Numerical investigation of the noise radiated from hot subsonic turbulent jets

Numerical Prediction of the Noise Emission from a Turbulent Argon Thermal-Plasma Jet Issuing into Ambient Air

“…(23,24) Pertinent two-dimensional conservation equations for continuity, momentum, energy, species, turbulent kinetic energy and turbulence dissipation rate were solved to determine the turbulent plasma jet flow characteristics, and then the noise emission intensity-frequency characteristics and the noise intensity levels were calculated in the same way as used by Fortuné and Gervais. (19) It was found that among the contributions due to, respectively, aerodynamic noise source, entropic noise source and their mixed effect, the contribution of the entropic noise source was the dominant one for the noise emission from the turbulent plasma jet with inlet temperature 13000 K. (22) However, although the entropic noise source had been shown to be the most important factor, the entropic noise source in the turbulent plasma jet was still simply calculated in Ref. 22 as in Ref.…”

“…see (17)(18)(19) and the references cited therein) since the pioneering work of Lighthill. (20,21) Although most of those studies are concerned with the noise emission from cold or hot turbulent gas jets with temperatures not too high (usually lower than 1500 K, which is much lower than the thermal plasma jet temperatures), the theoretical approaches employed in those studies are still of significance for the present study.…”

“…The contribution of jet temperature fluctuations to the jet noise emission was not considered in Tam's model (17,18) even for the hot gas jets. On the other hand, by ignoring the viscous stress term in Lighthill's tensor (20,21) and using ρ(2K/3) and (ρ ∞ /T )∂(v T )/∂r to approximate the noise source term containing velocity fluctuation correlation (so-called aerodynamic noise source term) and the noise source term containing velocity-temperature fluctuation correlation (so-called entropic noise source term), respectively, Fortuné and Gervais (19) proposed their expressions for predicting the far-field noise emission from turbulent hot gas jets to a sideline far-field observer. The turbulent kinetic energy and other related information were also calculated by use of the K-ε two-equation turbulence model, and the velocity-temperature correlation v T (or radial Reynolds heat flux component) appearing in the entropic noise source term was calculated approximately by…”

“…Reasonable agreement with some available experimental data with jet inlet temperature of 786 K was reported. (19) The above-mentioned studies are all concerned with the turbulent non-ionized air jet with comparatively low jet temperatures. In Ref.…”

“…In Ref. (22), the modeling approach proposed by Fortune and Gervais (19) for predicting the noise emission from the hot air jet to a sideline observer was used to predict the noise emission from a turbulent argon plasma jet issuing into ambient air with the atmospheric plasma spraying as the research background. The diffusion of ambient air into the plasma jet was handled by use of the combined-diffusion-coefficient method proposed by Murphy.…”