(Georgia Institute of Technology, 2024-01-16)
Hatashita, Luis H.
Jet in crossflow (JICF) has been a subject of research for several decades due to its
enhanced mixing properties, i.e. greater than free and coaxial jets. It is moreover encountered in nature in the form of volcano plumes, and in industrial applications. Fuel injection and dilution in jet engines or gas turbines are also of interest. Non iso-density ratio jet in a crossflow has only more recently been subject of studies. While jet mixtures are adjusted to alter the density ratio, fewer studies have been reported on varying temperature to achieve the same effect. The current work extends on previous studies to evaluate momentum ratio, crossflow temperature and jet molecular weight on mixing. The knowledge of governing mechanisms of mixing enables optimization of operational conditions, geometry and emissions for gas turbine and combustor applications.
High-fidelity numerical simulations are conducted and validated against experimental data, demonstrating the capability of the simulation to predict mixing. Furthermore, the simulation data is evaluated to predict reduced order model decomposition.
Results indicate that momentum ratio is the dominant parameter and the governing factor to control macroscopic features of the flow, such as jet penetration and concentration decay. Mixing is also enhanced for the set of fully developed turbulent jets. Crossflow temperature presents different non-negligible effects on mixing both in the near- and far-field, despite not affecting overall flow geometry. Scalar dissipation rate, spatial probability density functions and integral mixing metrics corroborate this result. Turbulence time scales and instantaneous scalar concentration fields demonstrate how temperature affects mixing. Molecular weight (within the range studied) on the other hand is shown to be a minor parameter and does not demonstrate significant changes to the metrics.
The influence of temperature on mixing is investigated through Proper Orthogonal and Dynamic Mode decomposition to extract and evaluate coherent structures. It is found that increase in temperature inhibits the formation of coherent structures such as wake vorticies.