Continuous head losses can be calculated using a plentitude of formula. However, some are more appropriate to be use in pipes, others in open channel, because of how they were originally obtained.

More recently, I've been thinking about the consequences of using one instead of another given I'm addressing pipe systems. My standard is Darcy-Weisbach with data obtained mostly by Nikurase. However, if I was to use Manning or Hazel Williams, what would the head losses look like for a standard table coefficient for the same material given the different formula and (above all) the way the experiments and formulations were developed?

I have been thinking of making a HRV, for home ventilation, I have seen people do it online out of corrugated plastic and making a traditional HRV core, although I have been thinking of doing one from 36, 10 foot copper pipes, in a 4 inch insulated duct. Since copper has a much higher heat transference coefficient.

The cold intake would be inside the pipes, and the warm exhaust would be on the outside. It seems the copper pipe wall is .028 inches in thickness, which is slightly thicker then 2 layers of a single wall of corrugated plastic with that being .015 inches, but I figured perhaps the higher heat conductivity of the copper might counteract that, although I don't know the math behind calculating heat transference. I have also heard from someone that the extra thickness of the pipe might transfer heat along the length of the pipe which would cause more inefficiency, I thought about putting thermal breaks in the pipe, as in, cut the pipe every foot or so, and add a gap with some sort of spacer and seal it, to prevent thermal bridging, but I am not sure if this would be an issue or if the transfer along the length of the pipe wouldn't actually be an issue. I would imagine the only other issue with a thicker material as it would take more time to reach temperature, as it has higher thermal mass, but as this would be running continuously I don't think that would be an issue, although I could be wrong.

From what I have read online the surface area of most HMV cores are around 125 square feet. I cant seem to find online if lower flow rate HMVs need less surface area, as I would think lower flow rate would increase the time to transfer heat. The flow rate I would need would only be around 30cfm as the building I am ventilating is only 350 square feet. This would be quite a bit less with around 47.2 square foot of pipe surface area through the whole thing, although the time it takes for the air to go through 10 feet of ducting would be much longer then it takes air to go through other HRV cores, but I am not sure if only surface area and flow matter in heat transfer, or if its any different if the surface area is spread out over a longer distance. Also not really sure if the pipes being quite large would negatively impact heat transference significantly, or if only surface area matters.

If there is something that would make this more practical, like larger duct and more pipes, to make the surface area more in line of what a normal HRV core would be, or just more and smaller pipes, I wasn't sure if it would be too difficult for a fan to pull the air through pipes that small through such a long distance.

Let me know what you think about this idea, I am not much of an HVAC engineer so perhaps this is out of my league, but I am curious if this has any chance of working, and getting a reasonable amount of efficiency out of it. I am not sure if there are other ones similar to this that are available commercially, or if its just foolish idea for some reason or another. I have seen similar setups for liquid to liquid heat transfer, I would think it would work for air to air, as, unless I am mistaken their usually treated the same in fluid mechanics, the only thing is I believe its more difficult to transfer heat in gas.

If there are any free fluid dynamics simulations people know of where I could simulate this without building it let me know, I looked online, but they all seem to be, more for large companies and cost money. Although I would imagine it probably takes a lot of computing power to develop and run them, so I could see why if there aren't any free ones.

Here is a rudimentary Microsoft paint drawing to better illustrate my idea.

https://preview.redd.it/jnw7cmset54e1.png?width=941&format=png&auto=webp&s=f5e9f3c9e415073ca764c1fe73130dac40501bc5

Thank you for any input you may have.

https://preview.redd.it/ma9r42ic0q3e1.png?width=708&format=png&auto=webp&s=f846abf1d0f2a2ac0e6531f9ab91718bcdd7ec03

Apparently, my teacher gave us the answer which is that the velocity through the porous wall is V=0.001 m/s, yet some of my peers and I can't seem to understand it. Any help? I know that it may not be a very difficult problem, but there's something I think I'm missing...

Hi everyone,

I'm working on CFD projects and considering using Python to visualize flow fields and CFD data.

My questions:

1. Performance: Is Python powerful enough for complex flow visualizations?
2. Recommended Libraries: Which Python libraries are best for vector fields and streamlines?
3. Integration: How well does Python integrate with common CFD software (e.g., OpenFOAM)?

Looking forward to your experiences and recommendations!

Thanks in advance!

Hi first I'll like to excuse my bad English, please let me know if something doesn't make sense.

I'm a Mechanical engineer and have a project I'm working on for a class, and I'm stuck on understanding how the mechanics of how to overturn/capsize a boat/ship that will be modeled as a rectangular box. I know how to calculate the buoyancy force, but what I'm having trouble is understanding how much force would be needed to capsize the boat. My professor gave me this feedback:

" So, you need to model pirate vessel as floating rectangular box and then show that jet strike will cause it overturn. This means you will need to apply momentum balance on floating box and determine the velocity and discharge required to topple the vessel. If the moment due to force of striking jet about center of mass is greater than that due to offset buoyancy force due tilting, the vessel will be toppled/capsized. The offset line of action of buoyancy force for some worst case scenario like 45 degree tilted box about its lengthwise axis can be determined by computing centroid of submerged volume via SolidWorks."

I know how to work backwards once I get the reactant force need and from then determine my velocity. What I'm stuck with is just understanding how to determine the line of action for the buoyancy force once the tilt is taken into effect. I attached a very simple sketch of cut section of the front view, since I'm working under the assumption that the water will strike the vessel at one of it's sides. I'm sure I'm overthinking it, but it doesn't help my solidworks isn't working at the moment.

https://preview.redd.it/7zmowsetfk3e1.jpg?width=4000&format=pjpg&auto=webp&s=a0a293d2c84045cfa418ddb5b7d54cfbe00c36f9

I'm a mechanical engineer working on simulating particle flow through a pipe, which I’ve designed in SolidWorks. My background isn’t in simulations, so I’m looking for software recommendations—not someone to do the work for me.

Does anyone know of any software that can simulate suspended particles in a channel? Specifically, I need to model how the particles move through the pipe and how, when the channel splits, the hydrodynamic forces affect on the particles.

Thank you ❣️

My first question is regarding thickness of turbulent boundary layer. I found two formulas that provide different results for the same case. The first formula from the book Boundary Layer Theory (9th edition) Hermann Schlichting Klaus Gersten on page 34

d*U_inf / nu = 0.14 Re_x / ln(Re_x) * G(ln(Re_x)), where d is thickness. The authors editonaly say that function G is weakly dependent on ln(Re_x), and for 10^5 < Re < 10^6 could be taken as 1.5 and approach 1 as Re_x approaches infinity.

The second formula from Wikipedia

d = 0.37 * x / Re_x^1/5

I have a case with a flat plate (length = 6 m) and U_inf = 6 m/s, rho = 1 kg/m^3 and nu = 0.00002. From the first formula I'm getting d = 0.087 m and from the second 0.125 m. I'm not sure if I understand the first formula correctly.

The second question is regarding thickness of displasment in turbulent boudary layer. A little bit of background, I am trying to simulate flow between 2D plates in Ansys Fluent (initial data as in first question) and analytically find velocity at the exit and then compare this value with results of simulation. I already made it with laminar flow using conservation of mass and laminar displacement thickness:

d1 = 1.721 * sqrt(nu * x / U_inf)

But I did not find an analogy formula for turbulent layer; are there any? And if it is not, how can I calculate velocity at the exit for the turbulent case?

https://preview.redd.it/n4efw7hsh33e1.png?width=2043&format=png&auto=webp&s=163b8af182f3709d344a5c2f098ec8db391c19e2

I'm studying fluid mechanics in university currently and I'm solving a problem that has 2 disks spinning with different angular velocities h distance apart from eachother. They both have a radius of R and the velocity profile is linear. It isn't given which velocity is greater (I assumed omega 1 is greater than omega 2) I'm wondering if I got the velocity profile correct and if I can make it simpler as shown in the picture. Thanks.

The moderators at r/Physics didn't approve of my post, so I'm sharing it here instead.

Hi, I am studying natural sciences at an educational institution equivalent to high school, where completing a thesis is mandatory. I chose to study ferrofluid because it looks cool. My goal is to investigate how an electrical current passing through copper coils, which generates a magnetic field, affects the displacement of ferrofluid along the y-axis.

However, I am struggling with the physics formulas, as they are quite advanced for me. I need help finding the correct formulas to calculate the displacement to demonstrate that the observed behavior in my experiment also works theoretically.

In the video of my experiment, I used two copper coils with pointed metallic objects on top. My teacher and I found that these provided the best results. The pointed metallic objects are aligned in the same direction. In the experiment, only direct current (DC) was used to generate the magnetic field. The current is displayed in amperes on the display. For some reason, the ferrofluid formed a valley in the middle instead of a peak, but let’s set that aside for now. The Link to the video: https://drive.google.com/file/d/1ORFR-ME_KfdfEHAOk_fOBmsTCnrhduCe/view?usp=sharing

I understand that magnetic flux density is essential for these calculations, so I have also collected data on how the magnetic flux density depends on the electrical current.

During my research into relevant formulas, I came across the Navier-Stokes Equation, but I learned that it is unsolvable in its general form (which you probably already know). I also learned that it is unnecessary to use the equation.

I would greatly appreciate any help you can provide. If you know which formulas I need to use, please include their names so I can easily look them up online later. If you need more information about my experiment or my level of prior knowledge, I’d be happy to provide it.

Thank you in advance!

in tank where where it is divided 80% liquid and 20% vapor, closed system, at Pressure P1 and temprture saturation,, we know Q in Watt entering the cloesd system heating it up and evaporating the liquid, which increases the pressure.
if i want to calcualte the time it take we reach P2, m_total {Delta u }/Q = time
and to calculate u1 and u2= u_L+x_g(u_g-u_L)
where x_g for the P2 state i calcualte it using conservation of Mass
M at P1 = M at P2 = mg + ml= m_g/density_g + ml/densit_l
i feel my error is in the way i am finding the fraction of the liquid and vapor at P2 state as i am using the saturation state at P2, but maybe this is wrong, any suggestions i would be thankful?

Has anyone made a general coding to iteratively find friction factor of a pipe problem using Colebrook's equation?

I think it is possible to construct the program by assuming either Re and f, then computing the error in respect to the value that we know (Velocity, Pressure) to make sure if the result is good enough, just got in to the topic so i don't know much myself until i try one.

https://preview.redd.it/do1qtpfyjy1e1.png?width=961&format=png&auto=webp&s=271ff1944c2b83b8b6e483b5f8ae06ab2816670b

Hello, I am trying to size a pipe to have laminar flow. I estimated a 54 inch dia, so 4.5 ft, which is nearly the biggest I will be able to go in this scenario. The flow rate Q is 80 cfs, and I calculated the velocity to be 5.03 ft/sec. Since this is for water at normal temp/pressure, I used a look up table and got v to be 1.08E-5 ft^2/sec. What I am struggling to grasp is how this number is so high.... my Re is 2 million, nowhere near laminar flow. How can any large-scale water conveyance pipelines that operate at any capacity possibly be laminar?

If my math is correct (which I am no longer sure it is), to get a Reynolds number less than 2000 you would practically need a 10ft diameter pipe, or 0.01 cubic feet per second of flow, or something like that. Please let me know where you see my errors (since I am apparently incapable of finding them). Thank you!

Say I put a sponge into a vat of water. Then I applied a cyclic force to the sponge, say with some sort of press that loads and unloads the sponge. The water would flow in and out of the sponge. What principles and equations would dictate this flow. Is it really all just capillary action or is there any other principals that could be applied?

Hi all

Suppose I have a 20m high tank of water. I connect a pipe to drain the tank under gravity to a location lower in elevation.

Does it make any difference to the flow rate whether I connect the pipe to the bottom of the tank or say half way up it?

In one case I have half the static head in the tank acting on my pipe. But if I use Bernoulli's between top of the tank and discharge location, there is no difference so I'd get the same flow?

(Assuming pipe discharges to same location & elevation in both circumstances, ignoring slightly higher pipe frictional losses for longer pipe for higher connection point)

Thanks Jon

Disregarding cost associated with investment, maintenance and difficulty. Which one will provide better performance in this case higher flow rates at any given restriction?

In case of spreading pumps across the loop does it make any difference to have only 1 reservoir before one of the pump vs having reservoirs before every pumps?

Thanks.

Hi guys, as title says, i am writing my thesis about vorticity in pumps, i am looking for tips on books and articles for the theory part. I dont want you to do my job, i am only asking, if you stumbled upon something interesting and related on this topic, i would be happy if you shared it with me.

I call upon the brilliant minds of Reddit!

I'm currently trying to approximate the speed of water entering a pipe from a river and quite frankly, it is far beyond my very limited mathematical arsenal.

If someone could help me by providing an equation, or just explaining it to me step-by-step of working this out, then I would be so grateful.

So, the Info I have is:

• The water flow of the river is 16.128 m^(3)/s.
• The river is 17.2m wide
• The river is 0.6m deep at this location
• The V-shaped notch in the riverbed is 1m² and 0.3m deep.
• The opening of the pipe is 0.3m in diameter
• The angle of the pipe is roughly 45° toward the water flow.

If there's any additional information you might need, I will try my best to provide it.

Honestly, thank you.

Apologies for the terrible picture.

Hi everyone, I am trying to analyse some of my aortic valve FSI simulation results by modelling the flow downstream of the valve using Womersley Flow connected in series to a 3-element Windkessel Model in Matlab. However, the results I am getting by dividing my pressure by the total impedance is not exactly great. I am getting this sine wave at the end of diastole that shouldn't be there, and the amplitude of that sine wave seems to be added to my peak flow in systole. I think I have a problem with the values at the 3rd harmonic frequency (just above 3 Hz).

Here is the link to my Matlab forum post for more info and the code:
https://uk.mathworks.com/matlabcentral/answers/2165769-calculating-the-aortic-flow-downstream-valve-using-womersley-and-3-element-windkessel-model-calculat?s_tid=srchtitle

Thank you!

While referring to different sources I found totally different views on lagrangian and eularian acceleration.

http://brennen.caltech.edu/fluidbook/basicfluiddynamics/descriptions/accelerations.pdf

Here Eularian acceleration is given by partial derivative of velocity wrt time du/dt (here d being partial operator)

And Lagrangian acceleration is given as the material derivative (Du/Dt).

But in some books it just the opposite (Fluid Mechanics' by Pijush K. Kundu and Ira M. Cohen.)
Eularian acceleration is given as the material derivative (Du/Dt).

Lagrangian acceleration acceleration is given by partial derivative of velocity wrt time du/dt (here d being partial operator)

At some videos/articles its mentioned both are equal

Which is the correct description

Hi everyone,

I am designing a system that needs to pump water at a certain flow rate through a system to test some sensors. It needs to be able to pump (at least) 3.6L/sec through a 12 inch pipe (largest), and 0.13L/sec through a 2 inch pipe (smallest). I used some calculators and it seems that a 3/4-1hp pump should be enough for this, the total length of pipe/hose will be under 30ft, and will have to go a maximum of 5 ft back up off the ground into the top of the starting tank which will hold the pump. My question is, if the pump starts off pumping from a 2inch hose, and I use adapters to increase that into 4, 6, or 8 inch hoses, how will that affect the power requirements of the pump? I know water velocity will decrease when entering a larger pipe/hose, but will these transitions put more stress on the pump? Any help is appreciated, thank you!

Hi Everyone. i am doing a solidworks flow for a cold plate. SImiliar to the one in the picture. Aluminium base plate and copper tube with 50/50 glycol water mix. I need to determine the COP of the plate for different flowrates. According to my understanding COP= Qout/Win and Win can be calculated as Pressure Drop x Flowrate. Both my flowrate and pressure drop is very low, 0.125 L/min (massflow=0.00225 kg/s, Re=133) and around 300 Pa and with a Qout of around 100 W this results in very High COP which doesn't make sense when compared to other systems. Am I understanding something wrong or is it jus because of the low flow rate and pressure drop? WHat is a better way to determine COP for a plate like this.

https://preview.redd.it/rlvqnlycqh0e1.png?width=500&format=png&auto=webp&s=67fd4a15461fcdaebc551cd07fc66d102a654ae6

Why do the head losses in each loop within a parallel piping system = 0? We use the hardy cross method to solve. So separate in Loop1, 2, 3,etc.

Hello mechanics, I should preface by saying i know nothing about fluid physics or engineering. This is literally just an uneducated strain of thought i found interesting enough to investigate a bit further.

The other day i was riding on the bus and remembered hearing about vegetable oil being used in old diesel engines. i read online somewhere that the main problem of doing this to a modern diesel engine is the viscosity of the oil, which needs to be heated somehow. I'm not sure how true this even is though, does already liquid oil actually get less viscous as you heat it up like that? and can vegetable oil reach that of diesel oil without building like a incredibly complicated special pressure chamber?
Anyways, this got me thinking if it would be possible to have a vehicle with two motors, a diesel and a electric motor. I can't remember where but i thought i once read somewhere a major problem with electric motors in cars is the heat they produce, unfortunately cant remember where. i think it was an interview with a guy at tesla or something.
So how feasible would it be to build a contraption in which a hybrid/electric motor heatsource is placed underneath/around a tank of vegetable oil, which is then fed into a diesel motor to power it? This would probably not be profitable given the amount of custom redesigning needing to be done but in any case, the theory of it is still quite interesting to me regardless. Maybe there are some of you out there who know how to properly calculate this and feel like helping. Let me know what you think of this

I'm also aware that there's probably better/cheaper/easier ways to heat the oil, i just wanna entertain this specific idea of utilizing wasted hybrid heat. If it even exists that is.
Also Let me know if this is even the right place to ask this!

otherwise, have a nice day :)