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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Unrestricted Cockswain

Hello I am researching first millennium BC Nile freighter rudders. They sailed upstream and came back down with the current. The Greek writer Herodotus tells us that going downstream they were towed ...
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Finding exit velocity from a compressed CO2 canister

I’m trying to find P3 and v3 (exit velocity and pressure) to plug into a CFD simulation, but I’m having trouble finding v2 and P2 (velocity and pressure before the valve). I’ve looked online and many ...
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Calculating flow rate of compressed air to push another liquid out of a tank at a desired flow rate

I am working on a system for a university project which uses pressurised air to eject the contents of a tank through a pipe into the atmosphere. I am working on figuring out the flow rate and pressure ...
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Using one electrical pump for multiple hoses

I'm currently trying to figure out a cheap way to build a cocktail machine. For now the machine should have about 20-30 possible input liquids. These liquids should remain in their original bottle ...
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How to add a controlled amount of a nutrient solution to a water line

I have an existing water supply system for the cattle on my farm whereby 6 troughs located in different fields are all fed from a common header line. The pressure in that line ranges from 3-5 bar (It’...
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How do those “dipole-shaped” weights attached to sections of electrical power lines work?

I see these frequently on tall power lines like the one in the image below, sometimes a single one at each end, sometimes pairs as are shown here. Sometimes on one side of the tower but not the other. ...
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How far out from the rear of the pod does the vacuum bubble extend in the Hyperloop?

Are there advantages to inducing the vacuum at the front vs. rear?
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How do I Calculate Pressure at Multiple Points in Time while Filling a Container with Water?

Say I have a container completely full of water with a volume of 3000 gallons and I'm filling this container with water at a rate of 8.2 gallons per minute, it's already full at 200 PSI, how do I ...
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In a sheet polymer/metal extrudate, why does the thickness varies while exiting the die and how much is the variation of thickness?

When a metallic or polymer/rubber sheet is extruding and leaving the die, it is seen that the variation of thickness occurs at the location of the die opening and at a distance far from the die ...
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22 views

Describe the replacement flow of water at the stern of a large ship

What is the flow path of water immediately at the stern of a large, deep draft ship (like a container ship 250+m long for example)? Does it fill in the area displaced by the hull from all sides ...
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Is it possible to have circulation without vorticity?

Both circulation and vorticity have to do with rotation of a fluid element.How are vorticity and circulation are related.
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computing volume of branching point

I am interested in computing the volume of sphere at branching points like the following The image is from reference link For instance, if a branch of radius R splits into two branches of radius R/...
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Energy required to cycle between pressures in a vacuum

Let's say I have a vacuum chamber of 1 m$^3$ . The initial pressure inside is 20mbar. I would like to know the actual energy consumed to cycle (and maintain) the pressure using a generic commercial ...
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21 views

Fluid dynamics' equivalent to current smoothing

Is there an arrangement of components the takes a source of gas with oscillating pressure and outputs a steady near constant pressure stream?
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Design automation using fluid dynamics simulations

I have a question about design automation or generative design. There is a company that creates pumps. Their work-flow is following: 1) create design of a pump using CAD 2) create mesh for ...
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43 views

How the design of ship help to survive in the water

I have seen bigg cargo, and other ships, and I like their structure very much., a question come sin my that why the ship structure is like this. Can anyone explain what was reason for this. I am not ...
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Airfoil meshing using ANSYS

Logged in a little time ago i have a new question. So I am trying to mesh an arifoil geometry using ANSYS meshing. Airfoil number is NACA 84-M profile. Running 2-D simulation my main objective is to ...
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1answer
16 views

Uses of orifice in Water Jet Cutting?

I wonder whats the usage of orifice/orifice plate in Water Jet Cutting Machines. To increase pressure(due to a smaller diameter with respect to the entrance cross-sectional area) or to convert to ...
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42 views

Why are/were sewers made large enough for somebody to walk down in there?

Today, I have been reading a lot about sewer systems on Wikipedia, in the hope that I would find information or at least photos showing what I think of as sewers, namely somewhere under the streets in ...
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Effect of bypass valve on flow rate and pressure

I have no background in thermodynamics or fluid dynamics, so please bear with me. Refer to the following figure: A working fluid with a flow rate of $1~kg/s$ enters a heater at a pressure of $1~MPa$ ...
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29 views

Deriving the ideal equation for sluice gate problems - incompressible inviscid fluid

I'm trying to figure this problem out, i know the correct answer, and i know the method, but for some reason i'm missing something and i'm just not getting there, any help would be greatly appreciated....
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23 views

Motion of an object due to movement of ship

I wanted to know how the movement of the object floating near the boat would be like. I've assumed the following scenario: The floating object is at the location $(x, y)$. The boat starts moving from ...
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1answer
26 views

Valve/Filter allowing through gas only, no liquid

I need to devise a way to ensure only NG passes through a pipe, and no condensates or other liquids. It is ok to shut down the pipeline if liquids would be detected. The dimensions involved are small ...
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Would there be rush of water underwater if a building was filled to the brim with water?

I'm writing something and I'm curious about how underwater currents would work. Say a five story apartment building was submerged on the coast of a beach, and it was filling with water. If water ...
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1answer
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Air flow bench connected with a manometer. Atmospheric pressure of the manometer changes each time the bench is restarted. Why?

I was doing the air flow in a 90 degree bend experiment. On the first run, I connected the manometer to the tappings on the outer wall, then I turned off the bench and changed the connections to the ...
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Can anyone explain calculation of net force due to pressure in a streamtube of fixed control volume and infinitesmal size

I am studying derivation of bernoulli equation from FM White's fluid mechanics and in that pressure distribution is as shown in the image 1. I am unable to understand force calculation as shown in ...
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Can Flowmaster be used to model an entire pipe run?

I just started using the Flowmaster program (ver 08.11.01.03 if relevant) to model a series of stormwater pipes which are almost certainly in a pressure flow situation based on a first round analysis ...
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1answer
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Lift and drag force measurement in a flume

I'm trying a test a hydrofoil in a low Reynolds flume, but struggling to find a way to mount the hydrofoil in the flume and measure the lift and drag force. I have some idea of using a load cell but ...
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Translation of vibrational motion in the 15-20 Hz range

Is anyone familiar with how to create a "shaking" fluidized bed. With vibrational amplitude in the 2" range and Hz 15-20? I'm constructing a vibrational fluidized bed dryer for the purpose of drying ...
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1answer
69 views

Question About Pumps in Series

I have a circulation tank that runs a piping loop out and back in with a motor pump on it to keep fluid constantly agitated in it. I want to add an inlet to the tank, so I can fill it without pouring ...
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How to calculate flow coefficient to choose a pressure regulator

I'm attempting to choose a pressure regulator(for use with an inert gas) for a personal project I am working on. I know that the inlet pressure will be 2000 psi and outlet pressure of 300 psi. I also ...
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33 views

How to derive a value from a transfer function

I have a scenario where a valve q_in(t) is pumping water into a tank of height h(t) and area A, which is then pumped out by a second valve q_out(t) that has a resistance to water flow R. I got this ...
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How to model the thickness of a liquid film between two flat surfaces?

Say there is a flat surface with a liquid drop in static equilibrium exposed to the atmosphere. Another flat surface [eg:glass surface] is place on top of the liquid drop and pressed down with an ...
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Hydraulic linear actuators as CNC axis instead of screws

Lately I've been watching some videos on machining and hydraulics as it always interested me. I was toying with the idea of building a budget CNC mill with threaded rod for the axes, but the issue of ...
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How is the Outlet flow rate in a water system controlled?

The Hardy Cross method for analysis of fluid systems assumes that in inlet flows and outlet flows for the system are known. However, when one constructs such a system in real life, how do we ensure ...
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Reformulate navier-stokes in terms of perturbation

I am reading this paper and trying to understand on page 14-15, First it rewrites Navier-Stokes in terms of a ''zero order problem'', and where $u_i = \mathscr{U}_i + u_i'$ , where $U_i$ is the base ...
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Flow through an Annular Orifice for Pintle Injector

Our rocket team is trying to finalize the design of our injector for a small liquid rocket engine. The current analysis challenge is verifying the correct pressure drop across the annular orifice ...
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Conceiving a wind turbine as a thermodynamic machine

Traditionally, and continuing till the present day, wind turbines are conceived/presented as power plants which harvest the (macroscopic) kinetic energy carried by an externally available airflow, ...
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Process control on reagent addition system

It's been a while since my fluid mechanics/process control courses at university. Due to my new role I have to dig up the old material again and start refreshing my brain! There is one scenario ...
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Reality check: Sub-sonic convergent nozzle for raising gas velocity to achieve required velocity head

The situation is as follows: atmospheric air is accelerated to 5 m/s with an idealized disk actuator, then passed into a convergent nozzle such that it's velocity is raised to 339 m/s and then flows ...
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Boundary Layer Thickness for Flat Plate

I did a Civil Engineering course some years ago and from my textbook I had a question on boundary layer thickness. So far I have been able to calculate the transition distance, but I am not sure how ...
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Finding Horizontal and Vertical Force on Bending Pipe

I did a Civil Engineering course some years ago and from my textbook I had a question on a bending pipe. The purpose of this question is to see if the way that I have calculated this is correct, as ...
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Find Torque and Force on Pipe with Bend

I did a Civil Engineering course some years ago and from my textbook I had a question on a pipe with a bend. Now I think I have the part of the question on force correct, but I am not sure how the ...
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1answer
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Low-Flow Nozzles for Corrosion Spray Testing

So, for a cyclic corrosion test system, I need a nozzle or arrangement of nozzles that provides a flow rate of 45ml-140ml of salt solution per hour to an area 60cm square. All commercial nozzles I've ...
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34 views

Valve that opens at low pressure closes high pressure

My fluid handling system requires a valve that will open at low pressures (2-6 PSI) and close at high pressures (8 PSI). Is there any commercially available valve that is suitable for this application?...
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Liquid delivery to a pump based on viscosity

I have a tank that is filled with a viscous liquid (~3000 CPs). At the bottom of the tank there is a pipe that leads to a gear pump. There is 22" of pipe straight down from the tank followed by a ...
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Calculate Power for pump

I did a Civil Engineering course some years ago and from my textbook I had a question on a pump with hoses. Unfortunately I haven't been able to find a solution to this yet. A pump feeds two hoses, ...
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Force exerted by a jet of water on a series of Radial Curved Vanes

Normally, when we calculate the force exerted by jet on vanes, we usually calculate the rate of change of momentum. The momentum change is calculated using the relative velocity of jet with respect to ...
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O-Ring Design for low pressure applications

I'm trying to figure out how to create a seal for a very low pressure gravity feed system. Essentially its a low pressure solenoid valve. Is there any equations to estimate the amount of force you ...
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Equation to calculate flow rate

Assume you have a solid walled sphere with an opening of diameter x. The sphere has volume 0.02 litres and has air at 1.4 bars. What general equation would be appropriate to correctly size the ...