Indeed, hydrodynamic drag, like aerodynamic drag, is not really all that much like friction. While, like in the case of friction, the nature of the materials in contact can have some impact in hydro/aero drag...overall object shape/size and air/water/whatever density are much larger effects usually.
Larger people pushed faster in current?
- Thread starter billt4sf
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Indeed, hydrodynamic drag, like aerodynamic drag, is not really all that much like friction. While, like in the case of friction, the nature of the materials in contact can have some impact in hydro/aero drag...overall object shape/size and air/water/whatever density are much larger effects usually.
htatton
Contributor
I can't resist:
1- the only time drag has any effect is if you are fining or anchored to a non-movable object.
2- once you are neutrally buoyant you are moving as part of the water column.
3- relative to the water column you are not moving at all you are stationary.
4- if you draw a box around your diving group, it is just like all of you swiming in pool on an ocean liner. The water is moving but not relative to you.
1- the only time drag has any effect is if you are fining or anchored to a non-movable object.
2- once you are neutrally buoyant you are moving as part of the water column.
3- relative to the water column you are not moving at all you are stationary.
4- if you draw a box around your diving group, it is just like all of you swiming in pool on an ocean liner. The water is moving but not relative to you.
- Messages
- 16,388
- Reaction score
- 5,206
- # of dives
- 1000 - 2499
htatton
Contributor
Absolutely, if the river was large enough to allow each to move absolutely neutrally buoyant. A better example would be would they move the the same in the gulf stream at a depth of 200 ft to avoid surface effects. Sure they would. assuming dead drift, neutral buoyant.
When we plot navigation in an airplane you use the speed of the moving air mass, and the velocity of the airplane, not the size of the airplane.
You plot the vector of your velocity relative to the medium you are moving in.
Okay, maybe I can answer this easier in this box. Cousteau, in his book, The Art of Motion The Ocean World of Jacques Cousteau, diagramed it very nicely. This affects how your body reacts to current. But if you are motionless in the water, the water will carry all at the same velocity.
I do a lot of river diving, and if you simply let the water current carry you, everyone will go at the same velocity. But if the group decides to stop on the bottom, then the drag of the equipment and size of the diver will matter, as different people will have different surface areas and different orientations to the water.
If you look at the different shapes shown below, and compare them to your own configuration, then you can get an idea of how to improve your streamlining.
SeaRat
I do a lot of river diving, and if you simply let the water current carry you, everyone will go at the same velocity. But if the group decides to stop on the bottom, then the drag of the equipment and size of the diver will matter, as different people will have different surface areas and different orientations to the water.
If you look at the different shapes shown below, and compare them to your own configuration, then you can get an idea of how to improve your streamlining.
SeaRat
Attachments
Last edited:
If you want to see the most streamlined scuba users, look to competitive finswimming:
It is not size, but rather streamlining that makes the difference is efficiency moving through the water. But when still in the water, all people (and other animals and plankton) should be moving together at the same rate.
SeaRat
It is not size, but rather streamlining that makes the difference is efficiency moving through the water. But when still in the water, all people (and other animals and plankton) should be moving together at the same rate.
SeaRat
Last edited:
Notice how big all those guys are?
Power/drag ratio is increased when you're bigger. Look at cycling time trialists...they almost are normal sized. LOL
That bigger people have an advantage moving themselves through a draggy medium (water, air, whatever). This is somewhat to the contrary of what the OP believes they have observed and is to the contrary of SeaRat's statement that size doesn't make a difference under water (which I don't think he really meant exactly like that).
Similar threads
