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A simple theory, based on observations of snowflake distribution in a turbulent flow, is proposed to model the growth of inertial particles as a result of dynamic clustering at scales larger than the Kolmogorov length scale. Particles able to stick or coalesce are expected to grow in size in flow regions where preferential concentration is predicted by a critical Stokes number $St=tau_p/tau_f simeq 1 $. We postulate that, during growth, $St$ remains critical, with the particle response time $tau_p$ evolving according to the specific flow time scale $tau_f$ defined by the vortices around which progressively larger particles end up orbiting. This mechanism leads to the prediction of the limiting size of aggregating particles in a turbulent flow. Such limit is determined by the extent of the turbulent inertial range, which can be formulated as a function of accessible integral-scale quantities. The proposed dynamically critical Stokes growth provides a framework to interpret particle aggregation, size growth and particle cluster growth in various geophysical multi-phase flows.
Turbulent flows under transcritical conditions are present in regenerative cooling systems of rocker engines and extraction processes in chemical engineering. The turbulent flows and the corresponding heat transfer phenomena in these complex processe
We present Lagrangian one-particle statistics from the Risoe PTV experiment of a turbulent flow. We estimate the Lagrangian Kolmogorov constant $C_0$ and find that it is affected by the large scale inhomogeneities of the flow. The pdf of temporal vel
Axisymmetric fountains in stratified environments rise until reaching a maximum height, where the vertical momentum vanishes, and then falls and spread radially as an annular plume following a well-known top-hat profile. Here, firstly, we generalize
We study the joint probability distributions of separation, $R$, and radial component of the relative velocity, $V_{rm R}$, of particles settling under gravity in a turbulent flow. We also obtain the moments of these distributions and analyze their a
In this visualisation, the transition from laminar to turbulent flow is characterised by the intermittent ejection of wall fluid into the outer stream. The normalised thickness of the viscous flow layer reaches an asymptotic value but the physical th