There was a column in Newsweek about an artificial wave tank for surfing. It said that the tank generates standing waves. Seems to me that it would difficult to surf a standing wave. Did Newsweek get it wrong? Is “standing wave” used to refer to something other than what it means in Physics? Or do people really surf standing waves?
Since a standing wave doesn’t move, it wouldn’t generate any lift. You’d just slide down the face. So I agree with you. The article probably messed it up.
No, actually this is fairly old news and Newsweek didn’t screw anything up. I first saw a news story about it 3-4 years ago.
You physics geeks need to get out of the lab more. In surfing, a standing wave is formed by the wake of a boat, or by the passage of a current past an obstruction, like a bridge support. The resulting wave “stands,” or is maintained over a long period of time. It is quite possible to surf such waves, as evident by http://www.surfingvancouverisland.com/surf/newgard/waves.htm. The difference between standing waves and moving waves is obvious when you think about it. A moving wave travels through a largely motionless body of water, whereas a standing wave is motionless (relative to the obstruction creating it) and the body of water moves.
No, I don’t agree with any of that. A standing wave would oscillate, but the nodes would not move–that’s the way it works on a piano or guitar string. There are areas that don’t move (the nodes) but others where the string moves from one extreme to the other.
Although I haven’t seen or heard about the standing wave surfers, I’d imagine they could surf down the wave towards the node, and then turn around and surf down into the trough that formed behind them, then ride the wave back up.
There are quite a few more one can find with Google. Also, it was either the Discover Channel or the Travel Channel which has done stories about wave surfing specially designed pools with stationary waves.
Surfing standing waves in kayaks and canoes is common. C’est moi in the top, and Paul Cook in the bottom:
http://www.tbaytel.net/culpeper/BrokenBridge.html
As water tries to go down a river, if there is a constriction it runs into the water that is already there, and as a result it piles up in a standing wave.
As far as surfing a standing wave goes, you face upstream. The water pushes you downstream, meaning up the face of the wave. As you get pushed up the face of the wave, gravity pulls you back down the face of the wave. Given the right shape of the wave and the right current, you can find an equilibrium that lets you surf on the face of the wave until the cows come home.
Cheers,
Richard Culpeper
Mayhaps it has no bearing, but you may wish to investigate solitons.
Your are wrong in this case, RMT, guitar strings notwithstanding. A standing wave is always in a current, so the nodes are moving, relative to the surface of the water. As the nodes are moving, the crest of the wave appears to stand still, and the surfer can ride the front of the wave indefinitely
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And when too much water heading downstream is stopped by the water already there (e.g. when the water pours over an obstruction into a pool), the wave face curls back down on its own upstream face, forming a hole in which surfing is easy, but stopping surfing and continuing downstream can be difficult.
For your surfing amsement, I offer the following:
Ottawa River’s Phil’s Hole. The Ottawa River has some lovely large rapids, including McCoy’s Phil’s Hole, which at some water levels can be as deep as eight feet, which it was the first time I tried kayaking past it. Previously, I had always used my Chestnut canoe, in which the move was a simple side-slip left in a back-ferry underneath Sattler’s Hole across the top of Phil’s Hole. So I tried the same move in a kayak. Big mistake.
That’s when I learned that kayaks don’t back ferry worth a bean when compared to canoes. The silly boat didn’t make it far enough across, so I had the distinctly unpleasant experience of almost making it through, only to fall back down into Phil’s.
First step: see if I can side-surf a kayak. Yup. Side surfs nicely. Lots of people swim Phil’s, so having stabilized on a side surf, I figure that I’ll find a way out, even if it means a swim.
Second step: Try running from one end of the forty or so foot wide hole to another, hoping to catch a corner. Almost make it, but just when I am within a few feet of the top, I am always pulled back in. Close only counts in horseshoes.
Third step: Try rolling while extending my paddle for bottom water. WhizzFlappityFlappityFlappityFlappityFlappity – you’ve never seen a window blind roll up so quickly. It’s dizzying.
Fourth step: Try endering out. After the windowshading, I’m leery of this approach, but I’m running out of options. Of course it does not work, and just to add insult to injury, it rips my helmet off.
Then I heard a blast on a whistle, and things got a little weird.
The raft guides thought I was deliberately playing in Phil’s, and were getting impatient at my holding up their runs, for I had been down in it for over five minutes. So their coordinator started running them through after warning me with the whistle. I backed up to one end of the hole, and watched the show. My word, the carnage was impressive. Some of the rafts made it through, but a couple were flipped back into the hole, sending their occupants spewing in all directions into the hole. Made me wonder why people paid hard earned cash to the rafting companies.
Eventually all the rafts passed through, so I went back to trying to find a way out. I was having some initial success at side-surfing the right of centre section with the deep water tongue, reducing my lean to increase my lift, and it almost worked, until the darn hole sucked my boat off of me. That was the last thing I had expected.
So there I was, with my boat cartwheeling in front of me, while I briefly bodysurfed with my paddle as if I were in a boat. Then the bad thing happened. The very bad thing happened.
Phil’s yanked my paddle out of my hand, which blew my bodysurf. I became yet another gorbie sacrificed to the River Gods. Phil’s then proceeded to unzip my PFD, unclip my PFD belt, remove my PFD, remove my paddling jacket, remove my paddling booties, and remove my shorts. We’re talking fully outfitted to buck nekkid in five seconds as I was rolled about and then swept out the bottom of the hole.
Now I wasn’t too worried about the public nudity, for at least Phil’s had finally flushed me out, and there were only a few dozen people gawking. At least that’s what I thought.
I learned differently that evening, when our crew went for dinner at a rafting company’s restaurant, where to entertain their patrons they had televisions, including big screen televisions, showing that day’s adventures along with commentary to hundreds of people. And there I was, on screen in full pink paddling pornography as Phil’s had its way with me. After a while my stark horror gradually reduced to whimpering humiliation.
And my friends purchased copies of the video just for the posterity of my posterior.
Since that memorable day, I have always pivoted at the corner of Sattler’s and front surfed to the left along the wave across the top of Phil’s. Never had a problem with Phil’s since. But will my friends let me live down my failed back ferry? Will they forgive my first effort at ferrying a kayak? Will they stop showing that darn video? Not a chance. I guess that’s what friends are for.
Cheers,
Richard Culpeper
www.tbaytel.net/culpeper
And sometimes the wave has such a steep face that surfing is not possible. First two pics (me again), click to enlarge: http://www.geocities.com/Yosemite/4444/wanphoto.html
Cheers,
Richard Culpeper
www.tbaytel.net/culpeper
I think the reason for the confusion is that, as the OP suspected, the term “standing wave” is used differently than in the physics sense. What they’re attempting to describe is a flow of water through a specifically designed shape which produces a trough (for example) which doesn’t move. The photos on Fear itself’s linked page are a good demonstration. The shape of the surface is unchanging, so gravity makes you slide down the face of the wave into the trough, but the friction of the water flowing in the opposite direction keeps you up on the face, so you’re effectively going downhill forever.
Fear itself, you’re only confusing the issue by trying to describe this in physics terms as if this phenomenon is the same as a standing wave in that context. In a true standing wave, the surface would be moving violently, and the only still spot would be the nodes. On these surfable “standing waves”, there are no nodes.
If you want to observe what physicists would consider a standing wave in liquid, take a bowl of water and jiggle the bowl side to side at the appropriate frequency (for a standard bowl of miso soup this seems to be in the neighborhood of back-and-forth every half second – I have a tendency to play with my food). When you hit just the right frequency, you’ll see that two spots on the liquid (presumably one-third of the distance from the center to either edge of the bowl along the axis on which you’re moving the bowl) will be hopping up and down violently, alternating with each other, and the spot at the center won’t be moving much at all. It’s hard to maintain this for long without getting it all over the place, though.
A few notes from having ridden the first one of these in the country. (Schlitterbahn)
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The experience is nothing like surfing or bodyboarding, but still quite a rush.
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The water moves FAST. More than one swimming suit was torn asunder to the great amusement of the grandstand full of onlookers.
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Even though the surface beneath the water is foam rubber, if you fall while standing ro on your knees, it does hurt.
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Basic tricks are easy. Hard turns and shooting up impressive amounts of water. Barrel rolls. 360’s. Getting up on one knee is not too bad. Two takes 10 or 20 runs (at an hour in line for each run).
Being a physicist, I can see the problem here, although it’s already been answered. In physics, a “standing wave” is a wave with fixed nodes (as R M Mentock notes), but with an amplitude that oscillates up and down between these fixed nodes. Think of a vibrating stick, or a rotating string.
But a “standing wave” for surfing and kayaking is where you have water flowing constantly, but the shape of the wave stays fixed. You can gwet these in rivers when there’s a submerged obstruction. It’s not the physicist’s “standing wave”, but you can see why they called it that – the node stays fixed, but the antinode stays “high”, without oscillating.
I’ve surfed one of these, with a bunch of rabid kayakers. I quickly got bored, but they insisted on going back for several retries.
Creating an artificial water wave for surfing is quite easy. They just create a specially designed bump on the bottom & run water over it at a high speed, which causes the water to rise up & fall over & thus, a wave to form & causes the wave to stay in one place because of the bump. This is probably the artifical wave tank you’re asking about.