# Questions tagged [fluid-dynamics]

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### How did Mt. Etna get so good at blowing smoke rings? Is this new?

Screenshots below are from Bloomberg News' April 10, 2024 Italy's Mt. Etna Puffs Out Smoke Rings (also available at AP News' April 7, 2024: Mount Etna blows spectacular smoke rings into the sky). Some ...
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1 vote
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### Why shear stress vector must be parallel to flow in this example?

In the book by S. Pal Arya "Introduction to Micrometeorology" there is a chapter about Laminar Ekman Layers. I refer to the following example: Variables are: U, V wind velocity in x, y ...
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### What is the correct velocity to calculate propagation speed of a Rossby Wave?

Rossby Waves have different phase- and group velocities. For a pure zonal wave with wave number k they are $$v_p=\overline u - \frac{\beta}{k^2}$$ $$v_g=\overline u + \frac{\beta}{k^2}$$ So group ...
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1 vote
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### Global Ocean Models not dissipative?

I keep hearing that the models used for global ocean simulations are not actually dissipative, even though they clearly have dissipative terms and we couldn't solve them if they didn't (here, "...
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### A problem of the 2-Layer hydrostatic model

The 2-layer hydrostatic model is like this And the pressure of the two layers and the top are and it is easy to find the horizontal gradient of $p_1$ and $p_2$ \begin{aligned} \nabla ...
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### Is continental drift a chaotic phenomenon?

Suppose that we reran Earth from two billion years ago changing the position of one atom. Would the continents drift to positions completely different from those today?
3k views

### What is the relationship between air pressure and temperature?

I'm trying to reconcile a paradox regarding air pressure and temperature. On the one hand, compressing air heats it up, while expanding it cools it. So density and temperature are proportional. On the ...
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### Similarities and differences between lava flows and fluvial geomorphology (rivers)

How are active lava flows similar to fluvial geomorphology? You can search youtube for these dramatic videos of lava flows, and they all seem to look very similar to streams or rivers. I know that the ...
81 views

### How do you find the relationship between the angle a weather front makes with the ground and the temperatures and along front winds either side of it?

I am working through David Andrews' "An introductuion to atmospheric physics". (2nd Ed) Question 4.8 concerns finding the relationship between the angle a weather front makes with the ground ...
60 views

### What is "small layer thickness" defined as in terms of bulk Richardson number approaching gradient Richardson number?

In many sources (https://glossary.ametsoc.org/wiki/Bulk_richardson_number), bulk Richardson number is defined as an approximation to gradient Richardson number. The prior only approaches the ladder ...
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### Can air be slowed down by Fricton? [closed]

Can wind/air that is moving at average speeds be slowed down by the cause of Friction? Also, Can Air bubbles in water be slowed down because of Friction? Please cite your sources.
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### Deriving shallow water equations: why is the vertical velocity equal to the material derivative of the surface level?

I'm reading about the derivation of shallow water equations, and I have a hard time understanding why $$w(\eta) = \frac{D\eta}{Dt}$$ where $w$ is the vertical velocity, $\eta$ is the (top or bottom) ...
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1 vote
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### Is COMSOL Multiphysics good for subduction CFD modelling? Are there alternatives?

As a beginner for CFD modelling of plate subduction, I heard comsol to be a good software. Can anybody suggests alternatives and the demerits of using COMSOL Multiphysics? Thank you.
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### Vertical air speed

Assuming that the divergence varies linearly with the pressure between the surface (1000 hPa) and the tropopause (200 hPa). Can someone tell me how do we calculate the vertical speed on the pressure ...
106 views

### Is it meaningful to assume static pressure to be constant along a streamline?

I am looking at Bernoulli's equation formulated in two dimensions, which reads $$\frac{v^2}{2}+c_p\theta_0\pi+gz \equiv \mathrm{const.}$$ along a given streamline $\gamma$, where $v=|\mathrm{v}|$ for ...
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### What is the simplest meteorological model to operate?

For teaching purposes I am looking for an atmospheric model that can be easily installed and the input data can be easily read and prepared. Preferably I would like to run a global low resolution ...
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### If the top layer of a large river freezes, is the remainder's rate of flow affected?

This question is a hypothetical, and has to do with the notion of cheap, modular turbines that can be sunk and anchored to a specific depth in a body of water. Each would not generate much power, but ...
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### Reasons for choosing LES in stead of RANS models?

In oceanography, is there any particular reason why choosing large eddy simulations in stead of RANS (regardless of the type of flow)? In both cases, 2d simulations would be used (shallow water model)....
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### What forms do groundwater flow equations have when Dupuit supposition is not considered?

Near pumping wells or near/beneath a stream, the groundwater flow is not totally horizontal and the vertical component of groundwater movement at these points cannot be ignored in reality. Often, ...
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### What is the difference between the Hydraulic diffusion equation and the Richards equation in groundwater dynamics?

What is the difference between the Hydraulic diffusion equation and the Richards equation in groundwater dynamics? I want also to understand the difference between the different storage coefficients (...
220 views

### What affects the surface characteristics of cumulus clouds?

I love looking at clouds. I love trying to describe them and compare what I see day to day. I have dozens of questions about the things I’ve observed and I would really like to understand the physics ...
209 views

### comparing use of Laplace equation with diffusion equation to simulate flow of fluid/water through porous media?

What is the difference in using Laplace equation (say only in 1D) to simulate water flow in a porous media with that of using diffusion equation for same purpose?
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### Link between different ways of modeling permeability

The most famous equation describing the permeability $k$ of a soil is the Kozeny-Carman equation: $$k = \frac{\phi}{8}r^2 \approx \frac{\phi}{c}\left(\frac{V}{S}\right)^2$$ $\phi$: porosity V: pore ...
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