Dissipation rate estimation from shear probes
From Atomix
The following items break down the derivation of the turbulent dissipation rate of kinetic energy ([math]\displaystyle{ \varepsilon }[/math]). Explanations for each step can be found after.
Briefly
- Extract the section defined in step 2.
- High-pass filter the shear-probe and (optionally) the vibration data.
- Identify each diss-length segment in the profile.
- De-spike the shear-probe data, and track the fraction of data affected by de-spiking within each diss-length segment. This will become a quality-control metric.
- Calculate the frequency spectra and cross-spectra of shear and vibrations for each diss-length segment using the method described here.
- Extract the original and the vibration-coherent clean shear-probe frequency spectra.
- Correct shear and vibration frequency spectra for the high-pass filter.
- Correct the cleaned frequency spectra for the bias induced by the Goodman algorithm.
- Convert the frequency spectra into wavenumber spectra using the mean speed for each diss-length segment. That is, make the wavenumber [math]\displaystyle{ \begin{equation}k=f/U\end{equation} }[/math] and the wavenumber kinetic energy spectrum [math]\displaystyle{ \begin{equation}E(\kappa)=UE(f)\end{equation} }[/math] .
- Correct the spectra of shear for the wavenumber response of the shear probe.
- Apply an iterative spectral integration algorithm to estimate the variance of shear, which is described here.
- Calculate the rate of dissipation by multiplying the shear variance by [math]\displaystyle{ 15/2 \nu }[/math] where [math]\displaystyle{ \nu }[/math] is the temperature-dependent kinematic viscosity.