Some remarks on the design of transonic tunnels with low levels of flow unsteadiness

The principal sources of flow unsteadiness in the circuit of a transonic wind tunnel are presented. Care must be taken to avoid flow separations, acoustic resonances and large scale turbulence. Some problems discussed are the elimination of diffuser separations, the aerodynamic design of coolers and the unsteadiness generated in ventilated working sections

Computer studies of hybrid-slotted working sections with minimum interference at subsonic speeds

A series of computations on tunnel boundary-interference effects for hybrid-slotted working sections was performed using the WALINT code. The slots were modeled as lines of porosity with linear crossflow characteristics. The basic shape evaluated was for a rectangular section with height-to-width ratio = 0.835 and its companion in the duplex mode (half model testing) with height-to-width ratio = 0.6. A best overall basic configuration was determined with seven slots on each wall with open area ratio on each wall of 17.5%. For both full-span and half-model testing, the optimum solution required closing all but two slots on each of the half-walls parallel to the plane of the wing (equivalent to four slots on the full floor and ceiling). The results are presented here for the best configurations and are shown to be within the figure-of-merit range of + or - 0.04 in upwash, and + or - 0.1 in curvature for the Mach number range 0.6 to 0.85. Blockage effects are shown to be small

Calculation of transonic steady and oscillatory pressures on a low aspect ratio model and comparison with experiment

Pressure data measured by the British Royal Aircraft Establishment for the AGARD SMP tailplane are compared with results calculated using the transonic small perturbation code XTRAN3S. A brief description of the analysis is given and a recently developed finite difference grid is described. Results are presented for five steady and nine harmonically oscillating cases near zero angle of attack and for a range of subsonic and transonic Mach numbers

Further buffeting tests in a cryogenic wind tunnel

Further measurements of buffeting, using wing-root strain gauges, were made in the NASA Langley 0.3 m Cryogenic Wind Tunnel to refine techniques which will be used in larger cryogenic facilities such as the United States National Transonic Facility (NTF) and European Transonic Wind Tunnel (ETW). The questions addressed included the relative importance of variations in frequency parameter and Reynolds number, the choice of model material (considering both stiffness and damping) and the effects of static aeroelastic distortion. The main series of tests was made on half models of slender 65 deg delta wings with a sharp leading edge. The three delta wings had the same planform but widely different bending stiffness and frequencies (obtained by varying both the material and the thickness of the wings). It was known that the flow on this configuration would be insensitive to variations in Reynold number. Additional tests were made on one unswept half-wing of aspect ratio 1.5 with an NPL 9510 aerofoil section, known to be sensitive to variations in Reynolds number at transonic speeds. For brevity the test Mach numbers were restricted to M = 0.21 and 0.35 for the delta wings and to M = 0.30 for the unswept wing

Guest Editors' introduction: philosophical contributions to leadership ethics

This article introduces the first of two special issues on philosophical approaches to leadership ethics. In it, we show some of the ways that philosophy contributes to the study of leadership and leadership ethics. We begin with an overview of how philosophers have treated some of the ethical aspects and challenges of leadership. These include discussions of self interest, the problem of dirty hands, responsibility, moral luck, power, gender and diversity, and spirituality. The articles in this issue draw on philosophy to explore a variety of ethical questions related to leadership and the relationships that leaders have with followers and others

Migratory landbirds of the lower Delmarva: habitat selection and geographic distribution

Each year billions of landbirds migrate between the northern and southern hemispheres of the New World. During the spring and fall, migrants may be seen over most of North America. However, large numbers of these birds follow broadly defined routes known as flyways. Within these routes, significant physical barriers such as mountain ridges and large bodies of water act as migration bottlenecks concentrating large numbers of birds within relatively small land masses. These concentration areas may have tremendous conservation significance to bird populations that depend on them for rest, refueling, and protection from predators. For southbound migrants, the Chesapeake Bay is one of the largest physical barriers along the east coast. Migrants that reach the mouth of the Bay in the hours just before dawn settle out near the tip of the Delmarva Peninsula. On mornings following strong cold fronts, millions of birds may be concentrated near the tip of the peninsula. Because birds passing through the Eastern Shore are members of breeding communities throughout northeastern North America and winter communities throughout the Caribbean and Latin America, local land use decisions may have far-reaching consequences. Managing human population growth while conserving sensitive natural resources is a major challenge confronting land-use decision makers throughout the coastal zone. The two-year Northampton Migratory Bird Project (NMBP) was initiated under Northampton County\u27s Special Area Management Plan (SAMP) to provide information to guide the development of enforceable policies that will protect and enhance migratory songbird habitat. This information will also be used in the development of a nature-based tourism industry. Several field projects were conducted between August and November of 1992 and 1993. The results that address the primary SAMP objectives suggest: 1. Both long- and short-distance migrants become concentrated within the lower 10 km of the peninsula, particularly along the shoreline of the Bay. 2. The majority of migrants appear to select habitats based on the density of understory vegetation. 3. Long-distance migrants pass through the peninsula in late summer and early fall, while short-distance migrants pass through the peninsula in mid to late fall. Management and policy implications are formulated for three general areas: 1. Zoning ordinances. 2. Vegetation protection standards. 3. Development of nature-based tourism initiatives