Nomenclature: Difference between revisions

From Atomix
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| <math>N</math>
| <math>N</math>
| Buoyancy frequency
| Buoyancy frequency
| <math> N = \sqrt{\frac{-g}{\bar{\rho}}\frac{\partial{\bar{\rho}}}{\partial z}</math>
| <math> N = \sqrt{\frac{-g}{\bar{\rho}} \frac{\partial\bar{\rho}}{\partial z}}</math>
| rad/s
| rad/s
|-
|-

Revision as of 15:05, 12 March 2021

Frame of reference

  • Define frame of reference, and notation. Use u,v,w and x,y, and z?
  • Decomposition of total, mean, turbulent and waves.


Turbulence Spectrum

Taylor's Frozen Turbulence for converting temporal to spatial measurements <math>\left(\bar{u}_1\frac{\partial }{\partial{x}} = \frac{\partial}{\partial{t}}\right)</math>


  • Missing the y-axis.
Symbol Description Eqn Units
<math>\Delta t</math> Sampling interval <math> \frac{1}{f_s} </math> s
<math>\Delta l</math> Sampling volume dimension m
<math>f</math> Frequency <math>\frac{\omega}{2\pi}</math> Hz
<math>f_n</math> Nyquist frequency <math>f_n=0.5f_s</math> Hz
<math>f_s</math> Sampling frequency <math> \frac{1}{\Delta t} </math> Hz
<math>k</math> Wavenumbers (angular) <math>k=\frac{f}{\bar{u}}=2\pi\hat{k}</math> rad/m
<math>\hat{k}</math> Wavenumbers <math>\frac{k}{2\pi}</math> cpm
<math>\hat{k}_\Delta</math> Nyquist wavenumber, based on sampling volume's size <math>\Delta l</math> <math>\hat{k}_\Delta=\frac{0.5}{\Delta l}</math> cpm
<math>\hat{k}_n</math> Nyquist wavenumber, via Taylor's hypothesis (temporal measurements) <math>\hat{k}_n=\frac{f_n}{u}</math> cpm
<math>\omega</math> Angular frequency <math>2\pi f</math> rad/s

Theoretical Length and Time Scales

Symbol Description Eqn Units
<math>\epsilon</math> Turbulent kinetic energy dissipation W/kg
<math>\nu</math> Viscosity of water for seawater at 35psu and 20 oC <math> 1\times 10^{-6}</math> m2/s
<math>N</math> Buoyancy frequency <math> N = \sqrt{\frac{-g}{\bar{\rho}} \frac{\partial\bar{\rho}}{\partial z}}</math> rad/s
<math>\eta</math> Kolmogorov length scale (smallest overturns) <math>\eta=\left(\frac{\nu^3}{\epsilon}\right)^{1/4}=\frac{1}{2\pi\hat{k}_K}</math> m [per rad?]