Modeling noise sources in non-axisymmetric jets

Coherent wavepackets occuring in turbulent jets are the dominant sources of noise. They are modelled effectively as linear instabilities of the turbulent mean flow, using both quasi-parallel flow linear stability theory (LST) and parabolized stability equations (PSE). We have extended extended these models to arbitrary non-axisymmetric jets -- like chevron jets and offset dual-stream jets. Encouraging agreement is obtained between the model predictions and experimental/simulation data. These models serve as efficient design tools aimed at understanding and minimizing jet noise.

Selected publications:

  • N. Sohoni and A. Sinha, Shooting method for linear inviscid bi-global stability analysis of non-axisymmetric jets, International Journal of Aeroacoustics, 20(3-4):361-389, 2021 (download)
  • N. Singh, N. Sohoni and A. Sinha, Modelling noise from offset two-stream jets using linear stability theory and Kirchhoff surface method, AIAA Paper 2019-2473 (download)
  • A. Sinha, K. Gudmundsson, H. Xia and T. Colonius, Parabolized stability analysis of jets from serrated nozzles, Journal of Fluid Mechanics, 789:36-63, 2016 (download)

Reduced-order modelling of steady aerodynamics

The aerodynamic design of missiles (and other stores like drop tanks) requires extensive numerical simulation that is expensive both in terms of cost and time. We develop extremely efficient, albeit approximate, semi-empirical reduced-order models for predicting the quasi-steady aerodynamics of such bodies. This significantly speeds up the generation of aerodynamic database of missiles (in freestream) as well as the prediction of store-separation trajectory in the influence zone of the parent aircraft. The modelling approach uses Proper Orthogonal Decomposition for identifying the dominant flow features from existing database that is sampled sparsely in the parameter space. Subsequently, the POD-reconstructed flow solution is found by minimizing the residual of the governing equations.

Selected publications:

  • A. Sinha and S. Garg, Reduced-order modeling of steady aerodynamics for 2d store separation analysis, AIAA Paper 2018-3168 (download)