An experimental determination of dynamic coefficients for the Basic Finner missile by means of the angular dynamic balance

Equipment developed in this Laboratory permits the determination of eight of the dynamic coefficients useful in describing the force and moment reactions on a submerged body moving in water. These coefficients comprise the partial derivatives of moment (about the yaw axis) and of force (in the horizontal plane, and perpendicular to the longitudinal axis) with respect to velocity and acceleration components in specified directions. So long as the instantaneous angles of attack are small and scale effects are absent, these coefficients have constant values. A complete list of coefficients is given in Ref. (1), as are definitions, sign conventions and formulas for making the coefficients nondimensional. The eight coefficients tabulated below are those pertinent to lateral translation and rotation about the yaw axis for a body of revolution: Nr' coefficient of rotary moment derivative Nr[dot]' virtual moment of inertia coefficient (angular acceleration) Nv' coefficient of static moment derivative Nv[dot]' virtual moment of inertia coefficient (lateral acceleration) Yr' coefficient of rotary force derivative Yr[dot]' virtual inertia coefficient (angular acceleration) Yv' coefficient of static force derivative Yv[dot]' virtual inertia coefficient (lateral acceleration) where the prime indicates that the coefficients are in dimensionless form. It is the purpose of the experimental program undertaken at this Laboratory to determine the numerical values of the above quantities for the Basic Finner missile (Fig. 1). Because of the required differences in the experimental methods, however, the program was divided into two parts. This report deals only with Part 1, and is restricted to the following quantities: Nr[dot]', Nv', Yr[dot]', Yv', and the linear combinations Nr' - Nv[dot]' and Yr' - Yv[dot]'. Remaining quantities will be the subject of another report

Superventilated flow past delta wings

Although delta wings have been known for some time in aeronautics (1)(2) their introduction into a hydrodynamic context has been quite recent. As in the flow of air, the delta wing provides a simple but useful configuration for investigating three-dimensional problems in cavity flows. At the start of the present work (1960), only one theoretical study on this subject was known (3). No information on flow patterns, force characteristics or other properties were available for these shapes. It was accordingly decided to embark on an experimental program with the aim of providing the basic characteristics of the cavitating flow past delta wings, to observe and outline any interesting features of these flows and, finally, to provide a physical basis for any mathematical analysis of the flow that might be undertaken. Measurements of lift, drag and pitching moment and pressure distributions were made on a family of simple flat plate delta shapes of varying apex angle; several configurations outside this family were also tested. These included a diamond plan form, reverse delta, and a delta with a 90 degree bottom. All were without camber and were tested with no yaw angle. After completion of this work, the exhaustive treatment of Reichardt and Sattler (4) appeared which also deals with cavitating delta wings. It is believed, however, that the current report and that of Reichardt are sufficiently different in scope and method to justify the presentation of the present results

A Preliminary Experimental Study of Vertical Hydrofoils of Low Aspect Ratio Piercing a Water Surface

Most types of problems which arise in connection with the use of a hydrofoil operating in water can be solved simply by treating it as an airfoil operating in air. For this purpose, use can be made of the great wealth of theoretical information and experimental data which can be found in the literature. There are, however, regimes of operation of the hydrofoil which are not duplicated by the airfoil excepting possibly under very special conditions. These regimes are identified by one of the following: (a) cavitation (b) ventilation (c) proximity to a free surface Cavitation is characterized by the presence of water vapor bubbles at regions in the flow where the pressure is less than the vapor pressure corresponding to the existing water temperature. Although most commonly observed on the blades of propellers or on the vanes of axial flow pumps, cavitation can also be present on fins used to stabilize high speed underwater missiles, on hydrofoils used as lifting surfaces, or on support struts of various kinds. Allied to this problem is ventilation, a condition which is like cavitation in that it results in discontinuities in density in the fluid surrounding the hydrofoil, although the initiating mechanism is fundamentally different and the lighter medium is air or gas instead of water vapor. A third type of flow regime which may be very important is that associated with a hydrofoil which approaches or intersects a water-vapor or water-gas interface. In this case the flow must satisfy the constant pressure boundary condition on that interface. The effect of gravity may or may not be important, and the hydrofoil can be oriented in any direction. A lifting hydrofoil would most likely be parallel, or nearly parallel, to the water surface, whereas a support strut or a stabilizing fin would inter sect the water surface nearly at right angles. It is this last mentioned type of ope ration which is investigated in this report, and which, as will be seen later, also implies a study of the effects of air ventilation. Among the specific fundamental questions which arise in considering a vertical hydrofoil piercing a flat water surface and which is at an angle of attack to the flow, are the following: (a) How does the presence of the air-water interface affect the apparent aspect ratio of the hydrofoil as compared with its geometrical value? (b) What is the effect of air ventilation on the value of cross-force developed by the hydrofoil, and what observations can be made regarding the inception of this phenomenon? Since no previous hydrofoil studies had been performed in the Free Surface Water Tunnel, it was also of interest to determine the suitability of that facility and its associated equipment for doing work of this kind. On the other hand, the investigation was intended only as a preliminary one and was, therefore, undertaken with limited resources

Development of an Organic Rankine-Cycle power module for a small community solar thermal power experiment

An organic Rankine-cycle (ORC) power module was developed for use in a multimodule solar power plant to be built and operated in a small community. Many successful components and subsystems, including the reciever, power conversion subsystem, energy transport subsystem, and control subsystem, were tested. Tests were performed on a complete power module using a test bed concentrator in place of the proposed concentrator. All major single-module program functional objectives were met and the multimodule operation presented no apparent problems. The hermetically sealed, self-contained, ORC power conversion unit subsequently successfully completed a 300-hour endurance run with no evidence of wear or operating problems

Measurements on fully wetted and ventilated ring wing hydrofoils

Force measurements and visual observations were made in a water tunnel on fully wetted and ventilated flows past a family of conical ring wings having a flat plate section geometry. The diameter-chord ratio was varied from one to three, and the total included cone angle was 12 degrees. The fully wetted flows all exhibited separation from the leading edge except for the largest diameter-chord ratio, a result which was in agreement with previous work. The effect of ventilation is to reduce markedly the lift curve slope. Pressure distribution measurements were also made under ventilating conditions for one member of this series. The effect of ventilation over only a portion of the circumference of the ring was also briefly investigated. Large cross forces were developed by such ventilation and some comparisons are made between this method of obtaining control forces and more conventional methods

The small community solar thermal power experiment

Contractors were asked to develop a preferred system concept, to perform sensitivity analyses, and to outline recommended approaches for the follow-on design program of a one-megawatt solar thermal demonstration plant. The systems recommended by the contractors in each of the categories were: (1) McDonnell-Douglas Astronautics Company: Central tower with field of south-facing heliostats; (2) General Electric Company: Field of parabolic dishes with steam piped to a central turbine-generator unit; and (3) Ford Aerospace and Communications Corporation: Field of parabolic dishes with a Stirling cycle engine/generator unit at the focus of each dish. A description of each of the proposed experimental plants is given

A laboratory experiment on simulated wave-riding dolphins

[no abstract

An Experimental Determination of Dynamics Coefficients for the Basic Finner Missile By Means of the Translational Dynamic Balance

Report number E -73.3, published by this Laboratory in June 1957, (Ref. 1) presents certain dynamic coefficients for a model of the Basic Finner Missile (Fig. 1) which had been measured on the angular dynamic balance in the High Speed Water Tunnel at this Laboratory. Several of the desired coefficients, specifically Y_r' coefficient of rotary force derivative Y_v' virtual inertia coefficient (lateral acceleration) N_r' coefficient of rotary moment derivative N_v' virtual moment of inertia coefficient (lateral acceleration) remained undetermined at that time. By employing the translational dynamic balance and its associated internal moment balance, it had been hoped that the missing values for these coefficients would be supplied. Only partial success has been achieved, insofar as numerical results are concerned, at contract expiration time. The coefficient of static force derivative, Y_v', and the virtual inertia coefficient, Y_v', have been measured as part of this investigation. These coefficients have been designated Z_w' and Z_ẇ' in this report to comply with the new direction of model motion with respect to the tunnel coordinate system. Since the first of these, Z_w', had already been determined in the angular dynamic measurements, only the presentation of a value for Z_ẇ' is new. This coefficient had appeared in linear combination with the coefficient of rotary force derivative; hence the latter important quantity also is now uniquely determined. In addition to the force reactions, the moments arising from transverse velocity and acceleration components were also measured, but under conditions of undetermined deflection of the model-spindle assembly. For this reason the moment coefficients have not been presented here, nor have the experimental procedures used to obtain them been included. Instead, a detailed discussion of both the apparatus and the experimental procedures has been planned for reference 3

A Two-Dimensional Working Section for the High-Speed Water Tunnel at the California Institute of Technology

A brief historical account is given of the development of a well-known water tunnel, culminating in a new two-dimensional working section leg. Limitations in the existing facility prompted a scale model study which verified the feasibility of critical features of the new design. Hydrodynamic design features include a novel transition nozzle, and a rectangular working section with walls which can be adjusted to control the longitudinal pressure gradient. Mechanical design features are discussed which are aimed at solving model fabricating and support problems. A brief description of the tunnel operating characteristics includes preliminary measurements and photographs of a base-cavitating wedge hydrofoil in the new working section