IMtrajectoryModel

A tool that converts heater state changes of a maneuverable melting probe to a trajectory.

The heater state changes can be provided by two possible input files, namely a logfile and a simplified logfile. An example for a logfile is given by test/logfile/icemole_state.log. Examples for simplified logfiles can be found in test/simplifiedLogfile/.

Geo Fluid Dynamics - A research group at RWTH Aachen University
Author: K. Schüller schueller@aices.rwth-aachen.de

Dependencies

• CMake

Getting Started

To build IMtrajectoryModel, create a build folder in the root directory

mkdir build
cd build

Then execute

cmake ..
make

To make sure that everything works as expected, you can run the tests by

make test

Run

./IMtrajectoryModel -h

to see all possible input options.

In order to use IMtrajectoryModel to calculate a melting trajectory from a logfile that includes heater states of a melting probe you can run

./IMtrajectoryModel -l LOGFILE -i INPUTFILE -o OUTPUTFILE

or for a simplified logfile that contains less information (see test/ for examples how those files should look like)

./IMtrajectoryModel -sl LOGFILE -i INPUTFILE -o OUTPUTFILE

in which LOGFILE is the location of the logfile that contains the heater states, INPUTFILE the location of the input file (e.g. inputs.ini) and OUTPUTFILE is the location where to save the melting trajectory.

Examples

turnright

driveU

Models

The models can be selected in the input file. Currently, there is only one model for curvilinear melting.

Straight melting models

Energy balance

Improved analytical solution based on close-contact melting theory

Using a model based on close-contact melting theory enables to use the force as an input parameter. The input file distinguishes

• F_H additional force, e.g. the force of an ice screw
• mass the mass of the melting probe
• gravity_vector the vector of gravitational acceleration (e.g. (0,0,9.81))

The total exerted force is then given by
F=F_H+m*g*cos(phi)
in which

• m is the mass
• g is the magnitude of the graviattional acceleration
• phi is the angle between the trajectory tangent and the gravitational acceleration

Curvilinear melting models

• Energy balance

Coordinate System (COS)

Melting Probe COS (local COS)

The IDs of the heating cartridges in the melting head and wall heaters are used to define the melting probe COS as shown in the following schematic (note that the viewer looks from the back of the melting probe to the melting direction)

Ice COS (global COS)

The global COS (x-, y- and z-direction) is connected to the melting probe COS by the initial normal vector n_0 and the initial tangent vector t_0, which can be set by the user. By default n_0=(1,0,0) and t_0=(0,0,-1), which means that the local coordinates X and Y are aligned to the gloabal coordinates x and y. Further examples:

• n_0=(-1,0,0),t_0=(0,0,-1): X aligns with -x, Y aligns -y
• n_0=(0,1,0),t_0=(0,0,-1): X aligns with y, Y aligns -x
• n_0=(0,0,1),t_0=(1,0,0): X aligns with z, Y aligns y

Heater States

Heater Name	Position in heater state array
Head Heater 1	1
Head Heater 2	2
Head Heater 3	3
Head Heater 4	4
Head Heater 5	5
Head Heater 6	6
Head Heater 7	7
Head Heater 8	8
Head Heater 9	9
Head Heater 10	10
Head Heater 11	11
Head Heater 12	12
Head Heater 13	13
Head Heater 14	14
Head Heater 15	15
Head Heater 16	16
Wall Heater 1	17
Wall Heater 2	18
Wall Heater 3	19
Wall Heater 4	20
Wall Heater 5	21
Wall Heater 6	22
Wall Heater 7	23
Wall Heater 8	24

Postprocessing

The trajectory given in the output file after successful execution of IMtrajectoryModel is given by

time	px	py	pz	tx	ty	tz	nx	ny	nz	distance	nx_fixed	ny_fixed	nz_fixed	U_0
0	px_0	py_0	pz_0	tx_0	ty_0	tz_0	nx_0	ny_0	nz_0	0	nx_fixed_0	ny_fixed_0	nz_fixed_0	U_0_0
...	...	...	...	...	...	...	...	...	...	...	...	...	...	...

in which
time is the time in seconds strating from 0
px, py, pz is the position in meter
tx, ty, tz is the tangential vector of the trajectory in meter
nx, ny, nz is the normal vector of the trajectory in meter
length is the total molten length (arc length) of the trajectory
nx_fixed, ny_fixed, nz_fixed is the normal vector that does not flip due to a heater activity change in the melting head (can be used e.g. for visualization)
U_0 is the melting velocity in m/h

Miscellaneous

• tau is the torsion, given in rad/m. With defining tau, the user can set the rotation around the melting probes' main axis. E.g. if the melting probe should rotate 180° every 2 meter, tau is simply pi/(2 m).
• If computing time is an issue, the user can prevent calculating the arc length of the trajectory using the --distance option with the value 0. The resulting output will still contain the column distance but with all values set to -1.

Limitations/Problems