Bernoulli’s Principle on Atomic Scale
Why Physics Stack Exchange recommends it
Physics Stack Exchange users cite it as a source for the kinetic-theory picture of Bernoulli's principle, whether they are building on it, using it as a reference, or questioning whether its explanation is correct.
Recommended by 2 people across 2 different months, 2020 to 2024.
What it is
A short animated explainer by Eugene Khutoryansky that tries to account for Bernoulli's principle at the level of individual atoms. It argues that when a fluid flows faster, atoms have less velocity perpendicular to the flow, so they push less on the walls and the static pressure drops.
What people said
Recommends silverbackgorilla · 2021-09 · Physics Stack Exchange · on “Pressure term in Bernoulli's principle”
I have encountered two different explanations of why the pressure term appears in the equation for Bernoulli's principle. The first one is: (1) "The fluid has to speed up as it enters the narrower region. That means that the bit of fluid just entering the region has to be being pushed from behind. So the pressure behind it must be larger than in front." (from this post [LINK] ) Here, the pressure we're talking about is the pressure in the direction of the fluid flow. The second explanation is: (2) The fluid molecules that enter the narrow region of a pipe are the ones that have a large velocity component parallel to the pipe. Because their velocities are aligned with the direction of the pip
Recommends GedankenExperimentalist · 2022-06 · Physics Stack Exchange · on “Why perpendicular axis are unaffected in special relativity?”
In SR why are $y=y'$ and $z=z'$ ? I understand the examples they give to show physical contradictions if this was not the case, but it seems highly unsatisfactory as there is no physical basis for this assumption ( $y=y'$ ) stemming either from the math or postulates of SR. An analogy to this would be the application of Bernoulli's theorem to a system of pipe that gets thinner as we move along it, but water density remains constant. Thus we say that velocity in that region increases to maintain density, however again this is unsatisfactory since we are just making conclusions based on what will happen if our conclusion weren't true and how it will affect our assumptions (constant density in
Cites Satwik · 2020-12 · Physics Stack Exchange · on “Pressure on walls due to streamlined flowing fluid”
Let us suppose that a fluid is flowing through a pipe (fully filled) of uniform cross section. The fluid is ideal and hence must flow in a streamlined path and must be in a steady state . This means that the path of particles of fluid must never intersect (streamlined flow) and hence the velocity of all particles must be parallel to the walls of the pipe and equal at point (steady flow). Note : The figure below is a horizontal cross section of the pipe [LINK] Since the path is streamlined, the velocity of particles are parallel to each other and to the wall, therefore the particle A will also have velocity parallel to the walls and hence no component of velocity of A is towards the wall. So
Cites Karolex · 2020-12 · Physics Stack Exchange · on “Deriving Bernoulli's equation with the kinetic gas theory: Missing 1/2 factor”
Inspired by Eugene Khutoryansky video about Bernoullis law ( [this video] ), I decided to put the thoughts and ideas from her video into mathematical terms. My derivation of Bernoullis law is as follows: Lets define the x-axis parallel to the fluid's velocity and the z-axis perpendicular to it. Since Force is defined as the time-derivative of the impulse (here $\tilde{p}$ ), we can rewrite the pressure $p$ as $$p=\frac{d\tilde p}{dtA}$$ We know that in a collision of $N_z$ particles with a stationary object an impulse of $dp=2mv_zN_z$ is being transferred onto it. Furthermore The amount $N_z$ of particles colliding with the wall can be rewritten as $$N_z=n_zdV=n_zAv_zdt$$ Where $n_z$ is the densi
Critical enbin · 2024-10 · Physics Stack Exchange · on “Is the explanation of the video 'Bernoulli's Principle on Atomic Scale' correct?”
I saw a video explaining at a microscopic level that places with high speed have lower static pressure. This video suggests that at the microscopic level, the larger the velocity component in the flow direction, the smaller the velocity component perpendicular to the flow direction. The velocity component perpendicular to the flow direction determines the magnitude of static pressure. I think the explanation in this video is incorrect. [LINK] As shown in the figure, this is a pipeline that narrows from wide to narrow, and the ideal fluid flows from left to right with a constant flow rate. Obviously, from the AA section to the DD section of this pipeline, the velocity of the fluid is constant