9 research outputs found
Application of extended self similarity in turbulence
From Navier-Stokes turbulence numerical simulations we show that for the
extended self similarity (ESS) method it is essential to take the third order
structure function taken with the modulus and called , rather than
the standard third order structure function itself. If done so, we
find ESS towards scales larger than roughly 10 eta, where eta is the Kolmogorov
scale. If is used, there is no ESS. We also analyze ESS within the
Batchelor parametrization of the second and third order longitudinal structure
function and focus on the scaling of the transversal structure function. The
Re-asymptotic inertial range scaling develops only beyond a Taylor-Reynolds
number of about 500.Comment: 12 pages, 7 eps-figures, replaces version from April 11th, 1997;
paper now in press at Phys. Rev.
Scaling of the irreducible SO(3)-invariants of velocity correlations in turbulence
The scaling behavior of the SO(3) irreducible amplitudes of
velocity structure tensors (see L'vov, Podivilov, and Procaccia, Phys. Rev.
Lett. (1997)) is numerically examined for Navier-Stokes turbulence. Here, l
characterizes the irreducible representation by the index of the corresponding
Legendre polynomial, and n denotes the tensorial rank, i.e., the order of the
moment. For moments of different order n but with the same representation index
l extended self similarity (ESS) towards large scales is found. Intermittency
seems to increase with l. We estimate that a crossover behavior between
different inertial subrange scaling regimes in the longitudinal and transversal
structure functions will hardly be detectable for achievable Reynolds numbers.Comment: 4 pages, 3 eps-figure
Different intermittency for longitudinal and transversal turbulent fluctuations
Scaling exponents of the longitudinal and transversal velocity structure
functions in numerical Navier-Stokes turbulence simulations with
Taylor-Reynolds numbers up to \rel = 110 are determined by the extended self
similarity method. We find significant differences in the degree of
intermittency: For the sixth moments the scaling corrections to the classical
Kolmogorov expectations are and \dx_6^T= -0.43
\pm 0.01, respectively, independent of \rel. Also the generalized extended
self similarity exponents \rho_{p,q} = \dx_p/\dx_q differ significantly for
the longitudinal and transversal structure functions. Within the She-Leveque
model this means that longitudinal and transversal fluctuations obey different
types of hierarchies of the moments. Moreover, the She-Leveque model hierarchy
parameters and show small but significant dependences on
the order of the moment.Comment: 20 pages, 10 eps-figures, to appear in Physics of Fluids, December
199
Multiscale correlations and conditional averages in numerical turbulence
The equations of motion for the nth order velocity differences raise the interest in correlation functions containing both large and small scales simultaneously. We consider the scaling of such objects and also their conditional average representation with emphasis on the question of whether they behave differently in the inertial or the viscous subranges. The turbulent flow data are obtained by Navier-Stokes solutions on a 603 grid with periodic boundary conditions and Re¿=70. Our results complement previous high Re data analysis based on measured data [A. L. Fairhall, V. S. L¿vov, and I. Procaccia, Europhys. Lett 43, 277 (1998)] whose preference were the larger scales, and the analysis of both experimental and synthetic turbulence data by [R. Benzi and co-workers, Phys. Rev. Lett. 80, 3244 (1998); Phys. Fluids 11, 2215 (1999)]. The inertial range fusion rule is confirmed and insight is obtained for the conditional averages (the local dissipation rate conditioned on the velocity fluctuations)
Developed turbulence: From full simulations to full mode reductions
Developed Navier-Stokes turbulence is simulated with varying wavevector mode
reductions. The flatness and the skewness of the velocity derivative depend on
the degree of mode reduction. They show a crossover towards the value of the
full numerical simulation when the viscous subrange starts to be resolved. The
intermittency corrections of the scaling exponents of the pth order velocity
structure functions seem to depend mainly on the proper resolution of the
inertial subrange. Universal scaling properties (i.e., independent of the
degree of mode reduction) are found for the relative scaling exponents rho
which were recently defined by Benzi et al.Comment: 4 pages, 5 eps-figures, replaces version from August 5th, 199
5,6-EET Is Released upon Neuronal Activity and Induces Mechanical Pain Hypersensitivity via TRPA1 on Central Afferent Terminals
Epoxyeicosatrienoic acids (EETs) are cytochrome P450-epoxygenase-derived metabolites of arachidonic acid that act as endogenous signaling molecules in multiple biological systems. Here we have investigated the specific contribution of 5,6-EET to transient receptor potential (TRP) channel activation in nociceptor neurons and its consequence for nociceptive processing. We found that, during capsaicin-induced nociception, 5,6-EET levels increased in dorsal root ganglia (DRGs) and the dorsal spinal cord, and 5,6-EET is released from activated sensory neurons in vitro. 5,6-EET potently induced a calcium flux (100 nm) in cultured DRG neurons that was completely abolished when TRPA1 was deleted or inhibited. In spinal cord slices, 5,6-EET dose dependently enhanced the frequency, but not the amplitude, of spontaneous EPSCs (sEPSCs) in lamina II neurons that also responded to mustard oil (allyl isothiocyanate), indicating a presynaptic action. Furthermore, 5,6-EET-induced enhancement of sEPSC frequency was abolished in TRPA1-null mice, suggesting that 5,6-EET presynaptically facilitated spinal cord synaptic transmission by TRPA1. Finally, in vivo intrathecal injection of 5,6-EET caused mechanical allodynia in wild-type but not TRPA1-null mice. We conclude that 5,6-EET is synthesized on the acute activation of nociceptors and can produce mechanical hypersensitivity via TRPA1 at central afferent terminals in the spinal cord
Hyperon signatures in the PANDA experiment at FAIR
We present a detailed simulation study of the signatures from the sequential decays of the triple-strange pbar p -> Ω+Ω- -> K+ΛbarK- Λ -> K+pbarπ+K-pπ- process in the PANDA central tracking system with focus on hit patterns and precise time measurement. We present a systematic approach for studying physics channels at the detector level and develop input criteria for tracking algorithms and trigger lines. Finally, we study the beam momentum dependence on the reconstruction efficiency for the PANDA detector