Internal Energy Level Population Redistribution of Carbon Dioxide in Laminar and Turbulent Flow

We show clear experimental evidence that in the laminar flow regime, there is a continuous redistribution of population on different vibrorotational energy levels as the flow rate increases. Such redistribution comes to an abrupt stop when the flow changes to turbulence. The population distribution then remains almost unchanged even up to the flow rate 10 times the laminar to turbulent transition. The flow status of carbon dioxide is therefore closely related to its internal energy level population distribution. In the past ten years, several experiments have been performed to test the long-accepted idea that when expressed in terms of dimensionless variables, such as the critical Reynolds number, the laminar-turbulent transition is independent of the fluid used in the experiment, a principle sometimes referred to as scale invariance, a fundamental tenet enshrined in the study of turbulence [1]. The experiments are of two types: (I) quasistatic [2–7] and (II) unconstrained free efflux [8–10]. Type I experiments have mixed results: [6, 7] support scale invariance, while [2–5] raise doubts on its validity. Type II experiments, using modern apparatus from the field of vacuum science and technology, are supportive of the theoretical studies which propose a quantum origin for a theory of turbulence [11–13]. The results of Type II experiments support the assertion that the critical Reynolds number, at which the laminar-turbulent transition occurs, is specie dependent. Thus, normal and heavy water have different critical Reynolds numbers, and so do the noble gases. Scale invariance and specie dependence are contrary to each other. Scale invariance comes from the classical continuum approach, proposed before atoms and molecules were discovered, while specie dependence is characteristic of a quantum view of nature. It is important to settle this controversy. In this paper, we report a Type III experiment: simultaneous spectroscopic measurements that compare the absorption spectra of an excited gas and its state of motion, in laminar or turbulent form. We have designed an experiment that correlates different populations of CO2 gas. There is only one species, pure CO2, but it has subspecies, namely, the different ground and excited states of this molecule. The tests in this experiment are more stringent than Type I and Type II experiments and certainly go beyond a classical continuum model. The experimental schematics are shown in Figure 1. The gas cell was made of stainless steel with inner dimensions of 10？mm × 10？mm × 500？mm. The infrared windows were made of