HUGE gust following cruise ship. what caused it?

[lakesurfsailor]

I was out sailing a few days ago and crossed paths with a massive cruise ship. We stayed well clear of the required 100 yard distance leeward of the boat and were close hauled going around the back of the ship. About 200 yards behind the ship we were hit with an insane gust that must have been 20-25 knots (the wind was 8 gusting to 12 at most but very steady the entire day before and after this occurrence).

Is there some sort of physics phenomenon where a large boat can cause a huge gust like that kind of like a sail or foil? Or was it just a coincidental random gust that happened naturally? Nothing bad happened it was just surprising as I have never experienced anything like it before and now I am curious

 

[rgranger]

It is very possible. Depending on the angle of the ship to the wind, you might have gotten in the wash from a foil effect were a vacuum was sudenly collapsed.

 

[Don S/V ILLusion]

That phenomenon is actually common and have noticed it almost every time we pass the leeward side of a cruise ship on their mooring.

 

[kloudie1]

Think of the wind hitting the wall of the winward side of the behemoth .. The wind will increase because of the blockage and go around the aft end adding to the native windspeed .. You'll see similar stuff around bridge pillars .

 

[stickinthemud57]

I would venture a guess that you experience the effects of vortex shedding:

https://en.wikipedia.org/wiki/Vortex_shedding

This is usually the result of wind moving around a stationary object, but it stands to reason that a similar phenomenon would occur with an object moving through the wind. Perhaps you happened to be in the path of one of the vortexes.

 

[sailcapt340]

As Kloudie stated, can also happen under bridges.
I had a similar experience a few years back, while heading south and started sailing under the Jamestown Verrazano Bridge, in Narragansett Bay.
We were hit with a gust of wind that spun us around almost in a full 360. It came out of nowhere. No evidence of wind on the water, nothing but a huge gust.
Never really made it under the bridge that day. No damage to us or the boat, but very unnerving
So yes, it can happen and often does.

 

[stickinthemud57]

spun us around almost in a full 360.

Yep. Sounds pretty vortex-y to me.

 

[lakesurfsailor]

wow.. that sounds like exactly what happened. Thanks for all the responses, it is fascinating! I will definitely be more vigilant around large structures

 

[stickinthemud57]

I think the image that accompanied the Wikipedia article was remarkable, seeing just how large and how far downwind the vortexes can travel.

https://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Heard_Island_Karman_vortex_street.jpg/1024px-Heard_Island_Karman_vortex_street.jpg

 

[Hollyberry]

We once did a complete 'about face' after a ferry passed us close to weather... auto-tack and spun out...

 

[lakesurfsailor]

I think the image that accompanied the Wikipedia article was remarkable, seeing just how large and how far downwind the vortexes can travel.

https://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Heard_Island_Karman_vortex_street.jpg/1024px-Heard_Island_Karman_vortex_street.jpg

Agreed, what an awesome image. It sent me down a Google rabbit hole where I found myself looking at wind speed models:

vortex shedding wind simulation speed - Google Search

www.google.com

it's amazing that it can cause such a huge increase in speed just from the pressure change. It was one of these Viking ships:

Viking Octantis

First, we invented modern river cruising. Then, we redefined ocean cruising. Now, experience all the comfort and elegance of our award-winning fleet with an expedition ship built specifically to explore the world’s most remote destinations and allow you to immerse yourself in these regions.

www.vikingcruises.com

It is kind of shaped like a foil with a square stern so it makes sense that it would send a fairly clean blast similar to some of those images. It was traveling about 30 degrees to the wind

 

[lakesurfsailor]

like figure 20:

https://pdfs.semanticscholar.org/08ed/f6781681ffc605aa6ffc462b290830f32c5f.pdf

OK I can be done geeking out on this haha

 

[WayneH]

It doesn't have to be a big ship. The admiral and I nearly ended up on the shore after passing a tugboat on the GICW. We went from ghosting along to heeled over and stampeding for the upwind bank.

 

[stickinthemud57]

This is VERY interesting. Never having been in these situations, I was unaware of the havoc that could be wrought!

 

[Davidasailor26]

I’ve never been in a wind shadow or vortex of one, but I did once pass too close behind a tug pushing a barge. The prop wash spun me pretty far around before I got out of it.

 

[stickinthemud57]

I’ve never been in a wind shadow or vortex of one, but I did once pass too close behind a tug pushing a barge. The prop wash spun me pretty far around before I got out of it.

Well, there's another thing to watch out for. Fluid dynamics can be a real bi...., er, issue.

 

[Joe]

That gust from the passing cruise ship was the vortex created by the massive emptying of 4,000 wallets.

 

[rgranger]

That gust from the passing cruise ship was the vortex created by the massive emptying of 4,000 wallets.

Lol
Reminded me of this guy

 

[thinwater]

Where did the "100 yards required" come from?

IMO 100 yards is pretty darn close to a cruise ship. I doubt the pilot appreciated that.

 

[lakesurfsailor]

I learned it in boater safety but I also bought and read the coast guard nav rules and regs book. 100yards is no go zone, 500 yards is travel at slowest speed possible while still able to steer