Transonic Navier-Stokes wing solution using a zonal approach. Part 1: Solution methodology and code validation
Abstract : A fast diagonalized Beam Warming algorithm is coupled with a zonal approach to solve the three dimensional Euler/Navier Stokes equations. The computer code, called Transonic Navier Stokes (TNS), uses a total of four zones for wing configurations (or can be extended to complete aircraft configurations by adding zones). In the inner blocks near the wing surface, the thin layer Navier Stokes equations are solved, while in the outer two blocks the Euler equations are solved. The diagonal algorithm yields a speedup of as much as a factor of 40 over the original algorithm/zonal method coded. The TNS code, in addition, has the capability to model wind tunnel walls. Transonic viscous solutions are obtained on a 150,000 point mesh for a NACA 0012 wing. A three order of magnitude drop in the L2 norm of the residual requires approximately 500 iterations, which takes about 45 min of CPU time on a Cray-XMP processor. Simulations are also conducted for a different geometrical wing called WING C. All cases show good agreement with experimental data.
A perspective of theoretical and applied computational fluid dynamics
O heighten his understanding of the fluid dynamics and aerodynamics pertinent to the early stages of the atmospheric flight-vehicle design process, the aerodynamicist has at his disposal three standard tools: analytical methods, computational procedures, and experimentation. Some of the advantages and disadvantages of each design tool are summarized in Fig. 1. Analytical methods provide quick, closed-form solutions, but they require unduly restrictive assumptions, can treat only simple configurations, and capture only the idealized aerodynamics. Through experimentation, representative or actual configurations can be tested and representative and complete aerodynamic data can be produced. Experimentation is costly, however, both in terms of the model and actual test time. In addition, the limited conditions that can be attained in wind tunnels restrict the scope of ex
Discourse Forms and Processes in Indigenous Lowland South America: An Areal-Typological Perspective
▪ Abstract In indigenous lowland South America there are several discourse forms and processes that are shared by groups of people of distinct genetic linguistic affiliations; this leads us to posit this large region, which we label greater Amazonia, as a discourse area, a concept that parallels the notion of linguistic area. The discourse forms and processes we examine are ceremonial dialogue, dialogical performance, templatic ratifying, echo speech, ceremonial greeting, ritual wailing, evidentiality, speech reporting practices, parallelism, special languages, and shamanistic language use. We hypothesize that in lowland South America, discourse is the matrix for linguistic diffusion, i.e., that linguistic areas emerge within discourse areas. What we propose then is a discourse-centered approach to language change and history, parallel to a discourse-centered approach to language structure and use. Our survey includes a plea for a careful archiving of recorded and written materials dealing with lowland So...