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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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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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1answer
14 views

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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1answer
31 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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28 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
33 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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1answer
53 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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34 views

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
21 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
38 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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1answer
23 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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2answers
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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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1answer
25 views

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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1answer
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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2answers
29 views

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
33 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
43 views

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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1answer
45 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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0answers
23 views

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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25 views

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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1answer
30 views

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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1answer
69 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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1answer
33 views

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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32 views

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(...
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1answer
56 views

Device with no moving parts to increase fluid pressure?

I'm currently designing an air rifle and am looking for ways to increase projectile velocity without resorting to combustion, modifying the projectile, barrel length or changing max pressure within ...
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1answer
29 views

What's the minimum area ratio required to achieve choking in Converging nozzle?

Is there any equation for minimum area ratio (Throat area (At)/ Combustion Chamber area (Ac) ) required for choked flow in convergent nozzle (just like equations for minimum Pressure ratio and ...
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22 views

Lagrangian Acceleration vs. Euler Acceleration

So I have a problem understanding a solution to an exersice I was given. I'll first show what they did, and then what I did. Exersice: A motion is given by the dimensionless velocity field $\vec{u}=(...
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21 views

Use of Absolute vs. Differential Pressure Transducers to Calculate Flow Through Annular Restriction

If using a laminar flow element, in conjunction with Poiseuille's equation, to calculate mass and volumetric flow rate, what would the benefit be to using two absolute pressure transducers to measure ...
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calculating pressure in siphon pipe

I've been posed the following question and I am stuck on the final part, part(c). A diagram of the problem is: I was able to complete part (a) and (b) okay, using the mechanical energy equation with ...
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10 views

Mach Number for Ideal gas flow in Nozzle?

Suppose we have a converging-diverging nozzle with an ideal gas as the working fluid.Assuming isentropic conditions, the speed of sound is given by: $c=\sqrt \frac{\partial (P)}{\partial(\rho)} $ ...
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1answer
44 views

Fluid Mechanic Buoyancy problem. How to determine the height?

I tried to solve it but I don't know how to bring the Area A in this equation. I used the area of the small vessel, but this one shouldn't be in the equation. Thanks a lot
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Eulerian description of fluid flow

In Eulerian description of fluid flow, we observe how the properties of the fluid are changing at a point. Since a point has zero dimension hence a zero area, how can we make sense of the 'finite ...
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2answers
47 views

Is such manned flight feasible?

We all know that manpower hydrofoils can fly over calm water. here Hydrofoil Surface Flight https://youtu.be/WszbRFF_WLk So is the manpower aircraft in the link below feasible? Manpower flight ...
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Volumetric & Mass Flow Rate Through a Piston-Cylinder Annular Gap with Laminar Flow?

I am attempting to define the proper equations used to calculate both volumetric and mass flow (based on pressure differential) through a Laminar Flow Element. The element consists of a piston ...
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1answer
28 views

How do drag and downforce in a rear spoiler of a car vary with angle of attack?

I ran an two aerodynamic simulations, one for a spoiler angle of 0 deg and the other for the same spoiler declined at 30 deg. The results showed a considerable increase in downforce, but only a slight ...
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1answer
22 views

Determine Cp of an oil from density and temperature?

I suspect I know the answer to this, but hoping someone may know something I don't here. Is there a way I can determine the specific heat capacity at constant pressure (Cp) of an oil if I know the ...
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3answers
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Is it possible to “expand” air flow area in a duct over a short distance?

Is it possible to increase an air column's diameter over a short distance? Let me explain: Imagine a small 10 cm electric computer cooling fan that's pushing air into a cone-shaped duct 20 cm long. ...
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Is the metacentric height independent of heel angle?

when the sides of a pontoon are verticle, BM(distance between center of buoyancy and metacenter) is given by I/V As well as for a small angle that expression is true. But when the heel angle ...
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How does this transformation actually happen?

I cant exactly give you the complete relevant details of the variables but assume the following (bold means vector): B(x) ~ $\frac{1}{8\pi}*(\nabla\frac{1}{r})\times\int \mathbf X'\times \mathbf \...
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2answers
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What are the difference between open loop and closed hydraulic system?

I'm trying to get informative resource material through this.
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1answer
27 views

Will the pressure inside a pressing mold will be constant if I'm working with a fluid inside?

I'm pressing glass and I want to know if the pressure that the walls of my mold feel is the same through all the internal surfaces. I'm willing to assume that glass will behave purely as a fluid (very ...
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43 views

Best spout shape to ensure minimal water sticks after pouring?

I have a tipping bucket rain gauge whose accuracy I feel could be improved by redesigning the shape of the bucket lip. In particular, after tipping, there tends to be a bead of water (approx 0.1 - 0....
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2answers
59 views

How to heat CO2 coming out of a gas canister to human breath temperature?

I am releasing CO2 from a cylinder into a ventilated room and want to mimic a human breathing (let's ignore the in/out breath). Problem is that the gas that comes out is at room temperature (or lower ...
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1answer
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Liquid Rocket Plumbing and Instrumentation Diagram: Standards and Presentation

I'm working on a team to build a liquid sounding rocket as a school project. We need to present our plumbing and instrumentation diagram, but we are butting heads on what program and standards we ...
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Flow rate and Pressure relation

I have a system involving a tank of nitrogen gas inflating a balloon, the tank pressure drops from about 4500 psi to 120 psi, inflating the balloon to 20 psi. How can I calculate the average flow rate ...
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1answer
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Evaluating drag and convection for a flower heat budget model

I am currently in the process of creating a heat budget model to compute stigma surface temperature. Stigmas are part of the reproductive organ of a flower (which in my case are flowers of orchards). ...
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2answers
63 views

Why vertical wind turbine don't be half covered

I think it would be more efficient for a vertical wind turbine to have a covered funnel about half of it Something like this figure It would protected the turbine from opposite wind and also ...
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ANSYS Fluent - Using Patch to set initial conditions, should I set the pressure and velocity or only one property to generate shock waves in a pipe?

I am fairly new to CFD and I am working in ANSYS Fluent. I am trying to model two specific shock waves in opposite directions in a length pipe. The shock waves need to be traveling at specific Mach ...