| Mon October 6th 2014 16:00 – 17:00 ZH286 | Seminar | DNS of compressible turbulent droplet-laden heated channel flow with phase transition Nastya Bukhvostova |
Details:Multiphase flows in which a large number of small droplets are dispersed in a gas, play an important role in a variety of technological applications. Dispersed multiphase flows not only exhibit dynamic turbulence modulation, but may in addition show effects arising from phase transition. Turbulent spray cooling is a prime example in which the effect of phase transition is exploited to enhance the desired cooling rate. We study turbulent flow in a differentially heated plane channel in which the dispersed droplet phase is treated as a discrete set of point particles whose motion in the carrier gas flow is tracked. As point of reference, we consider the flow of droplets of water in air, in which the presence of water vapor is accounted for. A key assumption in the modeling of dispersed gas-liquid multiphase flows pertains to the treatment of the carrier gas as either incompressible or compressible. We investigate in which cases the compressible formulation is needed by comparing the results from the two formulations. We focus on heat and mass transfer properties of the system.The Mach number of the considered system is low and, consequently, the stability requirement leads to small time steps in explicit time-stepping methods in the compressible formulation. In order to avoid this we developed a new numerical algorithm for droplet-laden compressible turbulent channel flow with phase transitions at low Mach numbers. The new method is an extension of a pressure- based method for incompressible flows and it permits to choose a time step independently of the Mach number. | ||
