Direct numerical simulation of turbulent jet in regular waves: A comparison between circular and non-circular cross-sections

• Published in: Ocean engineering 2023-11, Vol.288, p.116084, Article 116084
• Main Authors: Anghan, Chetankumar, Bade, Mukund H., Banerjee, Jyotirmay
• Format: Article
• Language: English
• Subjects: Instabilities in jet; Non-circular jet; Ocean outfall; Rectangular jet; Vortex dynamics
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2023.116084

Direct numerical simulations of circular and non-circular jets (square and rectangular) when released into regular waves are performed and reported in this article. In case of a rectangular jet, two different orientations of the nozzle have been simulated i.e major axis parallel (case 1) and perpendicular (case 2) to wave advancement direction. An analysis of the leading vortex ring reveals that axis switching in a rectangular jet takes place irrespective of nozzle orientation with respect to wave advancement direction. The axis switching is absent in the square jet. Further, the roll-up frequency of the non-circular jets is found less than the circular jet. Also, the roll-up frequency is independent of the orientation of the rectangular jet with respect to the wave direction. The braid region shows that the number of counter-rotating pairs are four for all the cases, however, the lateral jets are three for circular, square and case 1 of rectangular jets. The lateral jets in case 2 of the rectangular jet remain four due to change in orientation of the lateral jets owing to change in the nozzle orientation. The time-averaged quantities suggest increased mixing and entrainment in the rectangular jet as compared to circular jet. The highest mixing and shortest potential core are observed in case 2 of the rectangular jet. Therefore, for better mixing, the rectangular nozzle should be placed in the ocean outfall such that its major axis remains perpendicular to the direction of wave advancement. •Direct numerical simulations of non-circular jets in regular waves is presented.•DNS of rectangular jets reported for major axis parallel and perpendicular to wave advancement.•The roll-up frequency of non-circular jets is found lesser than the circular jets.•Lateral jets are three for square and rectangular jets with major axis parallel to wave advancement.•Mixing is highest for rectangular jet with major axis perpendicular to wave advancement direction.