10. EXAMPLE INPUT FILES

Example input files have been placed in the examples directory. These files are described below and should be used as templates for your own designs.

To use the example files, you must save the indicated example file as in.mlt in the main Michlet directory (i.e. the directory that contains the executable file). This will overwrite the current in.mlt with the example input file. You may be required to save additional files in the directory before running some examples.

Remember to use the Esc to escape from any screen when running the examples.

When you first install Michlet, the in.mlt file is a copy of the wigley_ex1a.mlt file described below.

MONOHULLS

Examples 1a, 1b, 1c, 1d, and 1e: Model-sized Wigley parabolic hull

These five examples use different methods to generate hull offsets.

wigley_ex1a.mlt: The table of offsets is contained inside the input file.

wigley_ex1b.mlt: Offsets are generated using hull Series 1.

wigley_ex1c.mlt: Offsets are generated using hull Series 8.

wigley_ex1d.mlt: Offsets are contained in a separate file. To run this example, first save the file wigley_ex1d.mlt as in.mlt in the same directory as the executable. You must also save the file wigley_useroff1.csv as useroff1.mlt in that directory.

wigley_ex1e.mlt: Offsets are generated using splines that are defined in a separate file. To run this example, first save the file wigley_ex1e.mlt as in.mlt in the same directory as the executable. You must also save the file wigley_sploff1.mlt as sploff1.csv in that directory.

To calculate resistance, press R from the main screen, then choose one of the display options.

To examine wave pattern plots, press Esc until you are back at the original screen. Now press W and choose the Transverse Cut view by pressing T. Note the small oscillations near the left-hand and right-hand edges of the graph. These are due to an insufficient number of theta intervals being used in the calculations. If Ntheta was increased to, say 1024, in the input file, these oscillations would not be apparent, however, calculations will take roughly twice as long.

Press Esc and the press R to see a contour plot of a rectangular region of the wave field. The striations inside the V-shape are due to an insufficient number of points being used. If the number of nodes in the x-direction and the y-direction were both increased to, say 301, the striations would disappear, but calculations would take almost nine times longer. Clearly, it is important to use as many points as is necessary for the particular task at hand.

Twenty-one stations and waterlines have been used in all five examples. When a table of offsets is used, as in examples 1a and 1d, it is not easy to increase (or decrease) the number of stations and/or waterlines. For the mathematical series (examples 1b and 1c) and the spline method (example 1e), all that is required is for the number of stations and the number of waterlines to be changed. Remember to use odd integers for both!

If you want a permanent copy of the input file you have just modified, save it using a meaningful filename in another directory. You should also save any associated files (e.g. useroff1.csv or sploff1.csv) in the same directory.

Note that there will be small differences between the hull parameters calculated for the five examples due to the different methods for representing hull offsets. Results will be most accurate for the method using the mathematical series. Less accurate are the methods using tables of offsets. The spline method is the least accurate of the five methods, but could be improved by using more nodes.

nplxx.mlt : Transom stern hulls

This series of input files contains the details of small hulls with transom sterns. Experimental trim and sinkage values have been included.

Note that the offsets for the NPL examples use the spline input method to generate offsets. Before running an example, make sure that you have saved the file npl_sploff1.csv as sploff1.csv in the same directory as the Michlet executable. The same spline file can be used for all NPL series hulls.

Comparisons of Michlet resistance predictions with experimental data for this series of hulls is available in the Excel spreadsheet located in the 'docs' directory.

m1x.mlt : Lightweight men's single rowing shell.

This input file contains the offsets and details of a small rowing shell.

ffg8.mlt : Frigate.

This input file contains the offsets of a U.S. frigate. Offsets (in spline format) are contained in the file named ffg8_sploff1.csv. Remember to save the file as sploff1.csv in the main Michlet directory before running the program.

ddg51.mlt : Destroyer hull with sonar dome.

This input file contains the offsets of a destroyer with a transom stern and a large sonar dome. Dimensions are those of the US vessel, Arleigh Burke.

ddgsig.mlt : Pressure signature of DDG51 destroyer.

This input file is identical to the ddg51.mlt file, except that water depth has been set to 120.0m, and the rectangular patch dimensions are different. For many calculations of interest, we would like to know the pressure on the bottom of the seabed around the entire ship, not just behind the vessel as we do with wave elevation calculations.

NOTE: Michlet's calculations have not yet been validated, and the scaling of the pressure has not been checked. Please treat this as an illustrative example only.

Run this example and press P from the opening screen to invoke the Pressure Signature menu. Then press R to calculate the bottom pressures. The maximum absolute pressure (above atmospheric) is about 590 Pa.

Press c and then enter 200. The high pressure zone forward of the bow should now be more apparent.

You can save the pressure data by pressing s. You can also save the contour plot as a .pcx file by pressing S.

lasub.mlt : LA Class submarine.

This input file details of a submarine which is submerged to the top of the conning tower. Offsets (in spline form) are contained in the file named lasub_sploff1.csv.

DIHULLS

model_tagos.mlt : Model SWATH

This input file contains the details of a model of the SWATH T-Agos.

proa.mlt : Proa with Wigley amas

A one tonne dihull with a 0.75 tonne main hull and a 0.25 tonne outrigger.

weinblum.mlt : Asymmetric SWATH

The shape of the demihulls, and the lateral and longitudinal spacing have been chosen to almost completely eliminate waves on the starboard side of the vessel at 3.875 ms-1.

This example calculates elevations at 151x151=22801 field points using Ntheta=512 which should take about 30 seconds on a 1GHz PC.

Remember to save wave elevation plots and data from the Waves screen before you exit the program if you require a permanent copy of the output.

TRIHULLS

arrow.mlt : Arrow-shaped trihull with Wigley amas

6.0 tonne trihull; the central hull is a 5.0 tonne T-Agos hull, the 0.5 tonnes amas are Wigley hulls.

leaning3.mlt : Trihull with PEP demihulls

This example illustrates the effects of large sinkage of the demihulls of a trihull. As speed increases, one ama lifts out of the water, the sinkage of the other ama increases by as much as the other ama emerges. At the highest speed, the starboard ama has emerged completely and the vessel is behaving like a proa.

flying3.mlt : Flying trihull with PEP hulls

This file is identical to leaning3.mlt, except that all demihulls lift out of the water. At a speed of 6 ms-1, the amas have both left the water completely. As speed increases further the central hull emerges more and more, until, at 12.0 ms-1, it too leaves the water. At that point the resistance of the submerged portion of the vessel drops to zero.

TETRAHULLS

diamond.mlt : Diamond-shaped tetrahull

This vessel has four LL4 demihulls in a diamond arrangement. The vessel was designed to produce very low waves on both sides at 3.875 ms-1. Compare with the Weinblum example which produces low waves on only one side of the vessel at the same speed.

This example calculates elevations at 301x301=90601 field points using Ntheta=1024 which should take about 4 minutes on a 1GHz PC. Since the wave field is (laterally) symmetric, that time could be halved by considering only one side of the vessel.

slice.mlt : SLICE with SWATH demihulls

A four-hulled vessel with two pairs of SWATH demihulls.

PENTAHULLS

vpenta.mlt : V-shaped pentahull

This vessel has five Wigley demihulls arranged in a V-shape. The input file can be used as a template for a pentahull or for comparing five different individual hull designs.


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