Ocean Currents and wind forces

[silent marshal]

In preparation to a new navigation mod (working title: ***8222;pretty new navigation mod***8220;) I wonder how SH5 deals with unattached dynamics like wind force and ocean currents.

I don***8217;t expect that SH5 has implemented currents or wind drifts, I think I***8216;ve never noticed this before (but I will make some tests tonight). So this leads me to some questions:

Q1) is it possible to slew an object (eg.u-boat; speed = 0!), whether on surface or submerged, with a predefined force-vector (direction and quantity)? If yes...

Now the ideas:

Step 1) implement wind drift (simple mode: force is independent from the exposed surface of the boat)
Step 2) implement ocean current (no tidal current at this stage):
Step 2a) surface and subsurface current (increasing constantly with depth); create ocean current maps (mip-mapping?) for gameplay; for calcualtion purpose the map will be divided into square-zones and each zone has it***8217;s specific current vector. But keep it simple!
Step 3) implement tidal current

The currents at the bottom of the ocean should be zero because otherwise an enduring creak***8217;n***8217;squeak would get on our nerves. This should be also true at harbors.

Facing some problems:
P1) boats speed = 0, heading 360°, wind from 270°at 5 kt; surface current = 0: the boats heading should remain constantly at 360°but it***8216;s position changes (with a reduction factor for the wind speed, of course).
P2) boats speed = 2 kt, heading 360, depth = 30m, wind = 0 (doesn***8217;t matter at all); subsurface current = 7kt from 360°: the boat should remain 360° but should be pulled back with less than 5kt with engines running forward .

This should be enough for this time. I read some threads for SH3 but haven***8217;t found some for SH5.

Would be very pleased if you tell me what you found out yet.

[THE_MASK]

I did a test . Started at 40Deg 5' north , wind 15m\s at 90Deg . Travelled west 270Deg for 3000klms . Finished position was 40Deg 34' north . Using real navigation .

[Commander Mysenses]

Go for it, sounds great.
Would love some currents to use/fight against in the narrows (channel, orkney, Gibraltar, etc). Windage would be interesting/bloody annoying (as real life can be), great idea.

[silent marshal]

Hi sober!

Can you explain the result, please? Does the wind has any effect? What happens if you set your boat's speed = 0, stormy condition and wait for 12 hours? Well, I guess, nothing will happen.

Thanks for your testride!

My idea is as follows:
a) for boats with speed greater or less than zero, we can choose the course at the compass, lets say 360°. Now the boat will turn to north, BUT: to consider surface current and wind influence, this input is adjusted by these factors (calculation done by software) and THEN the command ist given to SH5, in this case let's say 005°.

I can imagine that this would work properly, even SH5 doesn't support external forces.

That's good for boat speeds (much) greater than zero but what if the speed is 0 (like I mentioned in my first post - see P2): in this case the boat will turn it's bow to 180° - not what we would like to see.

[ETsd4]

Can you explain the result, please?
Yes.
There was a course drift of 1,1° by such a weather...
http://upload.wikimedia.org/wikipedia/commons/5/5c/Beaufort_scale_7.jpg

[silent marshal]

Ok, made some testrides:

A) Wind from 270° with 12m/s; boat's speed = 0; elapsed time = 6hr: delta position of the boat = 0.

B) Boat's speed = 0, depth = 40m; elapsed time more than 6hr: delta position of boat = 0.

My conclusion is that SH5 doesn't take any account of windforce and has no ocean currents implemented (what didn't surprised me at all).



The reason why I want current is it's influence on dead reckoning.

I am not so firm with modding or scripting or programming in python so I need help from you modders out there. If I can enthuse someone with my Idea, I would be very satisfied. The modded SH5 is a wonderful game, I want to make it even more realistic.

[LemonA]

What should be the drift in m/s for the type VIIC if the wind is 12m/s?

[TheDarkWraith]

I am not so firm with modding or scripting or programming in python so I need help from you modders out there. If I can enthuse someone with my Idea, I would be very satisfied. The modded SH5 is a wonderful game, I want to make it even more realistic.

Scripting is not going to be able to add this. The variables are read-only and thus no way to change them. The only way is the hard way - exe modifying.

[silent marshal]

What should be the drift in m/s for the type VIIC if the wind is 12m/s?

There are a couple of formulas which factor the viscosity of the surrounding water in (counteraction). But I think, we should keep things simple. For example just determine that a windforce with 12m/s will result a drift of the boat (independent of the boat's heading in relation to the wind vector) of, lets say: 1m/min. Is this too much? Is it too little? I depend on the experience of real-life skippers. They can estimate the effect best. In the same way, the ocean current could be considered.

The aim is not to create a finite element simulation but the objective factors have an influence on dead reckoning.

@TDW: nice to have a pro on board!! I can't rate what modifying .exe means - but it sounds to be hard work. So is it principally possible to consider such "outer" forces?
There are lifeboats in SH5 - how are they moved/propelled? Maybe a function similar to this can solve the problem.

Hope to get some good news...

[Sailor Steve]

1m/min. Is this too much? Is it too little?
1 meter per minute is 1.44 kilometers, or 2.28 nautical miles per day. After a week's travel with no sighting you would be about 16 nautical miles off course. I was a sailor but not a navigator, so I don't know if that comes close to the reality, but it sounds to me like it needs more.

[LemonA]

The aim is not to create a finite element simulation but the objective factors have an influence on dead reckoning.
So you want to make dead reckoning harder. Ok, but on the other side we must also be provided with the navigation aids, especially a List Of Lights for all buoys and lighthouses in the game to have a chance for coastal navigation. I can't rate what modifying .exe means - but it sounds to be hard work.
I rate it for you:
For beginners in (assembly-)programming it means 20.6.2013
For professionals and you are lucky it means 08.04.2012
For professionals and you have no luck it means 30.07.2012 - 31.12.2012


I would expect a wind-drift of 1 m/s or more if the wind is 090°Relative @ 12 m/s.

[elmusul]

It sounds great, really great! :up:
I think it would be more realistic, not to keep the right course in bad weather or even the currents move the submarine significantly ...
in real life, the waves can drag the boat against the shore, but in the game you can stop the engine in the storm and the submarine remains fixed in the same place ....

I imagine how hard it would take a submarine in the middle of the night against a convoy in motion and strong winds...

[quink99]

There are a couple of formulas which factor the viscosity of the surrounding water in (counteraction). But I think, we should keep things simple. For example just determine that a windforce with 12m/s will result a drift of the boat (independent of the boat's heading in relation to the wind vector) of, lets say: 1m/min. Is this too much? Is it too little? I depend on the experience of real-life skippers. They can estimate the effect best. In the same way, the ocean current could be considered.

The aim is not to create a finite element simulation but the objective factors have an influence on dead reckoning.

@TDW: nice to have a pro on board!! I can't rate what modifying .exe means - but it sounds to be hard work. So is it principally possible to consider such "outer" forces?
There are lifeboats in SH5 - how are they moved/propelled? Maybe a function similar to this can solve the problem.

Hope to get some good news...


Silent Marshal,

From both a navigational and a hydrodynamic standpoint there are several complex interreactions at play in determining the effect of wind and current on a vessel when they act simultaneously.

WIND 1) The flat plate surface area above the waterline and the surface area below the water line.
2) The duration, intensity, direction, and rate of change of the wind over time.
3) The course and speed of the vessel in relation to that wind.

CURRENTS - Much simpler. Not allowing for the wind, the direction, the speed, and the rate of change in both direction and velocity of the current, the vessel's movement would be the same as the current's.

The interreaction between the two elements makes the problem considerably more challenging but if you happen to have some time available on the neighborhood Cray computer you could probably make a pretty cool navigation MOD.

Good luck!

[silent marshal]

I have made some investigations and it seems that wind force will have no noticable influence for dead reckoning. There are of course some special situations when wind force will be a term to consider but for navigation purpose it is neglectable (in my opinion).

But the ocean currents are still from any interest. There will be no differentiation of surface (depth = 0) and subsurface currents because we can assume that for our depths the vector is constant.

Here is an example of ocean currents. As you can see, there are a lot of currents and it is obvious that currents of 2kt in the canal will have influence when subsurfaced and we saunter with electric motors to hide from the evil enemy. So we have to consider carefully when to dive because our battery capacity will expire much quicker. Maybe we have to choose against an subsurfaced brake through and wait for the night to sneak past.

Take a look at the map:

http://s7.directupload.net/images/120312/wx7oybfy.jpg

I still don't know how to implement external forces. Any suggestions yet? (There must be some senior modders who can give basic information!).

Greetings to you modders out there!

[LemonA]

Wind drift of the surfaced type viic u-boat is ca. 3% - 5% of wind speed.

12m/s wind from 270°Rel and u-boatspeed is 0.0 ktn then drift will be ca. 0.48m/s = 1.73km/h = 0.933 ktn/h