Editing Computational fluid dynamics (section)

====Coherent vortex simulation====

The coherent vortex simulation approach decomposes the turbulent flow field into a coherent part, consisting of organized vortical motion, and the incoherent part, which is the random background flow.<ref name="Farge_2001">{{cite journal|title=Coherent Vortex Simulation (CVS), A Semi-Deterministic Turbulence Model Using Wavelets|last1=Farge | first1= Marie | author1-link = Marie Farge|author2=Schneider, Kai|journal=Flow, Turbulence and Combustion|volume=66|issue=4|pages=393–426|doi=10.1023/A:1013512726409|year=2001|bibcode=2001FTC....66..393F |s2cid=53464243 }}</ref>  This decomposition is done using [[wavelet]] filtering.  The approach has much in common with LES, since it uses decomposition and resolves only the filtered portion, but different in that it does not use a linear, low-pass filter.  Instead, the filtering operation is based on wavelets, and the filter can be adapted as the flow field evolves. [[Marie Farge|Farge]] and Schneider tested the CVS method with two flow configurations and showed that the coherent portion of the flow exhibited the <math>-\frac{40}{39}</math> energy spectrum exhibited by the total flow, and corresponded to coherent structures ([[vortex stretching|vortex tubes]]), while the incoherent parts of the flow composed homogeneous background noise, which exhibited no organized structures.  Goldstein and Vasilyev<ref name="Goldstein_2004">{{cite journal|author1=Goldstein, Daniel|author2=Vasilyev, Oleg|title=Stochastic coherent adaptive large eddy simulation method|journal=Physics of Fluids A|year=1995|volume=24|page=2497|doi=10.1063/1.1736671|bibcode = 2004PhFl...16.2497G|issue=7 |citeseerx=10.1.1.415.6540}}</ref> applied the FDV model to large eddy simulation, but did not assume that the wavelet filter eliminated all coherent motions from the subfilter scales.  By employing both LES and CVS filtering, they showed that the SFS dissipation was dominated by the SFS flow field's coherent portion.