Water on Deck

GHS provides two special tank types for the purpose of modeling the effects of the extra burden of water on deck due to waves.

The first, FLOODED PLUS, is an extension of the FLOODED type. It raises the flooded waterplane above the external waterplane by an amount such that the increased volume is equal to the volume indicated by the LOAD setting.

The other type is called DECK. It is similar to the DAMAGED type with LOAD = 0 and an additional head of water added to that of the external waterplane. The parameter /HW: must be included with the TYPE command in order to specify the value of the additional head.

Following is a run which demonstrates the use of these types to model the two methods of treating water on deck.

macro makeship
enter pm
create hull
ends 0 100
top 20
bot 0
out 10
create deck.c
ends 15 85
bot 8
fit hull
macro interp `%1=x, %2=x1, %3=y1, %4=x2, %5=y2, %6=result var name
if %1<%2 then set %6 = %3 | exit
if %1>%4 then set %6 = %5 | exit
variable t
set t = %4 minus %1 times %3
set %6 = %1 minus %2 times %5 plus {t}
set t = %4 minus %2
set %6 = {%6} div {t}
macro wod
type = flood
variable hw,f,v
variable (string) u
set u = "{wunit}"
unit mt
.interp {HEIGHT}, .3, .5, 2, 0, "hw"
.interp {hs}, 1.5, 0, 4, 1, "f"
set hw = {hw} times {f}
if %1="NEU" then type = deck /hw:{hw}
mac t
type = intact
heel = 0 | trim = 0
load = .5
solve depth
set f = {HEIGHT}
set v = {TVOLUME}
set f = {f} minus 0.1
load = height:{f}
solve depth
set v = {TVOLUME} minus {v} times 10
\\Deck area is {v} sq. meters\
set v = {v} times {hw}
contents = fw
load = weight:{v}
type = flood plus
if %1="POE" then .t
unit {u}
macro stat
\With water on deck, wave height: {hs} meters hw: {hw} meters\
macro ra
heel = 0
ra /area /nowarn

`===== Start of project commands ======
`Get geometry
project testwod
if fexist {project}.gf then read else .makeship

`Set ship weight and C.G.
draft = 4.5
vcg = 5
solve weight, lcg

`Set point of damage
variable pod
set pod = "50a, 10s, 8" `Point of damage, also used to determine freeboard.
refpt (hull) = {pod}

`Select deck to be flooded
tank deck.c
refpt = {pod}
type = flood

`Induce heeling moment
tcg = 0.5

\\==== Initial condition without water on deck: ====\

`Set wave height
variable hs
set hs = 2.75 `Wave height in meters

macro case
\\%2 method\
.wod %1

.case neu "Northern European"
.case poe "Panel-of-Experts"

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