11,112 research outputs found
Generation of Suburban Terrain Inflow Conditions for Large Eddy Simulations
[[abstract]]To generate the suitable atmospheric boundary layer inlet for large eddy simulation, one of the most important techniques of computational wind engineering, the MDSRFG (modified discretizing and synthesizing random flow generation) was selected to numerically generate the inhomogeneous and anisotropic turbulence boundary
layer in this paper. A weakly-compressible-flow method along with the large eddy simulation (LES) was utilized to reproduce the unsteady flow field. Parameters, such as mean wind speeds, turbulence intensities and turbulence integral scales from fully-developed turbulent boundary layer flow were provided by well-established
wind tunnel tests. Furthermore, coherence between any two fluctuating wind speeds was taken into account for a more compact simulation of inflow. It was indicated that the method works well as a suburban turbulence boundary layer generator by comparing the characteristics of mean wind speed profiles, turbulence intensity profiles and power spectra at the centerline of several positions along longitudinal direction from wind tunnel
tests.[[conferencetype]]國際[[conferencedate]]20131210~20131214[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Chennai, Indi
Simulation of turbulent flows around a prism in suburban terrain inflow based on random flow generation method
[[abstract]]In this study, the modified discretizing and synthesizing random flow generation (MDSRFG) was adopted to generate an anisotropic boundary layer inlet for Large-eddy simulation. The statistical quantities including mean velocity, turbulence intensity, and turbulence length scale of inlet were defined by the measurements of suburban terrain at TKU BL-1 wind tunnel. The target spectra were also defined by von Kármán models. Results showed that the turbulence energy can be maintained from the inlet to the downstream position. Comparison of aerodynamic coefficient between simulation and experiments yielded consistent results. A square pressure model with aspect ratio h/D=3 was established for validation. The mean and fluctuating pressure distributions of simulation also showed good agreements with experiments. The result indicated that adopting a reasonable process in the MDSRFG method can be an effective numerical tool for generating a spatially correlated atmospheric boundary layer flow field.[[sponsorship]]University of Hamburg[[conferencetype]]國際[[conferencedate]]20140608~20140612[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Hamburg, German
Constraints on the Brans-Dicke gravity theory with the Planck data
Based on the new cosmic CMB temperature data from the Planck satellite, the 9
year polarization data from the WMAP, the BAO distance ratio data from the SDSS
and 6dF surveys, we place a new constraint on the Brans-Dicke theory. We adopt
a parametrization \zeta=\ln(1+1/\omega}), where the general relativity (GR)
limit corresponds to . We find no evidence of deviation from general
relativity. At 95% probability, , correspondingly,
the region is excluded. If we restrict ourselves to
the (i.e. ) case, then the 95% probability interval is
. We can also translate this
result to a constraint on the variation of gravitational constant, and find the
variation rate today as yr ( error bar), the integrated change since the epoch of
recombination is ( error
bar). These limits on the variation of gravitational constant are comparable
with the precision of solar system experiments.Comment: 7 pages, 5 figures, 2 table
Relativistic Theory of Infinite Statistics Fields
Infinite statistics in which all representations of the symmetric group can
occur is known as a special case of quon theory. However, the validity of
relativistic quon theories is still in doubt. In this paper we prove that there
exists a relativistic quantum field theory which allows interactions involving
infinite statistics particles. We also give some consistency analysis of this
theory such as conservation of statistics and Feynman rules.Comment: 7 pages, 3 figure
Measurement of the pairwise kinematic Sunyaev-Zeldovich effect with Planck and BOSS data
We present a new measurement of the kinetic Sunyaev-Zeldovich effect (kSZ)
using Planck cosmic microwave background (CMB) and Baryon Oscillation
Spectroscopic Survey (BOSS) data. Using the `LowZ North/South' galaxy catalogue
from BOSS DR12, and the group catalogue from BOSS DR13, we evaluate the mean
pairwise kSZ temperature associated with BOSS galaxies. We construct a `Central
Galaxies Catalogue' (CGC) which consists of isolated galaxies from the original
BOSS data set, and apply the aperture photometry (AP) filter to suppress the
primary CMB contribution. By constructing a halo model to fit the pairwise kSZ
function, we constrain the mean optical depth to be
for `LowZ North CGC',
for `LowZ South CGC', and
for `DR13 Group'. In
addition, we vary the radius of the AP filter and find that the AP size of
gives the maximum detection for . We also
investigate the dependence of the signal with halo mass and find
and
for `DR13 Group' with halo
mass restricted to, respectively, less and greater than its median halo mass,
. For the `LowZ North CGC' sample restricted
to there is no detection of
the kSZ signal because these high mass halos are associated with the
high-redshift galaxies of the LowZ North catalogue, which have limited
contribution to the pairwise kSZ signals.Comment: 11 pages, 11 figures, 2 table
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