Langley Research Center

About: Langley Research Center is a facility organization based out in Hampton, Virginia, United States. It is known for research contribution in the topics: Mach number & Wind tunnel. The organization has 15945 authors who have published 37602 publications receiving 821623 citations. The organization is also known as: NASA Langley & NASA Langley Research Center.

An overview of LITE: NASA's Lidar In-space Technology Experiment

Abstract: The Lidar In-space Technology Experiment (LITE) is a three-wavelength backscatter lidar developed by NASA Langley Research Center to fly on the Space Shuttle. LITE flew on Discovery in September 1994 as part of the STS-64 mission. The goals of the LITE mission were to validate key lidar technologies for spaceborne applications, to explore the applications of space lidar, and to gain operational experience which will benefit the development of future systems on free-flying satellite platforms. The performance of the LITE instrument was excellent, resulting in the collection of over 40 GBytes of data. These data present us with our first highly detailed global view of the vertical structure of cloud and aerosol from the Earth's surface through the middle stratosphere. This paper will discuss the LITE instrument, the LITE mission, and briefly present some results from the Experiment. These preliminary results highlight the benefits to be obtained from long duration satellite lidars.

Unsteady euler algorithm with unstructured dynamic mesh for complex – aircraft aerodynamic analysis

Abstract: An Euler solution algorithm is presented for unsteady aerodynamic analysis of complex-aircr aft configurations. The flow solver involves a multistage Runge-Kutta time-stepping scheme that uses a finite-volume spatial discretization on an unstructured grid made up of tetrahedra. A significant contribution of the research is the development and implementation of a moving mesh algorithm that is employed for problems involving static or dynamic deformation of the aircraft. The mesh algorithm is a general procedure that can treat realistic motions and deformations of complex-aircraft configurations. Steady and unsteady results are presented for a supersonic fighter configuration to demonstrate applications of the Euler solver and dynamic mesh algorithm. The unsteady flow results were obtained for the aircraft oscillating harmonically in a complete-vehicle bending mode. Effects of angle of attack and reduced frequency on instantaneous pressures and force responses were investigated. The paper presents descriptions of the Euler solver and dynamic mesh algorithm along with results that assess the capability.

Spectral Methods for Partial Differential Equations

Abstract: Origins of spectral methods, especially their relation to the Method of Weighted Residuals, are surveyed Basic Fourier, Chebyshev, and Legendre spectral concepts are reviewed, and demonstrated through application to simple model problems Both collocation and tau methods are considered These techniques are then applied to a number of difficult, nonlinear problems of hyperbolic, parabolic, elliptic, and mixed type Fluid dynamical applications are emphasized

Parallel volume rendering using binary-swap compositing

Abstract: We describe a parallel volume-rendering algorithm, which consists of two parts: parallel ray tracing and parallel compositing. In the most recent implementation on Connection Machine's CM-5 and networked workstations, the parallel volume renderer evenly distributes data to the computing resources available. Without the need to communicate with other processing units, each subvolume is ray traced locally and generates a partial image. The parallel compositing process then merges all resulting partial images in depth order to produce the complete image. The compositing algorithm is particularly effective for massively parallel processing, as it always uses all processing units by repeatedly subdividing the partial images and distributing them to the appropriate processing units. Test results on both the CM-5 and the workstations are promising. They do, however, expose different performance issues for each platform. >

Scattering and absorption property database for nonspherical ice particles in the near- through far-infrared spectral region.

Abstract: The single-scattering properties of ice particles in the near- through far-infrared spectral region are computed from a composite method that is based on a combination of the finite-difference time-domain technique, the T-matrix method, an improved geometrical-optics method, and Lorenz–Mie theory. Seven nonspherical ice crystal habits (aggregates, hexagonal solid and hollow columns, hexagonal plates, bullet rosettes, spheroids, and droxtals) are considered. A database of the single-scattering properties for each of these ice particles has been developed at 49 wavelengths between 3 and 100 μm and for particle sizes ranging from 2 to 10,000 μm specified in terms of the particle maximum dimension. The spectral variations of the single-scattering properties are discussed, as well as their dependence on the particle maximum dimension and effective particle size. The comparisons show that the assumption of spherical ice particles in the near-IR through far-IR region is generally not optimal for radiative transfer computation. Furthermore, a parameterization of the bulk optical properties is developed for mid-latitude cirrus clouds based on a set of 21 particle size distributions obtained from various field campaigns.