Questions tagged [fluid-dynamics]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
4 votes
1 answer
91 views

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{equation} \begin{aligned} \nabla ...
user avatar
  • 103
2 votes
0 answers
42 views

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?
user avatar
1 vote
2 answers
140 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 ...
user avatar
  • 113
8 votes
2 answers
290 views

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 ...
user avatar
4 votes
0 answers
28 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 ...
user avatar
4 votes
1 answer
47 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 ...
user avatar
-2 votes
1 answer
64 views

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.
user avatar
  • 328
3 votes
2 answers
146 views

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) ...
user avatar
  • 133
0 votes
1 answer
55 views

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.
user avatar
  • 15
0 votes
1 answer
66 views

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 ...
user avatar
3 votes
1 answer
78 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 ...
user avatar
  • 83
2 votes
2 answers
165 views

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 ...
user avatar
3 votes
1 answer
73 views

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 ...
user avatar
  • 31
1 vote
1 answer
148 views

Barotropic vorticity equation

I came across the barotropic vorticity equation (below) in Sakamoto (2002) and I cannot figure it out. The notation is not clear to me. How can it be derived from the Navier-Stokes equation? $$ \beta\...
user avatar
2 votes
1 answer
492 views

Hydrology- flow accumulation

I'm not specialist in hydrology, and I would be very grateful if you answer my question: What is flow accumulation in hydrology? Why algorithms used to calculate it over a raster DEM don't take ...
user avatar
  • 31
2 votes
1 answer
162 views

At what point are water droplets too small to make a rainbow?

This question asks How to tell if fog is made out of water droplets or ice crystals? I know that ice fog makes a rainbow where fog does not. Ice crystals aside: How does the water droplet size ...
user avatar
  • 1
1 vote
0 answers
27 views

Algorithm for anisotropic porous media reconstruction

I have a series of micro-tomography images of a porous material (received from experimental partners) with a resolution 10 $\mu m$ with total size 1cm $\times$ 1cm. Porosity of the porous material ...
user avatar
  • 111
5 votes
0 answers
49 views

Over what scales can we begin to apply fluid dynamics to accurately model properties of the mantle?

Over what size temporal/spatial scales do geophysicists and geodynamicists begin to apply fluid dynamics to model the mantle rather than elastic/plastic deformation theory?
user avatar
  • 360
4 votes
0 answers
137 views

Godfrey's island rule (stream function in multiply connected domains)

In this paper, the authors detail the methods to calculate the stream function $\psi$ from velocity data in the case of the global ocean (i.e., multiply connected domains). The general idea is to use ...
user avatar
  • 507
5 votes
1 answer
189 views

Why would geostrophic theory be invoked in the tropics with regards to the MJO?

In this paper reviewing the Madden-Julian Oscillation, frequently geostrophic theory (or approximately geostrophic) is often invoked. However, for geostrophic theory to be invoked, $$Ro=\frac{U}{f_0L}&...
user avatar
3 votes
0 answers
63 views

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)....
user avatar
3 votes
1 answer
60 views

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, ...
user avatar
5 votes
0 answers
272 views

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 (...
user avatar
2 votes
1 answer
181 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 ...
user avatar
4 votes
1 answer
178 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?
user avatar
4 votes
0 answers
50 views

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 ...
user avatar
  • 41
3 votes
1 answer
287 views

How to characterize flow of nonreactive tracer in a porous media?

About Tracer Experiment This experiment is conducted by injecting a fluid with nonreactive species of certain concentration inside a column or core composed of sand. The injection of fluid can either ...
user avatar
8 votes
1 answer
167 views

Unrealistic solution for advection-diffusion-reaction PDE with heterogeneous porous media

About the code: I have a code which simulates concentration from advection-diffusion-reaction PDE in 2D space (X,Y) with time. The solution is obtained using fully implicit finite-difference method ...
user avatar
8 votes
0 answers
127 views

Shallow water height as vertical coordinate

In atmospheric physics we use often a variety of vertical coordinates, $z$ the height above some reference surface, or $r$ as distance from the planetary center. However sometimes it simplifies the ...
user avatar
11 votes
1 answer
2k views

What is the difference between an inertial instability and a symmetric instability?

Inertial and symmetric instabilities are fluid instabilities present in atmosphere and ocean. What are the difference between an inertial instability and a symmetric instability?
user avatar
  • 211
32 votes
3 answers
4k views

Why does Coriolis determine the rotation direction of a cyclone but not my drain?

It is a common misconception that Coriolis is responsible for the direction the water swirls down a toilet, tub or sink drain. E.g. does a toilet flush the other way in the southern hemisphere? (If ...
user avatar
  • 13.9k
5 votes
3 answers
180 views

coriolis force in atmospheric/ocean modeling

The Coriolis force is not a real force, but depending on the reference system and how it does refer to an inertial system. Could this Coriolis force as widely used in atmospheric/climate modeling be ...
user avatar
16 votes
2 answers
4k views

Why is aerodynamic resistance defined inversely?

When I think of wind resistance, I always think of the friction co-efficient, in $\mathrm{ms^{-1}}$, because that's always the way that it was presented in highschool and undergraduate physics. But ...
user avatar
  • 5,317