Questions tagged [fluid]

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Discharge at an angle in a channel concept question

Now I agree that the velocity of the discharge and the area is not at right angles, but I don't understand how using $\cos \theta$ helps? Shouldn't I use the area perpendicular to the channel? Like so:...
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Difference between Front Tracking and Front Capturing Method

I am having difficulty understanding the difference between interface capturing and interface tracking schemes. It is important to track it for solving Navier Stokes equation and other fluid problems ...
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Calculating pressure forces (vertical) on a curve surface

I am particularly confused about finding pressure forces (specifically vertical force) on a curve surface. Although I understand the general method is to use sum of forces in the x/y direction (ie by ...
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Can anyone help me solve this problem?

I am a bit confused with this because the channel is not infinite in the z direction. I know that I have to do some things with the Fourier expansion but I'm not sure how. Would be great if anyone ...
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Effect of density of a fluid on laminar boundary layer thickness in external flow

We know that laminar boundary layer thickness depends on the distance from the leading edge and also characteristics of the fluid such as approach velocity, dynamic viscosity and density. I understand ...
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Why is the fluidization pressure drop profile different when this one is measured while increasing and decreasing fluid flows?

why is it that when measuring pressure drop across a solid particle bed at different fluid flows the pressure drop profile looks different? When you measure pressure drop while increasing fluid flow, ...
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Momentum equation in Fluid Mechanics

I have a question regarding the above image. I can work out velocity 1 and 2 fine, and they come out to be V1 = 1.95 and V2 = 21.6. However, when using the momentum equation to find the force value in ...
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Bernoulli equation is the opposite of continuity and pressure formula [closed]

In fluid physics, continuity says that with a smaller area comes more speed and since P=F/A that means with smaller area comes more pressure therefore with more pressure comes more speed. But ...
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Peristaltic pump - theory vs reality, where is a problem?

I'm building a test system (experiment) for peristaltic pump to check if pump is able to pump according to specification. The pump data: 6,3ul liquid moved per stroke. 5 strokes per revolution. The ...
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1 answer
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Triangle symbol in pneumatic diagrams

After searching details regarding direction control valves, I can understand that the diagonal line indicates solenoid valve actuation. The zig Zag line represents the spring action so in this case ...
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Vortex diameter

There exists clear definitions of the size of a vortex core, but vortices affects it surroundings beyond this core. An example is a wing tip vortex which has a small core, but can be seen as a big ...
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1 answer
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Isn't the Bernoulli equation just a special case of the Steady-flow equation?

This question is about the following two energy balance equations (assuming no energy input/output): Bernoulli: $\frac{p}{\rho} +\frac {v^2}{2} + zg = const.$ Steady-flow: $u +\frac {p}{\rho} +\frac{...
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Confusion between Steady flow and Space-Time invariant density field

Let's take the example of a steady flow with velocity field as $u=βr(\tilde{r})$. Now, we can find a density field $ρ(r,t)$ that satisfies the mass conservation equation of $∂ρ/∂t+∇(ρu)=0$. First, ...
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3 answers
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How do you imagine momentum?

If you want to explain it to a layman (who belongs to the science stream ofc!!) how do you explain it? Also, what is momentum transfer when it comes to fluid mechanics?
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Calculating liquid mass lost due to a pressure differential

Problem is about a liquid (water) contained in a pressurised vessel at 3 bar (absolute) and is transferred to another vessel at a higher height by bleeding a valve/suction due to drop in pressure at ...
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1 answer
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Fluid Dynamics - Auto filling a reservoir to a constant water-level

I have created a reservoir that is intended to automatically self-fill at exactly 1/4" depth. The idea is that the reservoir is hooked up to the airtight jug and dispenses the liquid until the ...
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1 answer
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How Do I Calculate the Velocity of the Flow That Is Sucked Into Two Parallel Walls by a Fast Moving Flow?

I'm trying to solve a problem where I calculate the velocity of the setup bellow. Basically I have two very long(basically infinite for calculation purposes) plates, and I have one central jet of gas ...
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1 answer
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Which kind of paper has highest absorption speed?

I am experimenting to analyse the liquid wicking(radial) behaviour of various liquids. I have performed initial studies and experiments on household paper towels but they tend to deform and stick to ...
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Solidworks flow simulation temperature drop

Using Soldiworks flow simulation, I want to calculate the temperature drop of water (40 degrees) which flows in 10 m steel pipe. How should I manage Wizards setting and goal?
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Selecting a water pump for low flow and 1 Bar pressure

I am designing a small automatic drip irrigation system. There will be about 10-15 drippers. Flow through the system will be about 1 l/minute, but this may change if expanding or reducing the system. ...
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2 answers
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Question on fluid flow measurement uncertainty

Say you are trying to measure the liquid flow rate (mass or volume) through a pipe and you want to get the best measurement possible, and you have two flow meters. In one scenario, you put one flow ...
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3 votes
2 answers
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How do I connect a 3mm water tube to a plastic box?

I need to connect a 3mm inside-diameter tube from a solenoid valve to a plastic box. The box wall thickness is 4.5mm. The purpose is to empty water in the box when needed. How should I connect it so ...
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How to have a watertight or airtight pipe seal that is rotating at a radius, with a stationary junction tube?

How would I have a watertight or airtight pipe that is rotating at a radius, if the main reservoir pipe is not? Since I'm pretty sure I didn't do a good job of describing what I mean, the image above ...
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1 answer
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A Doublet's stream function

We were learning about superpositions of potential flows. so, $$\Psi_{doublet} = \Psi_{source} + \Psi_{sink}$$ where: $\Psi_{source} = \frac{Q'}{2\pi}\theta_1$, and $\Psi_{sink} = \frac{-Q'}{2\pi}\...
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how to find torque from force due to pressures that change as a function of z

My teacher is very strict about copying his work so I will have to explain it. We have a wall with two fluids of different constant densities and depths. The wall is 'L' long. The wall has a section ...
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2 votes
2 answers
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If a gas is pushed through a widening section of a pipe with a piston, will the pressure increase?

Imagine I have a section of pipe that increases in cross-section at some point. If the gas in the pipe before this section is being displaced with a piston, will the gas increase its pressure and ...
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1 vote
0 answers
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What material can wick up fluids while not allowing micro-organisms to pass?

I'm looking for a material that can wick up a solution containing nutrients and sugars. The dirty side of the wick should touch a medium to draw up the solution, on the clean side of the wick ...
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3 votes
0 answers
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What is the purpose of the ink delivery disks found in most rollerball pens

See picture. In most rollerball pens there are those peculiar looking disks near the nib, the purpose of which I have not yet figured out, apart from being some kind of ink reservoir/flow control. ...
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1 vote
1 answer
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Hydraulic system dynamics modelling

I'm trying to mathematically model an actuation system and it comes down to relating the pressure across the pump and the actuator as shown in the picture. Assuming no friction in the pipes and the ...
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1 vote
2 answers
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Bernoulli equation on moving cart

Let’s say I have moving cart with velocity U . And water from pipe flows at velocity V with respect to ground The question asks to use Bernoulli equation , pressure is atmospheric in the top If I use ...
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1 answer
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Why does this glass tend to stick on surfaces

I have a glass here. This is the bottom face of the glass. Now this is on what I had kept my glass. There is a little much of water spilled on it. Let us call this thing as C Now , when I lifted the ...
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1 answer
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Why is the direction of pressure always perpendicular to surface area for fluids?

Why is the direction of pressure always perpendicular to surface area of a body for fluids ? We also assume that it is an ideal fluid here. So , pressure acts in all directions because fluid has a ...
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1 answer
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Finding all the pressure acting on base of cylidner

Water is filled in a flask up to a height of 20 cm. The bottom of the flask is circular with radius 10 cm. If the atmospheric pressure is $1.013 \times 10^5$ Pa,find total force exerted on the bottom ...
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1 vote
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Is Viscosity = Slope?

studying fluid mechanics, I see that viscosity relates shear stress to shear rate, like a slope. However, on graphs I see that they draw a triangle, and where I would expect to see $\Delta \tau $, I ...
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Why does use with air or water reduce the maximum temperature of certain high temperature / pressure hoses?

This example is a Parker Hannifin model 426/436 "SAE 100 R1 AT / SAE 100 R16 High Temperature Hose". Here are the temperature specifications: (Full data sheet) Although there is an asterisk ...
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2 votes
1 answer
537 views

Work calculation in a thermodynamics cycle process

To calculate work in a cyclic process (say Carnot cycle) we find area under p-v curve,or use net heat transfer= net work done. Why won't we simply add work calculated in each process of a cycle,like ...
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2 votes
1 answer
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Does the aerodynamic force qualify as a viscous damping force in the Mechanical Harmonic Oscillator

When reading about a harmonic oscillator, the most common form of damping is proportional to the velocity. $$F_D = c \;\dot{x}$$ Without giving much thought to viscous damping, one example I always ...
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2 answers
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Turbulent boundary layer development in channel flow

I'm currently working on my Bachelor's thesis about the numerical simulation of a turbulent air flow through a rectangular channel. As part of that I'd like to compare my results to empirical ...
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-1 votes
1 answer
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Fluid Mechanics Question

I am preparing for GATE(Chemical). I need the answer of this question part 2 (question 54) as I am not able to find the mistake in my logic. I have applied the logic here as: Initial energy stored in ...
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2 votes
1 answer
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At what volume would air bubbles become static in a fluid with viscosity of 7000cps

I would appreciate any help with this as its been a few years since my fluid dynamics courses at University! Basically I am trying to determine the cause of voids that we are seeing in a set resin. ...
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determine if the flow is laminar or turbulent [closed]

what would be the the type of flow if the water flows through stainless steel channel? would it be a laminar flow or turbulent flow. I assume the adhesive force of water to stainless steel is minimum.
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1 vote
2 answers
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Unequal water level in connected containers - Aquarium Sump

I have recently designed and had fabricated the following two sumps for my Aquarium (See image). I have a pump in the right hand container (section 4), and the return is coming back into the left ...
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2 answers
319 views

How to calculate flowrate of water through a crosssection of pipe?

Assume we have a pipe with a diameter of 10mm. Water is flowing through that pipe and we know that the water pressure at the 'open' end of the pipe is 2 atm. How would one go about calculating the ...
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-1 votes
2 answers
39 views

Can you help me to source a screw thread G1 3/4 inch to anything to fit in my stainless steel heat exchanger?

Last year I bought s heat exchanger for my above ground 12 foot paddling pool. I also bought a pair of 'gee' one and three quarter thread pva plastic adaptors to push in 50mm plain blank tapered holes....
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-1 votes
1 answer
79 views

What is the convective acceleration?

I want to gain a better understanding of the convective acceleration that occurs for instance in Navier. Why, in a permanent flow, there can still be acceleration? Thank you
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1 vote
0 answers
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What is the best way to find solved problems similar to the one at hand?

This is a general question, so sorry if it breaks the rules. However, I think it is very important as more often than not someone else has already solved a similar problem that can be applied to solve ...
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1 answer
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Calculating the flow rate of a siphon system

What i am looking for: I am looking for a formular to calculate the water output in $l/s$. My goal is to match a pump (pumping the water back up) with the following setup, to keep it going with as ...
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1 vote
1 answer
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Distribution of water through a pipe network

I have a network of stainless steel pipes that are distributing water throughout a building. I know the flow rate of water entering the system is 600 IGPM, but am unsure of how this water will be ...
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2 answers
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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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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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