The effect of blade aerodynamic modelling on the prediction of high-frequency rotor airloads

Interactions between the blades and vortical structures within the wake of a helicopter rotor are a significant source of impulsive loading and noise, particularly in descending flight. Brown's Vorticity Transport Model has been used to investigate the influence of the fidelity of the local blade aerodynamic model on the accuracy with which the high-frequency airloads associated with blade-vortex interactions can be predicted. The Vorticity Transport Model yields a very accurate representation of the structure of the wake, and allows significant flexibility in the way that the blade loading, and hence the source of vorticity into the wake, can be represented. Two models for the local blade aerodynamics are compared. The first is a simple lifting-line model and the second is a somewhat more sophisticated lifting-chord model based on unsteady thin aerofoil theory. A marked improvement in accuracy of the predicted high-frequency airloads of the HART II rotor is obtained when the lifting-chord model for the blade aerodynamics is used instead of the lifting-line type approach. Errors in the amplitude and phase of the loading peaks are reduced and the quality of the prediction is affected to a lesser extent by the computational resolution of the wake. Indeed, the lifting-line model increasingly overpredicts the amplitude of the lift response to blade-vortex interactions as the computational grid is refined, exposing clearly the fundamental deficiencies in this commonly-used approach particularly when modelling the aerodynamic response of the blade to interactions with vortices that are much smaller than its chord. In comparison, the airloads that are predicted using the lifting-chord model are relatively insensitive to the resolution of the computation, and there are fundamental reasons to believe that properly converged numerical solutions may be attainable using this approach

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

Job-based Coverage Drops for Adults and Children but Public Programs Boost Children's Coverage

Provides a profile of non-elderly Californians' health insurance coverage and lack of coverage, and describes how these rates have changed. Estimates the number of children and adults who are uninsured but eligible for coverage through public programs

Understanding the Higher-Order Approach to Consciousness

Critics have often misunderstood the higher-order theory (HOT) of consciousness. Here we clarify its position on several issues, and distinguish it from other views such as the global The higher-order theory (HOT) of consciousness has often been misunderstood by critics. Here we clarify its position on several issues, and distinguish it from other views such as the global workspace theory (GWT) and early sensory models (e.g. first-order local recurrency theories). For example, HOT has been criticized for over-intellectualizing consciousness. We show that while higher-order states are cognitively assembled, the requirements are actually considerably less than often presumed. In this sense HOT may be viewed as an intermediate position between GWT and early sensory views. Also, we clarify that most proponents of HOT do not stipulate consciousness as equivalent to metacognition or confidence. Further, compared to other existing theories, HOT can arguably account better for complex everyday experiences, such as of emotions and episodic memories. This makes HOT particularly useful as a framework for conceptualizing pathological mental states

Development in governmental auditing: Their impact on the academic and business communities

https://egrove.olemiss.edu/dl_proceedings/1140/thumbnail.jp

Discussant\u27s response to an historical perspective of government auditing with special reference to the U.S. General Accounting Office

https://egrove.olemiss.edu/dl_proceedings/1122/thumbnail.jp

The Recombinant DNA Debate

The questions surrounding the recombinant DNA research debate are not just questions of technique and safety. They involve the driving forces of scientific research, especially those premises and presuppositions concerning the expansion of knowledge versus our ability to use that knowledge wisely. Basically, we ask if policy--scientific, industrial, or political--should be an integral part of our future steps in recombinant DNA research and development. It is obvious from past mistakes involving pollution, waste of fossil fuels, and over-mechanization that we must try to avoid the crucial tendency that technology has of overrunning common sense and moral guidelines. This is especially true in light of the fact that we are looking at an area of research in which results are probably the most unpredictable of any area of biochemistry. There comes a point at which the scientist, seeing himself as providing good for mankind, becomes hostile at the thought of the regulator burdening down progress with red tape. The regulator, on the other hand, views the scientist as being too ambitious and uncontrolled, and sees himself as a protector of the real world from the eccentricities of the research scientists. In the recombinant DNA question, this conflict becomes strikingly real. The techniques and ideas are no longer hypothetical or theory; they are available for widespread use. A method of reducing risks while maintaining the potential benefits of recombinant DNA research must be found. On this point, there seems to be widespread agreement among scientists and lay-people. The real debate begins when the regulations for accomplishing this goal are proposed. Not only are the regulations themselves debated, but the validity of them is also a focal point of debate. Here, the challenges to validity comes from the rapidly changing knowledge concerning recombinant DNA techniques. Possibly, the answer is not in a set of fixed rules, but in rules that can be easily accommodated to current knowledge without endangering the public or the enviornment. Therefore, the following is a review of facts concerning recombinant DNA research, starting with the basic premises of molecular genetics and then reviewing National Institutes of Health guidelines, testimony before the United States House of Representatives Subcommittee on Science and Technology, and transcripts of the National Academy of Sciences\u27 Forum on Recombinant DNA research. Within this review, the risks, benefits, and existing regulations will be discussed, concluding with a general summary and commentary. It is hoped that this paper will serve as an informative summary of the author\u27s three semester study of the recombinant DNA research policy debate

Diabetes in California: Findings From the 2001 California Health Interview Survey

Examines the prevalence of diabetes in California, with particular attention paid to disparities between different population groups. Includes access to medical care, diabetes care and management, and identifying at-risk populations

12-Month Continuous Eligibility in Medicaid: Impact on Service Utilization

Summarizes findings on how allowing Medicaid enrollees to remain enrolled without reapplying for twelve months affected the number of Medi-Cal-enrolled children's emergency room visits and physician visits compared with those with discontinuous coverage