Simulations of a supersonic recessed-cavity flow are performed using a hybrid large-eddy/Reynolds-averaged simulation approach utilizing an inflow turbulence recycling procedure and hybridized inviscid flux scheme. Calorically perfect air enters a three-dimensional domain at a free stream Mach number of 2.92. Simulations are performed to assess grid sensitivity of the solution, efficacy of the turbulence recycling, and the effect of the shock sensor used with the hybridized inviscid flux scheme. Analysis of the turbulent boundary layer upstream of the rearward-facing step for each case indicates excellent agreement with theoretical predictions. Mean velocity and pressure results are compared to Reynolds-averaged simulations and experimental data for each case and indicate good agreement on the finest grid. Simulations are repeated on a coarsened grid, and results indicate strong grid density sensitivity. Simulations are performed with and without inflow turbulence recycling on the coarse grid to isolate the effect of the recycling procedure, which is demonstrably critical to capturing the relevant shear layer dynamics. Shock sensor formulations of Ducros and Larsson are found to predict mean flow statistics equally well.

关键词：大涡模拟;雷诺平均;湍流效应;超音速流动;混合动力车

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The hybrid wing body center section test article is an all-composite structure made of crown, floor, keel, bulkhead, and rib panels utilizing the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) design concept.

关键词：结构稳定性;故障模式;舱壁;加压舱；复合材料

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Mr. Follen has been invited talk on subject of Greening of Aerospace and Aviation Canada-Ohio Aerospace Summit 2013, February 25-26, 2013. This two-day, bi-national aerospace and aviation conference will focus on identifying business and research opportunities providing meaningful industry updates with ample opportunity to network and scheduled business-to-business and researcher-to-researcher meetings.

关键词：商用飞机；电力推进；混合动力推进系统；推进系统性能

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This paper significantly advanced the hybrid measure correlate-predict (MCP) methodology, enabling it to account for the variations of both wind speed and direction. The advanced hybrid MCP method used the recorded data of multiple reference stations to estimate the long-term wind condition at the target wind plant site with greater accuracy than possible with data from a single reference station. The wind data was divided into different sectors according to the wind direction, and the MCP strategy was implemented for each wind sector separately. The applicability of the proposed hybrid strategy was investigated using four different MCP methods: (i) linear regression; (ii) variance ratio; (iii) artificial neural networks; and (iv) support vector regression. To implement the advanced hybrid MCP methodology, we used the hourly averaged wind data recorded at six stations in North Dakota between the years 2008 and 2010. The station Pillsbury was selected as the target plant site. The recorded data at the other five stations (Dazey, Galesbury, Hillsboro, Mayville, and Prosper) was used as reference station data. The best hybrid MCP strategy from different MCP algorithms and reference stations was investigated and selected from the 1,024 combinations. The accuracy of the hybrid MCP method was found to be highly sensitive to the combination of individual MCP algorithms and reference stations used. It was also observed that the best combination of MCP algorithms was strongly influenced by the length of the correlation period.

关键词：风;算法;相关性;混合动力系统;发电

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We discuss two approaches for tackling algebraic systems, one is based on block preconditioning and the other is based on multifrontal and hierarchical matrix methods. First we consider a new preconditioner framework for supporting implicit time integration.

关键词：大气环流;计算机代码;分解;天气预报

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Studies were performed to carry out semi-empirical validation of a new measurement approach we propose for molecular mixing ratios determination. The approach is based on relative measurements in bands of O2 and other molecules and as such may be best described as cross band relative absorption (CoBRA). . The current validation studies rely upon well verified and established theoretical and experimental databases, satellite data assimilations and modeling codes such as HITRAN, line-by-line radiative transfer model (LBLRTM), and the modern-era retrospective analysis for research and applications (MERRA). The approach holds promise for atmospheric mixing ratio measurements of CO2 and a variety of other molecules currently under investigation for several future satellite lidar missions. One of the advantages of the method is a significant reduction of the temperature sensitivity uncertainties which is illustrated with application to the ASCENDS mission for the measurement of CO2 mixing ratios (XCO2). Additional advantages of the method include the possibility to closely match cross-band weighting function combinations which is harder to achieve using conventional differential absorption techniques and the potential for additional corrections for water vapor and other interferences without using the data from numerical weather prediction (NWP) models.

关键词：混合比例;吸收光谱;温度效应;光学雷达

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To reduce the influence of atmospheric turbulence on images of space- based objects we are developing a maximum a posteriori deconvolution approach. In contrast to techniques found in the literature, we are focusing on the statistics of the point-spread function (PSF) instead of the object. We incorporated statistical information about the PSF into multi-frame blind deconvolution. Theoretical constraints on the average PSF shape come from the work of D. L. Fried while for the univariate speckle statistics we rely on the gamma distribution adopted from radar/laser speckle studies of J. W. Goodman. Our aim is to develop deconvolution strategy which is reference-less, i.e., no calibration PSF is required, extendable to longer exposures, and applicable to imaging with adaptive optics. The theory and resulting deconvolution framework were validated using simulations and real data from the 3.5m telescope at the Starfire Optical Range (SOR) in New Mexico.

关键词：大气运动；空间监视；大气湍流；Gamma分布

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Neutral density shows complicated temporal and spatial variations driven by external forcing of the thermosphere/ionosphere system, internal dynamics, and thermosphere and ionosphere coupling. Temporal variations include abrupt changes with a time scale of minutes to hours, diurnal variation, multi-day variation, solar-rotational variation, annual/semiannual variation, solar-cycle variation, and long-term trends with a time scale of decades. Spatial variations include latitudinal and longitudinal variations, as well as variation with altitude. Atmospheric drag on satellites varies strongly as a function of thermospheric mass density. Errors in estimating density cause orbit prediction error, and impact satellite operations including accurate catalog maintenance, collision avoidance for manned and unmanned space flight, and re-entry prediction. In this paper, we summarize and discuss these density variations, their magnitudes, and their forcing mechanisms, using neutral density data sets and modeling results. The neutral density data sets include neutral density observed by the accelerometers onboard the Challenging Mini-satellite Payload (CHAMP), neutral density at satellite perigees, and global-mean neutral density derived from thousands of orbiting objects. Modeling results are from the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM), and from the NRLMSISE-00 empirical model.

关键词：层中性密度；密度变化;卫星的阻力;密度数据

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Clear-air Doppler radars, also known as clear-air radar windprofilers, have been used for decades to remotely monitor wind velocities in the troposphere, stratosphere, and mesosphere. The traditional assumption is that the Doppler velocity (the first normalized moment of the Doppler spectrum) is an unbiased measure of the radial wind velocity within the radar's observation volume. Here we show that 'intermittency fluxes,' i.e., covariances of the turbulently fluctuating clear-air radar reflectivity and the turbulently fluctuating radial wind velocity, lead to systematic differences between the Doppler velocity and the (true) radial wind velocity. We use turbulent fields computationally generated by means of a large- eddy simulation to quantify this effect. We show that these biases may amount to several tens of centimeters per second in the atmospheric boundary layer, which is consistent with the biases observed with vertically pointing boundary-layer radar windprofilers.

关键词：风速；无线电波；大气运动；边界层；布拉格散射；

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National Aeronautics and Space Administration (NASA) recognizes the risk of on-orbit collisions from other satellites and debris objects and has instituted a process to identify and react to close approaches. The charter of the NASA Robotic Conjunction Assessment Risk Analysis (CARA) task is to protect NASA robotic (unmanned) assets from threats posed by other space objects. Monitoring for potential collisions requires formulating close-approach predictions a week or more in the future to determine analyze, and respond to orbital conjunction events of interest. These predictions require propagation of the latest state vector and covariance assuming a predicted atmospheric density and ballistic coefficient. Any differences between the predicted drag used for propagation and the actual drag experienced by the space objects can potentially affect the conjunction event. Therefore, the space environment itself, in particular how space weather impacts atmospheric drag, is an essential element to understand in order effectively to assess the risk of conjunction events. The focus of this research is to develop a better understanding of the impact of space weather on conjunction assessment activities: both accurately determining the current risk and assessing how that risk may change under dynamic space weather conditions. We are engaged in a data-- mining exercise to corroborate whether or not observed changes in a conjunction event's dynamics appear consistent with space weather changes and are interested in developing a framework to respond appropriately to uncertainty in predicted space weather. In particular, we use historical conjunction event data products to search for dynamical effects on satellite orbits from changing atmospheric drag. Increased drag is expected to lower the satellite specific energy and will result in the satellite's being 'later' than expected, which can affect satellite conjunctions in a number of ways depending on the two satellites' orbits and the geometry of the conjunction. These satellite time offsets can form the basis of a new technique under development to determine whether space weather perturbations, such as coronal mass ejections, are likely to increase, decrease, or have a neutral effect on the collision risk due to a particular close approach.

关键词：风险;空间天气;避免碰撞;航天飞行;航天安全

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