OrcaFlex Manual - Orcina

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System Modelling: Data and Results, Lines Studless Studlink OD 1.80D 1.89D ID 0 0 Contact diameter 3.35D 3.6D Mass/Length 19.9D 2 21.9D 2 te/m for D in m Axial stiffness 0.854x10 8 D 2 1.01x10 8 D 2 kN for D in m Bend stiffness 0 0 Limit Compression yes yes Normal drag coefficient 1.0 1.0 Normal drag diameter 2.10D 2.26D Axial drag coefficient 0.4 0.4 Axial drag diameter 0.54D/π 0.60D/π Normal added mass coefficient 1.0 1.0 Axial added mass coefficient 0.08 0.07 Stress diameters '~' '~' Allowable stress '~' '~' Friction coefficient typically 0.4 - 0.8 depending on the seabed Reference Puech A, 1984. Geometry D = Nominal Diameter 3.35D (studless) 3.6D (studlink) Figure: Chain Geometry Data AEDGE 362 AFACE 6D 3.35D (studless) 3.6D (studlink) w Chains are widely used in a variety of offshore applications, most obviously in mooring. The Line Type Wizard helps derive a line type to represent a chain based on the following input data. Bar Diameter The diameter of the metal bar that forms the links. Link Type Can be either studlink or studless.
w Mechanical Properties Catalogue Data 363 System Modelling: Data and Results, Lines When modelling mooring chain the Line Type Wizard aims to derive data for a line type whose characteristics are equivalent to that of a chain. Warning: The values generated by the Wizard are approximate only and are intended as first estimates for preliminary use. They are offered in good faith, but due to variations in properties between products they cannot be guaranteed. Please use suppliers' data where this is available. In deriving these some of the available catalogue data will prove useful and we outline here the relevant aspects. The Mooring Chain figure shows the geometry of a pair of chain links. The values are given in terms of the nominal bar diameter of the chain (D), assumed to be in metres, and are given for both a studless chain and, where different, for a studlink chain. The geometry given in the figure is based on catalogue data available from the chain manufacturer Scana Ramnas (1990 & 1995), as is the following expression for mass per metre: Mass per metre (M) = 19.9D 2 te/m (studless) or 21.9D 2 te/m (studlink). The catalogue also gives the following value for the Young's Modulus of the chain that has been deduced from stressstrain relationships in which the cross-sectional area of two bars is taken to be the load bearing area: E = 5.44 x 10 7 kN/m 2 (studless) or 6.40 x 10 7 kN/m 2 (studlink). Minimum Breaking Loads For information, the properties window displays minimum breaking loads that depend on the nominal diameter and chain grade. They are derived using the following relationship, which was obtained from the manufacturer's catalogue: Min Breaking Load = c.D 2 .(44 - 80D) kN where c is a grade-dependent constant, given in the catalogue data as Grade 2: 1.37e4, Grade 3: 1.96e4, ORQ: 2.11e4, R4 - 2.74e4. Studless and Studlink chains with the same nominal diameters are stated to withstand the same break- and proofloads. Derived Data It will be useful to know the centreline length of bar needed to make a single link. We can obtain this by noting that, for a long chain, there is one chain link every 4D length of chain. Hence, the number of links per metre of chain is N = 1/(4D), and thus for a single link: Mass per link = M / N = 79.6D 3 te (studless) or 87 6D 3 te (studlink). Assuming that the chain is made from steel, and using ρs as density of steel (= 7.8 te/m 3 ), this then leads to: Volume per link = (M / N) / ρs = 10.2D 3 m 3 (studless) or 11.2D 3 m 3 (studlink). But, by considering the geometry of a link, we also have Volume = L . πD 2 /4, where L is centreline length of bar needed to make a single link (including the stud in the case of the studlink chain). Hence: L = Volume / (πD 2 /4) = 13.0D m (studless) or 14.3D m (studlink). Outer, Inner and Contact Diameter The Line Type Wizard sets up diameters for a chain as follows: Outer Diameter The effective outer diameter of the equivalent line is obtained using a similar argument to that deployed in obtaining the overall length of bar per link. Firstly, note that the volume per metre can be expressed as both: and also as Volume per metre = M/ρs Volume per metre = πOD 2 /4
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w Orcina Ltd. Daltongate Ulverston
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Contents 4 w 3.4 Libraries 40 3.4.1
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Contents 6 w 5.6 Dynamic Analysis 1
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Contents 8 w 6.5.23 Wave Scatter Co
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Contents 10 w 8.12 Results 444 8.13
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Introduction, Installing OrcaFlex
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Introduction, Parallel Processing M
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Introduction, References and Links
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Introduction, References and Links
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w 2 TUTORIAL 2.1 GETTING STARTED 21
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w 23 Tutorial, Dynamic Analysis sha
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w 3 USER INTERFACE 3.1 INTRODUCTION
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w Simulation Paused 27 User Interfa
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w Keys on Main Window New model Ope
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w Rotate viewpoint left (decrement
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w General: StaticsMethod: Whole Sys
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w A text data file saved by OrcaFle
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w 37 User Interface, Model Browser
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w Cut/Copy Cut or Copy the selected
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w 3.4.1 Using Libraries 41 User Int
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w 43 User Interface, Libraries Once
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w 3.5.1 File Menu New Deletes all o
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w New Vessel New Line New 6D Buoy N
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w 3.5.5 View Menu Change Graphics M
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w Preferences 51 User Interface, Me
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w 53 User Interface, 3D Views 3D Vi
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w 55 User Interface, 3D Views � D
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w 57 User Interface, 3D Views a lin
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w 59 User Interface, 3D Views � F
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w Replay Period 61 User Interface,
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w Frame interval in real time 63 Us
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w Numeric 65 User Interface, Data F
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w � For lines you must specify th
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w 69 User Interface, Results this i
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w 71 User Interface, Results Let th
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w 73 User Interface, Results remain
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w Results 75 User Interface, Result
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w Replays 77 User Interface, Graphs
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w Axes 79 User Interface, Spreadshe
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w Command Line Parameters 81 User I
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w Wire Frame Graphics Codec 83 User
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Automation, Batch Processing Multi-
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Automation, Batch Processing 88 w N
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Automation, Batch Processing Assign
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Automation, Batch Processing Line T
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Automation, Batch Processing SHEAR7
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Automation, Batch Processing PolarT
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Automation, Batch Processing Figure
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Automation, Text Data Files Data in
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Automation, Text Data Files Selecte
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Automation, Text Data Files SHEAR7L
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Automation, Text Data Files 4.3.2 A
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Automation, Post-processing 108 w F
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Automation, Post-processing 110 w N
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Automation, Post-processing Referen
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Automation, Post-processing Command
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Automation, Post-processing Figure:
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w 5 THEORY 5.1 COORDINATE SYSTEMS 1
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w 125 Theory, Object Connections Di
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w 127 Theory, Static Analysis Final
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w 129 Theory, Static Analysis metho
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w 131 Theory, Dynamic Analysis for
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w Static Starting Position Simulati
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w 135 Theory, Friction Theory The n
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w where μ = magnitude of the vecto
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w 139 Theory, Extreme Value Statist
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w where σ = GPD scale parameter ξ
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w 143 Theory, Environment Theory Th
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w where Pu(z) = Nc(z/D)su(z)D Pu-su
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w 147 Theory, Environment Theory
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w Repenetration Offset After Uplift
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w 151 Theory, Environment Theory sp
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w Extrapolation Stretching 153 Theo
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w 155 Theory, Environment Theory st
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w 157 Theory, Vessel Theory individ
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w 159 Theory, Vessel Theory RAOs ca
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w 161 Theory, Vessel Theory Notes:
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w 163 Theory, Vessel Theory ω is t
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w surge/sway/heave M M.L roll/pitch
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w 167 Theory, Vessel Theory that co
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w 169 Theory, Vessel Theory separat
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w 171 Theory, Vessel Theory At this
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w Segment 1 Segment 2 Segment 3 Act
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w 175 Theory, Line Theory � If to
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w where component of M2 in the Sx2
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w The hysteresis model is described
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w � (90,90,90) sets Ex along -GX,
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w = v1 + p' + ω×p Therefore its a
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w y End A Stress ID z Stress OD O S
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w 5.12.16 Hydrodynamic and Aerodyna
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w 189 Theory, Line Theory Another w
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w Drag Chain Seabed Interaction 191
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w 193 Theory, Line Theory OrcaFlex
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w 195 Theory, 6D Buoy Theory clashi
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w 197 Theory, 6D Buoy Theory For Lu
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w 199 Theory, 6D Buoy Theory (due t
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w 201 Theory, 6D Buoy Theory Note:
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w α is the angle between the relat
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w 5.13.6 Contact Forces Contact For
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w Dynamic Analysis 207 Theory, Winc
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w 209 Theory, Shape Theory Finally,
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Modal Analysis, Theory 432 w For si
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Modal Analysis, Theory 434 w This h
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Fatigue Analysis, Commands 436 w Fo
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Fatigue Analysis, Load Cases Data f
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Fatigue Analysis, Analysis Data 442
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Fatigue Analysis, Integration Param
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Fatigue Analysis, How Damage is Cal
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OrcaFlex Manual - Orcina

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