404 research outputs found
CFD simulations of turbulent flows in a twin swirl combustor by RANS and hybrid RANS/LES methods
A confined isothermal flow in a Twin Swirl Combustor (TSC) was studied under both steady and transient conditions. The Reynolds Averaged Navier-Stokes (RANS) simulation was carried out to investigate the timeaveraged flow features in TSC under different ratios of the primary air flow rate to the secondary air flow rate. The steady-state velocity profiles inside the combustion chamber were analyzed using both Renormalized Group (RNG) k-ε model and Shear Stress Transport (SST) turbulence model. For the transient conditions, the Scale Adaptive Simulation (SAS) method based on the SST model was used to probe the instantaneous three dimensional (3D) vortex structures to better understand the formation of the internal recirculation zone (IRZ). The existence of a pressing vortex cores (PVC) and a hurricane-shaped vortical structure in the TSC were captured by the SAS model. The SAS model can yield vortex-level results similar to large eddy simulation (LES) prediction while saves much more computational resource. This paper briefly reports some preliminary results of this study.Yinli Liu, Hao Tang, Zhaofeng Tian, Haifei Zhen
Sonic velocity in holographic fluids and its applications
Gravity/fluid correspondence acts as an important tool in investigating the strongly correlated fluids. We carefully investigate the holographic fluids at the finite cutoff surface by considering different boundary conditions in the scenario of gravity/fluid correspondence. We find that the sonic velocity of the boundary fluids at the finite cutoff surface is critical in clarifying the superficial similarity between the bulk viscosity and perturbation of the pressure for the holographic fluid, where we set a special boundary condition at the finite cutoff surface to explicitly express this superficial similarity. Moreover, we further take the sonic velocity into account to investigate a case with a more general boundary condition. In this more genaral case, although two parameters in the first order stress tensor of holographic fluid cannot be fixed, one can still extract the information about the transport coefficients by considering the sonic velocity seriously.Theoretical Physic
Phase separation and ferroelectric ordering in charge frustrated LuFe2O4-x
The transmission electron microscopy observations of the charge ordering (CO)
which governs the electronic polarization in LuFe2O4-x clearly show the
presence of a remarkable phase separation at low temperatures. Two CO ground
states are found to adopt the charge modulations of Q1 = (1/3, 1/3, 0) and Q2 =
(1/3 + y, 1/3 + y, 3/2), respectively. Our structural study demonstrates that
the incommensurately Q2-modulated state is chiefly stable in samples with
relatively lower oxygen contents. Data from theoretical simulations of the
diffraction suggest that both Q1- and Q2-modulated phases have ferroelectric
ordering. The effects of oxygen concentration on the phase separation and
electric polarization in this layered system are discussed.Comment: 11 pages, 5 figure
Measurements of the Mass and Full-Width of the Meson
In a sample of 58 million events collected with the BES II detector,
the process J/ is observed in five different decay
channels: , , (with ), (with
) and . From a combined fit of all five
channels, we determine the mass and full-width of to be
MeV/ and
MeV/.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays
By analyzing about 33 data sample collected at and around 3.773
GeV with the BES-II detector at the BEPC collider, we directly measure the
branching fractions for the neutral and charged inclusive semimuonic decays
to be and , and determine the ratio of the two branching
fractions to be
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
A study of charged kappa in
Based on events collected by BESII, the decay
is studied. In the invariant mass
spectrum recoiling against the charged , the charged
particle is found as a low mass enhancement. If a Breit-Wigner function of
constant width is used to parameterize the kappa, its pole locates at MeV/. Also in this channel,
the decay is observed for the first time.
Its branching ratio is .Comment: 14 pages, 4 figure
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