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DIRECT NUMERICAL SIMULATIONS OF NON-ISOTHERMAL AND REACTING WALL-JETS

Zeinab Pouransari
Linne FLOW Centre, Dept. of Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden

G. Velter
Linné Flow Centre, KTH Mechanics SE-100 44 Stockholm, Sweden

Daniel Ahlman
Linne Flow Centre, Dept. of Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden

Geert Brethouwer
Linne FLOW Centre, KTH Mechanics Royal Institute of Technology 100 44 Stockholm, Sweden

Arne V. Johansson
Linne FLOW Centre, Dept. of Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden

Аннотация

Direct numerical simulations of plane compressible turbulent non-isothermal wall-jets are performed and compared to an isothermal jet. The study concerns a cold jet in a warm coflow and a warm jet in a cold coflow. The influence of the varying density on the flow and scalar mixing are studied. Although the domain length is somewhat limited in the simulations, the growth rate and the turbulence statistics indicate approximate self-similarity in the fully turbulent region. The use of van Driest scaling leads to a collapse of all mean velocity profiles in the near wall region. However, taking into account the varying density by using semi-local scaling of turbulent stresses and fluctuations does not completely eliminate differences between the statistics of the cold, isothermal and warm jet. The temperature and passive scalar dissipation time scales are similar in all cases.
A direct numerical simulation of a simple reaction in a turbulent plane wall-jet with a slight coflow is also performed. At the jet inlet the fuel is added whereas the oxidizer is added in the coflow. The reaction time scale is finite and of the same order as the mixing time scale. As the jet propagates downstream and becomes turbulent the reaction occurs mainly in the upper shear layer, but further downstream also in the inner layer due to the turbulent mixing.