The prediction of broadband shock-associated noise using Reynolds-averaged Navier-Stokes solutions

Broadband shock-associated noise is a component of jet noise generated by supersonic jets operating off-design. It is characterized by multiple broadband peaks and dominates the total noise at large angles to the jet downstream axis. A new model is introduced for the prediction of broadband shock-associated noise that uses the solution of the Reynolds averaged Navier-Stokes equations. The noise model is an acoustic analogy based on the linearized Euler equations. The equivalent source terms depend on the product of the fluctuations associated with the shock cell structure and the turbulent velocity fluctuations in the jet shear layer. The former are deterministic and are obtained from the Reynolds averaged Navier-Stokes solution. A statistical model is introduced to describe the properties of the turbulence. Only the geometry and operating conditions of the nozzle need to be known to make noise predictions. Unlike other models, the developed broadband shock-associated noise model is a true prediction scheme and not calibrated for a finite range of operating conditions. The broadband shock-associated noise model developed represents the only prediction method in existence that has no restrictions on nozzle geometry or jet operating conditions. This overcomes the limitations and empiricism present in previous broadband shock-associated noise models. Extensive validation of the Reynolds averaged Navier-Stokes solution is performed using experimental data. Validation efforts of the Reynolds averaged Navier-Stokes solutions include comparisons of Pitot and static probe measurements and schlieren visualization. These validations show both the strengths and deficiencies for modeling strategies of supersonic jets operating off-design using Reynolds averaged Navier-Stokes equations and associated turbulence closure schemes. Predictions for various nozzle and operating conditions are compared with experimental noise measurements of the associated jets to validate the broadband shock-associated noise model. The operating conditions include under-expanded and over-expanded jets with and without heating.