Force and cavitation characteristics of the NACA 4412 hydrofoil

This report covers Water Tunnel measurements of the infinite aspect ratio characteristics and cavitation characteristics of a hydrofoil section. The profile tested is identical to the 4412 airfoil section of the National Advisory Committee for Aeronautics and is called the NACA 4412 hydrofoil in this report. Measurements and observations include lift, drag, and pitching moment and the inception and development of cavitation as functions of the angle of attack, velocity, and pressure of the flow. The purpose of this report is to present these measurements of the characteristics of this section in water, to compare the results with other available information on this shape, and to evaluate the Water Tunnel method for obtaining the complte hydrodynamic characteristics of hydrofoils

Cavitation Characteristics and Infinite Aspect Ratio Characteristics of a Hydrofoil Section

This paper describes "two-dimensional" tests in a water tunnel of a profile identical to the 4412 airfoil section of the National Advisory Committee for Aeronautics. The tests included photographic observations of the inception and growth of cavitation as influenced by velocity, pressure (submergence) and angle of attack, and measurements, during cavitation-free operation, of the hydrodynamic forces and moments as functions of Reynolds number and angle of attack. The relation between the angle of attack and the value of the cavitation parameter at which inception occurs is shown for each face of the hydrofoil. The effect of profile geometry in causing cavitation, and the significance of distinct~y different types of cavitation obtained with change in variables are discussed. Convenient curves are given showing the submergence required to avoid cavitation for different velocities and angles of attack. The measured hydrodynamic characteristics are presented in graphical form and are also compared with previously existing data from wind tunnel tests of a finite aspect ratio span. The experimental procedure and its reliability in indicating true infinite aspect ratio characteristics is discussed

Water Tunnel Tests of the 2 1/4" AA Rocket Projectile

The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 with the Office of Scientific Research and Development, and is sponsored by Division Six, Section 6.1, of the National Defense Research Committee. The report covers Water Tunnel tests of 1 - 1/2 " and 2" diameter models of the 2-1/4" AA Rocket Projectile. The drag, cross force, and moment acting on the models were measured and the position of the center of pressure relative to the center of gravity was calculated for various yaw angles. These results were compared with prototype field test data. The main findings are summarized as follows: i. The rocket is statically stable as indicated by a stabilizing moment coefficient and a center-of-pressure eccentricity of more than 0.26. Furthermore, the large area of 1he tail fins will probably provide sufficient damping to make it dynamically stable also. 2. The tail fins cause very large cross force coefficients compared to values for other cylindrical projectiles with folding fin or ring tails. Consequently, unless the rocket is rotated in flight, small misalignments of the tail fins can cause drifting and increase the dispersion seriously . 3. Both the cross force and moment coefficients increase with yaw at a greater than linear rate. 4. Comparison of Water Tunnel and field test data shows good agreement for the moment coefficient 5. The drag coefficient from Water Tunnel tests is 9% lower than the value of 0.46 measured during field tests in air. Scale effects, oscillation of the projectile during free flight tests, and compressibility effects on the drag in air are factors that could account for this difference. 6. The drag is nearly independent of yaw for small angles and increases rapidly for angles greater than about 4°. 7. The high drag coefficient for this projectile is caused by skin friction on the relatively large area of the body and fins and by pressure drag due primarily to a large eddying wake behind the blunt body

Cavitation Noise from Underwater Projectiles

This report describes measurements of high frequency noise produced by projectiles cavitating in a high velocity stream of water. Spherical and ellipsoidal focusing reflectors were used in conjunction with a Brush CC-11A hydrophone to locate the noise source

The Water Tunnel as a Tool in Hydraulic Research

The expanding scope of application of the water tunnel is largely the result of war research needs. Since the first known elementary water tunnel was used by Parsons in England in 1898 to investigate propellers, its application has remained primarily in the field of ship propeller testing. Meanwhile, investigations of other submerged bodies and of most fundamental phenomena in fluid dynamics have been performed in the many wind tunnels throughout the world. Even the broad development in hydraulic laboratory techniques that accompanied the revival of interest in scientific hydraulic research during the last twenty-five years did not emphasize the water tunnel as a general tool. In the early stages of World War II, however, there was a shortage of equipment in America, and apparently also abroad, to supply information for underwater ballistics design. Additional facilities in which flow could be produced with cavitation, as well as without, were needed, and these preferably of a type suitable to more general application than the existing propeller tunnels. As a result, there exists now, in addition to propeller testing tunnels, a limited number of water tunnels whose prime purpose is the investigation of flow about bodies in general. Two of these are in the United States, one at the University of Iowa, and one at the California Institute of Technology. This new practice with its additional techniques extends the role the water tunnel is destined to play in hydraulic research. Thus in the current period of reconversion, which applies to research objectives as well as production objectives, a discussion of the present development of water-tunnel equipment and the possible scope of its application in peacetime is appropriate

The Mediating Role Of EMS Teamwork As It Pertains To HR Factors And Perceived Environmental Performance

Little management theory or empirical results exist to guide managers in maximizing employee efforts to successfully implement Environmental Management Systems (EMS). In response, this study examines the relationship among Human Resource (HR) factors and employee perceptions of environmental performance. Four hundred thirty-seven (437) employees were surveyed in an organization with a well-developed EMS program and ISO 14001 certification. Results suggest that management support for EMS, EMS training, employee empowerment, and EMS rewards are related to perceived environmental performance. Furthermore, EMS teamwork plays a mediating role between some of independent variables and perceived environmental performance. Finally, implications for managers are discussed

The high speed water tunnel at the California Institute of Technology

The high speed water tunnel was established at the California Institute of Technology to study the forces acting upon moving bodies immersed in a fluid. The working section of the tunnel is 14 inches in diameter and 6 feet long and velocities up to 72 feet per second are obtained in it. The model to be tested is mounted on the spindle of a three component balance which measures the drag force, the yaw or lateral force and the moment about the spindle support. The angle of inclination of the model to the flow direction can be adjusted easily. From these measurements are determined the magnitude and location of the resultant forces acting on the model. In order to study cavitation, the pressure in the tunnel is made adjustable and a transparent working section is provided for visual and photographic observations. For qualitative assistance in interpreting the results of the tunnel studies in terms of the effects of the body shapes on the flow pattern, an auxiliary flume is available. The flow is made visible by use of a new technique employing polarized light

Social dimensions of fertility behavior and consumption patterns in the Anthropocene.

We consider two aspects of the human enterprise that profoundly affect the global environment: population and consumption. We show that fertility and consumption behavior harbor a class of externalities that have not been much noted in the literature. Both are driven in part by attitudes and preferences that are not egoistic but socially embedded; that is, each household's decisions are influenced by the decisions made by others. In a famous paper, Garrett Hardin [G. Hardin, Science 162, 1243-1248 (1968)] drew attention to overpopulation and concluded that the solution lay in people "abandoning the freedom to breed." That human attitudes and practices are socially embedded suggests that it is possible for people to reduce their fertility rates and consumption demands without experiencing a loss in wellbeing. We focus on fertility in sub-Saharan Africa and consumption in the rich world and argue that bottom-up social mechanisms rather than top-down government interventions are better placed to bring about those ecologically desirable changes

Nature and mental health: An ecosystem service perspective

A growing body of empirical evidence is revealing the value of nature experience for mental health. With rapid urbanization and declines in human contact with nature globally, crucial decisions must be made about how to preserve and enhance opportunities for nature experience. Here, we first provide points of consensus across the natural, social, and health sciences on the impacts of nature experience on cognitive functioning, emotional well-being, and other dimensions of mental health. We then show how ecosystem service assessments can be expanded to include mental health, and provide a heuristic, conceptual model for doing so

Selection of Reserves for Woodland Caribou Using an Optimization Approach

Habitat protection has been identified as an important strategy for the conservation of woodland caribou (Rangifer tarandus). However, because of the economic opportunity costs associated with protection it is unlikely that all caribou ranges can be protected in their entirety. We used an optimization approach to identify reserve designs for caribou in Alberta, Canada, across a range of potential protection targets. Our designs minimized costs as well as three demographic risk factors: current industrial footprint, presence of white-tailed deer (Odocoileus virginianus), and climate change. We found that, using optimization, 60% of current caribou range can be protected (including 17% in existing parks) while maintaining access to over 98% of the value of resources on public lands. The trade-off between minimizing cost and minimizing demographic risk factors was minimal because the spatial distributions of cost and risk were similar. The prospects for protection are much reduced if protection is directed towards the herds that are most at risk of near-term extirpation