“On the Turbulence Statistics of a Hot, Overexpanded Rectangular Jet”
Publication Type:
Conference
Authors:
Co-Authors:
S. Chakrabarti, D.V. Gaitonde, C. Stack, F. Baier, A. Karnam, and E. Gutmark
Year Published:
2020
Abstract:
Rectangular nozzles are receiving increased attention because of, among other reasons, the ease with which they may be integrated into the airframe. However, their dynamics have not been examined in as much detail as circular configurations, particularly at operating conditions relevant to practical applications. The present work investigates the nearfield dynamics of a rectangular heated overexpanded jet of aspect ratio 2 using a high-fidelity Large-Eddy Simulation (LES). The LES is validated through comparisons of nearfield as well as farfield measurements with corresponding experiments. Since the nozzle is not contoured in order to represent practical configurations, multiple shock trains arise; the first from a separation bubble slightly downstream of the sharp throat, a second from the reattachment of the flow downstream of the throat, and a third from the overexpanded operating condition. The first shock train displays significant unsteadiness and generates shocklets that destabilize the downstream shock cells. As the plume evolves downstream, the major axis shear layer of the jet experiences significant amplification of turbulent kinetic energy (TKE) compared to the minor axis, with the primary effect being manifested in peak fluctuations of the streamwise component of velocity. This is shown to be related to the more rapid lateral collapse of the potential core along the major axis, where the jet is relatively wider. The most prominent source of TKE on the major axis is shown to result from the strong mean flow gradients across the shear layer, and larger corresponding cross-plane components of Reynolds stress. In the very nearfield, the pressure perturbations from the turbulent fluctuations are shown to be asymmetric; however a symmetric distribution is recovered by approximately 2.25 equivalent diameters from the jet centerline. This is consistent with an azimuthally symmetric farfield acoustic signature in both computation and experiment.
Conference Name:
AIAA Science and Technology Forum and Exposition 2020
Conference Location:
Orlando, FL
Other Numbers:
Refereed Designation:
Date Published:
1/5/2020