Work

Numerical Study of Laminar Unsteady Circular and Square Jets in Crossflow in the Low Velocity Ratio Regime

Year: 2024

Type: article

Abstract: The unsteady three-dimensional flow interactions in the near field of square and circular jets issued normally to a crossflow were predicted by direct numerical simulations, aiming to investigate the effect of the nozzle cross-section on the vortical structures formed in this region. The analysis focuses on jets in crossflow with moderate Reynolds numbers (Rej=200 and Rej=300) based on the jet velocity the characteristic length of the nozzle and low jet-to-cross-flow velocity ratios, 0.25≤R≤1.4, where the jets are absolutely unstable. In this regime, the flow becomes periodic and laminar, and three distinct wake flow configurations were identified: (1) symmetric shedding of hairpin vortices at Rej=200; (2) the formation of toroidal vortices as the legs of hairpin vortices merge and the vortices roll up at Rej=300 and R≤0.67; (3) asymmetric shedding of hairpin vortices in the square jet at Rej=300 and R≥0.9, where higher-frequency hairpin vortex shedding combines with a low-frequency spanwise oscillation in the counter-rotating vortex pair. The dynamics of each of these flow states were analyzed. Power spectral density plots show a measurable increase in the shedding frequencies in Rej=300 jets with R, and that these frequencies are consistently larger in circular jets.

Source: Fluids

DOI: 10.3390/fluids9120292

Authors: Francisco C. Martins, José C. F. Pereira

Institutions: University of Lisbon, Instituto Superior Técnico, Instituto Superior Técnico Instituto de Engenharia Mecânica

Language: English

Topic: Fluid Dynamics and Turbulent Flows

Subfield: Computational Mechanics

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,046

Funders: Max-Planck-Gesellschaft, Fundação para a Ciência e a Tecnologia