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Mixing of a turbulent non-compressible jet of heavy fluid (SF6 gas) injected into coflowing air of lower turbulence is studied experimentally in a vertical wind tunnel. Velocity and density fields are measured simultaneously with Particle Image Velocimetry and Planar Laser Induced Fluorescence. The effect of buoyancy is investigated and compared for two Atwood numbers: 0.1 (Boussinesq case) and 0.6 (strongly non-Boussinesq case). In both cases the initial jet volume flow rates are matched. The high Atwood number jet with larger Reynolds number shows reduced lateral spreading compared to the low Atwood number jet with smaller Reynolds number in both velocity and density profiles, indicating stabilizing effect of buoyancy. The PDF of spatial density gradients for the high Atwood number has much stronger non-exponential tails than for the low Atwood number signifying the reduced rate of mixing of the strongly buoyant jet. The other statistical characteristics of the mixing important for modeling these flows such as spreading rate, turbulent mass flux, density weighted Reynolds stress, turbulent kinetic energy flux, and density specific volume correlation are also examined in the near and far field from the jet.
Author(s):
Sergiy Gerashchenko
Los Alamos National Laboratory
United States
Kathy Prestridge
Los Alamos National Laboratory
United States