removed toucan

.gitmodules

-[submodule "toucan"]
-	path = lattice-boltzmann.com/themes/toucan
-	url = https://git.42l.fr/HugoTrentesaux/toucan.git
 [submodule "lattice-boltzmann.com/themes/abridge"]
 	path = lattice-boltzmann.com/themes/abridge
 	url = https://github.com/jieiku/abridge.git

lattice-boltzmann.com/content/1-dimensionless-lbm.md

@@ -21,7 +21,7 @@ The incompressible Navier--Stokes equations reads
 $$
 \begin{align}
 &\bm{\nabla}\cdot\bm{u}=0,\\\\
-&\frac{\partial}{\partial t}\bm{u}+\bm{u}\cdot\bm{\nabla}\bm{u}=-\frac{1}{\rho}\bm{\nabla}p+\nu\bm{\nabla}^2\bm{u},
+&\partial_t\bm{u}+\bm{u}\cdot\bm{\nabla}\bm{u}=-\frac{1}{\rho}\bm{\nabla}p+\nu\bm{\nabla}^2\bm{u},
 \end{align}
 $$
 where $p$, $\rho$, $\nu$, and $\bm{u}$ are respectively the pressure, density, kinematic viscosity, and velocity of the flow.
@@ -34,7 +34,7 @@ $$
 \begin{aligned}
 &\bm{u}^\ast=\frac{\bm{u}}{U}, &p^\ast=\frac{p}{\rho U^2},\\\\
 &t^\ast=\frac{U}{L}t, &\bm{x}^\ast=\frac{\bm{x}}{L},\\\\
-&\frac{\partial}{\partial t^\ast}=\frac{L}{U}\frac{\partial}{\partial t}, &\bm{\nabla}^\ast=L\bm{\nabla}
+&\partial_t^\ast=\frac{L}{U}\partial_t, &\bm{\nabla}^\ast=L\bm{\nabla}
 \end{aligned}
 \end{equation}
 $$
@@ -42,7 +42,7 @@ Replacing these equations into the Navier--Stokes equations one gets
 $$
 \begin{align}
 &\bm{\nabla}^\ast\cdot\bm{u}^\ast=0,\\\\
-&\frac{\partial}{\partial t^\ast}\bm{u}^\ast+\bm{u}^\ast\cdot\bm{\nabla}^\ast\bm{u}^\ast=-\bm{\nabla}^\ast p^\ast+\frac{1}{\mathrm{Re}}\bm{\nabla}^{\ast 2}\bm{u}^\ast,
+&\partial_t^\ast\bm{u}^\ast+\bm{u}^\ast\cdot\bm{\nabla}^\ast\bm{u}^\ast=-\bm{\nabla}^\ast p^\ast+\frac{1}{\mathrm{Re}}\bm{\nabla}^{\ast 2}\bm{u}^\ast,
 \end{align}
 $$
 where $\mathrm{Re}=U\cdot L/\nu$ is the _famous_ Reynolds number which represents the ratio of the inertial over the viscous forces.
@@ -115,7 +115,9 @@ $$
 $$
 where the space, time, and microscopic velocity dependence is omitted and where
 $$
+\begin{equation}
 \mathrm{Kn}=\frac{\tau\xi_0}{L},
+\end{equation}
 $$
 is the Knudsen number.