commit b05ae7c474a318aa0ef1905daab7f1918c1143ec
parent 97ab410a7755da48d9b24f72a5f7e358f0b3042d
Author: Ivan Gankevich <igankevich@ya.ru>
Date: Sun, 31 Mar 2019 13:59:32 +0300
Translated all text.
Diffstat:
| main.tex | | | 121 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---- |
| references.bib | | | 22 | +++++++++++++++++++--- |
2 files changed, 134 insertions(+), 9 deletions(-)
diff --git a/main.tex b/main.tex
@@ -63,16 +63,45 @@ IGES.
\section{Introduction}
+
+\subsection{Digital models of ship lines and ship hull forms}
+
+Initial geometric model of a ship hull is very close to traditional hull
+blueprints which are naturally rendered as a table of plaza ordinates in ship
+theory. Such digital ship hull model quite reliably characterises ship lines
+and above-water hull parts, while preserving continuity in hydrostatic and
+hydrodynamic calculations in ship theory and hydromechanics. This is important
+for verification of newly created numerical experiments with a multitude of
+historical series of ship calculations, model basin experiments and sea trials.
+Obvious advantage of this digital format is that it is relatively simple and
+has compact data layout, and the data is prepared and refined as plain text
+strings representing stern and frame coordinate sequences.
+
+Numerous variants of ship hulls were systematically collected in VSL format in
+Saint Petersburg State University in Vessel database~\cite{vessel2015}. The
+database is maintained with the help of Hull software suite~\cite{hull2010}
+which allows for editing ship hull coordinates and calculates certain
+hydrostatic characteristics.
+
\section{Methods}
-\subsection{...}
+\subsection{Vessel format}
+
+Formalised description of ship hull geometric form is done using plain text
+data which include ship name, hull dimensions, and subsequent description of
+aft, main (table of plaza ordinates) and bow sections. When digital ship hull
+model is first added to Vessel database the following design characteristics
+are specified in the comments: displacement, wetted surface area, hull volume
+ratio coefficient, date and time of file creation. The diagram of a VSL file
+is presented in tab.~\ref{tab:forma}.
\begin{table}
\centering
- \begin{tabular}{p{1cm}p{1cm}p{8cm}}
+ \caption{VSL file format diagram.\label{tab:format}}
+ \begin{tabular}{p{1cm}p{1cm}p{9cm}}
\toprule
- \multicolumn{3}{l}{1. Technical vessel description (comments: \texttt{//}
- or \texttt{;}} \\
+ \multicolumn{3}{l}{1. Technical vessel description (lines starting
+ with \texttt{//} or \texttt{;} are comments)} \\
\multicolumn{3}{l}{2. Format magic number (30) and hull model name in
angle brackets \texttt{<...>}.} \\
\multicolumn{3}{l}{3. The number of frames and middle frame number.} \\
@@ -84,8 +113,8 @@ IGES.
& \multicolumn{2}{l}{6. \(Y(z)\)~--- transom width ordinates as a
function of applicates.} \\
\addlinespace
- & \rotatebox[origin=c]{90}{\parbox[t]{1.4cm}{\centering{}Frame abscissas}} & 7.
- \(Y(z)\)~--- frame curves as functions of
+ & \rotatebox[origin=c]{90}{\parbox[t]{1.4cm}{\centering{}Frame
+ abscissas}} & 7. \(Y(z)\)~--- frame curves as functions of
applicates of general hull line. \\
\addlinespace
& \multicolumn{2}{l}{8. \(Y(z)\)~--- bulbous bow width ordinates as a
@@ -99,6 +128,30 @@ IGES.
\end{tabular}
\end{table}
+\begin{figure}
+ \centering
+% \includegraphics{graphics/}
+ \caption{Aurora cruiser digital model.\label{fig:aurora-1}}
+\end{figure}
+
+\begin{figure}
+ \centering
+% \includegraphics{graphics/}
+ \caption{Aurora cruiser hull is prepared for a numerical ship
+ hydromechanics experiment. Although, the number of frame points
+ in the main section is relatively small, it allows for smooth
+ approximation of hull surface with desired accuracy.\label{fig:aurora-2}}
+\end{figure}
+
+
+In accordance with initial purpose of a digital ship hull model, Hull programme
+makes basic calculations of certain characteristics of a ship hull, blueprint
+curved elements and ship stability diagrams by fixing centre of gravity with
+respect to general line, centre of buoyancy, metacentre or current waterline.
+The programme also performs wave resistance calculations for arbitrary travel
+speeds taking into account radiation intensity and interference of ship waves
+with respect to waterline as a function of Froude number.
+
\subsection{Triangulation of a ship hull given by a collection of curves}
In the original programme~\cite{hull2010} that visualises ship lines and
@@ -242,6 +295,45 @@ visualisation.
\section{Results}
+\subsection{...}
+
+As an illustrative example of simulating seakeeping ship characteristics we
+consider ship stability diagrams for contemporary and historical ships, and for
+a ship that is purposely optimised for improved storm seakeeping.
+
+\begin{figure}
+ \centering
+% \includegraphics{graphics/}
+ \caption{Transversal projection of a ship hull (top left), static ship
+ stability diagrams for a fixed centre of gravity \(Z_g\) and metacentric height
+ equal to 1\% of a beam for contemporary (a), historical (b) and improved
+ storm seakeeping (c) ships.\label{fig:hydrostatics}}
+\end{figure}
+
+
+Fig.~\ref{fig:hydrostatics} shows that Aurora cruiser ship hull has excellent
+seakeeping characteristics in severe storm waves conditions, which guarantee
+safe small oscillations and smoothness of roll by reducing metacentric height~---
+initial ship hull stability. Additional positive stability appears for
+large roll angles and arbitrary changes in heave.
+
+\begin{figure}
+ \centering
+% \includegraphics{graphics/}
+ \caption{Wave resistance, radiation intensity and ship waves intensity
+ along the ship hull.\label{fig:stability}}
+\end{figure}
+
+More complicated usage scenario of computational model is optimisation of ship
+lines to achieve certain form of wave resistance curve
+(fig.~\ref{fig:stability}). In the calculations we build radiation intensity
+and ship waves interferences along the current waterline. By changing ship
+lines we reduce resistivity extrema for relative speeds (on Froude) on the
+order of 0.3 and 0.5 without sacrificing propulsion for minimum wave formation
+for speeds 0.4 and 0.2.
+
+\subsection{Triangulation}
+
To prove VSL viability for using it as an alternative to another format that
uses analytic curves called IGES~\cite{smith1983iges}, we measured
triangulation performance and measured how many vertices and faces are
@@ -337,6 +429,23 @@ representation.
\section{Conclusion}
+In computation experiments we used theoretical blueprints of Aurora cruiser
+which has excellent seakeeping characteristics and for which there can be no
+dangerous situations in severe storm waves. We presented the more complicated
+geometric ship hull form which is optimised for storm seakeeping. This ship
+hull has relatively small moments of inertia for the area of the current
+waterline (MICW). For this hull mutual compensation of external force
+excitations was proved in seakeeping trials in severe storm waves in model
+basin of Leningrad shipbuilding institute under the guidance of prof. Alexander
+Nikolaevich Kholodilin~\cite{khram2018}.
+
+Although, traditional plaza table of ordinates with a few frames
+has relatively small hull representation accuracy, it gives satisfactory
+representation of ship hydrostatic and hydrodynamic characteristics in
+computational experiments using multiprocessor machines and supercomputers.
+For research stages we used formalised simulation and trochoidal models
+of storm sea waves, for which digital ship hull models are quite optimal.
+
We described efficient plain text format for three-dimensional ship hull
geometry called VSL. This format uses longitudinal and transversal projections
of ship lines given in analytic form. This format is easy to write by hand and
diff --git a/references.bib b/references.bib
@@ -7,8 +7,8 @@
}
@Article{ smith1983iges,
- title = {{IGES}, A Key Interface Specification for {CAD}/{CALM} Systems
- Integration},
+ title = {{IGES}, A Key Interface Specification for {CAD}/{CALM}
+ Systems Integration},
author = {Smith, Bradford M and Wellington, Joan},
journal = {Computer-Aided Geometry Modeling},
pages = {279--319},
@@ -35,8 +35,24 @@
fipsnumber = {2015621368}
}
+@Book{ khram2018,
+ title = {Поисковые исследования
+ штормовой мореходности корабля},
+ subtitle = {История эволюционного развития
+ инженерно-технических решений об
+ обводах и архитектуре корабля, о
+ единении морских наук и хорошей
+ морской практики},
+ publisher = {Lambert Academic Publishing},
+ edition = {3},
+ isbn = {978-613-8-23643-6},
+ pages = {470},
+ year = {2018}
+}
+
@Misc{ opencascade,
- title = {Open {CASCADE} Technology, {3D} modeling \& numerical simulation},
+ title = {Open {CASCADE} Technology, {3D} modeling \& numerical
+ simulation},
author = {{Open Cascade SAS}},
url = {https://www.opencascade.com/},
year = {2019}
