Jackson Blue Conditions?

[Kthompso]

To answer your question Greenwood, the orientation does matter in this case due to the effects of gravity. The pipe orientation will change where the flow is the strongest.

Cave flow is more likened to river flows than pipe flows due to the surface roughness. The pipe flows are an excellent visualization of how water behaves in smooth pipe, but caves are rough and have more eddies.

[victorzamora]

I assumed the flow characteristics were relative to the bend. What I meant was if that pipe is a z to x or y bend, and we're talking about x to y bend in the caves, is there a significant difference in the relative characteristics. I don't imagine it does, since it's basically uniform in density and compressibility. But I really have no idea.

The flow in an otherwise straight passage, will tend towards the more regular surface. Like the flat floor of some of the early big areas in JB.

Jason, that assumption is correct. Gravity may have some correlation to the strength of the correlation of the flow, but it will be rather minimal. Either way, it's not THAT precise as that's a circular cross-section and there's no way we can get anything that precise in our diving....it's the general principal that matters.

[Jon Nellis]

Velocity is greatest on the inside of a bend. IIRC, the opposite of a river. In a river, the flow slows on the inside of a bend, depositing particles with lower settling velocities. Flow is highest on the outside of the bends.

There is more to fluid dynamics than a simple velocity profile. While the graphic shows slower flow on the outside of the curve, it does not show force or direction vectors. It may be slower, but it would also pin you to the wall. Additionally, this flow is turbulent, instead of the laminar flow you would be more likely see in caves. With laminar flow, the speed at the wall is zero, due to friction and gradually increases until it reaches a peak at the center of the conduit. By staying closer to the walls and out of the center of the passage, you will be out of the faster flow. For example, on the way into JB when the passage is a straight, wide ellipse with the line up the center, you would be much better off as far left or right as you can get.

Or you can ask Edd if you can borrow the Genesis 600 I sent him to play with and completely disregard the flow.

[rddvet]

There is more to fluid dynamics than a simple velocity profile. While the graphic shows slower flow on the outside of the curve, it does not show force or direction vectors. It may be slower, but it would also pin you to the wall. Additionally, this flow is turbulent, instead of the laminar flow you would be more likely see in caves. With laminar flow, the speed at the wall is zero, due to friction and gradually increases until it reaches a peak at the center of the conduit. By staying closer to the walls and out of the center of the passage, you will be out of the faster flow. For example, on the way into JB when the passage is a straight, wide ellipse with the line up the center, you would be much better off as far left or right as you can get.

Or you can ask Edd if you can borrow the Genesis 600 I sent him to play with and completely disregard the flow.

Is that a tester for him or a demo unit and he's going to be a dealer. It'd be nice to have easy access to your scooters and the ss models at the same place. I haven't gotten my cert yet but a big factor in when and where I get it is easy access to more than one scooter type or model.

[gasdiver]

There is more to fluid dynamics than a simple velocity profile. While the graphic shows slower flow on the outside of the curve, it does not show force or direction vectors. It may be slower, but it would also pin you to the wall. Additionally, this flow is turbulent, instead of the laminar flow you would be more likely see in caves. With laminar flow, the speed at the wall is zero, due to friction and gradually increases until it reaches a peak at the center of the conduit.

Whew, I thought you were going to launch into a boundary layer discussion

[victorzamora]

gasdiver: That kinda WAS a boundary layer discussion

About the scooter, I'm curious about Edd's genesis as well. I'll have to call him later today about it.

Back on the topic of flow, I wonder what boundary layer thickness is common in water. I'm an Aerospace Engineer (Aerodynamcs being my main focus)....but I'm unfamiliar with certain performance characteristics of Reynolds numbers found in water flow (despite having taken a course specifically about natural fluid flows). So, my question is this, what kind of boundary layer thickness are we actually looking at the Re values found in the caves we dive. In air, on planes, BL thickness is nearly negligible.

[Jon Nellis]

Is that a tester for him or a demo unit and he's going to be a dealer. It'd be nice to have easy access to your scooters and the ss models at the same place. I haven't gotten my cert yet but a big factor in when and where I get it is easy access to more than one scooter type or model.

I sent Edd a scooter to try for a while to see if he wants to carry them in the shop. It won't be there too much longer, since it is my wife's and she'll want it back before our next trip.

As for boundary layer, the Reynolds number is high (10^7 = turbulent), but one of the factors in pipe/river flow is surface roughness that disrupts linear flow. The channel resistance (from the Manning and Chezy formulas) drops the Equivalent Reynolds number down to the laminar range 10^2. Just think of it like a river, the water along the shore will always move slower than the very center.

[victorzamora]

I got all of that, I'm just wondering what the difference in velocity between the center and edges is (say 1ft from the edges). I'm also wondering what the velocity profile looks like in a "straight" area.

This would be an incredible interesting experiment to run, I think. It wouldn't be hard to do.....just release some dye in a line into the flow. I'll start sketching some designs tonight and seeing how feasible this is for a cave.

[Greenwood_60]

I'd love to see video of dye released at different points in different passages.

[Jon Nellis]

... or get a mechanical anemometer or cheap electronic anemometer and waterproof it.