Showing papers on "Fin published in 1978"

Hydrodynamic propulsion by large amplitude oscillation of an airfoil with chordwise flexibility

Abstract: The hydrodynamic forces due to the motion of a flexible foil in a large amplitude curved path in an inviscid incompressible flow are analysed. A parametric study of large amplitude oscillatory propulsion, with special emphasis on the effect of chordwise flexibility of the fin, is presented. This flexibility was found to increase the propulsive efficiency by up to 2% while causing small decreases in the overall thrust, compared with similar motion with rigid foils.

Drag and heat transfer on surfaces with small longitudinal fins

Abstract: An investigation is conducted regarding the drag characteristics of longitudinally ribbed surfaces using various configurations which attempt to confine the turbulent wall bursts to regions of small transverse extent in the initial birth region. The ratio of heat transfer increase to drag increase for the high area ratio rib configurations is determined and the heat transfer efficiency of the present surfaces is compared with data found in the literature. The drag data obtained indicate local 'wetted area skin friction' reductions but due to the increased surface area the planform drag is increased in most instances. There is no indication of drag reduction with the rectangular ribbed models that had sharp leading and fin tip edges. Heat transfer data indicate that several of the triangular grooved models have efficiencies approximately 10 percent higher than that of a smooth flat plate.

Effect of wing fins on lift-generated wakes

Abstract: A theoretical and experimental study has been made of the effect of wing-mounted fins on the vortex wakes of subsonic aircraft. The lateral lift on the fins injects vortices into the wake and redistributes the lift on the wing. The revised wake vorticity then interacts convectively to form a new configuration with low rotational velocities. The theory is used 1) to gain an understanding of wake alleviation by vortex injection and 2) to guide the experimental investigation. Wind-tunnel tests were used to evaluate the alleviation achievable and to find the optimum values for the various fin parameters. It was found that vertical fins mounted on the upper surface of a wing could lower the wake-induced rolling moments on an encountering wing by a factor of 3 or more. The most promising fin configuration found for the Boeing 747 model is a fin positioned 48% outboard from the centerline to the wingtip with a height equal to 0.014 wingspan, a chord equal to 0.085 wingspan, and an 18-deg angle of attack. This fin configuration caused a 10% increase in drag but no lift penalty.

An Efficient Algorithm for Evaluating Arrays of Extended Surface

Abstract: In the consideration of single longitudinal fins of rectangular, trapezoidal, and triangular profile and in arrays of extended surface composed of these fins, it is shown that conditions of heat flow and temperature excess at the fin or array tip induce conditions of heat flow and temperature excess at the fin or array base. In particular, there is a linear transformation between the aforementioned data at the fin tip and the fin base. The conventional fin efficiency is abandoned and single fins or arrays of extended surface are instead characterized by a single important parameter, the heat flow to temperature excess ratio, which is a function only of fin geometry and heat transfer parameters. Algorithms are provided for combining the effects of individual fins in arrays of extended surface. A modification of the procedures developed leads to an exact solution for the double stack with unequal heat distribution at opposite ends, a problem which has heretofore required iterative solution procedures.

Method and apparatus for producing a high fin density extruded heat dissipator

Abstract: A method of manufacturing a high fin density heat dissipator is disclosed in which the dissipator is extruded through a die in a partially cylindrical shape with the elongated fins arranged on the base and extending radially therefrom. The extruded dissipator is straightened under tensile and bumping forces in a manner such that the base assumes a planar shape and the fins become substantially parallel to each other. Apparatus for straightening the extruded dissipator and a die for extruding the same are illustrated and described.

Heat transfer surface and method of manufacture

Abstract: A heat transfer surface for nucleate boiling of liquids is formed on the outer surface of a heat exchanger tube. Helical ridges having two fins each encase the tube. A fin at each ridge is angled toward the adjacent fin on the adjacent ridge forming a gapped cavity therebetween. The method of making the tube includes rolling alternating deep grooves and shallow grooves in the outside surface of the tube and then flaring the fins to form the gapped cavity.

A Simple Method for Analyzing Fin-Line Structures

Abstract: A first-order design theory for fin-line circuits is developed by establishing a correspondence between a fin line and a set of rectanguIar waveguides. The usefulness of the method is demonstrated by applying it to the analysis of a transition from a fin line to a below-cutoff waveguide. Finally, theoretical and experimental results are given for a bandpass filter, which show a fairly good agreement.

Retainer/release mechanism for use on fin stabilized gun fired projectiles

Abstract: The tail section of a fin-stabilized, guided projectile having centrifuga deployed fins is disclosed. A fin retainer and release mechanism engages the projectile fins and holds the fins within the projectile diameter during normal stowage, handling and travel of the projectile down the gun tube. The fin retainer and release mechanism is designed to operate from the forces of gun launch to enable centrifugal deployment of the fins due to projectile rotation after the projectile leaves the gun tube.

Heat exchange enhancement structure

Abstract: A passive heat exchange enhancement structure which operates by free convection includes a flat mounting portion having a plurality of integral fins bent outwardly from one side edge thereof. The mounting portion is securable around a stovepipe, to a flat surface or the like for transferring heat from the pipe through the fins to the surrounding air by rotation-enhanced free convection.

Wind-tunnel investigation at supersonic speeds of a canard-controlled missile with fixed and free-rolling tail fins

Abstract: A wind tunnel investigation was made at free stream Mach numbers from 1.70 to 2.86 to determine the effects of fixed and free rolling tail fin afterbodies on the static longitudinal and lateral aerodynamic characteristics of a cruciform canard controlled missile model. The effect of small canard roll and yaw control deflections was also examined. The results indicate that the fixed and free rolling tail configurations have about the same lift curve slope and longitudinal stability level at low angles of attack. For the free rolling tail configuration, the canards provide conventional roll control with no roll control reversal at low angles of attack. The free rolling tail configuration reduced induced roll due to model roll angle and canard yaw control.

Fin collection and transport apparatus

Abstract: An apparatus for producing, collecting and transporting platelike fins, including fin forming apparatus for simultaneously forming plural fins in adjacent side-by-side relationship from sheet material. The forming apparatus causes the fins to be discharged outwardly in the lengthwise direction thereof. Fin handling are positioned adjacent the forming apparatus for collecting and transporting the fins. The fin handling apparatus includes an endless conveyor having a substantially straight upper reach positioned adjacent the forming apparatus and movable substantially transverse to the direction of movement of the fins as discharged from the forming apparatus. A plurality of elongated fin collectors are fixed to the endless conveyor, being spaced a predetermined distance apart throughout the lengthwise direction of the conveyor, the predetermined distance being equal to the centerline-to-centerline distance between adjacent fins as discharged from the forming apparatus. The collectors projecting outwardly in substantially transverse relationship to the endless conveyor for permitting a plurality of fins to be collected thereon in stacked relationship.

Molded nozzle for rocket motor

Abstract: A lightweight, relatively inexpensive rocket nozzle assembly which is heat resistant, ablative and electrically insulating. The body of the nozzle is molded in fibre reinforced thermosetting resin integrally with a forward metallic retaining ring, a rear metallic fin supporting ring and an electrical contact ring. A graphite throat insert is also provided and helical vanes are integrally molded into the rear portion of the nozzle to effect rotary motion of the exhaust gases. Wrap around fins are secured externally of the nozzle and provided with a retainer ring-shear pin assembly to hold the fins in the closed position for transport, and spring means to deploy the fins after firing and shearing of the shear pins.

Carriers for studs for footwear

Abstract: It is known for sports shoes, particularly golf shoes, to have carriers anchored in their soles for receiving replaceable studs provided with screw-threaded connecting portions. The invention provides a carrier of plastics material having an internally-threaded tubular body open at at least its lower end. The sole is moulded around the preformed carrier. The carrier has retaining formations to anchor it in the sole. The retaining formations comprise outwardly directed fins. That part of each fin adjacent to the body extends lengthwise, while the outer parts are less extensive and are interconnected by integral linking means, such as an annulus. The body portion extends beyond the linking means. In use the sole material envelopes the fins and the linking means.

Experimental investigation of wing fin configurations for alleviation of vortex wakes of aircraft

Abstract: A variety of fin configurations were tested on a model of the Boeing B747 in 40 by 80 foot wind tunnels. The test results confirmed that a reduction in wake rolling moment was brought about by the vortex shed by the fins so that a wide range of designs can be used to achieve wake alleviation. It was also found that the reduction in wake-induced rolling moments was especially sensitive to the location of the smaller fins on the wing and that the penalties in lift and drag can probably be made negligible by proper fin design.

Steering and control fin for surfboard underside - has sector shape pivoted by lever and holding ratchet mechanism which can be built within board

Abstract: The surfboard has a swivelling fin on its underside. This fin can be retracted and it is loaded with a spring holding the fin in an extended position. Ratchet elements are provided for keeping this fin in different tilted positions. The fin is rapidly adjusted for example for varying the course or the speed. On the upper side of the board (1) is arranged the mechanism for arbitrary retraction of the fin (2). This mechanism can be built within the board. The fin (2) is an obtuse angled sector and it is pivoted in the slot (5) which passes through the board. The wall of the slot (5) facing the curved part of passes through the board. The wall of the slot (5) facing the curved part of the fin is also accordingly curved. A lever (6) is connected between the fin top and an actuating arrangement connected to the ratchet mechanism.

Rocket missile extending stabilising fins - have sections extended progressively by springs and releasing charges

Abstract: The rocket propelled missile has stabilising fins extended in starting phase step by step. These fins are extended to match the stabilising requirements on launching. The fins are extended according to a specific programme. The fins are held so that they or their actuators do not project beyond the missile circumference. The stabilising fin sections (1, 2, 3) are extended in stages until the whole articulated fin is extended. Each fin section pivoting axis is parallel to missile longitudinal axis. These axes are spring (17) loaded. A folded fin section is released by pyrotechnical delay element which initiates releasing charge of locking bars (25).

Plate fin coil assembly

Abstract: A method of assembling a plate fin coil by making sheets of single pass single row plate fins from plate fin stock The fins within each sheet are connected by tabular portions and have openings for the receipt of hairpin tubes which form part of the flow circuitry of the heat exchanger A plurality of sheets are arranged in registration so that hairpin tubes may be inserted through the openings within the fins to form partially assembled heat exchanger coil cores The adjacent coil cores may be separated at this point by rupturing the tabular portions connecting the fins within the various sheets or additional process steps may be completed simultaneously upon the entire coil bundle having many coil cores At some time in the plate fin coil assembly process the rows of plate fins are separated into single or multi-row coils by rupturing the tabular portions to form the appropriate row size coil core A coil bundle formed by partially assembling coil cores having sheets of connected fins is also disclosed

Device for extensible fin blade on shell or the like

Abstract: An extensible fin assembly for attachment with the tail section of a gas propelled projectile and the like, wherein a plurality of similarly shaped, hollow fin members are positioned about the periphery of the tail section, with each hollow fin member having a fin blade mounted in a slot formed in the fin member for pivoting between retracted and extended positions relative to the respective fin members.

Method for increasing the fin density of a heat exchanger

Abstract: An apparatus (40) and method for increasing the fin density of a serpentine sheet (10) having a plurality of fins (14a, 14b, 14c), each fin having two sides (16, 18) coupled together at one end (20) with a space (22) between the sides. Blocks (30, 32) having receptacles (30a, 32a) for receiving the ends (20, 24) of one side (16) of a fin (14a) and being near opposite surfaces (A, B) of the sheet (10) are moved vertically into contact with such ends. Simultaneously, blades (34, 36), being near the opposite surfaces (A, B) of the sheet (10) are moved vertically into position at the other side (18) of the fin (14a). Then, the blades (34, 36) are moved horizontally towards the blocks (30, 32), which are now held stationary, to compress the fin (14a) a predetermined amount by moving the other fin side towards the one fin side. The blocks and blades are then withdrawn from the sheet to move another fin (14b) into position for another compressing operation. The apparatus (40) includes a mechanism (70) to prevent the sheet from fishtailing when a fin is being compressed.

An experimental wind-tunnel investigation of a ram-air-spoiler roll-control device on a forward-control missile at supersonic speeds

Abstract: A parametric experimental wind-tunnel investigation was made at supersonic Mach numbers to provide design data on a ram-air-spoiler roll-control device that is to be used on forward-control cruciform missile configurations. The results indicate that the ram-air-spoiler tail fin is an effective roll-control device and that roll control is generally constant with vehicle attitude and Mach number unless direct canard and/or forebody shock impingement occurs. The addition of the ram-air-spoiler tail fins resulted in only small changes in aerodynamic-center location. For the ram-air-spoiler configuration tested, there are large axial force coefficient effects associated with the increased fin thickness and ram-air momentum loss.

A linearized analysis for longitudinal fins with radiative and convective exchange

Abstract: The radiative exchange between fins may provide a signif- icant contribution to the energy balance for free-convection

Method for forming a serrated-fin tube

Abstract: A method of forming serrated-fin tubing to improve heat transfer performance is disclosed. The method comprises providing a round metal tube having an annular peripheral wall and integral inner metal fins projecting from such wall parallel to each other, and inserting a tool into said tube for interrupting the continuity of such fins so as to promote turbulence in the boundary layer of the flow in the tube thus improving heat transfer performance.

Formed coil assembly

Abstract: Apparatus and a method of manufacturing a formed coil having multiple single row coil cores of varying lengths. Sheets of fins are cut from plate fin stock such that the fins within each sheet are connected to each other by rupturable tabular portions. The sheets of fins are then arranged in registration such that openings within the fins for the receipt of tubes are aligned and tubular members or hairpins may be inserted within the fins to form part of the fluid flow circuit of the coil. Since the hairpins for adjacent coil rows are of different lengths, when the multiple row coil core is bent each coil row is formed about a separate radius curvature so that the formed coil will be in the desired configuration. Prior to bending, the hairpins are expanded to form a heat transfer bond with the fins, the expansion process acting to rupture the tabular portions connecting the fins such that the fins on the hairpins become separately spaced along each hairpin. Thereafter the coil core is bent to the desired formed coil configuration wherein the fins are spaced distinctly along each coil row notwithstanding that the fins were originally from the same sheet and connected to each other by the tabular portions.

An Aerodynamic Coefficient Prediction Technique for Slender Bodies with Low Aspect Ratio Fins at Mach Numbers from 0.6 to 3.0 and Angles of Attack from 0 to 180 Degrees

Abstract: : In order to extend the state-of-the-art aerodynamic coefficient prediction methodology at high angles of attack, a semi-empirical prediction technique has been developed for the prediction of normal force and pitching moment coefficients for slender body alone and slender body plus fin configurations. Additionally, installed fin normal force, root bending and hinge moment coefficients are calculated. The semi-empirical prediction technique is valid for slender bodies with low aspect ratio fins at Mach numbers from 0.6 to 3.0 and angles of attack from 0 to 180 degrees. The range of validity of the prediction technique for the low aspect ratio fins is: aspect ration from 0.5 to 2.0; taper ratio from 0 to 1.0 and span ratio from 0.3 to 0.5. Wind tunnel testing was accomplished in order to provide the data base from which the prediction technique was derived. The data base provides the first parametric set of data at angles of attack, from 0 to 180 degrees, and not only provided the base for the semi-empirical prediction technique developed herein, but will provide a standard of comparison for high angle of attack prediction methodology developed in the future. (Author)

Forming paper using a curved fin to facilitate web transfer

Abstract: A fin apparatus is transversely disposed beneath a wire to create a wave of positive pressure thereunder to urge a formed web off of the wire. The fin surface, in transverse cross-section, is a smooth convex curve that diminishes in radius toward the downstream end of the fin.

Attaching fin material to a heat transfer or like surface

Abstract: A heat transfer or like surface has fins attached thereto in a disconnected, spaced apart, substantially parallel relation, the fins standing upright on edge on the surface. A method of producing and attaching the fins has particular utility in the presence of a curved mounting surface, the fins being formed to allow them to be bent in conformance with the curved surface. Apparatus including an adjustable roller mechanism and a braze fixture are useful in forming and attaching the fin material.

Control fin for sailing surfboard - is made with contoured cut=out for rapid response and reduced drag

Abstract: The control fin for the windsurfer has the centre cut out into a profiled hole (3) to reduce the drag and lighten the structure. This provides very good steering response while allowing a large grip on the water. The fin provides the effect of a large fin at high speeds, while providing the improved lateral steering response of a small fin at lower speeds. The edges of the fin are made from stremlined cross section beading for a simple construction. The fin has a curved profile.