Nature and lifetime of localized disturbances at laminar-turbulent transition of a viscous liquid in a tube
In the article, based on the joint analysis of the combined equation of the rst and second laws of thermodynamics for a simple system and the Darcy-Weisbach equation, possible causes of the emergence and development of localized perturbations (pu s) during a laminar-turbulent transition are considered. It is shown that the cause of the appearance and development of gusts is the imbalance between the positive production of entropy and the negative ow of entropy, which is a condition for the stationarity of the process, according to I. Prigogine. The imbalance occurs with an increase in the Reynolds number, and up to Re ≥ 1000 the imbalance is growing. An exponential dependence of the ratio of the entropy of a turbulent ow to the entropy of a laminar ow on the Reynolds number is obtained. It has been shown that the lifetime of impulses is an exponential function of the ratio of entropies turbulent and laminar ows.