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 $\zeta = 0$. We find no evidence of deviation from general relativity. At 95% probability, $-0.00246 < \zeta < 0.00567$, correspondingly, the region $-407.0 < \omega <175.87$ is excluded. If we restrict ourselves to the $\zeta>0$ (i.e. $\omega >0$) case, then the 95% probability interval is $\zeta 181.65$. We can also translate this result to a constraint on the variation of gravitational constant, and find the variation rate today as $\dot{G}=-1.42^{+2.48}_{-2.27} \times 10^{-13}$yr$^{-1}$ ($1\sigma$ error bar), the integrated change since the epoch of recombination is $\delta G/G = 0.0104^{+0.0186}_{-0.0067}$ ($1\sigma$ 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 $\bar{\tau}=(0.53\pm0.32)\times10^{-4}(1.65\,\sigma)$ for `LowZ North CGC', $\bar{\tau}=(0.30\pm0.57)\times10^{-4}(0.53\,\sigma)$ for `LowZ South CGC', and $\bar{\tau}=(0.43\pm0.28)\times10^{-4}(1.53\,\sigma)$ for `DR13 Group'. In addition, we vary the radius of the AP filter and find that the AP size of $7\,{\rm arcmin}$ gives the maximum detection for $\bar{\tau}$. We also investigate the dependence of the signal with halo mass and find $\bar{\tau}=(0.32\pm0.36)\times10^{-4}(0.8\,\sigma)$ and $\bar{\tau}=(0.67\pm0.46)\times10^{-4}(1.4\,\sigma)$ for `DR13 Group' with halo mass restricted to, respectively, less and greater than its median halo mass, $10^{12}\, h^{-1}{\rm M}_{\odot}$. For the `LowZ North CGC' sample restricted to $M_{\rm h} \gtrsim 10^{14}\, h^{-1}{\rm M}_\odot$ 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