I've seen ice test, we are building an icebreaker and there is some videos stored from the Basic Engineering. It's done with a self propelled model, and it's run in different speeds and ice thickness. They also tested the main maneuvering tests, but with ice, boom!
Great video! I'm starting a masters in naval architecture at Memorial University in St. John's Newfoundland next year. That ice tank is right next door! Hopefully I can get some time on it and report back!
How do you allow for the fact that you are towing through waves with the craft moving at a constant speed? In reality a craft will slow down when it encounters a large wave and it 's pitch angle may well be different.
We hold the towing speed constant because that allows us to compare against other tests done in calm water. As part of that comparison, we calculate the additional power required to maintain speed with each wave. In reality, a ship can either approach waves with constant power output, or adjust its throttle to maintain constant speed. On the theoretical end, we tend to consider the ship as a constant speed, because it makes the math much easier.
I just saw the video about tow tanks and was wondering if there were tanks that simulated waves. Anyways, what I can imagine next is a floating laboratory where the model is placed out front and moved through the open water by the laboratory. Real world testing but limited ability to change testing characteristics.
Yes, in fact most towing tanks come with a wave maker. Wave simulation happens very frequently in towing tanks. We can specify the length and height of an individual wave, or we can specify a whole group of waves to simulate open ocean conditions. The really fun tanks are the ocean basins. Those often have wave makers in two directions. That allows us to simulate a very complicated water surface, and to occasionally create some fun visuals. Check out this fun video about the FlowWave tank: ua-cam.com/video/iWKFPTgkpXo/v-deo.html
I'm still perplexed about how we scale the size of the ship to be tested, but we don't alter the viscosity of the water to match the scale of the model ship...? The width of a water molecule that is pushing up the ship isn't scaled to the widths of the molecules of the ship surface. It would be like scaling tire designs and testing it on a regular asphalt surface.
Part of it is simple practicality. First, we can't scale the viscosity of the water. To do that, we need to use a different fluid. To scale it properly, we would need a range of different fluids, all with different viscosities. And then there is the cost of replacing a giant tank full of fluid for every new model. And the width of a water molecule touches on one of the major assumptions of fluid mechanics. We generally assume that the water molecules are so small that we don't need to think of them as individual particles. We don't need to worry about the individual molecules. And that assumption has proven fairly useful so far. Even at model scale, a water molecule is several thousand times smaller than the ship model. It is so small that it doesn't notice the difference between full scale or model scale ship surfaces. To use the tire analogy, it would be like the tires on your car had grooves that were spaced only 1 nm apart (much smaller than a human hair). With that close of a spacing, the surface looks the same, no matter the size of the vehicle.
@@DatawaveMarineSolutions You are still only making estimates though... hulls for performance should really be tested with a 1:1 ratio with sensors along the hull. Really the only logical thing that could be simulated would be something like a leveraged ballast to simulate equipment, crew, and possible cargo. I know its from a part of a school where you just have to produce an environment instead of gathering the budget for a full size test though. If only money works they way it should some day...
I've seen ice test, we are building an icebreaker and there is some videos stored from the Basic Engineering. It's done with a self propelled model, and it's run in different speeds and ice thickness. They also tested the main maneuvering tests, but with ice, boom!
Great video! I'm starting a masters in naval architecture at Memorial University in St. John's Newfoundland next year. That ice tank is right next door! Hopefully I can get some time on it and report back!
I think they have to add an earthquake tidal simulator also inside that maneuvering tank.
USNA NAHL Tow Tank on screen at 07:56
Bro, your hands are huge. Like damn lunch boxes. Have you ever thought of becoming a pro fighter?
How do you allow for the fact that you are towing through waves with the craft moving at a constant speed? In reality a craft will slow down when it encounters a large wave and it 's pitch angle may well be different.
We hold the towing speed constant because that allows us to compare against other tests done in calm water. As part of that comparison, we calculate the additional power required to maintain speed with each wave. In reality, a ship can either approach waves with constant power output, or adjust its throttle to maintain constant speed. On the theoretical end, we tend to consider the ship as a constant speed, because it makes the math much easier.
I just saw the video about tow tanks and was wondering if there were tanks that simulated waves. Anyways, what I can imagine next is a floating laboratory where the model is placed out front and moved through the open water by the laboratory. Real world testing but limited ability to change testing characteristics.
Yes, in fact most towing tanks come with a wave maker. Wave simulation happens very frequently in towing tanks. We can specify the length and height of an individual wave, or we can specify a whole group of waves to simulate open ocean conditions.
The really fun tanks are the ocean basins. Those often have wave makers in two directions. That allows us to simulate a very complicated water surface, and to occasionally create some fun visuals. Check out this fun video about the FlowWave tank:
ua-cam.com/video/iWKFPTgkpXo/v-deo.html
I'm still perplexed about how we scale the size of the ship to be tested, but we don't alter the viscosity of the water to match the scale of the model ship...? The width of a water molecule that is pushing up the ship isn't scaled to the widths of the molecules of the ship surface. It would be like scaling tire designs and testing it on a regular asphalt surface.
Part of it is simple practicality. First, we can't scale the viscosity of the water. To do that, we need to use a different fluid. To scale it properly, we would need a range of different fluids, all with different viscosities. And then there is the cost of replacing a giant tank full of fluid for every new model.
And the width of a water molecule touches on one of the major assumptions of fluid mechanics. We generally assume that the water molecules are so small that we don't need to think of them as individual particles. We don't need to worry about the individual molecules. And that assumption has proven fairly useful so far.
Even at model scale, a water molecule is several thousand times smaller than the ship model. It is so small that it doesn't notice the difference between full scale or model scale ship surfaces. To use the tire analogy, it would be like the tires on your car had grooves that were spaced only 1 nm apart (much smaller than a human hair). With that close of a spacing, the surface looks the same, no matter the size of the vehicle.
@@DatawaveMarineSolutions You are still only making estimates though... hulls for performance should really be tested with a 1:1 ratio with sensors along the hull. Really the only logical thing that could be simulated would be something like a leveraged ballast to simulate equipment, crew, and possible cargo. I know its from a part of a school where you just have to produce an environment instead of gathering the budget for a full size test though. If only money works they way it should some day...
In my next life I become an engineer 😉
Bromine? Did you mean chlorine?
toddlers at play few in kiddie pool far cheaper.