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Investigation of high-pressure turbulent jets using direct numerical simulation

Sharan, Nek and Bellan, Josette (2020) Investigation of high-pressure turbulent jets using direct numerical simulation. . (Unpublished)

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Direct numerical simulations of free round jets at a Reynolds number (Re_D) of 5000, based on jet diameter (D) and jet-exit bulk velocity (U_e), are performed to study jet turbulence characteristics at supercritical pressures. The jet consists of Nitrogen (N₂) that is injected into N₂ at same temperature. To understand turbulent mixing, a passive scalar is transported with the flow at unity Schmidt number. Two sets of inflow conditions that model jets issuing from either a smooth contraction nozzle (laminar inflow) or a long pipe nozzle (turbulent inflow) are considered. By changing one parameter at a time, the simulations examine the jet-flow sensitivity to the thermodynamic compressibility factor (Z), inflow condition, and pressure (p) spanning perfect- to real-gas conditions. The inflow affects flow statistics in the near-field (containing the potential core closure and the transition region) as well as further downstream (containing fully-developed flow with self-similar statistics) at both atmospheric and supercritical p. The sensitivity to inflow is larger in the transition region, where the laminar-inflow jets exhibit dominant coherent structures that produce higher mean strain rates and higher turbulent kinetic energy than in turbulent-inflow jets. Decreasing Z at a fixed supercritical ambient pressure (p∞) enhances pressure and density fluctuations (non-dimensionalized by local mean pressure and density, respectively), but the effect on velocity fluctuations depends also on local flow dynamics. When Z is reduced, large mean strain rates in the transition region of laminar-inflow jets significantly enhance velocity fluctuations (non-dimensionalized by local mean velocity) and scalar mixing, whereas the effects of decreasing Z are minimal in jets from turbulent inflow.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Sharan, Nek0000-0002-7274-8232
Bellan, Josette0000-0001-9218-7017
Additional Information:This work was supported at the California Institute of Technology by the Army Research Office under the direction of Dr. Ralph Anthenien. The computational resources were provided by the NASA Advanced Supercomputing at Ames Research Center under the T³ program directed by Dr. Michael Rogers.
Funding AgencyGrant Number
Army Research Office (ARO)UNSPECIFIED
Subject Keywords:turbulent round jets; high-pressure conditions; supercritical mixing; direct numerical simulation
Record Number:CaltechAUTHORS:20201027-074230260
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106287
Deposited By: Tony Diaz
Deposited On:27 Oct 2020 17:08
Last Modified:27 Oct 2020 17:08

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