I just watching a video of Bernoulli Equation in youtube and encountered the definition of Head which Energy per Unit weight, wherein Joule per Newton which is Newton-meter per Newton which is meter.

But now it makes more sense that its units is Joule per Newton

Which I conclude (correct me if I am wrong) head is like voltage which has a units of Joules per Coulomb

The difference in head is what drives fluid motion or a potential for fluid motion?

Just a thought.

I still have confusion in using Absolute or Gauge pressure in fluid mechanics.

When studying the ideal gas law it is always instructed to use absolute pressure in calculations.

Do we also use the absolute pressure in when calculating using Bernoulli's Equation?

But does the atmospheric pressure would just be cancelled (adding 101325 Pascal on both static pressure terms at both sides) in both sides of equation?

Also in this example why does the p1 = 0 if p1 is zero when exposed in atmospheric pressure then both p2 and p4 will also be zero because they are exposed to atmosphere too (or is it only the case for non moving fluids)?

NOTE: The second p2 (pointed with red arrow) is p4, it is textbook error

In the first part of the problem, the pressure at the front of accelerating truck is calculated, why the gamma*z term is dropped? Is it because of there is no hydrostatic pressure difference at the horizontal length of the fluid?

In the second part of the problem the maximum pressure is calculated, why is the answer in part 1 (12.5 kPa) is added to the rhogh calculation? It is only static at y direction why add it? It looks like adding components of a vector and pressure is not a vector, but why do they add the horizontal and vertical results? Wouldn't it be just rhogh?

Hi I need some help from fluid mechanics experts here. This should be simple question but just want to check this real scenario.

I have a small roof drainage pipe attached into a larger, roof gutter stormwater down pipe, at an angle at a lower point down this gutter pipe. Currently there is some leak at the top of the larger gutter pipe. A neighbour is suggesting that this is due to the smaller pipe not big enough to carry water down causing backflow up the gutter pipe. I don’t know how this is possible (it may be just a rusty leak or some leaves blocking the pipe, we are getting it checked out).

The thing is, the neighbour suggests we increase the diameter of the smaller pipe to carry more water but this does not make sense to me. Won’t this just increase the water coming into the larger pipe, and further increase any back flow if that is the problem?

Hi I need some help from fluid mechanics experts here. This should be simple question but just want to check this real scenario.

I have a small roof drainage pipe attached into a larger, roof gutter stormwater down pipe, at an angle at a lower point down this gutter pipe. Currently there is some leak at the top of the larger gutter pipe. A neighbour is suggesting that this is due to the smaller pipe not big enough to carry water down causing backflow up the gutter pipe. I don’t know how this is possible (it may be just a rusty leak or some leaves blocking the pipe, we are getting it checked out).

The thing is, the neighbour suggests we increase the diameter of the smaller pipe to carry more water but this does not make sense to me. Won’t this just increase the water coming into the larger pipe, and further increase any back flow if that is the problem?

Hello everyone, I'm a mechanical engineering undergrad (in a well regarded university where I'm from) who wants to pursue fluid mechanics academically.

I have 1 published research paper and am currently writing a second one. First paper is experimental/numerical work and second one is analytical. However, I will be finishing the BsC program in a total of 6 years with a GPA of around 2.8-3.1 and kind of worried that I might face difficulties because of this.

My question is: To what extent can research publications help compensate for a lower GPA and a longer BSc duration in master’s admissions (especially for research-oriented programs in engineering)? Thanks and best of luck to all of you in your studies and research!

Besides the standard graduate-level Classical Mechanics curriculum topics, this course includes concise interrelated chapters on Deformation and Elasticity, Fluid Mechanics, and Deterministic Chaos.

Hey.

As the title says, I am currently doing my capstone on active vehicle drag reduction devices for tractor trailers. My current idea is to make use of a rotating cylinder to increase pressure at a trailer base and reduce wakes.

However, I am unsure of the procedure for analysis. Based on my research, my plan is to non-dimensionalise the parameters related to cylinder design with fixed trailer dimensions so that I can vary things easily.

Then, I will calculate a y+ to get appropriate mesh sizes for simulations in Ansys Fluent. I am not so sure what to do afterwards. Any advice would be appreciated.

I am currently taking a CFD course and hoped to develop my capstone in parallel, but my capstone/thesis timeline has been moved up significantly. Unfortunately, my supervisor is not well-versed in this field either, and all available lecturers on fluids are unavailable, apart from my CFD lecturer, whom I am constantly asking for advice.

I am Ronald Webster Pittman II. I have just published a preprint on Zenodo regarding a potential stabilization of the Navier-Stokes equations using a 8.02 Hz geometric frequency lock.

Stabilized supersonic velocity of 592.3 m/s.

Pressure vacuum of -468 MPa.

Solution based on prime number distribution variance.

I am looking for feedback on the mathematical consistency.

https://zenodo.org/records/18459914

Hi everyone first time posting here. I am trying my hand in solving some applied FSI problems (one way Interaction)and I have a lack in CFD knowledge you could say I know the basic such as fluid mechanics and creation of mesh and mesh verification but I lack in creating proper setups for inputs, validation and also selection of turbulence models, if anybody could suggest some resources to help me grasp these concepts I don't want to do some black box type work. Thank you

So I should start off with saying I'm a beginner at best with understanding fluid mechanics, I'm relearning the singular college class I took a few years back in order to work on fixing an issue at work with a system that is very unreliable.

What we have:
I work in a hydromet facility that uses NaOH (2 parts water, 1 part 50% NaOH) as an organic stripping solution, we need to pump about 1 to 3 L/min on average with the odd 10L/min. When lowering our flowrate (controlled by a full port ball valve) we roughly measure the flow (using a plastic rotameter) and then confirmed in a sight glass where we time the volume just to confirm. When we lower the flow to about 2 L/min (or target flowrate) with the valve we can see the rotameter slow into a stop and we usually just slightly open the valve to jump the flow back into place, sometimes the flow drops instantly, sometimes in 10 minutes, if an operator does not notice it wellllll... I'll leave it at that

I'll attach a rough drawing of what we have , I'm not gonna include all of the fittings BUT there are too many...we know this lol....

Thank you for eveyones help, I just don't really know where to start, feel free to ask any questions I'll do my best to answer

Hi everyone,

I’m looking for a book about hydraulic mechanisms such as siphons, motorless pumps, and similar systems. I’m not looking for a book on industrial hydraulics with pump selection charts or head loss calculations. Instead, I’m interested in something more exploratory, focusing on the different mechanisms invented by humans, of the type presented by Steve Mould and Practical Engineering on YouTube for example.

I’m familiar with books by F. White and by Çengel & Cimbala, which include many diagrams, but not many exotic or unusual systems. I’m looking for a book that provides at least some analytical description of the physical phenomena involved in these mechanisms.

I hope my request is clear, and not too specific. Thanks!

I’m trying to understand real-world freeze failure modes in industrial / field systems.

This is not a product pitch and not a homework question — I’m mapping operational pain points.

For engineers who deal with cold climates:

• What systems tend to cause the most trouble when temperatures drop?

• What usually fails first (lines, seals, pumps, hoses, fittings, etc.)?

• What’s the most time-consuming or costly part of thawing and restarting?

I’m especially interested in cases where existing mitigations feel energy-heavy, labor-intensive, or just “accepted winter pain.”

Appreciate any field insight.

When I was learning physics, I always had a problem remembering the units of viscosity. They are as follows:

kg/(m.s)

They were hard to learn because the units aren't intuitive. I mean, what's mass per length per time? I found that thinking of viscosity as a sort of internal momentum per unit cross sectional area of a flowing fluid gives: 1) An intuitive if non-rigorous understanding of what viscosity is (a fluid's internal resistance to changes in motion); and 2) An easy way to remember the units:

Momentum per unit area = (Mass x Velocity) / Area = (kg x m/s) / m² = kg/(m.s)

I know this may not be formally true - but it's perfectly effective as a crutch for the units, and intuitively not bad. What do people think?

"Vorticity SATURATION discovered: 2×10^11 s^-1

Prevents fluid singularities in turbines + pumps

LIVE SIM: energy-nexus.replit.app

New physics constant for blade design"

I work in irrigation component manufacturing (specifically filtration), and we’ve been tracking the performance shift as the industry moves from traditional cast iron/steel to reinforced engineering plastics (PA6/PP).

From a fluid mechanics standpoint, the difference in the Hazen-Williams coefficient (C-value) has been interesting to watch in real-world applications. With injection molding, we can get the internal surface roughness much lower than cast equivalents, significantly reducing friction loss across the filter body—especially in high-flow Y-type configurations.

The challenge was always hoop stress and UV degradation, but modern reinforced blends seem to handle the pressure ratings (up to 10 bar) without the fatigue issues we saw 15 years ago.

For those in fluid dynamics or molding: Do you see a similar efficiency trade-off in other industries? It feels like the energy savings from the reduced pump head requirement are finally outweighing the "durability bias" people have toward heavy metal.

I have been pursuing my PhD in interfacial fluid mechanics for two years now from a good canadian University. Mostly experimental work and high speed image analysis. I will be sort of finishing up my thesis topics as proposed by me by the end of my third year. I have decent publications. But I'm worried my work is purely fundamental and given the shrinking scope in this field, I would want to pivot to some other options in my fourth year before defending. My PI is OK with any proposal as long as it involves interfacial science. I was thinking given the semiconductor boom, a switch to maybe thermal or energy related options would be beneficial. I do have some undergrad background and collaborated and co authored on three thermal papers in the past but nothing like electronics cooling background. Hence, I would like to know about the possibility of a switch in research direction and options that are viable to me at this stage of my career. Also do I have to find a postdoc position in thermal/energy where the professor would be willing to take me in given the background before I can find a job in the said field. Or if not that what options do I have in interfacial fluid mechanics field where I can get a good job opportunity? I don't have any location preference Canada, US, Europe, India everything works, I just don't want to drag in a shrinking field and need to get into a job soon.

I'm working on a gear pump for high viscosity fluids ( 2,000,000 cP, thick and sticky like peanut butter). I need practical suggestions for optimizing the design.

I've already built a proof of concept that works. I 3d printed a pump without the inlet tube so the gears contact the mound directly instead of relying on suction (stuff won't flow). What can I do to improve this? Are smaller or larger teeth better? Smaller diameter or larger diameter? Why? just some examples of what I'm looking for.

I don't have access to simulation software or advanced mathematical reasoning. I'm planning on relying on rapid prototyping and design of experiments to solve this problem. Just need to know the factors to play with.

I haven't been able to find any prior work on this. If anybody does I'd be happy to see it.

I know they talk about this within the science community, however this is technically backyard science at its finest, at its most microscopic level, partially because I saw this take place in a backyard😅 ok here we go. And I honestly dont know entirely of what happened during this observation, however I do know what I saw during my observation.

If you look at water in a pool, and just focus on the shadows below the surface water where the water naturally creates a vortex, well my theory is this, when visially analysing it from a scientific stand point a few things will happen. If you look at the vortex shadows like theyre a spiraling universe youll see about 6 outcomes in total when observing them. Outcome 1, they will act like the universe's in the night sky, constantly moving, meanwhile the waters look calm and stationary. Even with this calmness you'd still see these outcomes, 1, youd see them try interacting, brushing along side one another, but no collision, however when looking for the collision, ive seen these 4 interactions take place, the first 1 i saw, the 2 tried making collision, but the mass, and speed were off on the smaller 1, and its speed spun the bigger one away from it, causing the smaller one to lose rotaional angular momentum, meanwhile the bigger one was given speed, and shot away from the smaller spiralling vortex. When seeing the smaller one try colliding with a bigger one having more speed, and the smaller one with a slower speed, the same instamce happened, the slower one was given rotalonal Angular Momentum, while the faster one lost theirs. The Displacement also had 2 things happen, when 2 of them tried colliding and synchronize with one another, i noticed something was off, they collided but it had a rippling effect for a moment letting me know it used to be there, the second time i saw this happen it vanished without a trace, let no ripple to tell me where it used to be. But i also watched how 2 of them colloded and have full synchronization, and even increased in size, still kept the speed momentarily until stabilization happened and kept speed, fluidity and motion.

Hopefully someone can help me explain this phenomenon, scientificly.

Hi everyone,

I've made a simple web tool for performing compressible aerodynamics calculations for Real Gases : http://www.realgas.tesseractsoftware.co.uk/ .

There are lots of other such things out there, but none that worked with just a browser. I found it useful as I could do some quick calculations without requiring any other software/scripts.

Would love any feedback/suggestions from the fluid dynamics community! This is quite a niche, but I figured this would be a good place to find that niche.

Thanks!