Effect of Friction Lines on the Resistance of a Friction Plane

Attached is a short note that might help some boffins with their calculations
of total resistance using a variety of skin-friction formulas.

Also attached is a zip file containing Michlet files that can be used to make
similar computations.

Remember to save the input file as in.mlt and the offset file as sploff1.csv
before running Michlet.
One input file is for a draft of T=1.0m, the other is for T=1.2m.
The same offset file can be used for both cases.

Maxsurf's "HullSpeed" should give almost identical estimates of the wave resistance
for this very thin hull.

Have fun!
Leo.

 

Great input Leo, thanks!

 

Thanks, Alik.

Incidentally, Candries' thesis is available online. Search for Candries thesis. (The link is long and ugly, so I didn't post it).
Also, the pre-prints of the 26th ITTC are now available.
http://www.cmeventos.com.br/ittc2011/discussions/list.php

 

Thanks for the links.

 

Ta.

Fig.10....????

 

Looks Ok to me. My convention (which I foolishly didn't explain in the report) is for the bow to be on the left, i.e. at x/L = -0.5.

 

Leo

In the summary you refer to fig.10.
But there is no fig.10..i assume it is a typo and meant to read fig.1?

 

Fig 10 on page 11?

 

Ah ha.....bummer...my file corrupted during downlosd, i only got 3 pages.

I redid it, and hey presto, all the pages are there...doh!!

What an arse eh?!!

 

Leo, I can't get it to load. I am using mlt807w.exe. I changed waterline count from 101 to 81, and changed form factor from 3(dual) to 0 (none) and still no good. Can you check on the load on the free version, I think 'in' is calling on a crippled function or exceeding the bounds of the free version somehow.

 

You need the latest free version of Michlet. You can get it from:
http://www.boatdesign.net/forums/design-software/michlet-9-20-released-37816.html

Or you can just use the sploff1.csv file with a version 8.07 in.mlt file. Just copy over the values
of the speed, hull principal parameters etc.
Leo.

 

Thank you Leo for pointing out Candries' thesis, which I did not know. It is also a great test case for a boundary layer calculation. Hope I find some time to report about comparisons.
Uli

 

My pleasure, Uli.

There has been a lot of work done since Candries' work on the effects on resistance of surface treatments and roughness in general. Sadly, as some of the reports form the 26th ITTC show, we are not that more advanced in our ability to estimate the effects of roughness. It seems that Towsin's simple empirical method is still as good as anything else.

Leo.

 

Great timing Leo. Just what I am working on. Resistances.

I have downloaded michlet 9.20 and the nerdc4215 files and unzipped it. How do I make it work?

 

You really need to be familiar with Michlet, i.e. by reading the manuals and going through the examples. I warn users that it is not an easy program for beginners - it requires the user to make some considerable efforts to become proficient, as with most hydro computer programs.

1. Save the nsrdc4125_t1000_in.mlt file as in.mlt in the same directory as the Michlet executable.

2. Copy the sploff1.csv file to the same directory

3. Run Michlet, e.g. by double clicking on the michlet.bat file

4. Press R (that's uppercase)

5. Then press, for example w.
That should bring up a graph of the wave resistance after a minute or so.
This example runs fairly slowly because I have used a very fine mesh to ensure accurate estimates.

6. On exit from Michlet, results will be in the drag.mlt file.
This is just a text file that can be loaded into Excel.

Good luck!
Leo.