and Boundary Layer Flow Experiment, to verify this model and explore the validity of a prediction of transition. FRASTSAN program was used throughout this project to analyze the fractal time series and generate the results of Fractal Dimension, Jeffrey Divergence Measure and Hurst Exponent, respectively. By comparing and analyzing plots of the results in each channel, interpretations on the above-mentioned three measures were able to explain the observations from velocity data, and the prediction of a transition was found to be consistent with that made from the velocity data. Thus, it could be concluded that the model is credible and can make a dependable prediction of a laminar-turbulent transition. However, certain limitations cannot be neglected in multifractal analysis. As a result, some recommendations based on these limitations would be made to future researchers and work.