Analysis of Wind Turbine Wake Dynamics by a Gaussian-Core Vortex Lattice Technique

The development and deployment of the next generation of wind energy systems calls for simulation tools that model the entire wind farm while balancing accuracy and computational cost. A full-system wind farm simulation must consider the atmospheric inflow, the wakes and consequent response of the multiple turbines, and the implementation of the appropriate farm-collective control strategies that optimize the entire wind farm’s output. In this article, we present a novel vortex lattice model that enables the effective representation of the complex vortex wake dynamics of the turbines in a farm subject to transient inflow conditions. This work extends the capabilities of our multi-physics suite, CODEF, to include the capability to simulate the wakes and the high-fidelity aeroelastic response of multiple turbines in a wind farm. Herein, we compare the results of our GVLM technique with the LiDAR measurements obtained at Sandia National Laboratories’ SWiFT facility. The comparison shows remarkable similarities between the simulation and field measurements of the wake velocity. These similarities demonstrate our model’s capabilities in capturing the entire wake of a wind turbine at a significantly reduced computational cost as compared to other techniques

Theoretical infra-red, Raman, and Optical spectra of the B36N36 cage

The B36N36 fullerene-like cage structure was proposed as candidate structure for the single-shell boron-nitride cages observed in electron-beam irradiation experiment. We have performed all electron density functional calculations, with large polarized Gaussian basis sets, on the B36N36 cage. We show that the cage is energetically and vibrationally stable. The infra-red, Raman and optical spectra are calculated. The predicted spectra, in combination with experimentally measured spectra, will be useful in conclusive assignment of the proposed B36N36 cage. The vertical and adiabatic ionization potentials as well as static dipole polarizability are also reported.Comment: RevTex, 4 pages, 4 figures (TO appear in Physical Review A (Breif Report)

Simulation of the Multi-Wake Evolution of Two Sandia National Labs/National Rotor Testbed Turbines Operating in a Tandem Layout

The future of wind power systems deployment is in the form of wind farms comprised of scores of such large turbines, most likely at offshore locations. Individual turbines have grown in span from a few tens of meters to today’s large turbines with rotor diameters that dwarf even the largest commercial aircraft. These massive dynamical systems present unique challenges at scales unparalleled in prior applications of wind science research. Fundamental to this effort is the understanding of the wind turbine wake and its evolution. Furthermore, the optimization of the entire wind farm depends on the evolution of the wakes of different turbines and their interactions within the wind farm. In this article, we use the capabilities of the Common ODE Framework (CODEF) model for the analysis of the effects of wake–rotor and wake-to-wake interactions between two turbines situated in a tandem layout fully and partially aligned with the incoming wind. These experiments were conducted in the context of a research project supported by the National Rotor Testbed (NRT) program of Sandia National Labs (SNL). Results are presented for a layout which emulates the turbine interspace and relative turbine emplacement found at SNL’s Scaled Wind Technologies Facility (SWiFT), located in Lubbock, Texas. The evolution of the twin-wake interaction generates a very rich series of secondary transitions in the vortex structure of the combined wake. These ultimately affect the wake’s axial velocity patterns, altering the position, number, intensity, and shape of localized velocity-deficit zones in the wake’s cross-section. This complex distribution of axial velocity patterns has the capacity to substantially affect the power output, peak loads, fatigue damage, and aeroelastic stability of turbines located in subsequent rows downstream on the farm

Kondo resonances and anomalous gate dependence of electronic conduction in single-molecule transistors

We report Kondo resonances in the conduction of single-molecule transistors based on transition metal coordination complexes. We find Kondo temperatures in excess of 50 K, comparable to those in purely metallic systems. The observed gate dependence of the Kondo temperature is inconsistent with observations in semiconductor quantum dots and a simple single-dot-level model. We discuss possible explanations of this effect, in light of electronic structure calculations.Comment: 5 pages, four figures. Supplementary material at http://www.ruf.rice.edu/~natelson/publications.htm

Effect of Graded Levels of Condensed Tannin (CT) from \u3cem\u3eMimosa pudica\u3c/em\u3e on \u3cem\u3ein-Vitro\u3c/em\u3e Methane Production

Livestock in the country are primarily being fed on fibrous feed resulted in high enteric methane (CH4) emission along with low nutrients availability to host animal. Rumen methano genesis is necessary for the host system as this process ensure the removal of fermentative H2 through the reduction of CO2 into CH4. At the same time this process is wasteful because the emission also represents a loss of dietary energy (6-12% of gross energy intake) apart from contributing to global warming. Worldwide livestock contribute around 90-95 Tg methane to the pool with a contribution of 12-13% from the Indian livestock. Various nutritional and other approaches have been attempted with highly variable success rate in the country and elsewhere for the enteric methane amelioration. The cost of the item used for the mitigation purpose, adaptation of ruminal microbes and toxicity to either host animal or inhabiting microbes are few important criteria for an economic, sustainable and effective amelioration approach (Malik et al. 2015). Herbal materials are being used by the peoples since ages; however, their anti-methanogenic effect is recently established. The anti-methanogenic effect of different herbal materials mainly lies in their secondary metabolites which are highly effective even at very low concentration (Bhatta et al., 2014). Keeping these facts in view, a study was carried to ascertain the effect of varying levels of CT on in vitro total gas and methane production

Phosphorus recovery as struvite: recent concerns for use of seed, alternative Mg source, nitrogen conservation and fertilizer potential

Finite availability of phosphorus (P) resources makes recovery of this non-substitutable plant nutrient from alternative waste sources an increasingly attractive option of renewed interest. In this context, feasibility of struvite (MgNH4PO4·6H2O) recovery, an alternative P fertilizer is already demonstrated at laboratory scale from range of waste streams of farm, municipal and industrial origin, with reasonably high orthophosphate recovery efficiency (∼90%). However, apart from a few commercial extraction units using municipal sludge and urine, large scale struvite recovery is not widely adopted for many of these sources. Moreover, need of some research interventions that are restricting its profitable recovery are also highlighted by earlier studies. To increase recovery efficiency from identified potential sources in terms of cost and energy input, research focuses on some new aspects of the process such as prospects of alternative recyclable magnesium sources, different seed materials and their related issues, which are analyzed in this review. Prospects of nitrogen conservation through struvite recovery and fertilizer value of struvite considering its properties, comparative performance with conventional fertilizer and interaction with soil and plant growth are also critically reviewed

Effect of Selected Tanniniferous Leaves on \u3cem\u3ein Vivo\u3c/em\u3e Enteric Methane Emission in Sheep

Concentration of methane is continuously increasing in atmosphere and now almost 155% (IPCC, 2007) more than that recorded during pre-industrial era. Livestock production is a major sector accountable for high methane emission into atmospheric pool. World’s livestock is contributing around 15% of total atmospheric methane on annual basis feeds (Moss et al., 2000). Additionally, methane emission from ruminants leads to a loss of 2 to 15% of the dietary energy (Holter and Young, 1992). Due to these two crucial issues, researchers are working tirelessly to find a suitable and effective way for enteric methane amelioration accompanied with minimal inputs. So far numerous interventions have been tried with variable results, but due to one or another reason the search for effective strategy is on the priority of animal scientist. One of the possible approaches for enteric methane amelioration may be the use of plant secondary metabolites which are being traditionally used by the people since ages. Under the ICAR sponsored outreach project on Estimation of methane emission under different feeding systems and development of mitigation strategies more than 1700 feed, herbs and grasses samples were screened through in vitro gas production technique at different participating centres and finally selected few plant & herbs for evaluating the secondary metabolites on in vivo enteric methane emission. Three selected tanniniferous leaves were evaluated for their effect on enteric methane emission and feed fermentability in adult sheep

Incommensurate Transverse Anisotropy Induced by Disorder and Spin-Orbit-Vibron Coupling in Mn12-acetate

It has been shown within density-functional theory that in Mn$_{12}$-acetate there are effects due to disorder by solvent molecules and a coupling between vibrational and electronic degrees of freedom. We calculate the in-plane principal axes of the second-order anisotropy caused by the second effect and compare them with those of the fourth-order anisotropy due to the first effect. We find that the two types of the principal axes are not commensurate with each other, which results in a complete quenching of the tunnel-splitting oscillation as a function of an applied transverse field.Comment: Will be presented at MMM conference 200