Force per unit area.

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265 views

Definition of stress at the microscale

Take, for simplicity, a Lennard-Jones fluid below the critical temperature, which is to say that there is a phase separation into fluid and gas and thus an interface is formed. The macroscale picture ...
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1k views

Inflating a balloon (expansion resistance)

I am doing a quick calculation on how to calculate the pressure needed to inflate a perfectly spherical balloon to a certain volume, however I have difficulties with the fact that the balloon (rubber) ...
3
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112 views

How would water drain out of a sealed pipe?

While hiking through the Grand Canyon, I started wondering. Say we have a pipe for the purpose of transporting water across a canyon, with the bottom submerged in a pool of water. Like the blue line ...
3
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32 views

Is there a material with non-monotone density dependence on pressure?

Is there a material with such non-linear effects (including chemical reactions, phase transitions etc ...) so that there would be range where pressure increase would yield density decrease? What ...
3
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191 views

Second derivative of vapor pressure from a cubic equation of state

It is quite easy to compute the first derivative of vapor pressure with respect to temperature from a cubic equation of state at least at the critical point since there is a continuity with the ...
3
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61 views

Converting impact speed to pressure magnitude

In explosive safety and stability testing, a drop test is commonly used to determine the sensitivity to impact. In the test, an impactor of known mass is dropped. The initial height varies throughout ...
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36 views

Fluid flowing into small pores

I have some open porous foams with pore sizes ranging from 50-100nm. I want to flow water into this structure but even at 30 atmospheres it would NOT go in. I am looking for a way to calculate the ...
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69 views

How to calculate the strength of a silicon joint in an aquarium?

I'm building an aquarium, and i'm trying to answer the question "Will it catastrophically fail?" by reading the datasheet of the Silicon glue and doing a bit of calculation for worst-case scenario. ...
2
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127 views

Calculating PSI generated by water entraining air as it flows down a pipe

This is the concept used in a trompe. Basically, the idea is that if we allow water to flow down a pipe and if that pipe has inclined air intake orifices near the top where the water enters, then the ...
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110 views

Simple gas in cylinder modeling

I want to do a simple (physically plausible but not physically accurate) simulation of a gas in a cylinder as it works on or is worked on by a piston. Wikipedia gives a good example of an adiabatic ...
2
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49 views

Why does the perforated tin foil on a shisha pipe rise when smoking?

Imagine this setup (just without the windguard): When applying negative pressure at the hose, I can observe the perforated tin foil separating the charcoal from the bowl rise a few millimeters, ...
2
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194 views

How Temperature, Pressure and Altitude are related in the atmosphere?

I'm looking for an approximation for the temperature of the atmosphere at any height and pressure. Both altitude and pressure are known variables, I've derived this equation using maxwell's ...
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196 views

Modeling Syringes e.g. with the ideal gas law

Gentlemen I have a similar yet very practical problem that might provide further insight. I'm trying to model a moving plunger in a syringe (something like a piston in a cylinder). At time zero the ...
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188 views

Internal moment in the hull of a pressure vessel

This question is related to the course structural analysis. As part of our exam grade every student has been given different multiple homework assignments which we have to solve. One of the problems ...
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219 views

How do I calculate the energy balance of a trompe?

I was quite fascinated by the concept of an ancient type of air compressor, called a trompe. It entrains air bubbles into a falling stream of water via the Venturi effect, and extracts the air at a ...
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0answers
25 views

How do I calculate the maximum pressure a container can withhold?

Say I have a spherical container with a certain gas inside, heated to a very high temperature, and thus a very high pressure. The gas will exert a force radially outwards onto the container, and at ...
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26 views

Connection between gas flow rate and diameter of tubing

First time poster, long time troller and curious student. I have a bit of a conundrum that I would love some input on... Here's the problem. I have an air flow system is under constant pressure of ...
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28 views

Measuring variation of saturated vapour pressure with temperature

Is it possible to measure variation of saturated vapour pressure of water with time.I just hesitate about it.My suggested procedure which is incomplete is given below Procedure that I would like to ...
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0answers
42 views

Impact Force/Pressure of a wave on a vertical wall given PIV velocity field

I have PIV (Particle Image Velocimetry) data of liquid sloshing on a rectangular tank which produces a wave impacting one of the vertical walls. In the picture below you can see the wave about to hit ...
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57 views

Internal pipe flow - Pressure Drop

Let's say I have internal flow at some flow rate in a pipe that is 10 ft long and there are 2 straight sections and 2 bends. I am trying to determine pressure drop due to friction in the pipe. My ...
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52 views

How does force transmit through a solid block?

If you take a solid block, say, a cube of side length $l$ with density $\rho$, you place it upon a solid floor, and you apply an external pressure of $p(x,y)$ on the upper face ($x$ and $y$ define a ...
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21 views

Practical nozzle question / mass of finger?

A spray bottle i own broke off its compressor tip so i fashioned another one from a rubber tube, a pen lid, an ear plug and a 1 mm radius tube from a computer cleaning duster. The opening of the ...
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57 views

Regelation, ice cutting, and snowballs

Pressure decreases the melting point of ice, and applying pressure then releasing it will allow ice blocks to weld together by melting them and letting them freeze. See this video. The detractors of ...
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28 views

molecular explanation of pressure in water at depth

At 10 m under water, pressure is 2 atmospheres. As temperature is not different, and density is minimally different, how does pressure increase at the molecular level (collisions per unit area)?
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59 views

unknown stresses in double-layer glass window

I live in cold place where outside temperature drops to -20. Currently, we have -20 and on my window, which is doubled layer glass with trapped air in between, I found a "polarized stress spectrum" ...
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29 views

Nitrogen generator maximum flow check

We have a N2 PSA unit with following specs Now I have done some calculations as shown in the image. Assuming 0.8% of the air is (N2+inerts) rest being O2 can someone tell me that how 160CFM air ...
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56 views

Is work done on a fluid in a communicating vessel necessarily equal to work done by the fluid inside it?

During the explanation of Pascal's law the argument that work done by a force to move the fluid inside communicating vessel is equal to the work done by the fluid at the other end of the vessel was ...
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29 views

Distribution of refractive index of water when applied pressure wave

I was wondering when applying pressure wave, ultrasonic sound waves, under water, how I would be able to measure the distribution of the refractive index.
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47 views

Functional relationship of pressure and position(1d)

so today I started doing my research on oscillations in a course on advanced mechanics. The experiment was to mathematically model the speed of sound in air and experimentally prove the usability of ...
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108 views

What is the physical explanation for the phase relationship between acoustic pressure and particle velocity in plane and spherical waves?

I've been looking around for a decent physical explanation of the differences in the phase relationships between acoustic pressure and particle velocity in different types of waves. Mathematical ...
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0answers
95 views

Static,total and velocity pressure at a point

I have a past exam question that I am stuck on. $200$m$^3/s$ of air is entering a shaft of $5m$ diameter, the density is $1.18$kg/m$^3$, and I have shock loss of factor $X=.5$ I want static, ...
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78 views

Pressures in multiple hydraulic drive system circuits when driving common drive shaft

Assume that there are two 'idealised' and identical hydraulic drive system circuits each consisting of a connected positive displacement pump and hydraulic motor where both motors (from each ...
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116 views

Bernoulli's equation

So there's a pipe filled with water that has 4 other pipes with same radii connected to it. The question is to arrange heights from the smallest to the biggest level in it. $A_1$ and $A_2$ are ...
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63 views

If air was significantly compressed, and then the force compressing it suddenly disappeared (no container), what would happen?

Question: If air was significantly compressed, and then the force compressing it suddenly disappeared (no container), what would happen? Side Question: I'm imagining significantly compressed, but ...
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22 views

Radiation pressure at high temperature

I am reading a book on the history of the hydrogen bomb. The author describes the Teller-Ulam design and explains that the liquid deuterium charge was compressed by the radiation pressure generated by ...
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38 views

Electrical resistance of a metallic conductor in a gas

A long time ago I learned that the electrical resistance of a metallic conductor, when surrounded by a gas, varies with the pressure of said gas. • What is the name (if any) of the law involved? • ...
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177 views

Maximum pressure of a rubber balloon

I've had a question about this topic previously, but the material was inelastic. Forces in a balloon popping? What happens when a material is non-hookian? Say rubber, I've found this pdf on the ...
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0answers
57 views

Reconciling Different Vapor Pressure Definitions

In describing vapor pressure, I have often heard the following intuition: Assume a closed container that is partially filled with water. Above the water lies a vacuum. The water will vaporize until ...
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186 views

Horizontal Capillary Question

I have a fluid mechanics question, that I think is caused by a lack of understanding of some key concepts. Suppose we have a horizontal capillary with a radius of 10um. The fabrication process has led ...
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43 views

Bulk transport of an aerosol by a blast wave

I'm trying to model the behaviour of aerosols in response to blast waves. (This is for visual effects.) Intuitively, if a flare left a smoke trail above a field and then a bomb detonated elsewhere ...
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0answers
299 views

ideal gas law modelization in a vacuum chamber

I am trying to model a pressure sensor in COMSOL. The basic work is that there is current flowing inside it, if the pressure of the gas around it drops down, the temperature goes down as well (ideal ...
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141 views

How to solve state parameters using these givens for an ideal gas?

In a thermodynamic turbine using air as an ideal gas, given that you have a known inlet temperature value $T_i$, a known exit pressure value $P_e$, a known inlet and exit velocity $V_i$ and $V_e$, a ...
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46 views

pressure required for displacing a single electron off a crystal

I need to know this for my project- "power generation using the pressure applied on a keypad of a mobile electronic device". How much pressure does it take to displace a single electron off its ...
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0answers
59 views

Can I use computer fans and tubes to lower the air temperature below dew point?

I suppose to build a small dehumidifier, but I am narrowing the question down into its logics. I have relatively powerful computer fans, water cooling radiator and some metal tubings. With the idea ...
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94 views

Determining Water Level

Given a cylinder of a constant shape and size, how can the water level be calculated using the inside surface of the container? For instance, could the inside lining of the container be a pressure ...
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16 views

Magnus effect, Coanda effect, and the Bernoulli principle: What is balancing gravity on a spinning sphere vs. a stationary screwdriver?

I've seen videos of golf balls and screwdrivers levitated by a focused air stream. Reading the comments of these videos (and others), I see explanations of the machanics at work and their cause and ...
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0answers
11 views

What happens if you blow at a paper wad sitting at the doorway of an airtight room?

Sounds like a hilarious scenario, but this is why it got me thinking: A common experiment demonstrating air pressure is to put a paper wad at the mouth of a bottle, and then blow into the bottle. The ...
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0answers
19 views

Pressure gradient - derivation for air stream

I need help clarifying the statement made here that $$dp = l\frac{dp}{dx}$$ $\frac{dp}{dx}$ is an infinitely small change in pressure at some point x. $dp$ is the total change in pressure between ...
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21 views

What happens when heating water in a pressure vessel?

Suppose that I take a pressure vessel that can hold up to 2000PSI force. Now I fill it with water (not completely, but around ~90%) and now I start to heat it with direct flame, LPG gas cylinder. What ...
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15 views

Slow sustained liquid movement in a vacuum

Can water or any other liquid be made to “simmer” or “low boil” (slow sustained liquid movement) in a vacuum as opposed to go from liquid to all out boil when the vapor pressure is equal to the ...