What Characteristic Length Should Be Used for Fluids in Low Gravity?

[member 428835]

Hi PF!

Fluids in low gravity have a natural oscillation frequency $\lambda = \sqrt{\sigma / (\rho L^3)}$, where $\sigma$ is surface tension, $\rho$ density, $L$ characteristic length.

Then given a particular object, say a sphere, is $L=D$ or $L=r$? How about a channel; would $L$ be the length, width, or height, or what about, say, half-width? Any help is greatly appreciated!

 

[DEvens]

The characteristic dimension will depend on the vibration mode. For example, look here.

https://saviot.cnrs.fr/lamb/index.en.html
A sphere has entire families of vibration modes. Each one will have a different frequency because it involves different masses doing different things.

 

[member 428835]

The characteristic dimension will depend on the vibration mode. For example, look here.

https://saviot.cnrs.fr/lamb/index.en.html
A sphere has entire families of vibration modes. Each one will have a different frequency because it involves different masses doing different things.

Thanks for responding. I don't really see how to distinguish between using the radius vs diameter though.