# Questions tagged [fluid-dynamics]

The quantitative study of how fluids (gases and liquids) move.

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### Vorticity: what is the difference between $\nabla \times f$ and $\nabla \wedge f$?

I have always thought that we may obtain information about the vorticity of a vector field $f$ by considering the cross product $\nabla \times f$. In higher level texts on fluid mechanics I see that ...
11 views

### What's a good simple model for wind attacking drone?

I'm trying to simulate a drone on https://rapier.rs/. My idea is to do an X shaped object, with a force $P$ on each end of the X, always perpendicular to the drone plane. I want to simulate wind, ...
14 views

### Releasing compressed air with the loudest pop [closed]

Due to the dry summer I've been thinking about theory of making cracker/banger without fire. Would connecting a nozzle (de Laval?) to quick release valve from small cylinder with the pressurised air ...
11 views

### Kelvin–Helmholtz instabilities - how to solve these questions? [closed]

The Kelvin-Helmholtz problem occurs when horizontal wind and density change at a discontinuity with $U_1,ρ_1$ in the upper layer and $U_2,ρ_2$ in a lower layer. It can be shown that the phase speed ...
1 vote
36 views

### Linear drag for pendulum in air, justifiable or not?

So, when trying to measure the gravity constant $g$ at home through a pendulum I realized I wanted to try to model drag on the pendulum, to get a more accurate result. I am asking how we can justify ...
1 vote
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1 vote
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### Velocity at a place for fluid with a given pressure gradient?

In a spherical coordinate system, the origin is a sink with fluid extending to infinite distance. The pressure gradient generated in the fluid is: $$\nabla P \alpha \frac{1}{r^2}$$ where $r$ is the ...
30 views

### Does the Continuity Equation Imply it's Zero for Incompressible Flow?

This might be an incredibly simple question, but I haven't been able to figure it out on my own. I'm an engineer by trade, so please forgive my unfamiliarity with vector calculus. I'm interested in ...