Defaults and Parameters

To allow flexibility in using MOSES, the user is free to set many of his own defaults. When defining a model or altering its definition, there are a number of things which normally have the same value. In other words, many things have a "default" value. The default values used are defined with the command:

     &DEFAULT, -OPTIONS

Two basic options:

     -SAVE

     -REMEMBER

allow the user to "push and pop" the default stack. Suppose that one wishes to alter some of the defaults temporarily and then return to the initial set. This can be accomplished by issuing &DEFAULT -SAVE which "saves" the current settings on the default stack. Now, one can alter the defaults at will, and, upon issuing &DEFAULT -REMEMBER, the initial set will again become active.

Most of the options here are again used on some command. As a result, the documentation here may be brief so that a more detailed discussion may follow. If an option is used when one of these commands is issued, then values specified by the option will be used. Otherwise, the default (the values specified via &DEFAULT) will be used.

Defaults are also used to define the "current" coordinate system and frame of reference for defining: nodes, interest points, and diffraction vertices. The options defining these defaults are:

     -RECT

     -CYLINDER

     -SPHERICAL

     -LOCATION, XO, YO, ZO, RX, RY, RZ

     -LOCATION, XO, YO, ZO, *PT(1), *PT(2), *PT(3), *PT(4)

The first three options define the meaning of the three numbers which define the local coordinates. If -RECT is the last of these specified, then the numbers are rectangular coordinates in the current frame. Likewise they can be either cylindrical if one specifies -CYLINDER, or spherical coordinates when -SPHERICAL is used. Cylindrical coordinates require a radius, angle and Z coordinate, while spherical coordinates require a radius, angle in the XY plane and an azimuth angle.

The -LOCATION option defines a new frame of reference. Here, XO, YO, and ZO are the coordinates of the new frame of reference in the part system. The orientation of the new frame is defined by either three Euler angles RX, RY, and RZ, or by up to four nodes. When using the Euler angles, the new frame orientation is determined by three successive rotations about the Z, Y, and X axes respectively. When using nodes, the location and orientation both depend upon the number of nodes specified. For one node, the orientation of the frame is the same as the part frame, but the new origin is at the specified node. For two nodes, the new origin is at the first node and the orientation is the same as that of the element system of a beam between the two nodes. For three nodes, the new origin is at the midpoint between the first two nodes, the new X axis is perpendicular to the plane formed by the nodes, and the new Y axis points from the first node to the second one specified. Finally, for four nodes, the origin is at the midpoint between the second and the fourth nodes, and the Y axis points from the fourth node toward the second one, and the X axis goes from the origin to the midpoint of the line segment connecting the first and third nodes.

The options:

     -COLOR,   COLOR(1), FRAC(1), ... COLOR(n), FRAC(n)

     -TEXTURE, NAME_TEX, X_SCALE, Y_SCALE

define the default color and texture for the model. Here, COLOR(i) is either RED, GREEN, or BLUE and the FRAC(i) is the fraction of the color to be applied. For example

     -COLOR RED 1 BLUE 1

will give you magenta. The NAME_TEX value for -TEXTURE is the name of a file in either /X/data/textures or /X/data/local/textures (here MOSES is store in /X). The X_SCALE and Y_SCALE are scale factors which will be applied to the texture. The NAME_TEX of NONE will yield a null default texture.

The options:

     -BAS_CATEGORY, NAME_BAS

     -EXT_CATEGORY, NAME_EXT

define the default Category for structural element and additional load attributes respectively. NAME_BAS will be the category for all load attributes directly associated with a structural elements and NAME_EXT will be the category for all additional load attributes unless they are specifically defined on the element or load attribute command.

The default scheme is also used for defining material properties of element classes. These are set via the options:

     -SPGRAVITY, SPGR

     -DENSITY, RHO

     -EMODULUS, EMOD

     -POI_RAT, POIRAT

     -ALPHA, ALPHA

     -FYIELD, FYIELD

     -SN, TYPE(1), SN1_A, SN1_B, SN1_R, \
     TYPE(2), SN2_A, SN2_B, SN2_R, ......

Here, SPGR is used to define the material density by the ratio of its density to that of standard water, RHO is the material density (pounds/ft**3 or newtons/m**3), EMOD is the Young's Modulus (ksi or mpa), POIRAT is the Poisson's Ratio, ALPHA is the coefficient of thermal expansion (1/Deg F or 1/deg C), and FYIELD is the yield stress (ksi or mpa). For a discussion on the -SN option, see the section on associating SN curves.

Three options define the default resize properties for classes. These are:

     -RDE_SELE, TYPE(1), RD(1), TYPE(2), RD(2), ..........

     -KL/R_LIMIT, KLR

     -D/T_LIMIT, DOT

Here, TYPE(i) defines a section type and must be either: TUBE, BOX, PRI, BU, W, M, S, HP, WT, MT, ST, L, C, MC, WBOX, DL, LLEG, CONE, or PLATE. The values RD(i) are a selector which defines the default redesign selector for the section type TYPE(i). KLR and DOT are the default KL/R and D/T limits on shape selection for tubes.

Several options are available define element defaults:

     -USE, USE(1), USE(2), ..., USE(i)

     -NUSE, NOTUSE(1), NOTUSE(2),  ..., NOTUSE(i)

     -FLOOD,  FLAG

     -STW_USE,  FLAG

     -KFAC, KY, KZ

     -CMFAC, CMY, CMZ

     -DIR_BEAM, SAV1(1), SAV1(2), SAV1(3), SAV2(1), SAV2(2), SAV2(3)

     -DIR_PLATE, SAV1(1), SAV1(2), SAV1(3), SAV2(1), SAV2(2), SAV2(3)

     -SCF, TYPE(1), SCF(1), ....

All but the last of these will be discussed in detail along with the discussion of modeling elements. The last two define true default behavior. For a discussion of the -SCF option look in the section on associating SCFs with fatigue points.

The options:

     -CS_WIND, CSW_X, CSW_Y, CSW_Z

     -CS_CURR, CSC_X, CSC_Y, CSC_Z

define defaults for the wind and current multipliers of pieces. They are discussed in detail in the section on pieces.

While the previous options set defaults for modeling commands, those that follow set defaults for other types of options. The option:

     -FILL_TYPE, FTYPE

defines the default type of filling for compartments. Here, FTYPE must be either CORRECT, APPROXIMATE, APP_NONE, APP_WORST, FULL_CG, FCG_NONE, or FCG_WORST. The meaning of these types are discussed in the section on compartments.

The options:

     -WATER, RHOWAT

     -SPGWATER, SPGWAT

     -RAMP, RMPTIM

     -DEPTH, WATDEP

     -SP_TYPE,  TYPE

     -W_PROFILE, PTYPE

     -P_WIND, TW(1), TW(2), ...., TW(n)

     -W_DESIGN, DTYPE

     -W_SPECTRUM, STYPE

     -W_MD_CORRELATION, FACTOR

     -P_DRIFT, TD(1), TD(2), ...., TD(n)

     -PROBABILITY, STAT, PDATA

     -T_REINF, TB

define default values used by the &ENV command and they are discussed there.

The options:

     -HEADING, H(1), H(2), ...., H(n)

     -PERIOD, T(1), T(2), ...., T(n)

allow one to define the default headings and wave periods which will be used for several different commands. They are discussed in detail later.

The options:

     -SPE_MULTIP, SPEMUL

     -FM_MORISON, FMORFAC

     -WAVE_RUN, FLAG

define defaults which can be overridden with &DESCRIBE BODY commands.

The options:

     -AMASS, AMA_MULT

     -TANAKA, TANFAC

     -ROLL_DAMPING, CMUL

     -CS_WIND, CSW_X, CSW_Y, CSW_Z

     -CS_CURR, CSC_X, CSC_Y, CSC_Z

define defaults which can be overridden with &DESCRIBE PIECE or PGEN commands.

The final set of options define defaults for hydrodynamic calculations. The are:

     -MD_TYPE, DTYPE

     -MD_FORCE, DFORMU

Most of these define defaults which can be overridden with commands in the HYDRODYNAMICS MENU.

The &PARAMETER command is used to define parameters used in various computations. One of these commands is included in the file moses.cus so that one can alter these settings to suit their particular purposes. This file should be consulted to ascertain what settings are being used. This command functions in a manner similar to the &DEFAULT command in that any option specified on some other command with the same name as that here will override the default. The form of this command is:

     &PARAMETER, -OPTIONS

Again as with &DEFAULT, there are two basic options:

     -SAVE

     -REMEMBER

which allow for temporarily altering the parameters and returning to the previous ones. In particular, the -SAVE option instructs the program to save the current dimensions so that when -REMEMBER is used, the ones previously saved will then be used.

The options:

     -WCSTUBE, CSHAPE

     -DRGTUB, RE(1), DC(1), RE(2), DC(2), ........

     -F_CD_TUBE, CDTFREQ

     -DRGPLA, DCP

     -AMCTUB, AMT

define the hydrodynamic properties of generalized plates and tubular members. The wind shape coefficient for tubular members is defined by the option -WCSTUBE and here CSHAPE is the new value for the coefficient. The added mass coefficients of tubular members and generalized plates are taken to be constant. The drag coefficient for tubular members is a function of the Reynold's Number in the time domain and constant in the frequency domain. For generalized plates, the added mass is computed as defined in DNV Classification Notes 30.5. To define these properties, one can use -DRGTUB, -F_CD_TUBE, -DRGPLA, and -AMCTUB.

The options:

     -API_TDRAG, YES/NO

     -AF_ENVIRONMENT, YES/NO

are used in computing velocity square forces. The first one controls the relative velocity for tubes. If YES/NO is YES then the relative velocity is the component normal to the tube as in API RP2A. If YES/NO is NO then it is the true relative velocity. The second one controls the way wind and drag are computed on areas. If YES/NO is YES then the drag force is in the direction of the environment. If YES/NO is NO then it is perpendicular to the area. One should use YES to have the force depend on the projected area.

In many cases, MOSES will perform a numerical integration over either an area or a length. The precision of this integration can be controlled via the options:

     -MAXLEN, MAXL

     -MAXAREA, MAXA

     -MAXREFINE, MAXR

Here, MOSES will divide an element into pieces such that each length or area of each piece will be less than MAXL (feet or meters) or MAXA (ft**2 or m**2). The maximum number of pieces any one element will be broken into is MAXR.

The option:

     -M_DISTANCE, DISTANCE

is used to define the amount of refinement which will be performed on a diffraction mesh when hydrodynamic properties are computed. Here, DISTANCE (feet or meters) defines a maximum distance which the side of a panel or the length of a strip can have. Use of this option allows one to define a quite crude mesh and have MOSES automatically refine it to achieve any desired degree of precision.

When performing a simulation in the Static Process Menu, one needs to define two vectors which are used to measure the "roll and pitch" angles and a point which is used to measure height. This is accomplished with the options:

     -VERT, VX, VY, VZ

     -HORIZ, HX, HY, HZ

     -HEIPNT, X, Y, Z

All of these quantities are defined in the part system of the body being investigated. The height used to terminate a lift is defined by X, Y, and Z. The pitch angle is defined as angle formed by the vector VX, VY, and VZ with the waterplane, and the roll angle is the angle formed by the vector HX, HY, and HZ with the waterplane. Here, VX, VY, and VZ are the components of a vector in the part system which will be vertical when the jacket is in the installed condition.

The options:

     -STRETCH_SEA, YES/NO

     -NONL_SEA, YES/NO

control how the wave kinematics are computed. If YES/NO is YES for the first option, then the sea will be "stretched" above the mean water level. If not, then the linear kinematics equation will be used directly above the mean water level. If YES/NO is YES for the second option, then the wave profile will be computed using an estimate of the nonlinear pressure term. This results in the wave crest being higher than a trough is low. If it is NO, then a linear wave profile will be generated. the frequency domain.

The option:

     -FM_ROD, ROFACT

defines a multiplier for the computed viscous damping on rods in the frequency domain.