Novel Approach for Turbulent Flow- and Onset Analysis

Abstract

It is a well-known fact that the matching of experimental data to turbulence models have hitherto not been successful. An example of this is the inability to theoretically predict the Re number at which turbulence onset (transition) occurs. In this paper, some advantages of adopting a “far-from-equilibrium” irreversible process analysis are demonstrated: To illustrate, one may at a single geometric point near a solid wall, compute conditions for mass conservation, 1st, and 2nd laws of thermodynamics – assuming either Newton’s viscosity law- or an alternative far-from-equilibrium fundamental model to be valid. While these conditions generally differ for various flows, it is observed that these conditions numerically match each other at ReD around 2300 for a fully developed pipe flow, or at Rex between 5 × 105 to 3 × 106 in a developing flat-plate boundary layer flow. This suggests that turbulence onset can be correctly predicted using the novel approach. Criteria and recommendations for experimental flow measurements, i.e. testing conditions, within a proposed far-from-equilibrium zone (e.g. viscous sublayer) is discussed as well.