Natural Frequency

[LorenaGarate]

I am looking for information of the Natural Frequency of water and other compounds. Do any of you can help me to find information about the subject?

Thanks
Edgar

 

[yshij]

I do'nt think water has natural frequency, because water is not a elastic material. You may talk about the thing in molecular level?

 

[pja]

Only in recent years have people started looking at fluids with respect to modes..reduced order models can be formed using the modes found by solving the generalized eigenvalue problem of a fluid system. However the idea of what a fluid mode looks like is still a bit fuzzy. Dowell,Hall and others have done some research on using fluid modes to solve fluid dynamics/aeroelastic problems. They have papers which you can take a look at.

 

[ronfrend]

yshij is correct in saying that water does not have a natural frequency BUT what you can do is to calculate the speed at which sound (vibration) travels through water. The if you have a "pipe" or other limited length tube you can calculate the tone of the frequency like an organ pipe using c=fL

c=speed of sound in the fluid
f=frequency of the vibration
L=wavelength

Don't forget about half tones - there are differences if you have open/closed tubes.

The exact relationship between the velocity of the sound waves in water is:

V(water)=(bulk modulus/mass density)^0.5

Hope this helps

Ron Frend

 

[vanstoja]

I'm inclined to believe that, apart from ocean tidal change frequencies imposed by gravitational effects of the moon and sun, the natural frequencies of or water and other liquids are those imposed by the geometry of the confining structure whether open channel (dams, weirs, bays, lakes, etc) or closed channel in pipes and pressure vessels. In closed channels, one finds the infinite variety of so-called flow tones and flow-induced-vibration (FIV) sources that can disable or fail equipment and drive responsible equipment engineers to distraction if not pure insanity. One of the daunting problems of FIV troubleshooting is that the same physical geometry can generate more than one type of flowtone source (eg., Helmholtz resonator and annular channel standing waves), having vastly different frequencies, depending on the range of flow velocities passing the "mouth" of the cavity in the structural wall bounding the fluid flowpath. vanstoja

 

[MikeyP]

Microwave ovens are presumably designed to excite water molecules at their natural frequency. The frequency of microwaves generated by ovens is in the 1-2 GHz range, so I suspect the natural frequency of water molecules falls somewhere in this range too.

Michael

 

[LorenaGarate]

I understand that the Microwave excite the water molecules at their natural frequency, but I would like to find more information on the theory on how this natural frequency is given, and how can it be applied to some other molecules, my guess is that it will ressonance according to the type of configuration of the molecules. Do you know where I can find information on this? How can this be measured?

 

[LorenaGarate]

I also might add that maybe the correct term would be Ressonance frequency of Water rather than Natural frequency.

Thanks to all of you for your inputs....