Sat, 26 Jul 2008 07:24:30 BST CiteULike: l-alex's Yeung http://www.citeulike.org/user/l-alex/author/Yeung CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/l-alex/article/2948384 <i>Physics of Fluids, Vol. 20, No. 6. (2008)</i> Reynolds number dependence of relative dispersion statistics in isotropic turbulence Brian Sawford PK Yeung Jason Hackl Physics of Fluids, Vol. 20, No. 6. (2008) 2008-07-01T13:49:26-00:00 2008 Physics of Fluids 20 6 AIP dispersion lagrangian http://www.citeulike.org/user/l-alex/article/2573304 <i>Physical Review E, Vol. 56, No. 2. (1997), 1746.</i><br /><br />Motivated by a recent survey of experimental data [K. R. Sreenivasan; Phys. Fluids 7 ; 2778 (1995)]; we examine data on the Kolmogorov spectrum constant in numerical simulations of isotropic turbulence; using results both from previous studies and from new direct numerical simulations over a range of Reynolds numbers (up to 240 on the Taylor scale) at grid resolutions up to 512 3 . It is noted that in addition to k -5/3 scaling; identification of a true inertial range requires spectral isotropy in the same wave-number range. The new simulations indicate approximate inertial range behavior at lower wave numbers than previously thought; with proportionality constants C 1 and C in the one- and three-dimensional energy spectra; respectively; about 0.60 and 1.62. The latter suggests C 1 ≈0.53; in excellent agreement with experiments. However; the one- and three-dimensional estimates are not fully consistent; because of departures (due to numerical and statistical limitations) from isotropy of the computed spectra at low wave numbers. The inertial scaling of structure functions in physical space is briefly addressed. Universality of the Kolmogorov constant in numerical simulations of turbulence PK Yeung Ye Zhou doi:10.1103/PhysRevE.56.1746 Physical Review E, Vol. 56, No. 2. (1997), 1746. 2008-03-22T23:04:31-00:00 1997 Physical Review E 56 2 1746 American Physical Society universality http://www.citeulike.org/user/l-alex/article/1394397 <i>J. of Turbulence, Vol. 7 (2006)</i><br /><br />Lagrangian statistics are reported from a direct numerical simulation database with grid resolution up to 20483 and Taylor-scale Reynolds number approximately 650. The approach to Lagrangian Kolmogorov similarity at high Reynolds number is studied using both the velocity structure function and frequency spectrum. A significant scaling range is observed for the latter which is consistent with recent estimates of 6-7 for the scaling constant C0. In contrast to some previous results at low Reynolds number, the current results suggest that at high Reynolds number the dissipation autocorrelation is a two-scale process influenced by both the Lagrangian velocity integral time scale and Kolmogorov time scale. Results on the logarithm of the pseudo-dissipation are in support of its modeling as a diffusion process with one-time Gaussian statistics. As the Reynolds number increases, the statistics of dissipation and enstrophy become more similar while their logarithms have significantly longer time scales. Reynolds number dependence of Lagrangian statistics in large numerical simulations of isotropic turbulence PK Yeung SP Pope BL Sawford J. of Turbulence, Vol. 7 (2006) 2007-06-16T16:54:43-00:00 2006 J. of Turbulence 7 no-tag http://www.citeulike.org/user/l-alex/article/909958 <i>J.~Fluid Mech., Vol. 459 (2002), pp. 129-138.</i> Random-sweeping hypothesis for passive scalars in isotropic turbulence PK Yeung BL Sawford J.~Fluid Mech., Vol. 459 (2002), pp. 129-138. 2006-10-22T17:20:15-00:00 2002 J.~Fluid Mech. 459 129 138 no-tag http://www.citeulike.org/user/l-alex/article/909957 <i>J.~Fluid Mech., Vol. 207 (1989), pp. 531-586.</i> Lagrangian statistics from direct numerical simulations of isotropic turbulence PK Yeung SB Pope J.~Fluid Mech., Vol. 207 (1989), pp. 531-586. 2006-10-22T17:20:15-00:00 1989 J.~Fluid Mech. 207 531 586 no-tag http://www.citeulike.org/user/l-alex/article/909956 <i>J.~Fluid Mech., Vol. 503 (2004), pp. 93-124.</i> Relative dispersion in isotropic turbulence. Part 1. Direct numerical simulations and Reynolds-number dependence PK Yeung MS Borgas J.~Fluid Mech., Vol. 503 (2004), pp. 93-124. 2006-10-22T17:20:15-00:00 2004 J.~Fluid Mech. 503 93 124 no-tag http://www.citeulike.org/user/l-alex/article/909955 <i>Phys. Fluids, Vol. 9 (1997), pp. 2981-2990.</i> One- and two-particle Lagrangian acceleration correlations in numerically simulated homogeneous turbulence PK Yeung Phys. Fluids, Vol. 9 (1997), pp. 2981-2990. 2006-10-22T17:20:15-00:00 1997 Phys. Fluids 9 2981 2990 no-tag http://www.citeulike.org/user/l-alex/article/909946 <i>J.~Fluid Mech., Vol. 433 (2001), pp. 29-60.</i> Dynamics of scalar dissipation in isotropic turbulence: a numerical and modelling study P Vedula PK Yeung RO Fox J.~Fluid Mech., Vol. 433 (2001), pp. 29-60. 2006-10-22T17:20:14-00:00 2001 J.~Fluid Mech. 433 29 60 no-tag http://www.citeulike.org/user/l-alex/article/909945 <i>Phys. Fluids, Vol. 11 (1999), pp. 1208-1220.</i> Similarity scaling of acceleration and pressure statistics in numerical simulations of isotropic turbulence P Vedula PK Yeung Phys. Fluids, Vol. 11 (1999), pp. 1208-1220. 2006-10-22T17:20:14-00:00 1999 Phys. Fluids 11 1208 1220 no-tag http://www.citeulike.org/user/l-alex/article/909941 <i>Phys.~Fluids, Vol. 13 (2001), pp. 1974-1984.</i> Random Taylor hypothesis and the behavior of local and convective accelerations in isotropic turbulence A Tsinober P Vedula PK Yeung Phys.~Fluids, Vol. 13 (2001), pp. 1974-1984. 2006-10-22T17:20:14-00:00 2001 Phys.~Fluids 13 1974 1984 no-tag http://www.citeulike.org/user/l-alex/article/909914 <i>Phys. Fluids, Vol. 15 (2003), pp. 3478-3489.</i> Conditional and unconditional acceleration statistics in turbulence BL Sawford PK Yeung MS Borgas P Vedula A La-Porta AM Crawford E Bodenschatz Phys. Fluids, Vol. 15 (2003), pp. 3478-3489. 2006-10-22T17:20:12-00:00 2003 Phys. Fluids 15 3478 3489 no-tag http://www.citeulike.org/user/l-alex/article/853068 <i>Physics of Fluids, Vol. 13, No. 7. (2001), pp. 1974-1984.</i><br /><br />The properties of acceleration fluctuations in isotropic turbulence are studied in direct numerical simulations (DNS) by decomposing the acceleration as the sum of local and convective contributions (aL = u/t and aC = u·u), or alternatively as the sum of irrotational and solenoidal contributions [aI = –(p/) and aS = 2u]. The main emphasis is on the nature of the mutual cancellation between aL and aC which must occur in order for the acceleration (a) to be small as predicted by the "random Taylor hypothesis" [Tennekes, J. Fluid Mech. 67, 561 (1975)] of small eddies in turbulent flow being passively "swept" past a stationary Eulerian observer. Results at Taylor-scale Reynolds number up to 240 show that the random-Taylor scenario a2" align="middle">aC2" align="middle">" align="middle">aL2" align="middle">" align="middle">, accompanied by strong antialignment between the vectors aL and aC, is indeed increasingly valid at higher Reynolds number. Mutual cancellation between aL and aC also leads to the solenoidal part of a being small compared to its irrotational part. Results for spectra in wave number space indicate that, at a given Reynolds number, the random Taylor hypothesis has greater validity at decreasing scale sizes. Finally, comparisons with DNS data in Gaussian random fields show that the mutual cancellation between aL and aC is essentially a kinematic effect, although the Reynolds number trends are made stronger by the dynamics implied in the Navier–Stokes equations. ©2001 American Institute of Physics. Random Taylor hypothesis and the behavior of local and convective accelerations in isotropic turbulence Arkady Tsinober Prakash Vedula PK Yeung doi:10.1063/1.1375143 Physics of Fluids, Vol. 13, No. 7. (2001), pp. 1974-1984. 2006-09-21T13:41:09-00:00 2001 Physics of Fluids 13 7 1974 1984 AIP acceleration taylor-hypothesis http://www.citeulike.org/user/l-alex/article/851177 <i>J. Fluid Mech, Vol. 207 (1989), pp. 531-586.</i> Lagrangian statistics from direct numerical simulations of isotropic turbulence PK Yeung SB Pope J. Fluid Mech, Vol. 207 (1989), pp. 531-586. 2006-09-20T12:31:54-00:00 1989 J. Fluid Mech 207 531 586 homogeneous lagrangian http://www.citeulike.org/user/l-alex/article/851176 <i>J. Fluid Mech, Vol. 427 (2001), pp. 241-274.</i> Lagrangian characteristics of turbulence and scalar transport in direct numerical simulations PK Yeung doi:10.1017/S0022112000002391 J. Fluid Mech, Vol. 427 (2001), pp. 241-274. 2006-09-20T12:27:53-00:00 2001 J. Fluid Mech 427 241 274 homogeneous lagrangian http://www.citeulike.org/user/l-alex/article/851174 <i>Phys. Fluids, Vol. 9, No. 10. (1997), pp. 2981-2990.</i> One- and two-particle Lagrangian acceleration correlations in numerically simulated homogeneous turbulence PK Yeung Phys. Fluids, Vol. 9, No. 10. (1997), pp. 2981-2990. 2006-09-20T12:25:59-00:00 1997 Phys. Fluids 9 10 2981 2990 acceleration lagrangian http://www.citeulike.org/user/l-alex/article/697909 <i>Physics of Fluids, Vol. 18, No. 6. (2006)</i><br /><br />Direct numerical simulation (DNS) data at grid resolution up to 20483 in isotropic turbulence are used to investigate the statistics of acceleration in a Eulerian frame. A major emphasis is on the use of conditional averaging to relate the intermittency of acceleration to fluctuations of dissipation, enstrophy, and pseudodissipation representing local relative motion in the flow. Pseudodissipation (the second invariant of the velocity gradient tensor) has the same intermittency exponent as dissipation and is closest to log-normal. Conditional acceleration variances increase with each conditioning variable, consistent with the scenario of rapid changes in velocity for fluid particles moving in local regions of large velocity gradient, but in a manner departing from Kolmogorov's refined similarity theory. Acceleration conditioned on the pseudodissipation is closest to Gaussian, and well represented by a novel "cubic Gaussian" distribution. Overall the simulation data suggest that, with the aid of appropriate parameterizations, Lagrangian stochastic modeling with pseudodissipation as the conditioning variable is likely to produce superior results. Reduced intermittency of conditional acceleration also makes the present results less sensitive to resolution concerns in DNS. ©2006 American Institute of Physics Acceleration and dissipation statistics of numerically simulated isotropic turbulence PK Yeung SB Pope AG Lamorgese DA Donzis doi:10.1063/1.2204053 Physics of Fluids, Vol. 18, No. 6. (2006) 2006-06-16T07:39:15-00:00 2006 Physics of Fluids 18 6 AIP acceleration dissipation dns