Nomenclature

Frame of reference

• Define frame of reference, and notation. Use u,v,w and x,y, and z?
• Dumping a sketch would be useful

Reynold's Decomposition

• Variable names for Decomposition of total, mean, turbulent and waves.

Turbulence properties

Symbol	Description	Eqn	Units
$ϵ$	Turbulent kinetic energy dissipation		W/kg
$Ri$	Richardson number	$Ri=\frac{N^2}{S^2}$
$R{i}_f$	Flux gradient Richardson number	$\frac{B}{P}$ or Ivey & Immerger?
$\kappa$	Turbulent diffusivity	$\kappa =\mathrm{\Gamma }ϵN^{-2}$	m$2^{}$s${-1}^{}$

Fluid properties and background gradients for turbulence calculations

Symbol	Description	Eqn	Units
$S$	Background velocity shear	$S=\frac{\partial |U|}{\partial z}$	s${-1}^{}$
$\nu$	Viscosity of water for seawater at 35psu and 20 oC	$1\times 10^{-6}$	m2/s
$N$	Background stratification, i.e buoyancy frequency	$N=\sqrt{\frac{-g}{\overline{\rho }}\frac{\partial \overline{\rho }}{\partial z}}$	rad/s

Theoretical Length and Time Scales

Symbol	Description	Eqn	Units
${\tau }_N$	Buoyancy timescale	${\tau }_N=\frac{2\pi }{N}$	s
$L_E$	Ellison length scale (limit of vertical displacement without irreversible mixing)	$L_E=\frac{⟨\rho {\text{'}}^2{⟩}^{1/2}}{\partial \bar{\rho }/\partial z}$	m
$L_{\rho }$	Density length scale	$L_{\rho }$	m
$L_S$	Corssin length scale	$L_S=\sqrt{ϵ/S^3}$	m
$\eta$	Kolmogorov length scale (smallest overturns)	$\eta ={\left(\frac{{\nu }^3}{ϵ}\right)}^{1/4}=\frac{1}{2\pi {\hat{k}}_K}$	m
$L_o$	Ozmidov length scale, measure of largest overturns in a stratified fluid	$L_o={\left(\frac{ϵ}{N^3}\right)}^{1/2}$	m

Turbulence Spectrum

Taylor's Frozen Turbulence for converting temporal to spatial measurements $({\overline{u}}_1\frac{\partial }{\partial x}=\frac{\partial }{\partial t})$

• Missing the y-axi variable. CEB proposes:
  • ${\mathrm{\Psi }}_{variable}$ for model/theoretical spectrum of variable e.g., du/dx or u
  • ${\mathrm{\Phi }}_{variable}$ for observed spectrum of variable e.g., du/dx or u
• Lowest frequency and wavenumber resolvable

Symbol	Description	Eqn	Units
$\mathrm{\Delta }t$	Sampling interval	$\frac{1}{f_s}$	s
$\mathrm{\Delta }s$	Sampling volume dimension		m
$f$	Frequency	$\frac{\omega }{2\pi }$	Hz
$f_n$	Nyquist frequency	$f_n=0.5f_s$	Hz
$f_s$	Sampling frequency	$f_s=\frac{1}{\mathrm{\Delta }t}$	Hz
$k$	Wavenumbers (angular)	$k=\frac{f}{\overline{u}}=2\pi \hat{k}$	rad/m
$\hat{k}$	Wavenumbers	$\hat{k}=\frac{k}{2\pi }$	cpm
${\hat{k}}_{\mathrm{\Delta }}$	Nyquist wavenumber, based on sampling volume's size $\mathrm{\Delta }l$	${\hat{k}}_{\mathrm{\Delta }}=\frac{0.5}{\mathrm{\Delta }l}$	cpm
${\hat{k}}_n$	Nyquist wavenumber, via Taylor's hypothesis (temporal measurements)	${\hat{k}}_n=\frac{f_n}{u}$	cpm
$\omega$	Angular frequency	$2\pi f$	rad/s