Effects of Heave Plate on the Hydrodynamic Behaviors of Cell Spar Platform

2006 ◽  
Author(s):  
Fan Zhang ◽  
Jianmin Yang ◽  
Runpei Li ◽  
Zhiqiang Hu
Keyword(s):  
Added Mass ◽  
Wave Loading ◽  
Spar Platform ◽  
Perforated Plates ◽  
Damping Coefficients ◽  
Numerical Predictions ◽  
Different Types ◽  
A Cell ◽  
Heave Plate ◽  
Hydrodynamic Behaviors

This paper presents an experimental study on the effect of heave plates on the hydrodynamic performances of a cell spar platform. A variation of the cell spar concept, whose hard tank still consist of several cylinders (cells) with the same diameter and length, but the lower part is fitted with a truss section and several heave plates, is modeled and tested. As the effectiveness of heave plates is crucial to the heave performance, different types of heave plates are fitted to the truss structure, varying from the number and spacing to the form, such as perforated plates, to investigate various design aspects of the plates. Experimental results and numerical predictions for the responses of the spar to the wave loading, as well as loads and added mass and damping coefficients on the heave plates are presented.

Experimental Investigations on the Hydrodynamic Characteristics of Heave Plate

2013 ◽  
Author(s):  
Xinliang Tian ◽  
Jianmin Yang ◽  
Xin Li ◽  
Tao Peng
Keyword(s):  
Experimental Study ◽  
Added Mass ◽  
Thickness Ratio ◽  
Hydrodynamic Characteristics ◽  
Experimental Investigations ◽  
Damping Coefficients ◽  
Plate Shape ◽  
Motion Performance ◽  
Heave Plate ◽  
Heave Motion

Heave plates are installed in Spar platforms to improve the heave motion performance of the platforms. The heave plates not only increase the equivalent added mass of the platform but also provide extra damping to the system. This article presents an experimental study on the hydrodynamic characteristics of an isolate heave plate. The plate is forced to oscillate in the water at rest. The added mass and damping of the plate are used to represent its hydrodynamic characteristics. Influences of the thickness ratio, the plate shape, the corner radius and the porosity on the added mass and the damping coefficients of the heave plate are evaluated at various KC and β numbers.

Global Performance of the Perdido Spar in Waves, Wind and Current: Numerical Predictions and Comparison With Experiments

2010 ◽  
Author(s):  
Stergios Liapis ◽  
Shankar Bhat ◽  
Constantine Caracostis ◽  
Carl Webb ◽  
Curtis Lohr
Keyword(s):  
Gulf Of Mexico ◽  
Floating Body ◽  
Global Motion ◽  
Spar Platform ◽  
Mooring Lines ◽  
Numerical Predictions ◽  
Pumping Mode ◽  
Heave Plate ◽  
The Impact ◽  
Actual Geometry

In recent years, spars have become a preferred industry solution for certain offshore deepwater developments. Perdido is the first spar platform to be operated by Shell. The Perdido spar has been recently installed in the ultradeepwater Gulf of Mexico Alaminos Canyon and is scheduled for first oil in 2010. This Direct Vertical Access (DVA) spar will operate at a water depth of 7,825′ and will be the deepest spar production and drilling facility in the world. Numerical predictions of the spar global motions in waves, wind and current are presented in this paper. Motivation for this study comes from two facts: 1. Each spar platform design is unique in terms of its size, number and geometry of heave plates, riser system and mooring system. 2. Metocean design criteria have been increased in view of the recent hurricanes. Model tests of the Perdido spar were conducted at MARIN at a scale of 1:59.94. In these experiments, several Gulf of Mexico (GOM) wave, current and wind environments were considered. The six-degree-of-freedom motions, deck accelerations, air gap, as well as the loads on the heave plates, mooring lines and risers were measured. In this paper, global motion predictions of the Perdido spar are given using Shell’s in-house COSMOS/ WAMIT suite of programs. Extensive comparisons between the numerical predictions and the experimental results were undertaken. In all cases, the comparisons are very good. In order to include heave viscous loads and damping, special line members were included at the bottom of the hard tank, the bottom of the soft tank and each heave plate, in addition to standard line members used to describe the truss. These special members contribute heave viscous loads with drag coefficients selected from the Perdido experiments. Several heave plate configurations were considered to systematically study the impact of heave plates on the spar global motions. The influence of the heave plate geometry on the heave added mass and on the global motions was derived using WAMIT. The strakes’ actual geometry was also included in the WAMIT diffraction analysis. Most of the moonpool area at the bottom of the Perdido hard tank is closed. As a result, the pumping mode was not excited during the experiments. However, numerical simulations with WAMIT showed a sharp peak at the “pumping mode” resonant frequency. This peak was suppressed by introducing a second floating body that capped the moonpool at the water surface. Based on these learnings, recommendations for global motion modeling are presented in this paper.

Numerical Investigation of the Flow Features Around Heave Plates Oscillating Close to a Free Surface or Seabed

2014 ◽  
Author(s):  
Carlos A. Garrido-Mendoza ◽  
K. P. Thiagarajan ◽  
Antonio Souto-Iglesias ◽  
Benjamin Bouscasse ◽  
Andrea Colagrossi
Keyword(s):  
Free Surface ◽  
Vortex Shedding ◽  
Flow Characteristics ◽  
Added Mass ◽  
Offshore Structures ◽  
Vortical Structures ◽  
Damping Coefficients ◽  
Solid Disk ◽  
Flow Features ◽  
Heave Plate

Performance of heave plates used in offshore structures is strongly influenced by their added mass and damping, which are affected by proximity to a boundary. A previous paper by the authors presented numerical simulations of the flow around a circular solid disk oscillating at varying elevations from seabed [1]. The force calculated was used to evaluate the added mass and damping coefficients for the disk. The simulations suggest that as the structure moves closer to the seabed the added mass and damping coefficients (Ca and Cb) increases continuously. In order to understand the physics behind the added mass and damping trends, when a heave plate is moving near a seabed or closer to the free surface, the flow characteristics around the heave plate are examined numerically in this paper. Flow around oscillating disks is dominated by generation and development of phase-dependent vortical structures, characterized by the KC number and the distance from the seabed or free surface to the heave plate. Numerical calculations presented in this paper have comprised the qualitative analysis of the vortex shedding and the investigation of the links between such vortex shedding and, on one hand the damping coefficient, and on the other hand, pairing mechanisms such as the shedding angle.

Glycans in scaffold design in tissue reconstruction

2021 ◽  
pp. 088391152199784
Author(s):  
Nipun Jain ◽  
Shashi Singh
Keyword(s):  
Cell Attachment ◽  
Low Cost ◽  
Growth Conditions ◽  
Downstream Signaling ◽  
Cell Carrier ◽  
Wide Range ◽  
Proliferation And Differentiation ◽  
Different Types ◽  
Tissue Reconstruction ◽  
A Cell

Development of an artificial tissue by tissue engineering is witnessed to be one of the long lasting clarified solutions for the damaged tissue function restoration. To accomplish this, a scaffold is designed as a cell carrier in which the extracellular matrix (ECM) performs a prominent task of controlling the inoculated cell’s destiny. ECM composition, topography and mechanical properties lead to different types of interactions between cells and ECM components that trigger an assortment of cellular reactions via diverse sensing mechanisms and downstream signaling pathways. The polysaccharides in the form of proteoglycans and glycoproteins yield better outcomes when included in the designed matrices. Glycosaminoglycan (GAG) chains present on proteoglycans show a wide range of operations such as sequestering of critical effector morphogens which encourage proficient nutrient contribution toward the growing stem cells for their development and endurance. In this review we discuss how the glycosylation aspects are of considerable importance in everyday housekeeping functions of a cell especially when placed in a controlled environment under ideal growth conditions. Hydrogels made from these GAG chains have been used extensively as a resorbable material that mimics the natural ECM functions for an efficient control over cell attachment, permeability, viability, proliferation, and differentiation processes. Also the incorporation of non-mammalian polysaccharides can elicit specific receptor responses which authorize the creation of numerous vigorous frameworks while prolonging the low cost and immunogenicity of the substance.

scholarly journals Hydrodynamic Forces Exerting on an Oscillating Cylinder under Translational Motion in Water Covered by Compressed Ice

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 822
Author(s):  
Yury Stepanyants ◽  
Izolda Sturova
Keyword(s):  
Lift Force ◽  
Wave Motion ◽  
Translational Motion ◽  
Added Mass ◽  
Hydrodynamic Forces ◽  
Wave Resistance ◽  
Translational Velocity ◽  
Damping Coefficients ◽  
Incompressible Ideal Fluid ◽  
Theoretical Results

This paper presents the calculation of the hydrodynamic forces exerted on an oscillating circular cylinder when it moves perpendicular to its axis in infinitely deep water covered by compressed ice. The cylinder can oscillate both horizontally and vertically in the course of its translational motion. In the linear approximation, a solution is found for the steady wave motion generated by the cylinder within the hydrodynamic set of equations for the incompressible ideal fluid. It is shown that, depending on the rate of ice compression, both normal and anomalous dispersion can occur in the system. In the latter case, the group velocity can be opposite to the phase velocity in a certain range of wavenumbers. The dependences of the hydrodynamic loads exerted on the cylinder (the added mass, damping coefficients, wave resistance and lift force) on the translational velocity and frequency of oscillation were studied. It was shown that there is a possibility of the appearance of negative values for the damping coefficients at the relatively big cylinder velocity; then, the wave resistance decreases with the increase in cylinder velocity. The theoretical results were underpinned by the numerical calculations for the real parameters of ice and cylinder motion.

scholarly journals Numerical Evaluation of a Light-Gas Gun Facility for Impact Test

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
C. Rahner ◽  
H. A. Al-Qureshi ◽  
D. Stainer ◽  
D. Hotza ◽  
M. C. Fredel
Keyword(s):  
High Velocity ◽  
Numerical Evaluation ◽  
Impact Test ◽  
Experimental Tests ◽  
Reservoir Pressure ◽  
One Stage ◽  
Gas Gun ◽  
Numerical Predictions ◽  
High Velocity Impacts ◽  
Different Types

Experimental tests which match the application conditions might be used to properly evaluate materials for specific applications. High velocity impacts can be simulated using light-gas gun facilities, which come in different types and complexities. In this work different setups for a one-stage light-gas gun facility have been numerically analyzed in order to evaluate their suitability for testing materials and composites used as armor protection. A maximal barrel length of 6 m and a maximal reservoir pressure of a standard industrial gas bottle (20 MPa) were chosen as limitations. The numerical predictions show that it is not possible to accelerate the projectile directly to the desired velocity with nitrogen, helium, or hydrogen as propellant gas. When using a sabot corresponding to a higher bore diameter, the necessary velocity is achievable with helium and hydrogen gases.

Measured Static and Rotordynamic Coefficient Results for a Rocker-Pivot, Tilting-Pad Bearing With 50 and 60% Offsets

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Chris D. Kulhanek ◽  
Dara W. Childs
Keyword(s):  
Dynamic Stiffness ◽  
Mass Matrix ◽  
Excitation Frequency ◽  
Quadratic Function ◽  
Added Mass ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Tilting Pad ◽  
Frequency Independent ◽  
Direct Stiffness

Static and rotordynamic coefficients are measured for a rocker-pivot, tilting-pad journal bearing (TPJB) with 50 and 60% offset pads in a load-between-pad (LBP) configuration. The bearing uses leading-edge-groove direct lubrication and has the following characteristics: 5-pads, 101.6 mm (4.0 in) nominal diameter,0.0814 -0.0837 mm (0.0032–0.0033 in) radial bearing clearance, 0.25 to 0.27 preload, and 60.325 mm (2.375 in) axial pad length. Tests were performed on a floating bearing test rig with unit loads from 0 to 3101 kPa (450 psi) and speeds from 7 to 16 krpm. Dynamic tests were conducted over a range of frequencies (20 to 320 Hz) to obtain complex dynamic stiffness coefficients as functions of excitation frequency. For most test conditions, the real dynamic stiffness functions were well fitted with a quadratic function with respect to frequency. This curve fit allowed for the stiffness frequency dependency to be captured by including an added mass matrix [M] to a conventional [K][C] model, yielding a frequency independent [K][C][M] model. The imaginary dynamic stiffness coefficients increased linearly with frequency, producing frequency-independent direct damping coefficients. Direct stiffness coefficients were larger for the 60% offset bearing at light unit loads. At high loads, the 50% offset configuration had a larger stiffness in the loaded direction, while the unloaded direct stiffness was approximately the same for both pivot offsets. Cross-coupled stiffness coefficients were positive and significantly smaller than direct stiffness coefficients. Negative direct added-mass coefficients were obtained for both offsets, especially in the unloaded direction. Cross-coupled added-mass coefficients are generally positive and of the same sign. Direct damping coefficients were mostly independent of load and speed, showing no appreciable difference between pivot offsets. Cross-coupled damping coefficients had the same sign and were much smaller than direct coefficients. Measured static eccentricities suggested cross coupling stiffness exists for both pivot offsets, agreeing with dynamic measurements. Static stiffness measurements showed good agreement with the loaded, direct dynamic stiffness coefficients.

On the Radiation and Diffraction of Surface Waves by Submerged Spheroids

1989 ◽  
Vol 33 (02) ◽  
pp. 84-92
Author(s):  
G. X. Wu ◽  
R. Eatock Taylor
Keyword(s):  
Degrees Of Freedom ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Added Mass ◽  
Wave Radiation ◽  
Legendre Functions ◽  
Incoming Wave ◽  
Six Degrees Of Freedom ◽  
Damping Coefficients ◽  
Exciting Forces

The problem of wave radiation and diffraction by submerged spheroids is analyzed using linearized three-dimensional potential-flow theory. The solution is obtained by expanding the velocity potential into a series of Legendre functions in a spheroidal coordinate system. Tabulated and graphical results are provided for added mass and damping coefficients of various spheroids undergoing motions in six degrees of freedom. Graphs are also provided for exciting forces and moments corresponding to a range of incoming wave angles.

Ship Motions in Shallow Water

1970 ◽  
Vol 14 (04) ◽  
pp. 317-328 ◽  
Author(s):  
E. O. Tuck
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Incident Wave ◽  
Degrees Of Freedom ◽  
Added Mass ◽  
Exciting Force ◽  
Ship Motions ◽  
Wave System ◽  
Six Degrees Of Freedom ◽  
Damping Coefficients

The problem discussed concerns small motions of a ship, in all six degrees of freedom, but at zero speed of advance, due to an incident wave system in shallow water of depth comparable with the ship's draft. The problem is completely formulated for an arbitrary ship, and is partially solved for the case when the ship is slender and the wavelength much greater than the water depth. Sample numerical computations of heave, pitch, and sway added mass and damping coefficients and the sway exciting force are presented.

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