Physics Help Forum Free surface flow

 Jan 9th 2019, 09:28 AM #1 Junior Member   Join Date: Jan 2019 Posts: 5 Free surface flow ''' The surface can move with the fluid and so must be found as part of the solution '''; How can consider the surface as part of solution?! this topic is depends on flowing of fluid with free surface perturbed by an obstacle.
 Jan 9th 2019, 09:38 AM #2 Senior Member     Join Date: Jun 2016 Location: England Posts: 841 It does seem like an invalid sentence, however, without additional context, it is difficult to decide if the sentence is wrong or just poorly worded. __________________ ~\o/~
Jan 10th 2019, 02:15 AM   #3
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 Originally Posted by meriam04 ''' The surface can move with the fluid and so must be found as part of the solution '''; How can consider the surface as part of solution?! this topic is depends on flowing of fluid with free surface perturbed by an obstacle.
Flow problems depend heavily on geometry as well as the relative flow speed, $\displaystyle U_{\infty}$. If a substance is flowing past an object and the object starts to move, the $\displaystyle U_{\infty}$ reduces relative to the surface of the object and the flow could be different.

Last edited by benit13; Jan 10th 2019 at 02:45 AM.

Jan 10th 2019, 02:37 AM   #4
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 Originally Posted by Woody It does seem like an invalid sentence, however, without additional context, it is difficult to decide if the sentence is wrong or just poorly worded.
Please, take a look on page 02 pragraph 02 :
https://pdfs.semanticscholar.org/58a...6c20f52be0.pdf

Jan 10th 2019, 03:12 AM   #5
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 Originally Posted by meriam04 Please, take a look on page 02 pragraph 02 : https://pdfs.semanticscholar.org/58a...6c20f52be0.pdf
Yes, if you want to calculate any flows around some kind of object, the geometry of the object must be taken into account. If the object moves, that must also be taken into account.

As for how to take it into account? Perhaps it is discussed in the thesis you just linked?

Jan 10th 2019, 03:25 AM   #6
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 Originally Posted by benit13 Yes, if you want to calculate any flows around some kind of object, the geometry of the object must be taken into account. If the object moves, that must also be taken into account. As for how to take it into account? Perhaps it is discussed in the thesis you just linked?
But in this paragraph, he talked about the free surface without relating to an objects!

Jan 10th 2019, 05:59 AM   #7
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 Originally Posted by meriam04 But in this paragraph, he talked about the free surface without relating to an objects!
That's fine. The same is true if the object is instead another fluid. Different fluids passing across each other interact in really interesting ways.

 Jan 10th 2019, 09:34 AM #8 Senior Member     Join Date: Jun 2016 Location: England Posts: 841 I took a look at Charlotte's thesis via your link and it is as Benit points out. The free surface she is describing is free to move as the fluid forces act upon it rather than a fixed surface which will simply force the fluid out of the way. The interface between two immiscible fluids is an obvious example, indeed during my (very quick) scan of the thesis, I found that waves feature prominently. __________________ ~\o/~
Jan 16th 2019, 01:05 PM   #9
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 Originally Posted by Woody I took a look at Charlotte's thesis via your link and it is as Benit points out. The free surface she is describing is free to move as the fluid forces act upon it rather than a fixed surface which will simply force the fluid out of the way. The interface between two immiscible fluids is an obvious example, indeed during my (very quick) scan of the thesis, I found that waves feature prominently.

But, she mentioned the word 'solution' ; Please, what solution she meant?

 Jan 17th 2019, 02:28 AM #10 Senior Member   Join Date: Oct 2017 Location: Glasgow Posts: 341 You know... form equations... then solve them... the result is the solution... If you read the thesis, there is a literature review describing the equations used and solution methods. It seems that for most of the cases presented, the author calculates the pressure distribution across a fluid at some point in time (or as a function of time). I'm not an expert on fluid mechanics, but the thesis seems very well written (as it should!) and at face value it seems there is plenty of information available in the text.

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