9,113 research outputs found
An interactive multi-block grid generation system
A grid generation procedure combining interactive and batch grid generation programs was put together to generate multi-block grids for complex aircraft configurations. The interactive section provides the tools for 3D geometry manipulation, surface grid extraction, boundary domain construction for 3D volume grid generation, and block-block relationships and boundary conditions for flow solvers. The procedure improves the flexibility and quality of grid generation to meet the design/analysis requirements
Schwinger model on a half-line
We study the Schwinger model on a half-line in this paper. In particular, we
investigate the behavior of the chiral condensate near the edge of the line.
The effect of the chosen boundary condition is emphasized. The extension to the
finite temperature case is straightforward in our approach.Comment: 4 pages, no figure. Final version to be published on Phys. Rev.
A general multiblock Euler code for propulsion integration. Volume 1: Theory document
A general multiblock Euler solver was developed for the analysis of flow fields over geometrically complex configurations either in free air or in a wind tunnel. In this approach, the external space around a complex configuration was divided into a number of topologically simple blocks, so that surface-fitted grids and an efficient flow solution algorithm could be easily applied in each block. The computational grid in each block is generated using a combination of algebraic and elliptic methods. A grid generation/flow solver interface program was developed to facilitate the establishment of block-to-block relations and the boundary conditions for each block. The flow solver utilizes a finite volume formulation and an explicit time stepping scheme to solve the Euler equations. A multiblock version of the multigrid method was developed to accelerate the convergence of the calculations. The generality of the method was demonstrated through the analysis of two complex configurations at various flow conditions. Results were compared to available test data. Two accompanying volumes, user manuals for the preparation of multi-block grids (vol. 2) and for the Euler flow solver (vol. 3), provide information on input data format and program execution
A general multiblock Euler code for propulsion integration. Volume 3: User guide for the Euler code
This manual explains the procedures for using the general multiblock Euler (GMBE) code developed under NASA contract NAS1-18703. The code was developed for the aerodynamic analysis of geometrically complex configurations in either free air or wind tunnel environments (vol. 1). The complete flow field is divided into a number of topologically simple blocks within each of which surface fitted grids and efficient flow solution algorithms can easily be constructed. The multiblock field grid is generated with the BCON procedure described in volume 2. The GMBE utilizes a finite volume formulation with an explicit time stepping scheme to solve the Euler equations. A multiblock version of the multigrid method was developed to accelerate the convergence of the calculations. This user guide provides information on the GMBE code, including input data preparations with sample input files and a sample Unix script for program execution in the UNICOS environment
Parallel Exhaustive Search without Coordination
We analyze parallel algorithms in the context of exhaustive search over
totally ordered sets. Imagine an infinite list of "boxes", with a "treasure"
hidden in one of them, where the boxes' order reflects the importance of
finding the treasure in a given box. At each time step, a search protocol
executed by a searcher has the ability to peek into one box, and see whether
the treasure is present or not. By equally dividing the workload between them,
searchers can find the treasure times faster than one searcher.
However, this straightforward strategy is very sensitive to failures (e.g.,
crashes of processors), and overcoming this issue seems to require a large
amount of communication. We therefore address the question of designing
parallel search algorithms maximizing their speed-up and maintaining high
levels of robustness, while minimizing the amount of resources for
coordination. Based on the observation that algorithms that avoid communication
are inherently robust, we analyze the best running time performance of
non-coordinating algorithms. Specifically, we devise non-coordinating
algorithms that achieve a speed-up of for two searchers, a speed-up of
for three searchers, and in general, a speed-up of
for any searchers. Thus, asymptotically, the speed-up is only four
times worse compared to the case of full-coordination, and our algorithms are
surprisingly simple and hence applicable. Moreover, these bounds are tight in a
strong sense as no non-coordinating search algorithm can achieve better
speed-ups. Overall, we highlight that, in faulty contexts in which coordination
between the searchers is technically difficult to implement, intrusive with
respect to privacy, and/or costly in term of resources, it might well be worth
giving up on coordination, and simply run our non-coordinating exhaustive
search algorithms
Acoustic fatigue and sound transmission characteristics of a ram composite panel design
An experimental study to determine the acoustic fatigue characteristics of a flat multi-layered structural panel is described. The test panel represented a proposed design for the outer skin of a research application module to be housed within the space shuttle orbiter vehicle. The test specimen was mounted in one wall of the Wyle 100,000 cu ft reverberation room and exposed to a broadband acoustic environment having an overall level of 145 db. The test panel was exposed to nine separate applications of the acoustic environment, each application consisting of 250 seconds duration. Upon completion of the ninth test run, the specimen was exposed to a simulated micrometeoroid impact near the panel center. One additional test run of 250 seconds duration was then performed to complete the overall simulation of 50 flight missions. The experimental results show that no significant fatigue damage occurred until the test specimen was exposed to a simulated micrometeoroid impact. The intermediate foam layer forming the core of the test specimen suffered considerable damage due to this impact, causing a marked variation in the dynamic characteristics of the overall test panel. During the final application of the acoustic environment, the strain and acceleration response spectra showed considerable variation from those spectra obtained prior to impact of the panel. Fatigue damage from acoustic loading however, was limited to partial de-bonding around the edges of the composite panel
AN INVESTIGATION INTO THE IMPACT FORCE EXPERIENCED BY DIFFERENT TYPES OF FOOTBALLS
The impact force of kicking varies with different materials and the estimated force in powerful (maximal velocity) instep kick was 1100N (Tsaousidis and Zatsiorsky, 1996). The force may cause injuries and stress accumulated on the foot especially in novices, due to unfamiliar skill. Rubber is durable, cheap but stiffer; TPU (Thermoplastic Polyurethane) and PU (Polyurethane) material has higher elasticity and impact absorbability. The purpose of this study was to identify the impact force, max velocity and travelling distance with different material footballs
Mass Spectra of N=2 Supersymmetric SU(n) Chern-Simons-Higgs Theories
An algebraic method is used to work out the mass spectra and symmetry
breaking patterns of general vacuum states in N=2 supersymmetric SU(n)
Chern-Simons-Higgs systems with the matter fields being in the adjoint
representation. The approach provides with us a natural basis for fields, which
will be useful for further studies in the self-dual solutions and quantum
corrections. As the vacuum states satisfy the SU(2) algebra, it is not
surprising to find that their spectra are closely related to that of angular
momentum addition in quantum mechanics. The analysis can be easily generalized
to other classical Lie groups.Comment: 17 pages, use revte
Simulating typhoon-induced storm hydrographs in subtropical mountainous watershed: an integrated 3-layer TOPMODEL
International audienceA three-layer TOPMODEL is here constructed by integrating three components, diffusion wave approach into surface flow, soil moisture deficit into interflow and exponential recession curve function into base flow. Sensitivity analysis reveals that D (soil depth), K (hydraulic conductivity), and mi (soil moisture decay) predominate simulated hydrograph shape and total discharge, yet, there are distinct effects on the three flows. A subtropical mountainous watershed, Heng-Chi and eighteen typhoon-induced storms with various rainfall type and wide-ranged total rainfall (81 to 1026 mm) were applied. The global best-fitted combination gives an average efficient coefficient of 75.1% and 76.0% for calibration (14 cases) and validation (4 cases), respectively. Most discharges of validation events fall within the 90% confidence interval derived from calibration events. Those results demonstrate the capability of the 3-layer TOPMODEL in subtropical watershed. Meanwhile, the upper confidence limit is suggested preferably when considering the flood assessment
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