Sinking Boat: Calculations & Results

[mfb]

I don't see how a pressure notably below ambient downstream pressure could be maintained in the stream. Such a pressure difference sucks in water from the outside. That is happening, of course, but I would expect that to form a somewhat stable vortex without large pressure differences.

 

[haruspex]

I don't see how a pressure notably below ambient downstream pressure could be maintained in the stream. Such a pressure difference sucks in water from the outside. That is happening, of course, but I would expect that to form a somewhat stable vortex without large pressure differences.

I had trouble finding anything on this that is not behind a paywall. Finally found https://books.google.com.au/books?i...zAG#v=onepage&q=flow submerged sluice&f=false. See eqn 5.24

 

[mfb]

I cannot access the previous page in the preview, which makes the formula unclear.

 

[haruspex]

I cannot access the previous page in the preview, which makes the formula unclear.

It has a diagram with H₁ as the depth in front of the sluice, H₂ as the general depth downstream of the sluice, and H₃ as the depth just after the sluice. The surface water is lower just after the sluice than further downstream, so H₃ < H₂, as per the formula. The height difference used for the flow rate is H₁-H₃.

 

[mfb]

Interesting, opening the PDF again I can now see the previous page, but not the page I saw before.

It discusses a notable effect as long as "a" (the height of the opening) is relevant compared to H₂. For a negligible hole size, and assuming we can adapt this to the vertical case, all the a/H terms vanish.

 

[haruspex]

Interesting, opening the PDF again I can now see the previous page, but not the page I saw before.

It discusses a notable effect as long as "a" (the height of the opening) is relevant compared to H₂. For a negligible hole size, and assuming we can adapt this to the vertical case, all the a/H terms vanish.

Ok.