Michlet 9.30 Released

[Leo Lazauskas]

The previous version (9.20) of Michlet was downloaded over 6000 times
and attracted 10 donations over the 2 last years. Many thanks for your
support!

If you find Michlet useful, please consider making a small (e.g.
$10 to $100) donation through PayPal on the Michlet page at:
http://www.cyberiad.net/michlet.htm

Only minor enhancements have been implemented in version 9.30.

The main change is to allow the hull to be submerged to a prescribed
depth. This makes it easier to study the effects of depth on the wave
resistance and far-field wave patterns of axi-symmetric and other
submarine-like bodies.

Three new hull series have been implemented to generate axi-symmetric
bodies that have been studied over the last 60 years and for which
experimental results exist in the open literature.

Summary of Changes
------------------

* Speeds can now be spaced non-uniformly. This makes it easier to
compare predictions with measurements at the same speed. It also
means that more speeds can be be used at low Froude numbers where
the wave resistance curve oscillates rapidly.

* Corrected type-setting error of mathematical equation describing
Series 1 offsets in the Michlet manual.

* Implemented hull submergence depth.

* Added Series 4: mathematical axi-symmetric bodies.

* Added Series 58: Gertler's mathematical axi-symmetric hull series.

* Added Series 5470: mathematical series to generate DARPA SUBOFF
bare hull.

INSTALLATION AND REMOVAL
------------------------
After downloading the file, unzip it into a convenient sub-directory.
To remove the program, just delete the directory. Michlet does not
change any system files.

Manuals are in the docs directory. Start with michman.pdf, the Michlet
manual.

< superseded by new version at http://www.boatdesign.net/forums/design-software/michlet-9-32-released-50211.html >

 

[Remmlinger]

Michlet lives!

Great !!

when I tried to model a submerged foil in:
http://www.boatdesign.net/forums/hy...-rudder-using-michlet-44531-2.html#post579068
I had to use all kind of tricks.
As soon as I will find some time, I will check if the new version will give the same (or even more accurate) results for the submerged foil.

Very useful addition to Michlet, thanks
Uli

 

[Leo Lazauskas]

Great !!

when I tried to model a submerged foil in:
http://www.boatdesign.net/forums/hy...-rudder-using-michlet-44531-2.html#post579068
I had to use all kind of tricks.
As soon as I will find some time, I will check if the new version will give the same (or even more accurate) results for the submerged foil.

Very useful addition to Michlet, thanks
Uli

Thanks, Uli.
I'm not sure if the latest change will be of much help to you.
You can submerge the whole ship, but not individual components
to different depths. I could have allowed that option in the
public release, but it would have meant that the Michlet input
file produced by Delftship would need modification before being
able to be used by Michlet. One of Michlet's strengths is that
Delftship produces a valid input file and I didn't want to ruin
that inter-operability.

 

[Remmlinger]

At the time when I started the old thread I was only interested to compare Michlet-results with the towing tank experiments of an isolated vertical foil (Kuhn and Scragg). The question was, if this foil (= rudder without hull) is lowered and the foil is not "wave-piercing" any more, how does this change the wave resistance. I assume Michlet 9.20 will make this simulation now easier.

 

[quequen]

Leo, what is wrong with this file? It comes from Delftship and is not showing any waterlines in the plan view. Michlet shows a wrong LCB also. Edit: it's not wrong, in fact! Now I realize LCB is taken in meters from amiship, positive front.

 

[quequen]

How is Submergence related to Fh and Water Depth?
Seabed Pressure Signature and Fh aren't related to Submergence. They seem to be related to WaterDepth and Fh solely. So changing inmersion of the ship don't change seabed pressures. Is this correct?

 

[Leo Lazauskas]

How is Submergence related to Fh and Water Depth?
Seabed Pressure Signature and Fh aren't related to Submergence. They seem to be related to WaterDepth and Fh solely. So changing inmersion of the ship don't change seabed pressures. Is this correct?

Yes, that is correct.
Sea-bed pressures are only valid for surface-piercing vessels in public releases
of Michlet.

Leo.

 

[quequen]

* Speeds can now be spaced non-uniformly. This makes it easier to
compare predictions with measurements at the same speed. It also
means that more speeds can be be used at low Froude numbers where
the wave resistance curve oscillates rapidly.

Leo, how is the syntax for this new feature? the 930 manual has no changes on this point:

7.4 Ship Speed Range
The next three parameters specify the speeds (in ms-1) at which to calculate the resistance and wave
elevations, via the minimum speed, Umin, the maximum speed, Umax, and the number of speeds, NU.
The minimum speed and maximum speed must be decimals. NU must be an integer greater than or equal
to 2 and less than or equal to 101.

 

[Leo Lazauskas]

Leo, how is the syntax for this new feature? the 930 manual has no changes on this point:

7.4 Ship Speed Range
The next three parameters specify the speeds (in ms-1) at which to calculate the resistance and wave
elevations, via the minimum speed, Umin, the maximum speed, Umax, and the number of speeds, NU.
The minimum speed and maximum speed must be decimals. NU must be an integer greater than or equal
to 2 and less than or equal to 101.

It was described in manuals for people who donated to the project at that
time. The next version (9.32) is almost ready to release but I'm waiting on
some donations before spending any more time on it.

 

[b1ck0]

Leo, I am wondering ... is it possible to analyze a drillship (including the moonpool) with this software ?

 

[Leo Lazauskas]

Leo, I am wondering ... is it possible to analyze a drillship (including the moonpool) with this software ?

Probably not.

For a drill ship wouldn't the moonpool be closed and the vessel stationary when
drillling?

I can understand it might be important for vessels that lay cables, i.e. they are moving and the moonpool is open.
Or am I missing something?

 

[b1ck0]

The moonpool is designed as a permanent recess and normally it's quite big (40m x 12m), because all drilling/lowering activities are done through it. Unfortunately it's not possible to cover the moonpool during transit, so we have another sloshing issues inside. My question was if I should model the moonpool in MICHLET or just to assume that it's missing ? I suspect that the moonpool cannot affect the wave pattern generated by the bow/stern of the vessel, but I would be happy if you can give your opinion also.

P.S:
Let me summarize:
1) The moonpool adds resistance to the overall picture. Check added resistance of moonpools (piston and sloshing modes)
2) Is the moonpool affecting the overall wave pattern generated by the ship ?