Dynamic Ship Loading Estimation Code: Description

0 downloads 10 Views 113KB Size Report
sections description can be augmented manually provided that all the involved ..... The file is intended for plotting time histories using Tecplot or the special ...

Dynamic Ship Loading Estimation Code: Description of the Program SLAVIB S. Sutulo 2003

1

Objective

The Fortran 90 program SLAVIB computes time histories of the dynamic and equivalent static vertical loads on the hull of a surface ship running at constant speed across an irregular seaway. The program is supposed to be used together with a slightly modified version of the program STRIP [1]. We shall designate this modified version as STRIPmod and all the alterations will be described here but most of the description [1] remains valid and it is supposed to be used together with the present one. Also, an auxiliary program SLAMVORM based on the EUMEDES system [3] is used for preparing a hull description file used by SLAVIB.

2

Used Methods and References

The program SLAVIB performs time-domain simulations of hydrodynamic loads (including nonlinear contributions and slamming), static loads, shear force, bending moment and equivalent statical loads resulting from hull girder vibrations (both springing and whipping). Remarks on the terminology. Throughout this document, the terms “station” and “section” are used as meaning the same (a plane or a contour), as opposed to “strip” or “slice” which mean a piece of ship hull between two neighbouring sections. The program SLAVIB uses transfer functions for relative displacements of sections computed before the simulation by the program STRIPmod. The method is described in [5].

1

3

Programs Use

3.1

Running Sequence

In the general case, three executable files must be created: slamvorm.exe (program SLAMVORM), stripmod.exe (program STRIPmod) and slavib.exe (program SLAVIB)1 . First, the preliminary hull discretisation program SLAMVORM must be run. Then, to estimate the loads with account for nonlinear effects and vibration, it is necessary to do the following (it is supposed that all the required input data files already exist, except for wave length and direction data): 1. The program SLAVIB is run in the preliminary mode (see the description of the input files). No simulation is then carried out, but the sets of random wave encounter angles and wavelengths, and the sections’ abscissae are obtained as result 2. The arrays of angles and wavelengths contained in file waves.dat and the array of the sections’ abscissae (file relmcoor.dat) are copied into the input file indata.dat for the program STRIPmod at the appropriate locations (angles near to the beginning, wavelengths near to the end, abscissae preceeding the wave lengths) 3. The content of the file strip sections.dat containing the description of the hull for the program STRIPmod is put in the file indata.dat replacing the corresponding data already contained in this file. Also, the number NX of the sections in the preceeding line (preceeding the draught) must also be corrected if necessary. Remark. The sections data produced by Slamvorm can omit some sections if they are not connected (that is consist of more than one part). In the case of need, the sections description can be augmented manually provided that all the involved numbers of sections etc. are corrected accordingly. 4. If necessary, the content of the file strip absc.dat must be used to replace the list of sections’ abscissae and integer flow separation indicators in the file indata.dat. 5. The program STRIPmod is run. It produces a file containing the sectional transfer functions. 6. The program SLAVIB is run in the main mode to perform the simulation. It reads the transfer functions produced by STRIPmod and reproduces the process in the time domain.

3.2

Intermediate Files Handling

The files are only mentioned in this subsection to facilitate data management. More detailed description of all the files is given in the following sections. 1

e.g. by commands like ‘‘f90 slamvorm.f slamplot.f90 -O -o slamvorm.exe’’; ‘‘f90 stripmod.for -O -o stripmod.exe’’; ‘‘f90 meinslavib.f90 -O -o slavib.exe’’.

2

3.2.1

SLAMVORM—SLAVIB (preliminary run)

If both programs are located in the same directory, nothing must be done. Otherwise— the file hullshape.dat must be copied or moved from the SLAMVORM directory to the SLAVIB directory. 3.2.2

SLAVIB (preliminary run)—STRIPmod

The content of the following files must be copied into the file indata.dat replacing the corresponding data: 1. File waves.dat 2. File relmcoor.dat 3. File strip sections.dat (or similar file with the name indicated in slamvorm.dat) 4. File strip absc.dat (or similar file with the name indicated in slamvorm.dat 3.2.3

STRIPmod—SLAVIB (main run)

If both programs are located in the same directory, nothing must be done. Otherwise, the following files must be copied or moved from the STRIPmod directory to the SLAVIB directory: 1. File addmass.dat 2. File raos slam.dat 3. File raos hvpt.dat

4 4.1

Program SLAMVORM General Information

Primarily, the program SLAMVORM is aimed at generating a uniform grid discretisation of the ship’s hull with given spacings along the ship’s length and height. It is based on the ship geometry handling system EUMEDES [3] and is in fact a development and a combination of two similar hull shape preparation programs SLAMVOR [4] and DITCHVORBEREIT, and of the plotting program DITCHKOERPERPLOT [2]. Also, this program produces the hull description for the program STRIPmod (this part is based on the program STRIPDATA).

4.2

Source Files

The main source code of the program is contained in the file slamvorm.for and three subroutines belonging to the module Plotting are located in the file slamplot.f90. 3

4.3

Input Files

All the input files are read in free format and the data are separated with spaces or line ends. 4.3.1

Input File “slamvorm.dat”

This file is primary and contains certain configuration information and data to be transfered to some of the output files although not used by the program itself. text — CHARACTER: a description of the object placed inside single quotes (not longer than 120 symbols including spaces) which will be used throughout all the computations len — REAL: the ship’s length in m drt — REAL: the ship’s draught in m trim — REAL: the ship’s trim in meters (positive by the stern) nx — INTEGER: the last section number (fine grid); the first one is 0; 200–400 recommended nz — INTEGER: the last waterplane number; the first one is 0; 400–600 recommended dx — REAL: the desired sections spacing in m dz — REAL: the desired waterplanes spacing in m x0 — REAL: the most aft section’s abscissa (section No. 0) in m z0 — REAL: the lowest waterplane’s applicate (waterplane No. 0) in m nx1vib — INTEGER: the last section number (spacing for vibrations calculations); the first one is 0; 50 recommended (the program Slavib requires only that nx1vib ≤ nx, but it must also match the capabilities of STRIPmod) nmin — INTEGER: minimum number of segments per section in STRIP calculations smax — REAL: maximum length of a segment in STRIP calculations, m (1 m recommended) infile name — CHARACTER: the name (not longer than 40 symbols) of the input file containing primary information about the hull’s shape prepared according to the system EUMEDES (a eum-type file) outfile name — CHARACTER: the name (not longer than 40 symbols) of the main output file containing the hull form description required by the program SLAVIB. If the file is supposed to be read immediately by the program SLAVIB, its name must be ’hullshape.dat’

4

stripout name — CHARACTER: the name (not longer than 40 symbols) of the file containing the hull form description required by the program STRIPmod (the name strip sectons.dat assumed in this description) stripout1 name — CHARACTER: the name (not longer than 40 symbols) of the file containing the list of the abscissae of the sections described in the previous file together with corresponding integer flow separation indicators ( 0 is put everywhere; the name strip absc.dat assumed in this description) preplot name — CHARACTER: the name (not longer than 40 symbols) of the postscript output file representing a plot of the body lines according to the primary EUMEDES description postplot name — CHARACTER: the name (not longer than 40 symbols) of the postscript output file representing a plot of the body plan created from the file with the name outfile name (see above) stripplot name — CHARACTER: the name (not longer than 40 symbols) of the postscript output file representing a plot of the body plan created from the file with the name stripout name (see above). 4.3.2

Input File “*.eum”

The actual name is defined in the file slamvorm.dat (ishi.eum in the supplied example for the Ishiguro ship. The description of the content of this file can be found in [3].

4.4 4.4.1

Output Files Output File “hullmon.dat”

1. File hullmon.dat—EUMEDES intermediate results (see [3]) 2. File striplog.dat—record of forming data for STRIPmod. . 4.4.2

Main Output File

This file is supposed to have the name hullshape.dat, serves as an input file for SLAVIB and is described in detail in the section dedicated to this program. However, its name is defined in the file slamvorm.dat and can be temporarily different from the indicated above (it can be then possible to create several hull shape files with different names and to rename then one by one for further use).

5

4.4.3

Postscript Output Files

The names of these files are also defined in slamvorm.dat. In the supplied example, the first one has the name preplot.ps and produces a plot of body lines according to the input file *.eum. The second file (named ishi 400 600 postplot.ps in the example) plots the fine grid control body plan created from the file hullshape.dat. The third file (named ishi stripplot.ps in the example) plots the body plan corresponding to the discretisation used by STRIPmod.

4.5

Recommendations on Setting Discretisation Parameters

It is recommeneded to set nx=200--400 and nz=400--600 for most hull forms (more detailed guidelines can be found in [5]). The spacing dx must be chosen in such a way that nx ∗ dx = len − ε where ε is a small distance which can be taken as, say, 5 mm for a 200 m ship. That is, the most forward section must be very small but with non-zero area. The succes of the choice of the parameters can be checked with the help of the post plot and approriate corrections can be introduced if necessary. The waterplanes spacing dz must be defined in such a way that nz ∗ dz = H where H is the height up to which the hull must be described. The maximum possible value of H can also be extracted from the eum-file.

5

Program STRIPmod

For the description of the original program STRIP see [1]. Here only the changes of that program and the input and output files are described.

5.1

Introduced Changes

The part of the program STRIP dealing with the ship in natural seaways does not make sense in connection with slavib. Thus for this application the first 3 data values of the input file should be 1 1 0. Some of the changes made were necessary to adjust the program to the needs of SLAVIB, whereas others were required by one of the used platforms (Microsoft Fortran PowerStation 4.0): 1. The exploitation of the symmetry principle at setting the wave directions was abandoned: the program computes the transfer functions for the indicated wave encounter angles. 2. Transfer functions of the sections’ relative motions are written into a separate file. 3. Further, heave added masses for the highest frequency are output. 4. OPEN statements defining the file names given below were added. 6

5. A few changes not affecting the algorithm were introduced to circumvent the used compiler’s deficiencies.

5.2

Files

The source code of the program is contained in the file stripmod.for. The input data file (the stream unit=5) is named indata.dat. See [1] for its contents. The program creates the following output files: 1. File hydro_human.dat (original: unit=7) contains the computed hydrodynamic section characteristics including text. 2. File hydro_comp.dat (original: unit=20) contains the same results without text as input for other program parts. 3. File raos_human.dat (original: unit=6) contains the computed transfer functions and response amplitude operators with text. 4. File raos_comp.dat (original: unit=21) contains the same results without text. 5. File raos_spec.dat (original: unit=23) contains other transfer functions (see [1] for comments). 6. File raos_slam.dat (additional: unit=24) contains the computed relative-motion transfer functions of sections without text to be used by SLAVIB. 7. File raos_hvpt.dat (additional: unit=26) contains the computed heave and pitch transfer functions without text to be used by SLAVIB. 8. File stat_human.dat (original: unit=8) contains statistical results on ship motions in a natural seaway with explaining text if such calculations have been specified in indata.dat. 9. File addmass.dat (additional: unit=25) contains high-frequency vertical added mass data to be used by SLAVIB.

6 6.1

Program SLAVIB General Characteristics

The program SLAVIB was designed to match as much as possible the program STRIP. It uses the same co-ordinate systems Kξηζ and Kxyz (see [1]); i.e. the axes are directed respectively ahead, to starboard, and down, and with the origin K lying in the midship plane on the keel. However, the use of Fortran 90 and a somewhat different design philosophy resulted in a different program structure: all the procedures are organised in modules (which can be contained in separate files). 7

Due to the use of dynamic allocatable arrays, there are no explicit constraints for the number of sections, wave components etc., although physical memory limits still apply. However, as SLAVIB is supposed to interact with STRIPmod, the latter program’s limitations must be respected. As the program is supposed to be used mainly for full-scale estimations, all the forces are represented and output in kilonewtons and all the masses in tons. However, the program can be also used for model-scale calculations without danger of loosing accuracy as all the real and complex constants and variables are defined with double precision.

6.2

Source Files and Modules

SLAVIB’s source code is organised in ten modules which may be and were originally contained in ten files: 1. File genconst.f90: contains the general constants (including the water density, Young’s modulus etc.) and types definition module GenConst. 2. File wspecdon.f90 — Donelan’s WaveSpectrumDonelanModule

wave

spectrum

computation

module

3. File process.f90 — the irregular sea process modeling module ProcessModeling; uses the module GenConst 4. File geometry.f90 — the module Geometry performs the hull shape input and related preliminary calculations; uses the module GenConst. 5. File auxfuncs.f90 — the auxiliary functions module AuxFunctions; uses the module GenConst. 6. File filters.f90 — the module FiltersV contains the Butterworth filters code (the vector/array variant); uses the module GenConst. 7. File filtersca.f90 — the module Filters contains the Butterworth filters code (the scalar variant); uses the module GenConst. 8. File massmode.f90 — the module Vibration supports the vibrations analysis; uses the modules Geometry, AuxFunctions, and ProcessModeling. 9. File impact.f90 — the largest module Impact contains procedures modeling nonlinear hydrodynamic loads (including slamming); it supports the process simulation and most of the output; uses the modules GenConst, Geometry, AuxFunctions, ProcessModeling, FiltersV, Filters, Vibration. 10. File slamtest.f90 — the calling programme SLAVIB; it uses the module Impact. However, in the supplied version, all the listed files are merged together into the single file meinslavib.f90. In case of need, the file can be split back into several ones (not necessarily, identically to the primary partition) but one must be aware that the module structure requires a certain compilation order. 8

6.3

Input Files

The input files are read using the * (free) format; i.e. the data in there must be separated from each other either by a space or by an end-of-line. 6.3.1

Input File “simulation.dat”

The file (unit=if_simul=3) is supposed to be created by the user. It contains main parameters determining the simulation process. It is read by the subroutine WaveReadAllocate (module ProcessModeling, file process.f90). Read are the following variables: irregular — LOGICAL: T for irregular sea, F for a regular wave (auxiliary mode). In the latter case the program simulates not exactly for the wave data specified in file spdwave.dat, but for the most similar regular wave used by the program Stripmod. reproduce — LOGICAL: T if the RANDOM_SEED subroutine is not activated, meaning that the same wave process will be simulated at every run; when reproduce=F, different sample processes will be generated in each run mode — INTEGER defines the program mode: 0 at the first (preliminary) run to generate random values for wave angles and wave lengths, skipping the simulation; and 1 for a simulation. The latter requires that STRIPmod were run before dt — REAL: “Main” time step in the simulation (in s). 0.005–0.01s was found appropriate for a ship for which L/V = 20 s and the natural heave period about 7 seconds; no adjustment is needed in most cases as the input integration step is automatically modified by the program in accordance with the actual estimated natural heave period but sometimes smaller steps can be necessary for short and fast vessels pfc — INTEGER: Printing FaCtor; i.e. number of time steps between any two consecutive process outputs vzn — INTEGER: Vibration Zoom Number; i.e. number of time steps dt1 used for the vibration simulation which are contained within a single “main” time step; 20 was found appropriate tm_stop — REAL: Simulation duration (s) thrpar — REAL: Nondimensional slamming threshold ix_first — INTEGER: Smaller station (strip) number for which the processes will be output ix_last — INTEGER: Larger station (strip) number for which the processes will be output

9

Remark. The parameters ix_first and ix_last vary from 1 to nx1 as defined in the file massdis.dat. The number of strips used in the vibrations analysis nx1 can be substantially smaller then the corresponding number nx defined in the file hullshape.dat and used for hydrodynamic loads computations. The file (unit=if_geometry=10) is created automatically by the program SLAMVORM and normally doesn’t need any manual interference. It contains a description of the hull shape by a large number of half-breadths. The file is read by the subroutine ShipReadAllocate (module Geometry, file geometry.f90). It must contain the following data: ship_id — CHARACTER(120): text, e.g. for ship identification, placed between quotes len — REAL: ship length between perpendiculars in m drt — REAL: ship draught at midship section in m trim — REAL: ship trim (positive by the stern) in m. nx — INTEGER: last station number; the first one is 0 nz — INTEGER: last waterline number; the first one is 0. dx — REAL: spacing of stations in m dz — REAL: spacing of waterplanes in m x0 — REAL: x coordinate of station no. 0 in m z0 — REAL: z coordinate of waterplane no. 0 in m (normally 0) nx1vib — INTEGER: last station number in the coarse sectionning used in vibrations and ship motions calculation; the first one is 0 ix_strip_start — INTEGER: first submerged section number in the coarse sectionning used in vibrations calculation: the aft sections with smaller numbers can stay completely out of the water in the given equilibrium position and these are disregarded in ship motion calculations performed by STRIPmod nx_strip — INTEGER: number of sections involved in the ship motions performed by the program STRIPmod: the spacing is the same as used in vibrations analysis but dropped are sections which are not submerged in equilibrium state and the sections with unconnected contours (i.e. consisting of more than one part that is typical for bulbuous bows) use_input_keel — INTEGER: code for the keel line defining method: 1 if the keel line is defined by the array which then follows; 0 if the keel line is generated by the program automatically (most typical). k_v — REAL(0:nx): array describing the keel line in the used coordinate system (must only be present when use_input_keel==1); y_m — REAL(0:nx, 0:nz): two-dimensional array of halfbreadths of the ship hull in m. The inner loop is over the waterlines, the outer one over the stations. 10

6.3.2

Input File “massdis.dat”

The file (unit=if_mass=20) is supposed to be created by the user. It describes the ship’s mass distribution over x. It is read by the subroutine MassInitil (module Vibration, file massmode.f90). It contains the following data: nx1 — INTEGER: this is the same as nx1vib in the file hullshape.dat i.e. number of strips in vibration calculations and these values must be equal. ms_v — REAL(1:nx1): one-dimensional array of strip masses in t. Their sum must be equal to the ship’s mass. 6.3.3

Input File “addmass.dat”

The file (unit=if_adms=21) is created by the program STRIPmod. It contains the highfrequency vertical added masses of nx_strip+1 stations starting from the station number ix_strip_start. It is read by the subroutine MassInitil (module Vibration, file massmode.f90). 6.3.4

Input File “freqshapes.dat”

The file (unit=if_mode=22) is supposed to be created by the user. It describes the ship girder natural frequencies and mode shapes. It is read by subroutine MassInitil (module Vibration, file massmode.f90). Read are: nom — INTEGER: number of modes used. Recommendation: 3 or 4. efq_v — REAL(1:nom): one-dimensional array of natural frequencies ω in rad/s mode_m — REAL(1:nom, 0:nx1): two-dimensional array of natural mode shapes in m. Each shape is supposed to occupy at least one line in the file. The inner loop is over the sections. 6.3.5

Input File “spdwave.dat”

The file (unit=if_spdwave=1) is supposed to be created by the user. It contains the ship speed and wave data. It is read by the subroutine WaveReadAllocate (module ProcessModeling, file process.f90). Read are: spd — REAL: ship SPeeD in m/s h13 — REAL: significant wave height in m in case of a natural seaway, or wave height in the case of a regular wave t_peak — REAL: wave spectrum peak period in s in the case of natural seaway, or wave period in the case of a regular wave

11

wanggen_dg — REAL: wave or seaway encounter angle in degrees (0 for following sea, 90◦ for waves from the starboard) wangm_dg — REAL: maximum deviation of encounter angles of wave components from wanggen_dg, in degrees fq_min — REAL: minimum frequency of wave components in rad/s fq_max — REAL: maximum frequency of wave components in rad/s num_fq — INTEGER: number of components of the natural seaway num_wang — INTEGER, the number of different encounter angles in the irregular sea simulation. The total number of wave components num_fq*num_wang is determined by the program. 6.3.6

Input File “raos slam.dat”

This file (unit=if_raos=2) is produced by the program STRIPmod. It contains the frequency transfer functions (FTF) as a list of complex values: (((raorel_sm(i,j,k),k=0,nx),j=1,num_fq),i=1,num_wang), where i distinguishes encounter angles, j frequencies, and k sections. 6.3.7

Input File “raos hvpt.dat”

This file (unit=if_raos=4) is produced by the program STRIPmod. It contains the frequency transfer functions of heave and pitch motions as a complex list (((raohv_m(i,j,k),k=0,nx),j=1,num_fq),i=1,num_wang).

6.4 6.4.1

Output Files Output File “simustat.dat”

This file (unit=of_stat=500) is the principle output. It is self-explaining and contains ship data and main results of the computation: maxima and minima of loading, shear force and bending moment and the positions where they occur, as well as maxima and minima of the bending moment amidships for both rigid and elastic hull. 6.4.2

Output File “dynforce.dat”

This file (unit=of_dynf=100) is generated by SLAVIB. Each of its lines contains the following data: 1. Current time tm in seconds 2. Water surface heights at stations ix_first to ix_last 12

3. Total vertical load per length F (sum of statical and wave-induced part) at stations ix_first to ix_last in kN/m The file is intended for plotting time histories using Tecplot or the special program dynforceplot. 6.4.3

Output File “staforce.dat”

This file (unit=of_staf=200) specifies the equivalent static loading of the hull girder by the following data: 1. Current time tm in s 2. Water surface heights at stations ix_first to ix_last in m 3. Equivalent static load Fs at stations ix_first to ix_last in kN/m The file is intended for plotting time histories using Tecplot or the special program staforceplot. 6.4.4

Output File “vibratns.dat”

This file (unit=of_vibr=300) specifies the vibratory displacements: 1. Current time tm in s 2. Vibratory displacement z(x, t) at stations ix_first to ix_last in m The file is intended for plotting time histories using Tecplot or the special program vibratnsplot. 6.4.5

Output File “maxvalue.dat”

This file (unit=of_maxv=400) specifies maxima (along the ship hull) of the load FRB , the shear force and the bending moment and their longitudinal positions: • Current time tm in s • Maximum rigid body load FRB in kN/m • Station number where the maximum occurs • Minimum load FRB in kN/m • Station number where the minimum occurs. • Corresponding 4 results for the total load Fs in kN/m 13

• Corresponding 4 results for the vibratory displacement z in m • Corresponding 4 results for the shear force of the elastic hull in kN • Corresponding 4 results for the bending moment of the elastic hull in kNm • Corresponding 4 results for the shear force on the rigid hull in kN • Corresponding 4 results for the bending moment of the rigid hull in kNm The file is intended for plotting time histories using Tecplot. 6.4.6

Output File “midbendm.dat”

This file (unit=of_midb=600) contains bending moments at the midship section: 1. Current time tm in s 2. Relative water surface height at the midhsip section in m 3. Midship bending moment on the elastic hull in kNm 4. Midship bending moment on the rigid hull in kNm The file is intended for plotting time histories using Tecplot. 6.4.7

Output File “detectn.dat”

This file (unit=of_detec=84) indicates slam times: 1. Current time tm in s 2. Slamming indicator: 1 if, at any station, the slam criterion is satisfied The file is intended for plotting time histories using Tecplot. 6.4.8

Output File “keelline.dat”

This file (unit=of_keel=108) contains the z coordinate of the keel line as actually used by the program in the form of a real array in the free format starting from the station 0 and ending with the station nx 6.4.9

Output File “relmcoor.dat”

The file (unit=of_relative=12) contains the coordinates of nx+1 points along the hull at which the relative motion frequency transfer functions must be computed by the program STRIPmod. The file contains nx+1 lines and each of them contains the coordinates x, y=0, and z=0 corresponding to each section in their natural order. 14

6.4.10

Output File “waves.dat”

This file (unit=of_waves=10) gives wave data: 1. Number num_wang of encounter angles of the harmonic wave components 2. Array of the wave angles in degree 3. Number num_fq of wave lengths 4. Array of the wave lengths in m 6.4.11

Output File “mon mass.dat”

This file (unit=of_mamo=25) contains the following data together with explaining texts: 1. Number nx1 of stations in vibration computations 2. Number of modal shapes nom 3. Ship mass in t 4. Ship mass per length at nx1 stations in t/m 5. Vertical infinite-frequency added mass for the whole ship in t 6. Array of the type REAL(0:nx1) of ship vibratory added mass distribution in t/m 7. Array of the type REAL(1:nom) of natural frequencies in rad/s 8. Array of the type REAL(1:nom, 1:nx1) of modal shapes

6.5

Adjustable Parameters

Several constant parameters defined in the module Impact (file impact.f90) can be modified by a competent user although it is recommended to change the default values only in exceptional cases. 1. The boolean parameter auxiliary_output must be set to .TRUE. if additional output like various force components etc. is required. Default: .FALSE.. 2. The integer parameter ix_out indicates the number of “strips” (from 1 to nx) for which the auxiliary output is provided (only meaningful if auxiliary_output = .TRUE.). 3. The boolean parameter piling is normally .TRUE.. If set to .FALSE., the water pile-up is neglected 4. The real parameter fn_thresh is the section’s immersion threshold Froude number at which the fully developed pile-up is supposed to occur. Default: 0.45.

15

5. The integer parameter max_num_iter is the maximum number of iterations in the pile-up computations. Default: 20. 6. The integer parameter filter_order is the order of the Butterworth filter used at computing the entry velocity to smooth the computed slamming force. Possible values: 0 to 4; 0 means no filtering. Recommended: 2 or 3. If the parameter is set to another positive integer (≥ 5), a default RC-filter is activated. 7. The integer parameter filterv_order corresponds to filter_order, but it refers to the final ”presentation” filter. 8. The real parameter t0_cuf is the reference (related to the natural heave period 7 seconds) cutoff period in s for the Butterworth filters. Default: 1 second. Other typical options could be 0.5, 2, 4. Bigger (than 1) values can lead to overfiltering while too small values make the filtering insufficient. The actual cutoff period used during the simulation is however adjusted by the program in compliance with the natural period of heave. 9. The real parameter t0_rlx is the same as t0_cuf but corresponds to the default RC-filter.

References [1] S¨oding H. Beschreibung des Programms STRIP. — Institut f¨ ur Schiffbau der Universit¨at Hamburg: 1994. 7 p. [2] S¨oding H. Berechnung der Flugzeugbewegung beim Notwassern. — TUHH: 1999. 18 p. [3] S¨oding H. User Manual of Programs EUMEDES and ARCHIMEDES II. — TUHH: 2001. 59 p. [4] Zhou Y., S¨oding H. Berechnung von Stoßkr¨aften auf schnelle Schiffe. — Manuscript 1999. 11p. [5] Sutulo S., S¨oding H. Estimation of Ship Dynamic Wave Loads in Irregular Sea. — Manuscript 2003. 46p.

16