Large eddy simulations of single and multiple turbulent round jets

Abstract

We present results from three large eddy simulations (LES). The first two were those of a single jet at a Reynolds number of 11000 with different cell density distributions. The simulation results are validated with earlier experimental and computational studies at the same Reynolds number and almost the same boundary conditions. We establish the repeatability and reproducibility of the characterisation of a single axisymmetric jet. Additionally, we performed an LES of five round jets using the same discretisation schemes and boundary conditions. The five jets were placed in a cross or plus configuration, with a central jet surrounded by four outer jets. The mass flux, momentum flux and the Reynolds number of the five jet configuration were set to be equal to those of the single jet. Further, we analyse the near-field development of the multiple jets, along with entrainment and symmetry characteristics as the jet evolves. LES's ability to provide information about large-scale motions was used to compute conditional statistics. We, then, present details of an initial attempt to characterise the turbulent non-turbulent interface boundary and the coherent structures in the core of the jet in a unified manner using helicity density as the detector variable.

Keywords:

• CFD
• LES
• jets

Acknowledgments

We thank Dr P. Jeyajothiraj, Dr Pradeep Kumar, Dr Aadhimurthy, Prof. Ramamurthy of ISRO, Profs. J. Kurian, S. R. Chakravarthy, R. I. Sujith, M. Mathur of I.I.T. Madras, Dr Pannerselvam, Dr Parminder Singh of ARDB for enabling successful completion of this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

We thank the Aeronautics Research and Development Board (ARDB) and Indian Space Research Organisation (ISRO) for establishing the CIFAAR computational facility in the Department of Aerospace Engineering, IITM, that made this computational work possible through grants [DARO/08/1031495/M/I] and [ICSR/ISRO-IIT(M)/ASE/0708/115/NRPA].