Modelling the aerodynamics of coaxial helicopters : from an isolated rotor to a complete aircraft

This paper provides an overview of recent research on the aerodynamics of coaxial rotors at the Rotorcraft Aeromechanics Laboratory of the Glasgow University Rotorcraft Laboratories. The Laboratory's comprehensive rotorcraft code, known as the Vorticity Transport Model, has been used to study the aerodynamics of various coaxial rotor systems. Modelled coaxial rotor systems have ranged from a relatively simple twin two-bladed teetering configuration to a generic coaxial helicopter with a stiff main rotor system, a tail-mounted propulsor, and a horizontal stabiliser. Various studies have been performed to investigate the ability of the Vorticity Transport Model to reproduce the detailed effect of the rotor wake on the aerodynamics and performance of coaxial systems, and its ability to capture the aerodynamic interactions that arise between the various components of realistic, complex, coaxial helicopter configurations. It is suggested that the use of such a numerical technique not only allows insight into the performance of such rotor systems but might also eventually allow the various aeromechanical problems that often beset new helicopter designs of this type to be circumvented at an early stage in their design

A computational study of helicopter coaxial rotor aerodynamics and performance.

Imperial Users onl

Effect of Phosphatic Fertilizer Rates Level on Growth, Crude Protein Content and Nitrogen Fixation Ability of Alfalfa at Sowing Year

The experiment was conducted to determine effects of phosphate fertilizers on growth characteristics, crude protein content and nitrogen fixation ability of alfalfa (Medicago sativa L) in the sowing year. Two rates of phosphate (200 and 400 kg/ha P) were applied to phosphorus -deficient native soil in Korea and samples were taken every 7 days from the 30th to the 93rd day. Number of branches, root length and dry matter weight at phosphate fertilizer level of 400kg in sowing year more increased than those at 200kg/ha. The number of nodules did not differ due to phosphate fertilizer rate. The crude protein contents of leaves, stems and roots were not significantly affected by the phosphate fertilizer levels, except for those of leaves with 400kg/ha at 72 days after sowing that were higher. The crude protein contents of each plant along the growing stages were higher at the 44th and 72nd day after sowing. The dry weight of roots did not significantly respond to phosphate rates from 30 days to 51 days after sowing, but that was increased at phosphate fertilizer level of 400kg/ha from 51 days after sowing. The amount of ethylene evolved by samples during 2 hours and the calculated amount of nitrogen fixed were higher on phosphate fertilizer level of 400kg/ha from 30 days to 58 days after sowing, but decreased that

Intensifying Gated Exclusiveness of Apartment Complex Boundary Design in Seoul, Korea

The proliferation of private residential development is evident worldwide. In Seoul, these developments have distinctive spatial and morphological characteristics. Originally, government housing policies drove the construction of apartment complexes to ensure massive housing supply. Over time, development shifted, becoming more market-driven, aimed at the middle class, and built by the private sector. During the late 1990s, an increase in luxury high-rise apartment complexes increased, reflecting a tendency to live in a socioeconomically homogeneous community and propelling the proliferation of self-contained gated communities. To understand the continually increasing exclusive nature of apartment complexes in Seoul, we examine two areas with apartment complexes of different periods and development methods: Mok-dong, where the 1980s ‘Housing Site Development’ resulted in the simultaneous construction of multiple apartment complexes according to a single master-plan, and Geumho-dong, a neighbourhood transforming by apartment complexes under ‘Housing Redevelopment’ from the 1980s to the present. The research focused on 28 complexes, and measured the surrounding vertical borders, pedestrian paths, and roadways, and access control. Tracing these features over time, we investigated the increasingly exclusive nature and decreasing public nature of apartment complexes, consequences of development for physical and social space during different periods, and degree of public or private intervention

Determination of Cutting Date and Interval on Native Grass Management of Agricultural Waterways in South Korea

Agricultural waterways provide a buffer zone between crop fields and adjacent rivers or streams. Waterways are important resource for agriculture water management, water quality and biodiversity conservation. The total linear distance of waterway in Korea is about 180,000 km, and about 40% are concrete and about 60% are grassed waterways. At present, the percentage of concrete waterways is increasing because of their water management efficiency. Some argue that continued expansion of concrete waterways is not sustainable because it leads to potential-degradation of the earth\u27s environment. This concern has led to renewed efforts to use grassed waterways as an alternative to concrete. In addition, grassed waterways enhance the environment-friendly image of agriculture that Korea farmers want to promote. The objective of this experiment was to determine the effect of cutting date and interval of native grasses for water management efficiency of agricultural waterway