Questions tagged [fluid-mechanics]

Questions relating to fluids at rest (fluid statics) or the forces and effects of fluids in motion (fluid dynamics).

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What version of ANSYS is useful for simulation flow in a fin heat sink?

I'm interested in learning flow simulation in ANSYS and have found several tutorials. However, none say which version of ANSYS to download. The options are "Discovery Live Student", "Discovery AIM ...
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40 views

Could boiling water inside a semi-enclosed pipe be a low-cost method for a silent marine propulsion system? (redesigned)

I am wondering if boiling water that is trapped inside of a semi-enclosed pipe would be a low-cost method of creating an underwater thruster that would function as a silent marine propulsion system. ...
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32 views

Laminar flow hood/air straightener

I was looking at laminar flow filters to aid in my mycology work I'm doing. Most filters use an aluminum extrusion with fins. I figured the options out there are pretty expensive for what you get and ...
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26 views

What pressure drop is needed to get 15-20 gpm?

Scenario: There's a 1 inch, rubber hose, with fluid flowing in it at 75 psi. The density of the fluid changes (but I'll just be calculating with a specific known density, 8.35). So, I want to get the ...
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How to simulate the penetration of a liquid between two contact surfaces using Comsol Multiphysics?

I am facing a problem to simulate the penetration of a liquid inside a hyperelastic structure. I have used a predefined model of a water balloon based on FSI simulation I found on Comsol's website, ...
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water pump problems

I am presently facing a problem in water plant . In a tank there are four pump placed at equal distance named A B C D .in this arrangement A and D positioned at near corner of the tank . I started ...
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How to minimize temperature increase caused by compression of a cryogenic liquid in a multistage high pressure turbopump?

The cryogenic fuel I'm using is methane at 100 K and 300,000 Pa. Based on my calculations, after compression, the pressure is 55 MPa and using the ideal gas equation the temperature is approx. 800 K. ...
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How can I connect F=ma to Drag=1/2*Cd*(rho)*V^2*A?

I previously posted a different question that was very vague. I have kept working on the problem, and now I have a different question. Please let me know if I should have just added it to the old ...
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Which version of the Kozeny-Carman equation is valid?

I am learning fluid mechanics, and I've come across the Kozeny-Carman equation for a packed bed in laminar flow conditions as: $$\frac{\Delta P}{L}=\frac{150\bar{v_0}\mu}{\phi^2D_p^2}\frac{(1-\...
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What is this weird upside down U shaped pipline for?

There is this tall upside down shaped U pipe near a sugar refinery on Maui and I can't figure out what it's for ? I've also see these in other industrial areas near salt flats.
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How to ensure uniaxal and uniform force application on uneven samples using pressurized fluids

I am trying to apply a compression force to samples using air. I do not want to directly apply my loading since my samples are irregular. I do not wish to process them with a flattening step. I hope ...
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71 views

Heat Transfer in Different Wire Configurations

I am trying to create a program which estimates the final temperature of a magnet made of copper wire. I have different configurations in mind, but I will start off with a straight square wire with a ...
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Static charge, PVC pipe and water

I know it's possible for a PVC pipe to develop a staic charge due to fluids flowing through them. This is a twist on that idea. Can a sealed length of pvc (say 3.5 feet in length) - tethered below ...
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What is up with the spaced rudders on the SMX-31/Barracuda?

You can see it in the video here for the Barracuda: https://youtu.be/_NZKyvQVRd0?t=124 And here's a pic of the SMX-31: http://www.hisutton.com/images/Fr_SMX-31_cutaway.jpg What are the advantages ...
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Efficiency of TurboJet engines with nozzles

As per Bryton Cycles, most of TurboJet engines' Thermodynamic efficiency should be around 40%. Rest of energy gets rejected as waste heat in exit gases of after the turbine. But if these hot gases ...
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37 views

Can someone please give me a hint on how to draw velocity triangles for this specific inward flow reaction turbine problem?

I'm trying to calculate the hydraulic efficiency for this turbine by using the formula: E(hyd) = (VwU)/gH where Vw= Velocity of whirl at inlet, U=velocity of runner at inlet, H=Given Head, and g=...
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Pushing fluid through microfluidics

my team is working on a project where fluid (mostly water) need to be pushed through small channels (like small pipes) in order to reach larger reservoir. We were considering using air to push the ...
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Design of Gating & Runner system in Gravity Die Casting

How to design gating and runner system in permanent dies so that material flows smoothly throughout the design without spilling back from the gating channel. What should be the shape of gating system ...
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Is there some temperature at which all “5w” oils should have about the same viscosity?

Is there some temperature at which all "5w" motor oils should have about the same viscosity? (5w-20, 5w-30, 5w-40, 5w-50, etc.) I am looking for SAE or ASTM wording or chart that says it straight ...
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48 views

What is the axis of a pipe?

Sorry, it seems like the answer to this question is just a quick google search away; but I have not found a page defining what the axis is. My guess was that the axis of a piple is the imaginary line ...
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24 views

Low pressure Diesel pumping with High pressure Gasoline pump?

We are in desperate search of suitable pumps for one of our applications. We need to be able to pump Diesel fuel in a range going from 5bars to 125bars. To do such thing, I've been looking at Bosch ...
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How to increase pressure in an axial fan using additional inlet and outlet vanes?

I have a fan used to push hot air out of a storage room through a pipe. For this purpose I therefore chose an axial heatsink fan with high static pressure. I discovered that it's possible to 3D print ...
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2answers
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Measuring viscosity with tools other than viscometer

I would like to measure viscosity, but do not have access to a viscometer. If possible, I would like to avoid having to purchase one. I have access to many other flow measuring devices, including ...
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How to calculate flow rate and direction in system with multiple blowers

I have an odour control system where foul air is being extracted from multiple sources and then pushed into a scrubber vessel. Normally, all my designs look something like this: https://ibb.co/...
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How much force is required to push a liquid out of a syringe? [duplicate]

It's about 3D bioprinting and I need a calculation on how much force is required (pressing on the syringe piston) to push out the solution with known density. Moreover, there are few more ...
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Supersonic isentropic flow

how to know if a deflection in a supersonic isentropic flow causes compression (oblique shock) or expansion (Prandtl-Meyer expansion) Thanks in advance. an example of a problem that is related to my ...
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Couette-Poiseuille flow between non-parallel plates

I have a Couette-Poiseuille flow (both flows combined) where the plates are not parallel. So h, the thickness of the flow, changes along the x axis. Can I use a mean h to calculate the viscid stress?...
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33 views

What's a good way to equalize pressure between 2 spaces without allowing gas exchange under normal circumstances?

I have a reaction chamber where gasses are injected to maintain a certain mixture. The container is sort of like a bell, where the bottom is submerged in water to make a seal. The issue I have is ...
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38 views

Difficulty to reach Mach 1 by blowing into a small converging-diverging nozzle?

I'm learning about the basics of converging/diverging nozzles in my thermodynamics class, and it has me curious. Could you theoretically blow into a tiny converging/diverging nozzle and break the ...
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1answer
42 views

Buckingham-Pi Dimensional Analysis when there is a non-dimensional parameter: How is it accounted for?

I am in the process of completing a design project for my fluids course in which Buckingham-Pi /Dimensional Analysis is needed to find the optimal parameters needed to achieve a rotational rate of 120 ...
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61 views

Pneumatic-based, paddle wheel-type lifting apparatus for aircrafts

I am wondering if a pneumatic-based, paddle wheel-type lifting apparatus would have any practical application within the aeronautical or aerospace fields. Please reference the conceptual drawing ...
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Fluid is flowing from nozzle in upward direction

If a nozzle is projected upwards with water flowing with a certain flow rate then in how many ways can you find the diameter of the jet of water at a certain height from the nozzle exit? One ...
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1answer
22 views

How to determine ideal flow path length for specified pressure drop

I have designed a flow resistance element and I would like to be able to keep the total pressure drop across the element to < 5.0 inches of water (from 5cc/min to 5,000 cc/min). I have run some ...
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1answer
42 views

How to design and make thermal inkjet print head / nozzles

I'm recently interested in print-heads, especially thermal inkjet print heads. I would like to design a simple print head with nozzles in a row with no chambers, but only a straight linear pipe-like ...
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31 views

When finding flow generated by a pump, where do points A and B go?

I tried to find the answer in past posts, but couldn't locate it. I have a pump (100% efficient, for simplicity) that runs on 100kW and follows the equation: Power(pump) = (Specific Weight)(Flow)(...
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When To Ignore Changes In Pressure When Computing Flow Energy For Gases?

In reference to this example problem (only partially shown), I need to understand why for $\Delta h$ the change in enthalpy, which is $\Delta P/\rho + \Delta u$, the change in pressure is ignored in ...
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Determining the headloss according to Darcy-Weisbach with pipes in parallel and series

Given the following situation: Pipe A and B have a known and identical length and diameter, and are in parallel. I'm assuming the flow trough pipes A and B are also identical, as is the roughness of ...
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27 views

The mechanism of submerged hydraulic jump

Is there a mathematical analysis of the submerged hydraulic jump, such as under what condition it is formed, the speed and trajectory of the circular flow therein, etc.? Is there a good mathematically ...
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Is this pump design possible? (NPSH Question)

I have been assigned a hands-on project with an adequate budget. The client has given a minimal but adequate description of what they want. The problem is, it seems impossible, especially at certain (...
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Estimating Static Pressure @ Target Airflow (boost fans)

How do I estimate a pressure/flow curve for a filter of specified area, efficiency rating, MERV and MPR?(Duct work is negligible) I am trying to pick an appropriately rated fan/fans to maintain a ...
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1answer
39 views

Frictionless Flow

Suppose we have a water reservoir at some elevation say z and the flow is frictionless then by Bernoulli's equation we have the exit velocity (2gz)^0.5 . This means that the static pressure in the ...
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2answers
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Open pipe and relation between pressure and flow rate

If a pipe (of unknown/arbitrary length) with cross section area $A$ and with a continuous supply of a simple fluid with a known pressure $p$ at the opening to the atmosphere, which has a pressure of $...
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73 views

Calculate output pressure of a syringe pump

I've built this syringe pump following those instructions. Now I would need how do I calculate the output pressure given the step rate of the stepper motor, and vice-versa. I don't know if it is ...
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Will a video projector submerged in mineral oil still work?

I’ve seen folks submerge computers in mineral oil to cool them- but would doing the same to a video projector profoundly throw off its internal optical aspects? I’m considering one of those small “...
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Finding Drag coefficient for flows with both Laminar and Turbulent part

How will we find the overall drag coefficient for a steady flow which is laminar initially and then becomes turbulent after a critical distance?
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How to calculate divided irrigation discharge from a Parshall flume

How do I calculate the discharge from a Parshall flume that flow over a bulkhead (XY) into three partitions (A, B and C) divided 25%/50%/25%. There is no restriction of flow when the pipe gates are ...
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70 views

A naïve question about computer chips

Is it true that computer chips "float" inside of the computers ? Can someone give me references(books, articles, papers...) about that fact ?
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Pump Characteristic Curve

I am bit confused about the curve: We could observe from the [Pump curve] that Total Head decreases with increase in flow rate, but for [System Curve], it is opposite, i.e, Total Head increases with ...
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Flow Simulation for Laminar Flow in Annular Gap?

Would anyone be able to run an air flow simulation through the following geometry at 100 cc/min? I'm curious if any dead spots occur and if the geometry of the annular gap will produce laminar flow. ...
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Is it feasible/possbile to do regenerative cooling of ScramJet or Ram jet powered aircraft surface?

Thinking of ScramJet/RamJet powered aircraft for unmanned vehicle. One of the challenges in designing such an aircraft is surface heating. Just like Rocket nozzles are cooled regeneratively with fuel(...