Force per unit area.

learn more… | top users | synonyms

9
votes
0answers
241 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 ...
4
votes
0answers
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
votes
0answers
62 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
votes
0answers
30 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
votes
0answers
175 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
votes
0answers
55 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 ...
3
votes
0answers
172 views

Bubble in a pipeline

I am just thinking about this phenomenon: We have a horizontal pipeline with a flowing liquid, which contains a small bubble of gas. How do the dimensions of this bubble change when it reaches a ...
2
votes
0answers
23 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
votes
0answers
99 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 ...
2
votes
0answers
67 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
votes
0answers
42 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
votes
0answers
138 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 ...
2
votes
0answers
167 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 ...
2
votes
0answers
172 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 ...
1
vote
0answers
16 views

Can sound frequency create more ideal conditions for fire?

You may have seen the recent story of a device that engineers claim can extinguish flames using sound frequency. An older article loosely explains the theory behind how this works: Sound travels ...
1
vote
0answers
15 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 ...
1
vote
0answers
16 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 ...
1
vote
0answers
17 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)?
1
vote
0answers
38 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" ...
1
vote
0answers
22 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 ...
1
vote
0answers
38 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 ...
1
vote
0answers
23 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.
1
vote
0answers
42 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 ...
1
vote
0answers
70 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 ...
1
vote
0answers
65 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, ...
1
vote
0answers
58 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 ...
1
vote
0answers
106 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 ...
1
vote
0answers
59 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 ...
1
vote
0answers
20 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 ...
1
vote
0answers
27 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? • ...
1
vote
0answers
140 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 ...
1
vote
0answers
54 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 ...
1
vote
0answers
167 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 ...
1
vote
0answers
41 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 ...
1
vote
0answers
259 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 ...
1
vote
0answers
126 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 ...
1
vote
0answers
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 ...
1
vote
0answers
183 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 ...
1
vote
0answers
56 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 ...
1
vote
0answers
87 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 ...
0
votes
0answers
17 views

Behaviour of Gases

Gases tend to move from higher pressure to lower pressure, thats fine. But why they are so aggressive in this regard. For example, in vacuum-lifters they are able to lift mass (weight) of up-to ...
0
votes
0answers
9 views

Altitude altimeter application

What is the most precise formula to calculate altitude and what parameters should i considet such as pressure, temperature, dew point, ... I am developing an altimeter app and i don't know what the ...
0
votes
0answers
8 views

Comparing work required at compressing gas & pumping liquid

In one of online lectures comparing Vapour compression cycles (conventional refrigerators) with Thermal compression cycles (absorption chillers) it was said that former required more 'high quality' ...
0
votes
0answers
24 views

Does spin degeneracy affect ideal Fermi gases in any way as T->Infinity?

In other words, given any system comprised of an ideal Fermi gas, in the high-temperature (classical) limit, are there any observable thermodynamic quantities (pressure, volume, energy, density, etc.) ...
0
votes
0answers
12 views

Can a volume of N2 be more negative than -14.7 psi?

Ok. I’m getting -30 PSI on a gauge calibrated at 0 for 1 ATM. Let’s say I have a chamber with a volume of 20L of N2 at 1 ATM. A vacuum pump that can pump to absolute vacuum let’s say 1X10^-10mTORR. ...
0
votes
0answers
69 views

How does a heated constant volume flow behave, for an expanding flow tube leading into the free atmosphere

I have a helium gas flow with a flow rate that has been set to a constant value ($0.3\,m^3/h$). It's streaming upwards in the picture, and beyond the upper big red dot position, it meets the ...
0
votes
0answers
25 views

Will increased air pressure increase efficiency of solute diffusion into a membrane?

Biophysics question: I have a container with a biological tissue inside of solution where the solute slowly diffuses across the membrane and binds inside of the tissue. If I were to put this unsealed ...
0
votes
0answers
19 views

Vertical pipe longer than 10m, full of water, top end closed, bottom end under water?

Normal surface air pressure is around 1 bar which is roughly the same pressure of a 10m water column. If I have a pipe full of water that is more than 10m long, top end closed, leave the bottom end ...
0
votes
0answers
29 views

Why does opening the sun roof at high speeds cause the air pressure to change inside?

When I'm driving at fairly high speeds (80mph for example), I've noticed that opening / closing the sun roof causes the air pressure inside to shift significantly, a change that I feel clearly in my ...
0
votes
0answers
32 views

What's the relation between the type (Gender) of a balloon and its internal pressure

I'm working on a project about balloons and I need to know the relation between the gender of the balloon and its internal pressure. As far as I know, there are some parameters such as " Elasticity of ...