Horizontal and Vertical Turbulent Fluxes Forced by a Gravity Wave Event in the Nocturnal Atmospheric Surface Layer Over the Amazon Forest

A nocturnal gravity wave was detected over a south-western Amazon forest during the Large-Scale Biosphere–Atmosphere experiment in Amazonia (LBA) in the course of the dry-to-wet season campaign on October 2002. The atmospheric surface layer was stably stratified and had low turbulence activity, based on friction velocity values. However, the passage of the wave, an event with a period of about 180–300 s, caused negative turbulent fluxes of carbon dioxide (CO₂) and positive sensible heat fluxes, as measured by the eddy-covariance system at 60 m (≈30 m above the tree tops). The evolution of vertical profiles of air temperature, specific humidity and wind speed during the wave movement revealed that cold and drier air occupied the sub-canopy space while high wind speeds were measured above the vegetation. The analysis of wind speed and scalars high frequency data was performed using the wavelet technique, which enables the decomposition of signals in several frequencies allowed by the data sampling conditions. The results showed that the time series of vertical velocity and air temperature were −90° out of phase during the passage of the wave, implying no direct vertical transport of heat. Similarly, the time series of vertical velocity and CO₂ concentration were 90° out of phase. The wave was not directly associated with vertical fluxes of this variable but the mixing induced by its passage resulted in significant exchanges in smaller scales as measured by the eddy-covariance system. The phase differences between horizontal velocity and both air temperature and CO₂ concentration were, respectively, zero and 180°, implying phase and anti-phase relationships. As a result, the wave contributed to positive horizontal fluxes of heat and negative horizontal fluxes of carbon dioxide. Such results have to be considered in nocturnal boundary-layer surface-atmosphere exchange schemes for modelling purposes.     

Three‐dimensional numerical modeling of the Bulle effect: the nonlinear distribution of near‐bed sediment at fluvial diversions

The Bulle effect is a phenomenon in which a disproportionately higher amount of near‐bed sediment load at a fluvial diversion moves into the diverted channel, even for cases in which the proportion of water (with respect to the main flow) entering the diversion channel is relatively small. This phenomenon has wide‐ranging implications for both engineered and natural systems: from efficient design of channels to redirect water and sediment for reclaiming sinking deltas, designing navigational channels that do not need frequent dredging, to morphological evolution of river bifurcations. The first ever, and one of the most extensive set of experiments conducted to explore this phenomenon, were conducted by Bulle in 1926 . In the current study the experiments conducted by Bulle have been simulated using an open‐source, free‐surface finite‐element‐based hydrodynamic solver. The main objectives were to explore to what extent the complex phenomenon of the Bulle effect at the scale of a laboratory experiment can be simulated accurately using Reynolds‐averaged Navier–Stokes (RANS)‐based hydrodynamic solver, and to understand the details of the hydrodynamics that Bulle could not analyze through his experiments. The hydrodynamics captured by the simulations were found to match the observations made by Bulle through his experiments, and the distributions of sediment at the diversion predicted by the numerical simulations were found to match the general trend observed in the laboratory experiments. The results from the numerical simulations were also compared with existing one‐dimensional models for sediment distribution at bifurcations, and the three‐dimensional numerical model was found to perform appreciably better. This is expected due to the complex flow features at the diversion, which can only be captured satisfactorily using a three‐dimensional hydrodynamic model. Copyright © 2017 John Wiley & Sons, Ltd.     

2D stream hydrodynamic,sediment transport and bed morphology model for engineering applications

A 2D depth‐averaged hydrodynamic, sediment transport and bed morphology model named STREMR HySeD is presented. The depth‐averaged sediment transport equations are derived from the 3D dilute, multiphase, flow equations and are incorporated into the hydrodynamic model STREMR. The hydrodynamic model includes a two‐equation turbulence model and a correction for the mean flow due to secondary flows. The suspended sediment load can be subdivided into different size classes using the continuum (two‐fluid) approach; however, only one bed sediment size is used herein. The validation of the model is presented by comparing the suspended sediment transport module against experimental measurements and analytical solutions for the case of equilibrium sediment‐laden in a transition from a rigid bed to a porous bed where re‐suspension of sediment is prevented. On the other hand, the bed‐load sediment transport and bed evolution numerical results are compared against bed equilibrium experimental results for the case of a meander bend. A sensitivity analysis based on the correction for secondary flow on the mean flow including the effect of secondary flow on bed shear stresses direction as well as the downward acceleration effect due to gravity on transverse bed slopes is performed and discussed. In general, acceptable agreement is found when comparing the numerical results obtained with STREMR HySeD against experimental measurements and analytical solutions. Copyright © 2007 John Wiley & Sons, Ltd.     

The role of the Antofagasta–Calama Lineament in ore deposit deformation in the Andes of northern Chile

During the Late Jurassic–Early Oligocene interval, widespread hydrothermal copper mineralization events occurred in association with the geological evolution of the southern segment of the central Andes, giving rise to four NS-trending metallogenic belts of eastward-decreasing age: Late Jurassic, Early Cretaceous, Late Paleocene–Early Eocene, and Late Eocene–Early Oligocene. The Antofagasta–Calama Lineament (ACL) consists of an important dextral strike-slip NE-trending fault system. Deformation along the ACL system is evidenced by a right-lateral displacement of the Late Paleocene–Early Eocene metallogenic belts. Furthermore, clockwise rotation of the Early Cretaceous Mantos Blancos copper deposit and the Late Paleocene Lomas Bayas porphyry copper occurred. In the Late Eocene–Early Oligocene metallogenic belt, a sigmoidal deflection and a clockwise rotation is observed in the ACL. The ACL is thought to have controlled the emplacement of Early Oligocene porphyry copper deposits (34–37 Ma; Toki, Genoveva, Quetena, and Opache), whereas it deflected the Late Eocene porphyry copper belt (41–44 Ma; Esperanza, Telégrafo, Centinela, and Polo Sur ore deposits). These observations suggest that right-lateral displacement of the ACL was active during the Early Oligocene. We propose that the described structural features need to be considered in future exploration programs within this extensively gravel-covered region of northern Chile.     

A Similarity Model of Subfilter-Scale Energy for Large-Eddy Simulations of the Atmospheric Boundary Layer

A scale-similarity model to estimate the subfilter-scale energy using the trace of the Leonard stress tensor is proposed and evaluated for large-eddy simulations of the atmospheric boundary layer (ABL). The model is derived from a stability-dependent model of the energy spectrum in the ABL, which accounts for the effects of buoyancy and mean shear as a function of z/L, the Monin–Obukhov stability variable. An a priori test using ABL turbulence data demonstrates that the model has accurate performance for dimensionless filter widths of Δ/z = 2, 1, and 0.5 for stabilities of −1 ≤ z/L ≤ 0.5, and improves considerably upon a similar model that is derived using an infinite κ ^−5/3 spectrum. This improvement is especially significant in the first several grid points near the surface in large-eddy simulations of the ABL, where Δ/z is necessarily large. The modelling procedure is then extended to develop a similarity model for the subfilter-scale scalar variance; it is shown to have robust performance for temperature.     

Static cosmological solutions in wesson's 5D theory of gravitation

Assuming that the fifth dimension subspace in Wesson's gravitational theory is also homogeneous and isotropic like in the usual cosmological model, we find static solutions for the length's scale-factor, while other quantities of the theory may still vary, like masses, as in the static model of the conformally invariant theory of Hoyle and Narlikar.     

General Relativistic Machian Universe

The Machian Universe, is usually described with Newtonian Physics, We give an alternative General Relativistic picture for Mach’s Universe. As such, we show that, in the correct Machian limit, Schwarzschild’s metric is coherent with Robertson-Walker’s, on condition that there be a cosmological constant, or the Universe’s rotation—or both. It is now confirmed that the Universe is accelerating, so the former condition applies. The latter was also confirmed one more time with the recently discovered NASA space probes anomalies. From Kerr-Lense-Thirring solution, we find an inverse scale-factor dependent angular speed; we then, show that the cosmological “constant” may have Classically originated from a centrifugal acceleration field.     

A general relativistic rotating evolutionary universe

We show that when we work with coordinate cosmic time, which is not proper time, Robertson-Walker’s metric, includes a possible rotational state of the Universe. An exact formula for the angular speed and the temporal metric coefficient, is found.     

Ruprecht 55: an OB association at the edge of our Galaxy

We present new spectroscopy in the optical range and 21-cm H  i data covering the Ruprecht 55 (Ru 55) field in the Puppis window where several authors have proposed the existence of one (or two) clusters.
We have determined new MK spectral types for about 50 stars in the region, finding 43 OB-type stars among them. LS 985 was found to be an O9 V + O9.5 III binary and it is the earliest type of star in our observed sample.
We have identified a stellar OB association (Ru 55), which is most likely related to a depletion detected in our H  i data, as: (i) they are located at the same distance (6 kpc), within observational errors; (ii) both have similar radial velocities (∼67 km s⁻¹); (iii) current OB stars could have provided the energy needed to blow the cavity; (iv) the dynamical time-scale for the hole buildup matches the age estimated for the earliest OB stars; and (v) LS 985 might be responsible for ionizing the H  i cavity inner walls close to it.     

The angular-diameter distance maximum and its redshift as constraints on Λ≠ 0 Friedmann–Lemaître–Robertson–Walker models

The plethora of recent cosmologically relevant data has indicated that our Universe is very well fitted by a standard Friedmann–Lemaître–Robertson–Walker (FLRW) model, with     and  Ω_Λ≈ 0.73  – or, more generally, by nearly flat FLRW models with parameters close to these values. Additional independent cosmological information, particularly the maximum of the angular-diameter (observer area) distance and the redshift at which it occurs, would improve and confirm these results, once sufficient precise Type Ia supernovae data in the range  1.5 < z < 1.8  become available. We obtain characteristic FLRW-closed functional forms for   C = C ( z )  and     , the angular-diameter distance and the density per source counted, respectively, when  Λ≠ 0  , analogous to those we have for  Λ= 0  . More importantly, we verify that for flat FLRW models z _max– as is already known but rarely recognized – the redshift of C _max, the maximum of the angular-diameter distance, uniquely gives  Ω_Λ  , the amount of vacuum energy in the universe, independent of H ₀, the Hubble parameter. For non-flat models, determination of both z _max and C _max gives both  Ω_Λ  and Ω_M, the amount of matter in the universe, as long as we know H ₀ independently. Finally, determination of C _max automatically gives a very simple observational criterion for whether or not the universe is flat – presuming that it is FLRW.