Session LK: Multiphase Flows V
3:35 PM–5:45 PM, Monday, November 23, 2009
Room: 101J
Chair: Marios Soteriou, United Technologies Research Center
Abstract ID: BAPS.2009.DFD.LK.10
Abstract: LK.00010 : An identification of coherent structures in an inhomogeneous turbulence
5:32 PM–5:45 PM
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Abstract
Author:
Ryuichi Nagaosa
(RISS, AIST)
This study proposes a proper scaling of a vortex indicator for practical identification of coherent structures (CS) from an inhomogeneous wall turbulence at the Reynolds numbers of $Re_{\tau}=180$ and $400$. The Laplacian of the pressure, $\Theta$, is scaled by its time-space average $\Theta_{ave}$ and root-mean-square value $\Theta_{rms}$ to obtain a proper scaling for effective identification of CS, $\hat\Theta=\left(\Theta-\Theta_{ave}\right)/\Theta_{rms}$. Numerical turbulent flow realizations with a wall and a gas-liquid interface obtained by a direct numerical simulation technique are employed to confirm suitability of the proposed scaling. The results of this study exhibit that the probability density function (PDF) of $\hat\Theta$ is very similar without respect to the distance from the wall, unlike PDF of unscaled $\Theta$. Because of this statistical similarity, identification of CS based on $\hat\Theta$ is shown advantageous to separate all the essential CS from disorganized turbulent background using a unique threshold level, especially in the region adjacent to the wall and the gas-liquid interface. Several turbulent flow signatures at the gas-liquid interface suggest that a threshold of $1\le\Theta\le 2$ is preferable to identify all the essential CS in the whole of the turbulent flow domain, without ``contamination'' caused by misidentification of meaningless structures.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.DFD.LK.10