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LARGE-EDDY SIMULATION OF ACCELERATED TURBULENT FLOW IN A PIPE

Seo Yoon Jung
Mechanical Engineering, Imperial College London London, SW7 2AZ, U.K.; Advanced Reactor Development Institute Korea Atomic Energy Research Institute 898-111, Daedeok-daero, Daejeon 305-353, Korea

Yongmann M. Chung
School of Engineering and Centre for Scientific Computing University of Warwick Coventry CV4 7AL, UK

Abstrakt

Large-eddy simulations of unsteady turbulent pipe flows were performed to investigate the response of near-wall turbulence to temporal acceleration. The simulations were started with the fully-developed turbulent pipe flow, and then a constant temporal acceleration was applied. The Reynolds number of the pipe flow, based on the pipe diameter and the bulk-mean velocity, increased linearly from ReD = 7000 to 45200. Various turbulence statistics revealed distinctive features of the delays responsible for turbulence production, energy redistribution, and radial propagation. It was found from the LES results that turbulent viscosity was frozen in the early transient, followed by a rapid increase. This delay was due to the slow response of the wall shear stress and Reynolds shear stress. The vorticity field showed the delayed response of the near wall structures after the onset of temporal acceleration.