Introduction to Fluid Mechanics: Surface Tension

[@FluidMatters]

All the videos (and pdf downloads) for this introductory Fluid Mechanics course are available at: www.drdavidnaylor.net/

[@huanyu770]

Very clear video. If you never learn about surface tension, watching this video is enough! Slides are nice. Examples are easy to understand. You solved all confusion I have. This is the best video I about the surface tension I saw in youtube

[@FluidMatters]

Thanks for the kind words. Glad to hear it was helpful.

[@franciscoramos8361]

My professor left me feeling confused about this topic until I watched this video. Everything makes sense now - the slides and examples were very helpful. Thank you!

[@FluidMatters]

Glad it helped!

[@nikan4now]

Thanks. There's something I cant quite understand. If we do a free body diagram of the segment of the curved bulk of fluid you showed, we can see tensile forces acting across the two slanted faces but these are ignored in calculations and only the surface tension is considered. Why? I know there's an imbalance of forces on the individual molecule at the top but as a bulk in thst segment shown there are tensile forces all the way across the two faces too. I'm focusing on a FBD of that slice of the sphere.

[@FluidMatters]

I think you are referring to the diagram at 2:19. This is not a free body diagram. It shows the directions of the cohesive forces between water molecules, as a way to explain why the surface layer of molecules are in tension. Ultimately, the surface will deform such that the molecules on the surface will be in static equilibrium, with no imbalanced force. I hope that helps.

[@nikan4now]

@@FluidMatters Thanks for thst. I'm interested in a free body diagram of thst segment to figure out why there's tension at the top edge only and not along the two radial surfaces.

[@nathanaelmccooeye3204]

I guess marangoni droplet bursting is what happens when you put pine sap on a stick and throw it in a pond. It also explains the rainbow colors that form

[@FluidMatters]

I'm not 100% sure, but I think that the same physics. The sap lowers the local surface tension near the end of the stick, causing local surface outflow, producing propulsion.

[@shmuelelkeslasi4876]

thank you. you saved me (love)

[@brentlackey8316]

What happens when there isn't any detergent on the tooth pick?

[@FluidMatters]

Never try such a dangerous experiment! ;)

[@brentlackey8316]

Why isn't Patm=101.325 kPa?

[@FluidMatters]

That is STANDARD atmospheric pressure at sea level. It is not the LOCAL atmospheric pressure. The local atmospheric pressure is almost never 101.325 kPa. Just listen to your local weather channel or read a barometer. Local atmospheric pressure has a large variation (+/- several percent) from 101.3 kPa due to weather alone, never mind altitude of your location. Also, it rarely makes sense to specify local pressure to six significant digits!

[@littleprinceofmath]

This is a great video, really helped me understand the formulas in a more comprehensive and intuitive way, thank you !

[@sobhan5613]

Thank you so much

[@ImTheReal]

That aknowledge should be used to make tests using a liquid with in the same scale when scientists are studing a what happens in/with a large ship. Like: If you are testing a ship that are in a scale 1:100, the liquit won't be water, but another that have the same tension surface (1:100) or something nearly it. But it's only the begining to discover the for the best what'll happen in a 1:1 scale.

[@emilsriram92]

lol look at dis mans spelling oh may gawd

[@ImTheReal]

@@emilsriram92 You'll laugh really hard if you listen to me, for sure. 😂😂