Cavitation Profiles

Halcyon · 09-09-17, 02:05 AM

. . .

FPSchazly · 09-11-17, 01:42 PM

I've heard this can be determined mathematically by examining the cavitation profile specified for each boat in the boat config file. Forgive the vague terms, I'm not sure of the specifics.

My point is it's not necessary to determine these empirically.

-Pv- · 09-11-17, 01:48 PM

Do you have an example of doing this as you describe or the ID of someone who claims to have done this?

When I look at the cavitation numbers in the default submarines, they are all the same, but the exact depths/speeds are a little different for each sub I have used. So far, I've found no other way than experimenting, the easiest is to use the Navigation mission with each sub.
While I have started creating tables of my own, they are not detailed down to the knot yet.
-Pv-

FPSchazly · 09-11-17, 02:45 PM

Did some digging.

http://www.subsim.com/radioroom/showthread.php?t=232919

It's just a linear formula y=mx + b, where x is the speed in knots and y is the depth in feet, with m equal to the first parameter (20) and b equal to the second parameter (-100). Were you testing the depths manually or using the new automated depth control?

Although 19 vs 20 are in fact not identical, they're very close. Honestly, when you're diving and the boat is at an angle, I don't know how useful the keel depth would be to determine cavitation given that the bow and stern would be at different depths. I'm not sure if the game takes that into account.

-Pv- · 09-11-17, 03:13 PM

In all the default sub vessel files CavitationParameters=20,-100 is used yet the actual 3D sim values are slightly different from each other when tested.
There is more to this than the obvious.
-Pv-

FPSchazly · 09-11-17, 04:03 PM

It could be related to the distance between keel and screw centerline.

-Pv- · 09-11-17, 05:11 PM

^^^
Makes sense.

Halcyon · 09-11-17, 08:31 PM

Quote:

Originally Posted by FPSchazly

Did some digging.

http://www.subsim.com/radioroom/showthread.php?t=232919

It's just a linear formula y=mx + b, where x is the speed in knots and y is the depth in feet, with m equal to the first parameter (20) and b equal to the second parameter (-100). Were you testing the depths manually or using the new automated depth control?

Although 19 vs 20 are in fact not identical, they're very close. Honestly, when you're diving and the boat is at an angle, I don't know how useful the keel depth would be to determine cavitation given that the bow and stern would be at different depths. I'm not sure if the game takes that into account.

I tested by manually adjusting the ballast to go down 1 foot at a time. I went back and forth several times between +19 or +20 feet for several speeds to find which depth triggered the cavitation.

The slope intercept formula isn't linear in my testing. Maybe they round up or down for fractional depths...but that data is locked into the code and the only way you know for sure is manually testing.

As far as angles, my boat was level the entire time during testing because I left the planes at 0.

-Pv- · 09-11-17, 09:06 PM

Nice
-Pv-

Kazuaki Shimazaki II · 09-12-17, 01:53 AM

Maybe the real lesson here is to actually play it for real and not un-necessarily take your boat right to the theoretical limit. I remember doing similar things back in Dangerous Waters, and it is easier to do now that you are allowed knot-by-knot control. But should we be encouraging such "gamey" behavior?

Kazuaki Shimazaki II · 09-12-17, 05:57 AM

I agree just being completely ignorant or cavalier is gamey. However, neither do real submariners go "According to theoretical calculations, my submarine will cavitate at 10 knots at under 99 feet. I am now exactly 100 feet, so I will order 10 knots. When I get to exactly 113 feet, I will order exactly 11 knots."

You do such things in a game (I did too, in DW) because it is completely predictable in this regard and really your boat is free. If your lives depended on it, most likely you'll wait till say 150 feet before putting the 10 knots on, just in case.

So I suggest it might be more immersive and realistic if you just ran with a basic idea of roughly where the line is and play it safe from there.

-Pv- · 09-12-17, 01:18 PM

If cavitation charts are no good to you, ignore them.
-Pv-

Capt Jack Harkness · 09-12-17, 08:28 PM

Quote:

Originally Posted by FPSchazly

It could be related to the distance between keel and screw centerline.

Isn't the depth shown actually the vessel center line rather than keel?

FPSchazly · 09-12-17, 11:02 PM

In the game? I have wondered that based on the "Conditions" tab. It's supposed to be from the keel.

Halcyon · 09-13-17, 03:49 AM

Quote:

Originally Posted by FPSchazly

In the game? I have wondered that based on the "Conditions" tab. It's supposed to be from the keel.

Looks like it goes off the bottom of the rudder.

09-09-17, 02:05 AM	#1
Halcyon Helmsman Join Date: Feb 2010 Location: West Coast, USA Posts: 106 Downloads: 105 Uploads: 3	Cavitation Profiles . . . Last edited by Halcyon; 01-22-22 at 01:32 AM.

09-11-17, 01:42 PM	#2
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Beantown Posts: 776 Downloads: 15 Uploads: 1	I've heard this can be determined mathematically by examining the cavitation profile specified for each boat in the boat config file. Forgive the vague terms, I'm not sure of the specifics. My point is it's not necessary to determine these empirically. __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

09-11-17, 02:45 PM	#4
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Beantown Posts: 776 Downloads: 15 Uploads: 1	Did some digging. http://www.subsim.com/radioroom/showthread.php?t=232919 It's just a linear formula y=mx + b, where x is the speed in knots and y is the depth in feet, with m equal to the first parameter (20) and b equal to the second parameter (-100). Were you testing the depths manually or using the new automated depth control? Although 19 vs 20 are in fact not identical, they're very close. Honestly, when you're diving and the boat is at an angle, I don't know how useful the keel depth would be to determine cavitation given that the bow and stern would be at different depths. I'm not sure if the game takes that into account. __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

09-11-17, 04:03 PM	#6
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Beantown Posts: 776 Downloads: 15 Uploads: 1	It could be related to the distance between keel and screw centerline. __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

09-12-17, 11:02 PM	#14
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Beantown Posts: 776 Downloads: 15 Uploads: 1	In the game? I have wondered that based on the "Conditions" tab. It's supposed to be from the keel. __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

09-11-17, 01:48 PM	#3
-Pv- The Old Man Join Date: Apr 2006 Posts: 1,434 Downloads: 5 Uploads: 0	Do you have an example of doing this as you describe or the ID of someone who claims to have done this? When I look at the cavitation numbers in the default submarines, they are all the same, but the exact depths/speeds are a little different for each sub I have used. So far, I've found no other way than experimenting, the easiest is to use the Navigation mission with each sub. While I have started creating tables of my own, they are not detailed down to the knot yet. -Pv-

09-11-17, 03:13 PM	#5
-Pv- The Old Man Join Date: Apr 2006 Posts: 1,434 Downloads: 5 Uploads: 0	In all the default sub vessel files CavitationParameters=20,-100 is used yet the actual 3D sim values are slightly different from each other when tested. There is more to this than the obvious. -Pv-

09-11-17, 05:11 PM	#7
-Pv- The Old Man Join Date: Apr 2006 Posts: 1,434 Downloads: 5 Uploads: 0	^^^ Makes sense.

09-11-17, 09:06 PM	#9
-Pv- The Old Man Join Date: Apr 2006 Posts: 1,434 Downloads: 5 Uploads: 0	Nice -Pv-

09-12-17, 01:53 AM	#10
Kazuaki Shimazaki II Ace of the Deep Join Date: Jan 2006 Posts: 1,140 Downloads: 5 Uploads: 0	Maybe the real lesson here is to actually play it for real and not un-necessarily take your boat right to the theoretical limit. I remember doing similar things back in Dangerous Waters, and it is easier to do now that you are allowed knot-by-knot control. But should we be encouraging such "gamey" behavior?

09-12-17, 05:57 AM	#11
Kazuaki Shimazaki II Ace of the Deep Join Date: Jan 2006 Posts: 1,140 Downloads: 5 Uploads: 0	I agree just being completely ignorant or cavalier is gamey. However, neither do real submariners go "According to theoretical calculations, my submarine will cavitate at 10 knots at under 99 feet. I am now exactly 100 feet, so I will order 10 knots. When I get to exactly 113 feet, I will order exactly 11 knots." You do such things in a game (I did too, in DW) because it is completely predictable in this regard and really your boat is free. If your lives depended on it, most likely you'll wait till say 150 feet before putting the 10 knots on, just in case. So I suggest it might be more immersive and realistic if you just ran with a basic idea of roughly where the line is and play it safe from there.

09-12-17, 01:18 PM	#12
-Pv- The Old Man Join Date: Apr 2006 Posts: 1,434 Downloads: 5 Uploads: 0	If cavitation charts are no good to you, ignore them. -Pv-