reformulating (#187)

Co-authored-by: Cristopher-Morales <[email protected]>

Author: Cristopher-Morales

_docs_v7/Theory.md

@@ -264,11 +264,12 @@ $$S$$ is a generic source term, and the convective and viscous fluxes are
 
 $$\bar{F}^{c}(V) = \left\{\begin{array}{c} \rho Y_1 \bar{v} \\ ... \\\rho Y_{N-1} \, \bar{v} \end{array} \right\}$$
 
-$$\bar{F}^{v}(V,\nabla V) = \left\{\begin{array}{c} D \nabla Y_{1} \\ ... \\  D \nabla Y_{N-1} \end{array} \right\} $$
+$$\bar{F}^{v}(V,\nabla V) = \left\{\begin{array}{c} \rho D \nabla Y_{1} \\ ... \\  \rho D \nabla Y_{N-1} \end{array} \right\} $$
 
 with $$D$$ $$[m^2/s]$$ being the mass diffusion. 
+For turbulence modeling, the diffusion coefficient becomes:
 
-$$D = D_{lam} + \frac{\mu_T}{Sc_{T}}$$
+$$\rho D = \rho D_{lam} + \frac{\mu_T}{Sc_{T}}$$
 
 where $$\mu_T$$ is the eddy viscosity and $$Sc_{T}$$ $$[-]$$ the turbulent Schmidt number.