Direct Noise Computation of a Shocked and Heated Jet at a Mach Number of 3.30

Abstract

An overexpanded axisymmetric jet at an exit Mach number of 3.30 and a Reynolds number of 10 5 is computed by compressible large-eddy simulation (LES) to determine directly its radiated sound field, using low-dissipation schemes in combination with an adaptative shock-capturing method. At the jet nozzle exit, static pressure and temperature are respectively equal to 0.5 × 10 5 Pa and 360 K, and a laminar flow profile is imposed. To assess the validity of the simulation, the mean aerodynamic field and the near-field pressure levels, obtained directly by LES, are compared to available literature data. The axial velocity fluctuations in the shear-layer are also characterized using azimuthal decomposition, and exhibit properties close to those observed in screeching jets. The acoustic field is dominated by axisymmetric and first azimuthal modes, and noise sources are investigated from the acoustic near field: Mach waves, shock-associated noise and turbulent mixing noise occuring around the end of the potential core are identified.

Large-Eddy Simulations of a Supersonic Heated Jet

“…The results are in good agreement with available experimental data. Recently Caqueray et al [12] have carried out simulations of an overexpanded axisymmetric circular jet at an exit Mach number of 3.30 and exit temperature of 360K. Their near-field overall pressure levels are in a fair agreement with experimental data.…”

“…To speed up this transition, we have adopted an approach similar to what used in Ref. [12]. A small amount of random pressure perturbations is added inside the nozzle near the C-D nozzle surfaces.…”

Finite differences for coarse azimuthal discretization and for reduction of effective resolution near origin of cylindrical flow equations

“…To examine their behaviours for more complicated flow configurations, additional work would naturally be necessary. It must however be noted that the methods have already been successfully employed in large-eddy simulations of turbulent round jets [21][22][23] solving the 3D cylindrical compressible Navier-Stokes equations.…”

“…Considering this, finite-difference schemes, which are relatively easy to implement, and whose cost increases linearly with n h , can be interesting to apply in the azimuthal direction. This has successfully been done by the authors over the last two years in large-eddy simulations of turbulent round jets [21][22][23] based on the three-dimensional cylindrical compressible Navier-Stokes equations. In these simulations, great care have been taken to minimize numerical errors and to preserve computational efficiency.…”

Effect of Nozzle-exit Flow Conditions on the Flow and Acoustic Properties of Imperfectly Expanded Supersonic Jets

“…Randomly perturbing pressure or velocity field has been used to increase the turbulence level at the nozzle exit in simulations of jet flows [6,[9][10][11]. For example, randomly perturbed pressure has been used by Bogey and Bailly in their simulations of subsonic jets [4] and Cacqueray et al in their simulations of an over-expanded heated jet [8]. Nozzle geometries are not included in those simulations, so analytical velocity and temperature profiles are used at the nozzle exit.…”