Showing papers on "Spar published in 1999"

Hull/Mooring Coupled Dynamic Analysis of a Truss Spar In Time Domain

Abstract: Nonlinear coupled dynamic analysis of a moored truss spar in waves with collinear winds and currents is numerically carried out in the time domain and the results are compared with 1:61 scale experiments and uncoupled analyses. The first- and second-order wave forces, added mass and radiation damping, and wave drift damping are calculated from the hydrodynamics program WINTCOL. The total wave force time series are then generated based on a two-term Volterra series model. The mooring dynamics are solved using the software WINPOST which is based on a generalized-coordinate-based finite element method. The mooring lines are coupled to the platform through generalized springs and dampers. A case study was conducted for the Marlin truss spar with nine taut mooring lines in 3240-ft water depth. The numerical results show that dynamic effects are very important for the present mooring design. The motion and tension spectra of uncoupled analyses with linear spring or nonlinear spring are also compared with those obtained from fully coupled analysis to assess the importance of hull/mooring coupling.

Composite airfoil structures and their forming methods

Abstract: A box-structure airfoil is constructed of a composite material upper skin, a composite material lower skin 12 and a spar. Ribs and an elongate projection are formed integrally on the inner surface of each of the two skins. The upper and lower skins and the spar are simultaneously bonded by an adhesive to form a single structure. Since the ribs and the elongate projection are one-piece formed with each skin, it is possible to reduce the number of principal constituent components. Furthermore, since assembly operation is made by using the adhesive, there is no need for fasteners or the like for assembling. Moreover, the spar is bonded not only to Moreover, because not only a web but also flanges on both sides of the spar are bonded to the respective skins, it is possible to obtain a large strength. According to the invention, it is possible to reduce the number of principal constituent components and that of assembling components of an airfoil, thereby achieving its cost reduction.

Reliability of Floating Structures: Extreme Response and Load Factor Design

Abstract: The reliability of a floating offshore platform against extreme offsets is studied. Methods are illustrated to perform more refined analyses of extreme loads and load effects. These include the effect of nonlinear diffraction under random wave excitation. They permit inclusion of randomness in significant wave height Hs, in peak spectral period, Tp given Hs, and also in the extreme load effect given both Hs and Tp. Numerical effects are demonstrated by applying these methods to a specific floating structure: a deep-draft spar buoy. Design of the spar has been considered in two deep-water sites, one in the Gulf of Mexico and another in the Northern North Sea. Appropriate joint contours of significant wave height and peak period are developed, and these are used to develop load and resistance factors for each of the two sites.

Apparatus for reducing thermal stress in turbine airfoils

Abstract: A turbine airfoil includes at least one spar arrangement having a length less than an associated turbine airfoil length. During operation, the turbine airfoil has an outer skin surface which operates at a substantially higher temperature than that of an internal supporting parted spar arrangement. The parted spar arrangement permits the turbine airfoil outer skin surface to thermally expand between spar arrangements, thus preventing self-constraining thermal stresses from forming within the spar arrangement or the airfoil skin surfaces.

Propeller blade for wind power generator and method for manufacturing it, and main spar for propeller blade and method for manufacturing it

Abstract: PROBLEM TO BE SOLVED: To provide a propeller blade for a wind power generator excellent in durability capable of lightening weight in the case the blade of this kind is very large enlarged and preventing generation of damage and crack even in use for long years. SOLUTION: This propeller blade is constituted by a main spar 13 having a sectional shape of closed curve state to be positioned in a wind pressure center part, front/rear reinforcing members 14, 15 arranged in both sides of this main spar 13, and a reinforced resin-made skin layer 12 wrapping the peripheral total unit of these reinforcing materials 14,15 and this main spar 13, also to be connected in a side of a leading edge 11a which is a side of this blade 10 cutting a wind of a reinforced cloth provided in the skin layer 12.

A Variable Stiffness Spar (VSS) approach for aircraft maneuver enhancement using ASTROS

Abstract: An innovative Variable Stiffness Spar (VSS) approach is studied for the enhancement of aircraft roll performance. In this concept, some of the existing wing spars are replaced by the adaptive-structure VSS to control the stiffness as a function of Mach number and altitude to optimize the roll rate. The VSS mechanism consists a segmented spar having articulated joints at the connections with wing ribs and an electrical actuator capable of rotating the spar. The wing stiffness provided by the spar varies sinusoidally as a fimction of the rotation angle. The objective of the present study is to explore when and how to best apply this concept and assess its payoffs in terms of performance gains. F/A-IS Pre-Roll-Modification (PRM) aircraft is selected as the baseline aircraft for its low torsional wing stiffness and available flight data. The multidisciplinary design optimization software ASTROS* is utilized for performing the analyses in the Mach number range of M=O.S-1.2 at altitudes up to 35000 ft. The VSS stiffness scheduling is designed to maximize the roll rate while satisfying flutter, control surface hinge moment and maximum deflection constraints. Results show that VSS -can amplify the aeroelastic forces and significantly enhance roll performance of aircraft.

Stability Indicating Hplc Method for the Determination of Sparfloxacin (Spar)

Abstract: A rapid, sensitive and stability indicating method for the determination of sparfloxacin (SPAR) by RP - HPLC has been developed on a Merck RP - Select B (5 μm; 12.5 cm x 4.0 mm) column using a mobile phase of water: acetonitrile: triethylamine (80 : 20 : 0.2 v/v) pH of which was adjusted to 2.6 with orthrophosphoric acid. The flow rate was 1 ml / min. and the detection was carried out at 304 nm using Waters 486 variable wavelength detector. The retention time for SPAR was 7.2 min. Linearity range was from 8 - 1000 ppm. The method showed good precision and accuracy when applied to two brands of tablets containing SPAR. In alkaline media SPAR is stable where as it undergoes degradation in acidic and oxidising conditions generating different degradation products the nature of which is required to be established. The proposed method nicely separates the degraded products from SPAR and hence can be used as stability indicating method for the assay of SPAR.

Passenger seat for bus, boat or aircraft

Abstract: The seat has a profiled rail (2) which in its center cross sectional region has an approximately rectangular longitudinally extending box spar (3). Connecting rails (4,5) are connected to both sides of the box spar, the first with a lower side slotted opening (6) for fitting of a support foot, and the second, located above the first, with an upper side slotted opening (7) for fitting of the sitting section (8). A closed outer spar (12) is formed between the connecting rails and one side wall (2A,2B) of the profiled rail. In the corner regions inside at least one of the outer spars and/or the center spar a circular housing channel (13A-D) is formed for the fitting of seat accessories and/or components for attachment to the floor, wall or ceiling.

Attachment system for lateral spar of fence

Abstract: The system comprises a holder shoe (9) which connects at one end to the spar via a bearing sleeve (11). It is capable of being connected at the other end to a main post (3)

Flexible spar for bearingless unit of helicopter main rotor

Abstract: FIELD: aeronautical engineering. SUBSTANCE: spar has six areas in span: area 12 of attachment to hub; first narrowing area 14; second narrowing area 16; pitch area 18; narrowing outer adapter area 20 and area 22 for attachment to tubular structure according to torque of propeller blade. According to this version, spar is made from continuous unidirectional glass fibre at orientation of fibres of 0 deg, unidirectional layers of glass fibre of varying length at orientation of fibres of 0 deg and transversal graphite fibres at orientation of fibres of 45 deg. Spread position of ends of layers (fibres) ensures relatively smooth propagation of impact loads in spar into laminated structures. EFFECT: enhanced ballistic resistance. 3 cl, 4 dwg

Reliable Riser Systems for Spars

Abstract: The Spar concept as a floating vessel is now recognized as a reliable and economic option for developing deepwater offshore hydrocarbon reservoirs. Many of the advantages of the Spar concept are attributed to the variety of riser systems that can be accommodated. This paper presents a discussion of design considerations for the top tensioned and steel catenary risers deployed from a Spar offshore production vessel. Results from extreme event strength analysis, Spar motion and current-induced fatigue analysis, and a riser-to-riser wake interference analysis are presented. Steel catenary risers are presented, including a comparison of results for risers supported by a Spar and a Semi. These analyses demonstrate that simple and reliable riser systems can be designed for use with the Spar platform concept.

Wavelet ridge analysis of nonlinear dynamic spar responses

Abstract: In this work it is demonstrated that the wavelet ridge technique is applicable for tracking the time-dependent frequencies and corresponding amplitude envelopes of natural modes of spar platforms. This preliminary study examines the case where nonlinear mooring line stiffness induces time-dependent frequency behavior for a numerically modeled spar platform. Free decay tests of the spar are performed and the wavelet ridge technique is applied to track the instantaneous frequencies of the surge and pitch modes. Finally, frequency tracking of the natural modes of a spar platform subject to irregular wave loading is considered.

Method for assembling a floating offshore structure

Abstract: An assembly method involves mating the topsides (26) on a floating offshore structure such as a spar hull (10), joining components of the spar hull (10), and/or a combination or variation of these procedures. Generally, the installation is carried out as follows. Once at the mating site, the spar hull component (12) is upended, outfitted with controls and hardware (20) necessary to effectuate controlled submergence of the spar hull component, and submerged to a predetermined depth below the water surface to have a zero water plane area. The second component (26) to be mated with the top of the spar hull component (12) is positioned to float above the submerged spar hull component (12). The draft of the submerged spar hull component (12) is decreased until the two components (12, 26) are fully engaged.

Characterizing the excitation and response of a spar buoy in random seas

Abstract: The spar concept has found many applications in oceanographic science and ocean engineering. These include oceanographic buoys, the FLIP research vessel and the much larger Neptune and Diana spar platforms in the Gulf of Mexico. Based upon these actual designs one can establish the range of wave and platform design parameters to be used in the numerical simulation for this study. Attention in this study is focused upon the characterization of the excitation and the response of spar buoy designs using Slepian modeling techniques. A Slepian model provides conditional estimates of behavior above a specified threshold level. It requires knowledge of the covariance structure of the various underlying processes and its first or second derivatives depending upon the type of model. For a Type I Slepian model, information on the derivatives at the point of threshold crossing and its distribution are needed to complete. On the other hand information on peaks and the distribution of the second derivative at the peaks are needed to develop a Type II Slepian model. Simulated wave data and wave-induced response of a spar buoy are used as the basis for investigating the Slepian models. Estimates of mean behavior after an event are modeled as well as probabilistic behavioral estimates. Earlier researchers have established that for a very few special cases analytical probability distribution functions can be tied to covariance functions. These ideas are examined for practical use and the issue of scaling the analytical results discussed. The practical application of this approach for characterizing the response behavior is discussed by application to oceanographic and larger ocean platform spar buoy problems.

Flat bed body for lorry, especially semi-trailer

Abstract: The flat bed body has a guide tongue (14) is fitted on one end (1.1) of a spar section (1). The tongue protrudes over the spar end, and slides into a guide on a second spar section (2). The tongue further carries a guide pin (15) fitted at a distance away from the tongue end furthest away from the spar. The guide pin is accommodated in an elongated slot (12) formed in a guide rod (11) protruding over the end of the second spar section.

A varl4ble stwfness spar (vss) approach for aircraft maneuver enhancement

Abstract: An innovative Variable Stiffness Spar (VSS) approach is studied for the enhancement of aircraft roll performance. In this concept, some of the existing wing spars are replaced by the adaptive-structure VSS to control the stiffness as a function of Mach number and altitude to optimize the roll rate. The VSS mechanism consists a segmented spar having articulated joints at the connections with wing ribs and an electrical actuator capable of rotating the spar. The wing stiffness provided by the spar varies sinusoidally as a fimction of the rotation angle. The objective of the present study is to explore when and how to best apply this concept and assess its payoffs in terms of performance gains. F/A-IS Pre-Roll-Modification (PRM) aircraft is selected as the baseline aircraft for its low torsional wing stiffness and available flight data. The multidisciplinary design optimization software ASTROS* is utilized for performing the analyses in the Mach number range of M=O.S-1.2 at altitudes up to 35000 ft. The VSS stiffness scheduling is designed to maximize the roll rate while satisfying flutter, control surface hinge moment and maximum deflection constraints. Results show that VSS -can amplify the aeroelastic forces and significantly enhance roll performance of aircraft.