https://preview.redd.it/nschl7ys4m9e1.png?width=1556&format=png&auto=webp&s=b35767f3350e5da93e5e17c9599889b3aa0a4d12

Hello dear community,

please prepare yourself mentally for a rather unusual post.

In short, my goal is to build a beer funnel that measures how long it takes to drink the beer it contains.

I have outlined my basic concept in the attached pictures. It is basically a normal beer funnel. In addition, an ultrasonic sensor is attached near the mouthpiece below the hose, which measures whether or not there is still beer in the hose. This is used to calculate the drinking time.

The problem is that you cannot put your mouth directly next to the sensor, so there has to be another short piece of hose after the sensor. The sensor cannot of course take the beer in this section of the hose into account and the measurement is therefore distorted.

I am an electrical engineer and therefore know very little about fluid mechanics. But I am sure that this problem occurs frequently in your field and there is a solution for it. Maybe there is an elegant solution where you only have to change the shape of the hose(?) I have a 3D printer if that is necessary to solve the problem.

https://preview.redd.it/tkdacicqjl9e1.jpg?width=2524&format=pjpg&auto=webp&s=3307c8ecc48039168eabb8fc556b379569290dfe

I'm trying to calculate the terminal velocity of a bubble rising in a liquid column, but there's also a returning flow through a pipeline from the top that opposes the bubble's motion.

How can I account for the buoyancy, drag, and the effect of the returning flow to find the terminal velocity? And what's the best approach I should use for this problem. ? Are there specific equations or simplifications I should consider?

I have some confusion regarding the simplified Bernoulli theorem.

In the form

P/(d∗g)+V^2/(2∗g)+z=constant

(where d is density and z is height), is P really the hydrostatic component, meaning the pressure of the fluid if it were at rest? So, is P=Pexterior+d∗g∗z?

I ask this because I noticed that in several exercises, I am asked to calculate the velocity of the fluid or another variable, but not the pressure of the fluid in motion. When I try to calculate it, I draw a flow line from some arbitrary point 1 to the point where I am interested in finding the pressure at point 2. Then, I use the same formula with the values for each point (P_1 and P_2, V_1 and V_2, etc.), and then I solve for P_2 to find the pressure of the fluid. The problem is that if the Ps in the formula are the hydrostatic pressures, I can again set the result of P_2 equal to Pexterior+d∗g∗z, and in the end, I don't get any pressure at all lol.

I'm sure I'm complicating things but well... need some help to get the idea

A horizontal pipeline of diameter 300 mm conveys water at a steady rate of 0.02 m³/s. At one section of the pipeline (Point A), a piezometer tube is installed, and the water level rises to a height of 2.5 m above the centerline of the pipe. At another section located 10 m downstream (Point B), the pipe diameter reduces to 200 mm, and the height of water in the piezometer is observed to be 1.8 m above the centerline.

Assume:

1. The density of water is 1000 kg/m³.

2. Neglect losses due to friction.

3. Assume the velocity profile is uniform across the sections.

Tasks:

1. Calculate the pressure difference between Points A and B.

2. Verify the velocity at Points A and B.

3. Determine the energy gradient line (EGL) and hydraulic gradient line (HGL) levels at Points A and B relative to the centerline of the pipe.

Hint: Use Bernoulli’s equation and the continuity equation.

Hi everyone, sorry if this is off topic; if so Mods please feel free to remove.

My background is in the commercial side of industrial HVAC, so I know enough to get me in trouble, but not enough to engineer my way out of it….

I have a frozen pipe in my house and I’m trying to work out how likely it is to rupture.

The pipe in question is rated to 160 psi; domestic water pressure is generally between 40-60 psi, so let’s assume it’s at the higher end. Meanwhile, if I understand correctly, water increases in volume by roughly 9% when it freezes, but my gut feeling is that the resulting increase in pressure won’t be linear.

So my question is: if water at 60 psi freezes, will the resulting pressure be 65.4 psi? Or something greater? If so, how to I calculate what it will be? Taking it a step further, will the pressure increase further as it gets colder?

I think I’ve found where the cold is getting in but due to the work involved I’ll need a professional to take care of it, and that unfortunately won’t be happening for the next few days, so really I just want to know how much I should be letting this bother me over the holidays…

Any thoughts would be very much appreciated!

So if a ideal fluid were in a closed container on a table, and is under the influence of gravity why is the pressure at its surface 0? I thought that pgh was the change in its pressure due to the gravity weighing it down, but if the pressure at the surface is 0, that would mean that of it weren't in the influence of gravity, the pressure would be uniformly 0, but that doesn't make sense since I thought that the particles would undergo elantic collisions in a ideal fluid, so there would still be collisions wth the walls of the container, leading to pressure?

So if a ideal fluid were in a closed container on a table, and is under the influence of gravity why is the pressure at its surface 0? I thought that pgh was the change in its pressure due to the gravity weighing it down, but if the pressure at the surface is 0, that would mean that of it weren't in the influence of gravity, the pressure would be uniformly 0, but that doesn't make sense since I thought that the particles would undergo elantic collisions in a ideal fluid, so there would still be collisions wth the walls of the container, leading to pressure?

Hello! Could you guys recommend me your favorite textbooks for fluid mechanics? I'm the kind of person who likes learning from multiple textbooks at once. Preferrebly a conceptual textbook and a more technical one.

So if a ideal fluid were in a closed container on a table, and is under the influence of gravity why is the pressure at its surface 0? I thought that pgh was the change in its pressure due to the gravity weighing it down, but if the pressure at the surface is 0, that would mean that of it weren't in the influence of gravity, the pressure would be uniformly 0, but that doesn't make sense since I thought that the particles would undergo elantic collisions in a ideal fluid, so there would still be collisions wth the walls of the container, leading to pressure?

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Hey guys, I'm applying for a CFD research firm. Where they will be asking really difficult and conceptual Fluid Flow question from following areas: Properties of fluid, Turbulence, Various Equations, Boundary Layer, Non dimensional numbers, Modeling etc. If any one has any questions they can share along with answers, It would be really appreciated.

A few months ago I had a conversation with an engineer who was talking about fins or baffles mounted on and down and around the insides of a cylindrical settling tank that facilitated particulate settling. He mentioned that there was a specific slope that was best as well as that the should not be continuous. he also said something about a "kicker" at the tip of these fins that would direct vortices towards the center and also helped with settling. I cannot find schematics of such a tank design. Unfortunately the engineer has lost his drawings. I am wondering if anyone has an understanding of this design and can advise me in the making tanks. I need to make tanks because shipping tanks as large as I need is very expensive and it is far more cost efficient to simply weld my own tanks.

I will be making Cylindrical tanks about 10' in diameter with an over all height of about 14' with the bottom 5' being the cone. I expect to input the dirty water about 18" up the vertical side with a water outlet near the top and a concentrate removal port at the bottom of the cone.

The purpose is to remove stone solids created by sawing stone from water so that the water can be cleaned and recycled and reused

Thanks

I tried to calculate the height h of a forced vortex. A forced vortex is caracterized by a radial velocity equal to zero and a tangential velocity equal to K.r. With r the radial distance and K the angular velocity. So, I used Bernoulli (I suppose a incompressible fluid):

p/rho+v^2/2+g.h = constant.

Furthermore I want to look at the height of the surface, therefore is suppose that p is also a constant and therefore I have:

v^2/2+g.h = another constant

Therefore:

h = (another constant)/g - v^2/2

h = (another constant)/g - (K.r)^2/(2.g)

Which means the height has a inverse u-shape in function of the radial distance r. Practically speaking, this does not seem correct. I suppose in reality it should be just a u-shaped parabola as in the picture.

https://preview.redd.it/1845yxs73d7e1.jpg?width=347&format=pjpg&auto=webp&s=e91787abee27a2d4e2af56985d4ef2ad3fe84083

Hi, I am performing a pump model testing. I have created 4 Pi groups to match: The head coefficient, flow coefficient, Reynolds number, and (shaft) power coefficient to represent pump efficiency. I wonder do I have to match the specific speed (Ns) as well? I am not sure how the specific speed is derived, and it seems not to come from the Buckingham Pi's theorem, but I understand that the value is important for geometrically similar pump. I also heard about Froude number, but I couldn't find any information on that either. Thank you.

Hi, I am performing a pump model testing. I have created 4 Pi groups to match: The head coefficient, flow coefficient, Reynolds number, and (shaft) power coefficient to represent pump efficiency. I wonder do I have to match the specific speed (Ns) as well? I am not sure how the specific speed is derived, and it seems not to come from the Buckingham Pi's theorem, but I understand that the value is important for geometrically similar pump. I also heard about Froude number, but I couldn't find any information on that either. Thank you.

Hi could someone guide me on how to solve this problem ?

https://preview.redd.it/l194kf0agu6e1.png?width=550&format=png&auto=webp&s=541825531bdc8aad3c1f1b01194eee2469810098

Thanks

I'M NOT PROPOSING A PERPETUAL MOTION MACHINE. I'm just wondering if with the right timing of when to start the siphon loop and also the Stirling engine, the right placement of the straws, and the right proportions of all the different parts, including the fluid; if this could work?

Examples:

https://www.youtube.com/watch?v=M2JP2LNbqIk

https://www.youtube.com/watch?v=qYUxa-BVoPA

The goal being to keep the siphon loop going indefinitely.

Here is a bad example of how it would potentially look like.

https://preview.redd.it/9ctizzj6ys6e1.png?width=1906&format=png&auto=webp&s=703279f47c99aedc9c4025eb7acb1aa51564262f

I know this is a fairly commonly asked question but I am confused because there are posts saying yes and no.

I know in a smaller tubing I will lose more fluid pressure due to friction, but that is not my question.

If I have a pump running at a fixed flow rate, and I step down the tubing, using a convertor fitting, from the original diameter to a smaller one, then shouldn't the fluid pressure increase? I think this because the greater amount of fluid in the larger tubing will all be "pushing" the fluid in the smaller tubing, thus causing the water in the smaller tubing to have more pressure.

What would happen in a c-d nozzle for a compressible flow if the throat area was smaller than the theoretical area for choking the flow?

I thought it would still just be choked, but my professor said that was not the case and gave a slightly confusing explanation. I then asked ChatGPT and it said the flow would end up being subsonic, but I’m not super sure to trust ChatGPT. Can someone please explain?

Question: In this problem do I have to use Bernoulli's equation to find the velocities in sections 2,3 and 4 or do I have to assume uniform flow and assume that relative velocity at every cross-section shown in the picture is equal?

Assumptions I made for this problem: Flow is steady, inviscid, incompressible, and frictionless. Also, the water jet is in contact with the atmosphere and we can neglect the pressure forces acting on the water jet.

Also, I've already used the continuity equation to find a relation between velocities at each cross-section but that's where I get stuck, uniform flow assumption seems to help in solving this problem but since the flow's cross-sectional area is not constant across the control volume I don't think that is the reasonable assumption. I also added my work to the picture.

I appreciate any help or hints to help me solve this problem, and thanks in advance.

https://preview.redd.it/9zp5bksftn6e1.png?width=739&format=png&auto=webp&s=c2c302da79b6b0356086ef2131129c958cd3c868

From

Pulsation behavior of a bubble generated by a deep underwater explosion

by

Haozhe Liang (梁浩哲) & Qingming Zhang (张庆明) & Renrong Long (龙仁荣) & Siyuan Ren (任思远) .

Maybe some of you goodly folk, being Fluid Mechanicists , have seen much better - IDK … but I thought I'd bung it in anyway , as I'm rather chuffed with it.

Annotation of It

FIG. 3. Images of bubble pulsation. Detonation is at t = 0. For depths 0.8m, 100m, and 200m, the image width is 195mm and the image height is 190mm. For depths 300m and 350m, the image width is 170mm and the image height is 165mm.

(a) Bubble motion at a depth of 0.8 m (t = 0.13ms, 0.27ms, 0.4ms, 0.53ms, 0.67ms, 0.8ms, and 37.8ms).

(b) Bubble motion at a depth of 100m (t = 0.13ms, 0.27ms, 0.4ms, 0.67ms, 2.1ms, 3.7ms, and 4.8ms).

(c) Bubble motion at a depth of 200m (t = 0.13ms, 0.27ms, 0.4ms, 0.67ms, 1.06ms, 1.34ms, and 2.8ms).

(d) Bubble motion at a depth of 300m (t = 0.13ms, 0.4ms, 0.67ms, 0.93ms, 1.4ms, 1.7ms, and 2.13ms).

(e) Bubble motion at a depth of 350m (t = 0.13ms, 0.4ms, 0.67ms, 0.93ms, 1.4ms, 1.7ms, and 1.87ms).

Let's say we have two sufficiently large, insulated, sealed containers. The only difference between them is that one is filled with air of normal temperature, pressure and density, and the other is a vacuum. We name the air one "chamberA" and the vacuum one "chamberB".

Take an ordinary bamboo dragonfly and measure the speed of its rotation when it can hover in the air. E1 is the rotational energy corresponding to this speed.

By the way, bamboo dragonfly is a little copter. It is a toy that originated in East Asia and later spread to Europe. It is the ancestor of the helicopter.

Create a special bamboo dragonfly that has the same total mass as an ordinary bamboo dragonfly. What's special about it is that its blades and pole are not integrated but connected through a rough bearing. Concentrate the mass on the pole section so the two parts don't reach co-speed too early. We name the ordinary one "dragonflyA" and the special one "dragonflyB".

Use a separate motor to consume the electrical energy of E1 to drive dragonflyA to rotate, then release dragonflyA from a height H. All this happens inside chamberA.

Use the same kind of motor to consume the same amount of electrical energy of E1 to drive dragonflyB to rotate, then release dragonflyB from the same height H. All this happens inside chamberB.

Since the center of gravity of dragonflyB is slightly lower than that of A, in order to avoid the two turning over after landing and causing different energies transmitted to the floor, both fell vertically into a hole of the same depth. In this way, we ensure that the changes in gravitational potential energy of the two are the same.

When all macroscopic motion ceases, measure the total heat change in the two chambers separately. QA is for chamberA, QB is for chamberB.

On the website called stack exchange, people are divided into two groups. One group believes that according to Newtonian mechanics and James Joule's experimental results, QB = mgh + E1, and QA = (mg-F)h + E1, QA<QB. (The integral symbol should be used here but it is too difficult to type)

The other group believes that according to the law of conservation of energy, QA=QB，But they have no way to prove it mathematically.

Because this would (at least) require demonstrating:

1. dragonflyA makes significantly more energy dissipate into air than internal energy generated by friction of dragonflyB when the rotational energy of both decreases by the same amount.
2.  the extra energy at any given moment is equal to the ΔEp of draonflyA minus its current translational kinetic energy.

I just saw this and thought it is worth discussing, so I copied and pasted it here. Hopefully someone among you can prove it mathematically.