Questions tagged [fluid]

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1 answer
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Calculate height of water column to keep tank with fixed drain rate constantly filled?

I would like to know how to calculate the height of a water source connected with a 1/2 inch hose to a tank that is constantly draining @600L/H, such that the tank would never empty, i.e, the rate of ...
0 votes
1 answer
14 views

Hydrostatic pressure on submerged surface

Can someone help me calculate the hydrostatic pressure on an immersed inclined body like the one in the figure? I know the force acting on the triangle is changing with height thus I can use an ...
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2 answers
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Water pump's output going down

So I have a submersible pump (Which I do not use submerged but just connect hose to both ends) who's output is consistently falling. While guessing for the causes I am tempted to blame one instance ...
0 votes
1 answer
43 views

Movement caused by buoyancy

I have a rod that can rotate about a point, the rotation is caused by the buoyancy of 3 balls connected to the rod as in the picture: I need to calculate the angle at different heights and the ...
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1 vote
0 answers
18 views

Entropy in Euler equations for compressible flows

In compressible Euler equations, everyone knows the energy equation can be written as $$ \dfrac{Ds}{Dt} =0 $$ which implies the entropy is constant along the path line. However, we have shockwave as a ...
0 votes
1 answer
51 views

Understanding continuity equation

The volume for an open tank is given: <$V = L \cdot L \cdot h(t)+ h(t)^2 \cdot tan(\theta)$> Where h is the volume of the liquid within the tank. I want to calculate the change in height as a ...
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1 answer
44 views

Submerged fraction buoancy force

How can I calculate the height of the submerged part of a partly filled bucket? (The liquid both inside and outside is freshwater). The bucket is trapezoidal such that the volume of the submerged can ...
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0 votes
1 answer
25 views

Correct Hydraulic Symbol for Check Valve

I was looking in a few different hydraulic power textbooks for symbol information and I noticed that on of them referenced a check valve with this symbol: Is this "full" block symbol ever ...
0 votes
1 answer
25 views

How does decreasing the cross-sectional width of a channel impact steady flow?

The continuity equation states that for a constant mass flow rate, if the cross sectional area of a channel is decreased, then velocity is increased. What happens if the channel has high walls and is ...
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1 vote
1 answer
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Is supersonic flow not possible in a venturi tube?

I'm trying to design a venturi tube that will have a pressure drop of 91525 Pascals where the inlet pressure is at 1 atm and the throat pressure is at 9800 Pascals. I calculated the minimum throat ...
0 votes
1 answer
32 views

Calculating the leakage of water in a pressurized vessel based on initial and final pressures?

Let's say you have a piping system containing liquid water under high pressure. One section of the pipe of ~70L gets isolated, and it is initially at the same pressure as when it was isolated, which ...
4 votes
3 answers
92 views

Why do we need continuum approximation in fluid mechanics?

We know that a fluid in reality is not continuous. It has spaces and voids between atoms and molecules. Continuum approximation is a famous approximation that is taken in any fluid mechanics textbook. ...
0 votes
2 answers
52 views

How to solve transient heat conduction equation at a point in space with volumetric heat source?

My system is a fluid exposed to light and I want to calculate the temperature change with time at a point, hence there are no spatial effects or convection due to the flow of the fluid. The heat ...
1 vote
2 answers
170 views

Airflow visible over the airplane wing

What's that visible airflow over the airplane wing and what causes it?
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2 votes
0 answers
25 views

Consistent Fluid or powder flow through an orifice

This is a really odd and specific question, and I'm not sure this is even where to ask. A few weeks ago I thought about making a clock based on water flowing from an orifice. The obvious issue is that ...
0 votes
1 answer
31 views

What is a good working fluid in the temperature range of 150 - 180 °F?

I am looking for a good working fluid whose boiling point is in the range of 150 - 180 °F for a waste heat recovery system. The fluid should be minimally flammable, preferably nontoxic, and low in ...
0 votes
2 answers
74 views

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:...
0 votes
1 answer
33 views

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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1 vote
2 answers
123 views

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 ...
0 votes
0 answers
33 views

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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0 votes
0 answers
49 views

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 ...
0 votes
0 answers
16 views

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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0 answers
136 views

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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2 answers
35 views

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 ...
0 votes
1 answer
49 views

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
203 views

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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0 answers
32 views

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 vote
1 answer
99 views

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{...
1 vote
0 answers
36 views

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, ...
0 votes
3 answers
93 views

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?
1 vote
1 answer
69 views

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 ...
0 votes
1 answer
45 views

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 ...
0 votes
1 answer
54 views

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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1 vote
0 answers
32 views

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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0 answers
75 views

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. ...
0 votes
2 answers
68 views

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
882 views

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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0 votes
1 answer
200 views

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 ...
0 votes
1 answer
63 views

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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0 votes
2 answers
65 views

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
65 views

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 ...
1 vote
0 answers
23 views

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 ...
3 votes
0 answers
43 views

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. ...
1 vote
1 answer
85 views

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 ...
1 vote
2 answers
107 views

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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0 votes
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 vote
1 answer
3k views

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 ...
0 votes
1 answer
44 views

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 ...
1 vote
0 answers
126 views

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 ...