“Application of NavierStokes based Mean-Flow Perturbation Method to Supersonic Jet Noise"
S. Bhaumik, D. Gaitonde, K. Goparaju, and M. Waindim
Several aspects of the dynamical behavior of a turbulent flow-field, can be investigated by analyzing the evolution of disturbances in its mean flow (or basic state). Recently, we have further advanced one such method of tracking disturbances based on full nonlinear Navier-Stokes equations following the method proposed by Touber & Sandham (Theor. Comput. Fluid. Dyn., 23, 79-107, 2009) in the context of shock wave turbulent-boundary layer interactions. This method degenerates to the LST, global and PSE analyses under suitable conditions. However, it poses an initial value problem (IVP) and unlike PSE, which makes an assumption of the slow-variation of the mean-flow, can also be applied to flows with sharp gradients or discontinuities (shocks). Here, we apply this “Navier-Stokes Equation based Mean-Flow Perturbation”analysis (NS-MFP) to obtain characteristics of disturbance evolution in the mean flow the turbulent ideally and under-expanded Mach 1.3 jet to investigate sound generation mechanisms. Results for the perfectly-expanded Mach 1.3 jet show definitive directivity of noise radiation depending on excitation Strouhal number. The Maximum intensity of radiated noise along the downstream directions is obtained when the excitation Strouhal number is close to 0.3. The sound pressure level variation for multi-periodic excitation shows a qualitative match with the F-spectrum along downstream directions. For the under-expanded jet the characteristics of noise radiation are markedly different as interactions of shock-cells with disturbances play a major role to determine far-field noise. For this case, the maximum intensity of radiated sound is observed along sideline and downstream directions when the excitation Strouhal number is close to unity.
2016 AIAA Fluid Dynamics Conference, AIAA Aviation Forum