Study of Dual-Jet Interference and Scalar Mixing using Direct Numerical and Large-Eddy Simulations

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In this research, turbulent interference of dual jets and dual scalars emitted from different shaped nozzles is investigated using large-eddy simulations (LES) and direct numerical simulations (DNS). This research subject represents a complex multi-scale physical phenomenon in the area of turbulent heat, mass and fluid flows, and has vast applications in mechanical, chemical and environmental engineering. For example, the knowledge on turbulent mixing of jets and scalars is critically important for designing highly-efficient twin-jet engine exhausts of a fighter aircraft and twin mufflers of a vehicle. The transport processes of momentum and scalars (passive or active) are determined by many factors such as the nozzle shape, nozzle separation distance, Reynolds number, Schmidt number, Grashof number, and length scales of the plumes and turbulent eddies. Furthermore, the engulfing and entrainment processes through the dynamically evolving dual-jet interfaces that separate the instantaneous turbulent and non-turbulent (T/NT) flow regions play a significant role in the turbulent mixing processes.     The long-term objective of this research is to obtain in-depth knowledge on the physics of turbulent interference of jets and mixing of scalars, to enhance our fundamental understanding of turbulence theory as well as practical skills in engineering applications, and to develop high-fidelity simulation tools for improved numerical prediction of turbulence phenomena. The first short-term objective focuses on a study of the interference of dual jets emitted from different shaped nozzles. Both 2D and 3D jets will be tested, emitting from planar, round and concentric circular nozzles, and from elliptic and rectangular nozzles of different aspect ratios. The LES results on dual jets will be compared against experimental and DNS data at high and low Reynolds numbers, respectively. The second short-term objective includes one more degree of complexity, an additional body force due to the use of active scalars. To this purpose, buoyant jets will be studied, and the effect of buoyancy on the coupled transport of momentum and thermal energy will be investigated. The third short-term objective is to develop and test several novel subgrid-scale models for improved LES predictions of turbulent flow and scalar mixing.     The proposed research will provide an excellent opportunity for the applicant and his students to conduct innovative research on turbulent interference of dual-jets and dual-plumes using both DNS and LES. The advanced knowledge gained and numerical tools developed through the proposed research are of significant theoretical and practical values. The proposed research will also provide a valuable opportunity to train highly qualified personnel (HQP) in areas related to numerical modelling, engineering fluid mechanics, heat and mass transfer, and high-performance scientific computing based on the use of in-house computer codes and supercomputers.