Comparison of finite element and lumped parameter methods for oceanic cables

Leonard, John W.; Nath, John H.

doi:10.1016/0141-0296(81)90024-9

Cited by 47 publications

(16 citation statements)

References 5 publications

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“…In the lumped mass model, mooring line is spatial discretized into lumped mass nodes which are connected by massless springs. Discretization in this way simplifies the problem and provides numerical efficiency, which has been performed in many other studies (Chai et al, 2002;Huang, 1994;Leonard and Nath, 1981;Low and Langley, 2006;Orcina, 2009). Furthermore, each item in the lumped mass model has a clear physical meaning, which facilitates the inclusion of the soil-chain interactions.…”

Section: Introductionmentioning

confidence: 95%

Dynamics of a taut mooring line accounting for the embedded anchor chains

2016

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Section: Introductionmentioning

confidence: 95%

Dynamics of a taut mooring line accounting for the embedded anchor chains

2016

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“…M T , the moment due to cable tension, is derived from Equation 3 as follows: First, the relative position of the cable attach point, a , with respect to the glider center of gravity is expressed in body-fixed coordinates as shown in Equation 4. (4) Next, the moment about the glider center of gravity due to cable tension is computed using a vector cross product. The result is given in Equation 5.…”

Section: =0 = 7 -Lc +Ds +W-jsmentioning

confidence: 99%

Longitudinal equilibrium solutions for a towed aircraft and tow cable

Norris

Andrisani

Coefficient³

2001

AIAA Atmospheric Flight Mechanics Conference and Exhibit

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A series of flight tests involving a modified F-106 fighter aircraft towed behind a C-141 cargo aircraft was completed at NASA's Dry den Flight Research Center in February 1998, under the title of the Eclipse Project. 1 This paper presents a numerical approach used to compute tow cable shapes and altitude offsets in the vertical plane for the towed configuration as a function of trimmed flight condition. Each solution was generated in two distinct steps. First the trim condition of the towed aircraft was found using an existing aerodynamic database. Correction factors for this database were extracted from data measured during untowed steady-state test glides. The second step was numerical integration of the differential equations governing cable shape in the presence of distributed aerodynamic and gravitational loads. The aircraft trim condition from the first part of the solution provided the initial conditions needed for the second part. Computational results for nominal test conditions are compared with flight test measurements of aircraft altitude offset, angle of attack, pitch angle, cable pitch angle, and cable tension. Altitude offsets were measured using highly accurate differential GPS receivers. Families of computed cable shapes are presented as a function of elevator deflection and flight path angle.

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“…Lumped parameter derivations must necessarily place all mass at discrete nodes and then write the governing equations. Finite element methods can derive the governing equations using an integration of the mass over the entire element, thus leading to the "consistent" mass formulation [62]. The starting point for finite element methods as applied to the marine cable problem is typically a discrete element, much like the lumped parameter methods.…”

Section: Spatial Discretizationmentioning

confidence: 99%

The dynamics of geometrically compliant mooring systems

Gobat¹

2000

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Geometrically compliant mooring systems that change their shape to accommodate deformations are common in oceanographic and offshore energy production applications. Because of the inherent geometric nonlinearities, analyses of such systems typically require the use of a sophisticated numerical model. This thesis describes one such model and uses that model along with experimental results to develop simpler forms for understanding the dynamic response of geometrically compliant moorings.The numerical program combines the box method spatial discretization with the generalized-α method for temporal integration. Compared to other schemes commonly employed for the temporal integration of the cable dynamics equations, including box method, trapezoidal rule, backward differences, and Newmark's method, the generalized-α algorithm has the advantages of second-order accuracy, controllable numerical dissipation, and improved stability when applied to the nonlinear problem. The numerical program is validated using results from laboratory and field experiments.Field experiment and numerical results are used to develop a simple model for dynamic tension response to vertical motion in geometrically compliant moorings. As part of that development, the role of inertia, drag, and stiffness in the tension response are explored. For most moorings, the response is dominated by inertial and drag effects. The simple model uses just two terms to accurately capture these effects, including the coupling between inertia and drag. The separability of the responses to vertical and horizontal motions is demonstrated and a preliminary model for the response to horizontal motions is presented.The interaction of the mooring line with the sea floor in catenary moorings is considered. Using video and tension data from laboratory experiments, the tension shock condition at the touchdown point and its implications are observed for the first time. The lateral motion of line along the bottom associated with a shock during unloading may be a significant cause of chain wear in the touchdown region. Results from the laboratory experiments are also used to demonstrate the suitability of the elastic foundation approach to modeling sea floor interaction in numerical programs.

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Comparison of finite element and lumped parameter methods for oceanic cables

Cited by 47 publications

References 5 publications

Dynamics of a taut mooring line accounting for the embedded anchor chains

Dynamics of a taut mooring line accounting for the embedded anchor chains

Longitudinal equilibrium solutions for a towed aircraft and tow cable

The dynamics of geometrically compliant mooring systems

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