Flow structure around a suspended droplet in turbulent air stream

Investigations of flow mechanism around a suspended droplet in turbulent freestream flow are performed for Reynolds number between ∼60 to 1000. The objective is to understand how the flow structure around a droplet can be influenced by the turbulent freestream conditions and how the turbulence influences the global heat/mass transfer rate of the droplet. Investigations are also conducted in order to assess the effects of droplet support geometries and liquid surface blowing due to evaporation. Different flow visualizations techniques with different model droplets are employed to obtain qualitative flow information. A laser Doppler velocimetry (LDV) system is used to measure frequency and strength of the fluctuating flow in the core region of the sphere wake.; The flow visualization images show significant differences of flow mechanism surrounding the droplet for the laminar and turbulent freestream flow conditions. The flow structure is highly susceptible to the droplet suspension geometry. The entrainment of fluid particles in the wake region is significantly higher when the freestream is turbulent as compared to the laminar freestream flow case. The internal circulation patterns of liquid droplet are strongly influenced by the flow characteristic inside the wake region and the droplet suspension geometry.; Freestream turbulence can induce vortex shedding at a much lower Reynolds number than for laminar freestream flow. Once the vortex shedding processes are fully developed, the shedding frequencies are relatively similar between the laminar and turbulent freestream conditions. The mean fluctuation velocity in the core wake region for the turbulent freestream cases are significantly higher than those in the wake region for laminar freestream flow cases. This difference increases with increasing Reynolds number. Accordingly, the global heat/mass transfer rate of a sphere can be influenced more by turbulent freestream effects at higher Reynolds numbers as the separation region dominates a larger portion of the sphere's total surface area.