The goal of the mooring package is to facilitate computations in the R language of the deformation of oceanographic moorings by ocean currents. It builds on Fortran code discussed by Moller (1976), which evolved into a new form as discussed by Hamilton, Fowler, and Belliveau (1997) and Hamilton (1989), and then a Matlab form discussed by Dewey (1999). It is more limited than these earlier works, e.g. in considering only unidirectional currents, in ignoring the stretching of mooring components, and in ignoring the stresses involved during mooring descent.
In addition to a fairly broad suite of functions, the package also provides crude interactive tools for exploring simple moorings.
Conventional R help is provided, in addition to several vignettes, and a youtube playlist.
At the moment, mooring only handles bottom-anchored moorings in which the top buoyancy element is below the sub-surface.
Installation
You can install the development version of mooring from GitHub by typing the following in an R console. (Uncomment the first line, if the devtools package is not already installed on your computer.)
# install.packages("devtools")
devtools::install_github("dankelley/mooring")Example
The following shows how to assess the knockdown of a mooring consisting of a bottom anchor, 100 m of wire, and a 16-inch Viny float, in a region of water depth 120 m with a constant current of 0.5 m/s (roughly 1 knot). To learn more, (a) alter the current and observe changes in the mooring shape, (b) set the which argument of plot.mooring() to focus more directly on the knockdown, and (c) explore the effects of specifying depth-dependent currents in the knockdown() call. After a few steps like this, you ought to examine the vignettes and the documentation of the package’s functions, so you can tackle a practical case of your own.
library(mooring)
#> Loading required package: S7
# Design a mooring with a 16-inch Viny float attached to a bottom
# anchor with 100m of wire cable.
m <- mooring(anchor(), wire(length = 100), float("16in Viny"), waterDepth = 120)
# Segmentize wire portion (to 1m spacing).
ms <- segmentize(m)
# Apply a depth-invariant 0.5 m/s current.
msk <- knockdown(ms, u = 0.5)
plot(msk, fancy = TRUE)
Acknowledgments
The mooring-element properties that are stored in the mooringElements database stem from three main sources. The first was Richard Dewey’s Matlab code (see Dewey (2023) for an updated version). The second was in spreadsheets and other documents provided by Jay Barthelotte and Matthew Lawson of the Bedford Institute of Oceanography (BIO). And the third was in spreadsheets and other documents provided by Danielle Dempsey and Nicole Torrie of the Centre for Marine Research (CMAR). These sources are designated "Dewey", "BIO" and "CMAR", respectively, in mooringElements.
Conversations with Clark Richards and Chantelle Layton (both of BIO) were helpful in identifying data sources and in clarifying the nature of mooring systems.
