Conditional Velocity Statistics in Turbulent Jets

The objective of the present work is to study the combined statistics of the velocity and scalar fields, in particular the conditional averages of velocity, which arise [1,2] in turbulent combustion models based on probability density functions (pdfs). When these approaches are applied on the single point statistics level, two kinds of processes need some closure assumptions, namely, the so-called micro-scale mixing, that is molecular diffusion enhanced by the small scale turbulence, and the turbulent convection. The micro-scale mixing was, and it still remains, a subject of numerous works the recent reviews of which can be found in [2,3]. The transfer of probability functions by the fluctuating turbulent velocity field in non-homogeneous flows, to which the present article is devoted, has gained less attention. Since the pioneering measurements of Bezuglov [4] and Scherbina [5], the experimental works on this subject remain scarce, which partly explains rather slow theoretical progress. The objective of this work is to present measurements associated with the transfer of iso-scalar lines by fluctuating velocity field in non-reacting jets and to provide comparison with the existing models.