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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Where should I restrict the flow of a pump?
I am using a 1/2 hp sump pump to provide flood coolant to a CNC milling machine. The sump pump has a 1.5" outlet. The milling machine already has a 1/2" adapter and manifold which connect to ...
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Stop Spa-to-Pool Siphoning Thru Spa Pump
I have a partially above ground Spa and an in-ground pool. When the spa is filled to spillover with pumps off, water siphons through the spa pump and into the pool until the spa water level drops ...
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Analytical solution for the 1D convection-diffusion equation
The Ogata and Banks analytical solution of the convection-diffusion equation for a continuous source of infinite duration and a 1D domain:
where C [mol/L] is the ...
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How to determine the slope for the gravity flow of highly viscous fluids (eg. gum)?
I am looking for a method to determine the slope of the pipe required to maintain a gravity flow for highly viscous fluid.
The Hazen-Williams equation for gravity flow is applicable for liquids which ...
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Metal casting simulation and the solidification analysis
Casting process analysis
Mold filling affects the quality of a casting. The fluid flow phenomena are closely related to the casting quality and surface finish. The dimensional accuracy of a casting ...
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How could we aproach development of touchscreen with morphing surface or morphing keyboard?
There is this technology of braille e-readers. It is relatively simple and reliable but it never had much commercial success probably because small customer base.
In past a company called Tactus tried ...
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Stirling Engine Cooled Engine
Could a Stirling Engine replace the cooling system of an engine?
Instead of having a clutch and fan attached to the main drive shaft to cool an engine, could a Stirling Engine and clutch share that ...
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Orifice flow meter equation applicability, modeling leak flow
I am trying to determine the correct equation to model ideal gas flow rate through an orifice as a function of pressure. The equation below I found in Marks' Handbook for Mech Eng 8th Ed, p. 3-64 ...
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Double Meniscus of Capillary Tube
I recently realized that if I turned my coffee cup downward, all the liquid spills out easily. This amazement prompted me to wonder about the impacts of surface tension for a situation in which the ...
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What is the theoretical explanation of flow work/energy?
Given the following definition of flow work:
Reading and following the derivations I understand that in theory, this is only accurate when the fluid accelerates from rest. However, if we consider ...
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Effect of pipe size on water flow rate in municipal water system
am expanding my house and the town is requiring us to increase the size of the water line from the street from 3/4 inch to 1 inch diameter.
intuitively i understand that a bigger pipe results in more ...
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Total dynamic head calculation of a submersible pump with different dia pipes connected to its discharge
I have to install a submersible pump for pumping ground water to irrigate land. I have six inch diameter metal pipe already available that I plan to use in the project. The pump delivery is 5 inches ...
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Modeling a two tank system which will be regulated using a single valve
This is a mix between a physics and controls engineering question. At first I thought it was mostly a physics question and I therefore asked it at physics stack exchange. But they said this was mostly ...
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What happens when electrolytic process rotameters are swapped for a much bigger one?
electrolytic process rotameter were swapped for much bigger rotameters. Inlet pipes are the still the same. What effect does the bigger rotameter have in the concentration of catholyte in the cell?
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Can someone explain why this sprayer arm wouldn’t simply accelerate to infinite angular velocity?
If mass-flow-rate * velocity = force, then this sprayer arm (frictionless and horizontal to gravity) should accelerate to infinity being the force remains constant. I am assuming I am missing ...
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How to estimate air velocity at turbine in turbojet?
I am designing a small turbojet. I wanted to know how to calculate the air volume expansion to predict the outlet velocity of air towards the turbine. Theoretically, I wouldn't know the flame ...
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Shaped charges and fluid dynamics
Watching this video https://twitter.com/Rainmaker1973/status/1713599092968787987 of objects being dropped into water and the resultant shape of the displaced fluid reminded me of videos showing how ...
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How to calculate mass flow rate at the Multiple Channel Outlets?
I have a basic question regarding the calculation of mass flow rates of a channel with multiple outlets. In the scenario depicted in the image below, we have a single inlet with a mass flow rate (m1) ...
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Hydrographic Survey Problem
I have been trying, but I can't figure out how I should solve this using the area velocity method. It is the only method as our professor taught us.
Any help would be appreciated.
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Will hot object near ceiling vent create more draft?
As in the picture, we have a room with vents at the bottom to let cold air in and at the top to let hot air out. Normally the air flow is limited by the temperature gradient (correct me if I'm wrong). ...
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How to fluidize sand inside a 55gal Steel Barrel?
Looking for recommendations on how to make a fluidized sand bed inside of a 55 gal steel barrel. I've seen many examples of it done with pipes but I am worried about the evenness of the fluidization. ...
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How can I make sure that my outflow is the same as my inflow?
I have a basin that is 110 mm wide, 200 mm long, and 15 mm deep. The walls are 2 mm thick. It has water being pumped into it at a rate of 0.1078 gpm from one side. In order to ensure that this pan ...
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What does a dynamic-pressure loss coefficient of more than 1 mean (for eg air going through bend)?
Air flow (eg in a duct) has a dynamic pressure, and when the air flow goes through e.g. a 90°-bend the bend has a dynamic-loss-coefficient.
The dynamic-loss-coefficient is used to calculate the total-...
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How much air pressure is needed to push liquid out of a tank
I want to use compressed air to push diesel out of a 100 gallon rectangular tank for fueling equipment. Tank is 24” tall with a 30’ 3/4” hose reel on top. Height of the nozzle would be 6’ ft from the ...
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Unable to validate hypersonic flatplate case in DSMC SPARTA
I'm trying to learn a software called DSMC SPARTA. I'm validating the hypersonic flatplate case mentioned in one of the tutorials on the website (Page 17). This was my test case:
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Calculate heart valve flow rates over time. What formulas are involed?
I'm trying to program a simulation of a human heart which I want to produce results close to the following:
(Source: https://en.wikipedia.org/wiki/Cardiac_cycle#/media/File:Wiggers_Diagram_2.svg)
For ...
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How do I determine the moment of force that would have to be applied to the shaft to open the gate in this question on fluid statics?
I am presently studying fluid statics from Munson's textbook. I do not understand part (b) of example 2.6. The full question is as follows:
GIVEN The 4-m-diameter circular gate of Fig. E2.6a is ...
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Question About Dimensions and Figures Surrounding A Pressurised Nitrogen Canister
I need a nitrogen gas canister that will nitrogenate a beverage much like how SodaStream carbonates. Here are some approximate numbers:
The beverage to nitrogenate is 600 - 1000 mL
I want to be able ...
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How does this fluid-fill stop mechanism work?
I bought an interesting shaped water fill-stop valve from ebay a while ago. Very convenient form factor, even though there was some forward pressure requirement.
I want to now make a custom version ...
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I'd like to create a column of smoke that goes as high as possible. Is there a fan or configuration of fans that is best?
Budget ~$5k
Current setup:
2x 20k cfm water-based smoke machines facing each other 6' apart blowing across the top or bottom of a fan or set of fans. I was hoping there could be a way to get a vortex ...
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Split tubing assembly
I am designing a tubing (TPE) assembly that splits a single inlet line into either four or eight outlet lines. The goal is to achieve an approximately equal flow rate of mildly viscous liquid at each ...
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Magnetic Float Switch inside Filling Nozzle
I want to design a Liquid Flow Nozzle that has a Magnetic Float Switch inside, The Idea behind is that there is a system that has a Manifold with 10 to 12 Nozzles connected with it.
Now I want to fill ...
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Some variables relation for the Turbulent flow
I have the internal area of the pipe(ft^2), flow rate(gpm at 7ft/min), Reynolds number, pressure drop(psi/100ft), and pressure drop(ft/100ft) shown on the flow table as attached. May I know what ...
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Why are Reynolds Stresses time-varying?
The time-averaging operator definition gives us
$$\overline{u_iu_j}=\lim_{T\rightarrow\infty}\frac{1}{T}\int_{0}^{T}u_i(x,t)u_j(x,t)dt.$$
From my understanding, this should mean that the Reynolds ...
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Can I use water flow meter for measuring flow of glycol accurately. Why yes/no?
I have water flow meter and I was wandering if i could reuse it in new project for glycol.
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Compression phenomenon in Axial flow compressor
It is quite difficult for me to visualize how axial flow compressors work, as in, how air gets compressed by just flowing through a series of aero-foil shaped stator and rotor blades. How and where ...
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What is the ideal oil for an electric razor?
As in the title, what is the ideal oil for an electric razor, and why? I might add that the electric razor will only be used at room temperature.
What oil would an engineer select for their electric ...
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Heat losses of warm fluid in a cold pipe
I'm looking for a way to calculate/estimate heat loss in a fluid flowing trough a pipe for a length (l) and travel time for the fluid (t). The flow is intermittent and the initial pipe temperature (...
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What's the hydraulic loss of this overflow?
Consider the following image:
what we see is are upright pipes into a water vessel, upper end of the pipes above the max. water level. Water is pumped into the pipes from below. We need to consider ...
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Finding the time taken for pressurised tank to reach 1 atm (Exam Prep)
A gas tank has an internal volume of 0.3m3. It is filled with helium pressurized to 32 bar (absolute). The gas tank is in thermal equilibrium with its surroundings and so the gas is at a temperature ...
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How can I determine the size of holes along a pipe so that the flow rate is equal out of each hole?
Suppose I have a pipe with holes on its top (kind of like a flute, but with different sized holes). One end of the pipe is open and the other is closed. The pipe is submerged in water horizontally, ...
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Increasing airflow of fan
I learned at at young age from a physics kit that one can blow up a large bag with your mouth by blowing into it from a distance and letting the air pick more air with it. Later in life when Dyson ...
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Backpressure vs Pressure Drop
We were asked by a customer to calculate the backpressure of an exhaust system we were supplying a muffler for. The system includes piping from the engine to our muffler, then from the muffler to the ...
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Optimal blade/paddle design for low-budget Friction Heater (Joule Machine)
Generating heat by stirring fluids
I am interested in the direct conversion of mechanical energy into thermal energy as it was done by James Prescott Joule. For context: I was inspired by the danish ...
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Vacuum Tank Emptying Transient Equation
I am trying to derive the differential equation for pulling vacuum on an air tank.
The solution to the ODE:
$$P(t)=P_2 \cdot exp(\frac{dV}{dt} \cdot \frac{t}{V_s})$$
Where $\frac{dV}{dt}$=
flow rate ...
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SU2 vs OpenFoam for highly unsteady aerodynamics. Suggestions?
I am trying to simulate aerodynamic interactions between high speed propeller downwash and wings of a cruising aircraft. Confused between OpenFoam and SU2. Open to other opensource software ...
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Recent breakthrough on Inertial Confinement Nuclear Fusion at NIF
For the very first time, it has been demonstrated that it is now possible to make Nuclear Fusion generate more energy than is required for its equipment to operate, but it is not entirely clear as to ...
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Where are the energy losses here?
This hydroelectric system, described in The Study of Syphon and Applied in Hydroelectricity Power Production, is said to be continuous once it has been set up. Once set up it is claimed that it will ...
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How to find work done by compressors
Which one is correct method to find work done by a isentropic compressor?
Method-1:
Compressor power = mCpdT
Where m = mass flow rate
Cp = specific heat at constant pressure
dT = Temperature ...
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Why does the water pressure initially drop then stabilize when pressure testing a valve?
Sometimes the dropping goes on so long(10-15 minutes) that the test is thrown out and the valve is opened and filled with water for a longer period of time. Pressure testers claim that it is because ...
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