Geometry requirements for unsteady aerodynamics in aeroelastic analysis and design

Aircraft geometry requirements for unsteady aerodynamic computations are discussed and differences between requirements for steady and unsteady flow are emphasized within the framework of a general potential-flow aerodynamic formulation. Its implementation in a computer program called SOUSSA (Steady, Oscillatory, and Unsteady Subsonic and Supersonic Aerodynamic is detailed

Measured and calculated effects of angle of attack on the transonic flutter of a supercritical wing

For abstract see A82-30143

From microscopic to macroscopic descriptions of cell\ud migration on growing domains

Cell migration and growth are essential components of the development of multicellular organisms. The role of various cues in directing cell migration is widespread, in particular, the role of signals in the environment in the control of cell motility and directional guidance. In many cases, especially in developmental biology, growth of the domain also plays a large role in the distribution of cells and, in some cases, cell or signal distribution may actually drive domain growth. There is a ubiquitous use of partial differential equations (PDEs) for modelling the time evolution of cellular density and environmental cues. In the last twenty years, a lot of attention has been devoted to connecting macroscopic PDEs with more detailed microscopic models of cellular motility, including models of directional sensing and signal transduction pathways. However, domain growth is largely omitted in the literature. In this paper, individual-based models describing cell movement and domain growth are studied, and correspondence with a macroscopic-level PDE describing the evolution of cell density is demonstrated. The individual-based models are formulated in terms of random walkers on a lattice. Domain growth provides an extra mathematical challenge by making the lattice size variable over time. A reaction-diffusion master equation formalism is generalised to the case of growing lattices and used in the derivation of the macroscopic PDEs

Developments in steady and unsteady aerodynamics for use in aeroelastic analysis and design

A review is given of seven research projects which are aimed at improving the generality, accuracy, and computational efficiency of steady and unsteady aerodynamic theory for use in aeroelastic analysis and design. These projects indicate three major thrusts of current research efforts: (1) more realistic representation of steady and unsteady subsonic and supersonic loads on aircraft configurations of general shape with emphasis on structural-design applications, (2) unsteady aerodynamics for application in active-controls analyses, and (3) unsteady aerodynamics for the frequently critical transonic speed range. The review of each project includes theoretical background, description of capabilities, results of application, current status, and plans for further development and use

Prediction of transonic flutter for a supercritical wing by modified strip analysis and comparison with experiment

Use of a supercritical airfoil can adversely affect wing flutter speeds in the transonic range. As adequate theories for three dimensional unsteady transonic flow are not yet available, the modified strip analysis was used to predict the transonic flutter boundary for the supercritical wing. The steady state spanwise distributions of section lift curve slope and aerodynamic center, required as input for the flutter calculations, were obtained from pressure distributions. The calculated flutter boundary is in agreement with experiment in the subsonic range. In the transonic range, a transonic bucket is calculated which closely resembles the experimental one with regard to both shape and depth, but it occurs at about 0.04 Mach number lower than the experimental one

A study of compressible turbulent boundary layers using the method of invariant modeling

Model equations for studying compressible turbulen boundary layer

Going from microscopic to macroscopic on nonuniform growing domains

Throughout development, chemical cues are employed to guide the functional specification of underlying tissues while the spatiotemporal distributions of such chemicals can be influenced by the growth of the tissue itself. These chemicals, termed morphogens, are often modeled using partial differential equations (PDEs). The connection between discrete stochastic and deterministic continuum models of particle migration on growing domains was elucidated by Baker, Yates, and Erban [ Bull. Math. Biol. 72 719 (2010)] in which the migration of individual particles was modeled as an on-lattice position-jump process. We build on this work by incorporating a more physically reasonable description of domain growth. Instead of allowing underlying lattice elements to instantaneously double in size and divide, we allow incremental element growth and splitting upon reaching a predefined threshold size. Such a description of domain growth necessitates a nonuniform partition of the domain. We first demonstrate that an individual-based stochastic model for particle diffusion on such a nonuniform domain partition is equivalent to a PDE model of the same phenomenon on a nongrowing domain, providing the transition rates (which we derive) are chosen correctly and we partition the domain in the correct manner. We extend this analysis to the case where the domain is allowed to change in size, altering the transition rates as necessary. Through application of the master equation formalism we derive a PDE for particle density on this growing domain and corroborate our findings with numerical simulations

Archeological Investigations at the Hudnall-Pirtle Site (41RK4) An Early Caddo Mound Center in Northeast Texas

The Hudnall-Pirtle site (41RK4) is situated on a large T-1 alluvial terrace of the Sabine River in northern Rusk County in Texas. This area of the state, commonly called Northeast Texas, is part of the Southern Gulf Coastal Plain, a relatively level, sloping plain formed by the pre-Pleistocene embayment of the Gulf of Mexico. From a biogeographical perspective, the site is located in the Oak-Hickory-Pine forest of eastern Texas, otherwise known as the Pineywoods. This area represents the western extension of the southern coniferous forests and is dominated by shortleaf and loblolly pine trees. Hardwood trees, including various oaks, hickory, elm, and gum, are the dominant vegetation in the floodplains of rivers and major creeks in Northeast Texas

ALCOA #1 (41AN87): A Frankston Phase Settlement along Mound Prairie Creek, Anderson County, Texas

The ALCOA #1 (41AN87) site is a Frankston Phase (ca. A.D. 1400-1650) site located on a high alluvial terrace of Mound Prairie Creek, about seven kilometers northeast of Palestine, Texas. Mound Prairie Creek, a perennial stream, flows southeast to east across the county and drains into the Neches River. The site is approximately 10 meters above the Mound Prairie Creek floodplain, and the creek channel is 300 meters to the south. Although the investigations at the site have been rather limited to date, it appears that the ALCOA #1 site is a single component Frankston Phase homestead, or possibly a small hamlet. Other Frankston phase sites are known on Mound Prairie Creek, Hurricane Creek, Walnut Creek, and Brushy Creek, all Neches River tributaries, and the possibility exists that these may be part of a larger related Caddo community and settlement system

SOME EFFECTS OF VARIATIONS IN DENSITY AND AERODYNAMIC PARAMETERS ON THE CALCULATED FLUTTER CHARACTERISTICS OF FINITE-SPAN SWEPT AND UNSWEPT WINGS AT SUBSONIC AND SUPERSONIC SPEEDS

Subsonic and supersonic flutter calculations on swept and unswept wings to evaluate effects of variations in aerodynamic parameters and densit