Draining a Tank of Fluid | First Order Differential Equation example | Fluid Mechanics

#differentialequations #fluidmechanics
First Order Differential Equation example in Fluid Mechanics.
I absolutely love this example for understanding how differential equations work! In the video we derive the differential equation describing the draining of a bottle/vessel out of a small hole on its' side.
I have tried to talk through the problem in a way that I hope will seem intuitive. I wanted this to be a worked example that taught and refreshed the subject of differential equations for those that are studying for an exam, as well as introducing, those of you that have never heard of a differential equation, to the brilliance of them.
Please do comment below your thoughts on whether you'd prefer more maths, less maths, less talking through the maths, the maths done 'live' so you can follow along better... any feedback is much appreciated!
Further information:
1) At 6:01 in the note, it should be "...falling freely..".
2) Averaged timings: I did the experiment 4 more times after the one in the video. And calculated an average as follows: (55.4 + 53.73 + 55.32 + 53.35 + 52.67)/5 = 54.094... 54.094!! --- That's only 0.306s off our estimate!!
3) My uncertainty calculation: I am going to do another video on this, as a follow up to this video, since I did not practice it well whilst I was at university. For those of you that would like to check my calculation of the final uncertainty, I used a standard ruler with a minimum division of 1mm, but too say that I could measure the 6mm diameter of the jet hole to an uncertainty of +-1mm was a huge difference in comparison to the hole size. So I instead said that I could measure it to +-0.2mm and the diameter of the bottle to +-0.5mm and the height of the water too +-1mm. Using the relative errors I calculated ((Diameter of Bottle)^2)*sqrt(height)/((Diameter of the jet hole)^2) and used the upper and lower bounds of that in my calculation of the final time. I did not put any uncertainty into the gravitational acceleration 9.81m/s^2.
4) The fluid mechanics of the velocity coming out of the jet hole can be calculated using Bernoulli's equation and the continuity equation. With the assumption that the area of the jet hole divided by the area of the bottle is close to zero (negligible), you will get the same result as Torricelli did prior to modern understandings from Daniel Bernoulli. I chose to explain Torricelli's method since it was shorter and didn't detract too much from the differential equation at hand. Example 3.13 in Frank White's fluid mechanics explains this phenomenon.
Intro music by an amazing band called Wordy, check them out here:
/ escape-the-dream-4
Follow A Clever Chimp on Facebook!
/ acleverchimp

Пікірлер: 43

  • @esaumadzura
    @esaumadzura Жыл бұрын

    Fantastic illustration!

  • @jamielinsdell4900
    @jamielinsdell49003 жыл бұрын

    Great video demonstrating the predictive power of mathematical modelling. An outstanding result! Cheers

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Thanks Jamie! Yeah, in all honesty, I couldn't get over how close the prediction was to the actual result. I didn't really have any feel for what to expect, so it was brilliant to see.

  • @ramanandah.s.4116
    @ramanandah.s.41163 жыл бұрын

    Beautiful explanation. I was expecting the same. Thank you Ciaran

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Thank you Ramananda. Glad you enjoyed it. 👍

  • @barathykirupakaran9725
    @barathykirupakaran97252 жыл бұрын

    It's an amazing explanation with a clear demonstration. Thank you!

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    Жыл бұрын

    That's so good to hear. Glad you enjoyed the video.

  • @peasant8246
    @peasant8246 Жыл бұрын

    Finally somebody did an experiment to verify the results of calculation. Everyone else on YT is too lazy!

  • @ramanandah.s.4116
    @ramanandah.s.41163 жыл бұрын

    Thank you . Happy new year in advance. Marry Christmas.

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    And the same to you Ramananda. Have a brilliant new year! 🍻

  • @ytbasketball101
    @ytbasketball1012 жыл бұрын

    I love example you can experiment on in the real world thank you so much! 😁

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    2 жыл бұрын

    Thanks Brandon! Glad you liked the video.

  • @rananagy6754
    @rananagy6754 Жыл бұрын

    A great fantastic video ❤ Thank you ❤❤❤❤

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    Жыл бұрын

    Thank you very much Rana.

  • @anilkumarsharma8901
    @anilkumarsharma8901 Жыл бұрын

    Why it's become more advance by negative calculation of Whirlpool🌀 caused by this situation so we found out that unconditional situation of universe🌌🌌 according to which all the natural happening become phenomenal success🏆💪

  • @ramanandah.s.4116
    @ramanandah.s.41163 жыл бұрын

    Can you please share similar videos of mathematical modeling of real-life problems?

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Absolutely! I will be bringing more videos out similar to this in the new year. Cheers for your interest pal 🍻

  • @jamielinsdell4900
    @jamielinsdell49003 жыл бұрын

    Would be great if you could demonstrate other principles such as Newton's Law for Cooling etc with a similar approach. Calculus in action!

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Yeah! It's great to see principles tested out like that, isn't it. More videos like this are definitely in the pipeline! Just so you know, I post the majority of my updates on what's coming up next on Instagram and Facebook, @ciaranwamcevoy. Feel free to follow me to stay up to date.

  • @rio_agustian_
    @rio_agustian_2 жыл бұрын

    Cool explanation, Sir! I have I little bit confusion. The equation h(t) = (√(h0) - 1/2kt)² h(t) = h0 - √(h0)kt + 1/4 k²t². Your equation is good at some interval times, the equation shows that the h will decrease when the time increases. But, the h value blows up since it's quadratic equation. In the real world, the water can't go back to the bottle to increase the h. Could you explain to me why this is happening? Or, am I missing something about the equation? Thank you, amazing content 🤓

  • @jishnup1205
    @jishnup120510 ай бұрын

    ❤❤❤

  • @ashafaghi
    @ashafaghi2 жыл бұрын

    How do you model a spherical shape reservoir?

  • @user-bn6xo1sj5f
    @user-bn6xo1sj5f Жыл бұрын

    How would you go about finding the t(1/2) the amount of time that passess till the bottle is emptied to half its original level?

  • @kimbalcalkins6903
    @kimbalcalkins6903 Жыл бұрын

    it would be interesting to add a few drops of liquid detergent to eliminate surface tension?

  • @soninugroho6299
    @soninugroho62993 жыл бұрын

    Nice experiment and explanation, I want to ask, how if we isolated the top of the bottle, will the water still come out from the jet hole?

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Ooo nice thought! That would be the same as if you were to cover the top of a drinking straw and lift it from the liquid. After capping the top of the bottle, there'd be a little dribble out of the jet hole, as the air above the liquid expanded, to ensure that the pressure at the jet hole level was at atmospheric pressure both inside and outside the bottle.

  • @soninugroho6299

    @soninugroho6299

    3 жыл бұрын

    @@ciaranmcevoy9875 Thank you for the explanation, could you please give me the solution for equation to calculate time needed to stop draining in the case we isolate the top of the bottle. Thank you Ciaran.

  • @jamielinsdell4900
    @jamielinsdell49003 жыл бұрын

    Cool. For inspiration check out this little gem I think from the 60s - "Angles: Real life applications of trigonometry classroom videos". Skip to 8:00. The guy is very confident with his calculations. Not sure if it's a real world application but you never know what life can throw at you!

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Haha that is a little gem, what a classic math video!

  • @kimbalcalkins6903
    @kimbalcalkins6903 Жыл бұрын

    is it correct that if the tank drains fully in say 300 seconds that it will be 3/4 drained in 150 seconds? This could be tested by marking the cylinder at 1/4 full and see if it drains to that mark in 27.5 seconds ?

  • @lucaslaue2000
    @lucaslaue20003 жыл бұрын

    Seeing as the bottle will never truly become empty, does that mean that the final height being 0 is relative to the position of the hole? If so does that mean the initial height is the "true" height - the height below the hole?

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Hey Lucas. Both your statements are correct, however your desire to involve the "true" height is not necessary. In the majority of fluid dynamics problems you tend to set a datum from which you want the height to be measured from, this is completely up to us. So, for ease, I set the height at which the hole is to be zero, because, liquid below that hole is not of our concern since the flow will stop. So in other words, what you where imagining was setting the datum height to be at the bottom of the bottle. Hope this makes sense 🍻

  • @lucaslaue2000

    @lucaslaue2000

    3 жыл бұрын

    @@ciaranmcevoy9875 Absolutely! I have been trying to do this experiment myself, and the differential equation I apply does not match up with my recorded data. I noticed the difference between your experiment and mine is scale. The size of my jet hole is 3mm, the total volumetric capacity is closer to 5L. I was wondering if perhaps at that small scale (jet hole) other factors such as water tension play a bigger role, skewing my findings?

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Yeah there's always going to be differences in experiment set up etc. But the key thing I try and do is to constrain variables. For instance is your container the same cross sectional area all the way down? This was a key part of the experiment and equations (it's why my jet hole wasn't right at the bottom of the bottle). If it isn't then we'd have to include the rate at which the cross sectional area (CSA) would be changing as well as the height. The velocity of the the liquid out of the jet hole in my example comes from the fact that the CSA of the jet is much smaller than the CSA of the vessel. It needs to be to assume the velocity of sqrt(2*g*h). Another thing to consider is achieving laminar flow, of there's any turbulence at the jet then that'll change the results too I'd say. It's great to hear you having a go. I'd suggest trying to repeat my results and experiment first to see if you get the same result. Then move onto other sizes of vessels etc. I love to hear how you get on 👍👍

  • @PTNLemay
    @PTNLemay2 жыл бұрын

    Every time I see one of these problems, the formula we end up with is Flow rate over time, either as escape velocity of the water or volume flow over time. But it's never given as a height over time. It feels like this would be a simple alteration to the formula, bu I can't figure it out. The best I can do is isolate h in the formula and I get a height that's dependent on the flow rate. Not on time. What kind of manipulation do I need to do to find a simple h(t) function for a problem like this.

  • @franciscopen1681

    @franciscopen1681

    Жыл бұрын

    Well height is also on the volume' formula

  • @lucaslaue2000
    @lucaslaue20003 жыл бұрын

    Hello Ciaran, I am sorry to continuously bother you. I have been performing this investigation on my own however the predicted time for the experiment to cease simply does not match my findings. In my attempt at modelling the situation, I have used a cylindrical pipe, 10.5cm in diameter. In addition, I made an incision (the jet hole) which is 0.5cm in diameter (5mm). This incision is placed approximately 2cm above the base of the pipe. I fill my cylinder up with water, an equivalence of 5000 grams. Through density conversion, I know that this is the same as 5000mL. By applying basic maths I deduce that the initial height is 57.7cm Therefore the height difference between the crest of the water, and the top of the hole is 57.7 - 2, approximately 55.2 cm. My recorded time to have 0 height is 3 minutes and 43 seconds (223 seconds) However, the equation tells me "t=1463.24" If it is not too much of a bother, could you help me understand why I seem to be so far of the mark? I would appreciate any help a lot!

  • @ciaranmcevoy9875

    @ciaranmcevoy9875

    3 жыл бұрын

    Hey Lucas! No need to apologise. It's really not a bother at all. I'm interested in your findings. It's the one thing I didn't do is try this with different vessels. So my immediate thought is gave you checked your units? I'd recommend converting to metres since gravitational acceleration (g) is in m/s^2 or converting g to the other units. I did this and typed it in on me phone and got 147.9 seconds. It's of the same magnitude but still quite off your results. Is the pipe clear or opaque? Because the next thing I'd suggest is double checking your measurements specifically the initial height above the hole. Also, though I'm sure you have, be sure to measure the inner diameter of your pipe as the bottle's diameter in the equation. Also I timed the water to reach just above the hole, which is also where I measured my height from. This is because the flow gets that slow that water tension becomes a factor. Hope this helps pal. Let me know how you get on. 🍻

  • @lucaslaue2000

    @lucaslaue2000

    3 жыл бұрын

    @@ciaranmcevoy9875 Hey Ciaran! Thank you so much for taking the time to help me. Yes as you determined the equation does tell me 147.9 seconds (it certainly does help using correct units) The pipe I used is clear, therefore I can and did measure the initial height. What I did was measure the initial height above the base, and subtracted 2 (the approximate height between the hole and the base). I could assume that I was inaccurate, but that would leave me with at most + or - 2cm (let us say this to be strict) And yes, I did measure internal diameter. Even with the uncertainty of the height between the top of the hole, and the initial height (plus or minus 2). I don't see a way of getting from 3 minutes and 43, to 2 minutes and 23.9 seconds. I will perform my experiment again, and I will simply stop at 147.9 seconds, and from there determine how much height is left over between the hole and the water crest. Ill let you know what I got! Thank you again!

  • @ProcesswithPat

    @ProcesswithPat

    3 жыл бұрын

    I came to double check my calculations XD I am actually pleasantly surprised that the equation works as well as it does in this case. I suspect that it is because the vessel has a thin wall. I have conducted similar experiments from the perspective of Process Engineering - go check it out: kzread.info/dash/bejne/m394xqundZrdoag.html. Hope it's ok to post here @Ciaran

  • @anilkumarsharma8901
    @anilkumarsharma8901 Жыл бұрын

    Show flow path 👣 as equation💻 for💦 every time⌚⌚ and range of pressure😖 Show calculations💻 as Diffenrial equation💻💻💻

  • @anilkumarsharma8901
    @anilkumarsharma8901 Жыл бұрын

    How volume and📐 angle and📐 time⌚ and pressure are interlocking 😝😝😝😝

  • @anilkumarsharma8901
    @anilkumarsharma8901 Жыл бұрын

    Show path 👣of flow and📐 time⌚ derivative 😁😁😁😁