Experimental and Numerical Investigation of Flow Properties of Supersonic Helium-Air Jets

Heated high-speed subsonic and supersonic jets operating on- or off-design are a source of noise that is not yet fully understood. Helium - air mixtures can be used to simulate the total temperature ratio of heated jets and hence have the potential to provide inexpensive and reliable flow and acoustic measurements. Accurate knowledge of the mean flow is a crucial initial step for a complete understanding of the noise generation mechanisms. This study focuses on providing close comparisons between measured mean flow properties of helium - air mixture jets and results from simulations of similar mixed jets as well as heated air jets. Axisymmetric supersonic jets issuing from convergent and convergent-divergent nozzles are investigated, and the results show good agreement with heated air jet measurements. The flow properties are examined in detail to demonstrate the validity of simulating heat with the addition of helium. Excellent agreement is obtained in the presented data between the numerical predictions and the experiments, further justifying the helium addition methodology, as well as validating the frozen chemistry model used in the numerical simulations. [PUBLICATION ABSTRACT]