for all test functions $q$, where
@f{equation*}
\mathcal{A}\left(p,q\right)
- := \int_\Omega \left(\mathbf{K} \nabla p\right) \cdot \nabla q \;\mathrm{d}x,
+ \dealcoloneq \int_\Omega \left(\mathbf{K} \nabla p\right) \cdot \nabla q \;\mathrm{d}x,
@f}
and
@f{equation*}
\mathcal{F}\left(q\right)
- := \int_\Omega f \, q \;\mathrm{d}x
+ \dealcoloneq \int_\Omega f \, q \;\mathrm{d}x
- \int_{\Gamma^N} u_N q \; \mathrm{d}x.
@f}
Here, we have integrated by parts in the bilinear form, and we are evaluating
for all discrete test functions $q_h$, where
@f{equation*}
\mathcal{A}_h\left(p_h,q_h\right)
- := \sum_{K \in \mathbb{T}}
+ \dealcoloneq \sum_{K \in \mathbb{T}}
\int_K \mathbf{K} \nabla_{w,d} p_h \cdot \nabla_{w,d} q_h \;\mathrm{d}x,
@f}
and
@f{equation*}
\mathcal{F}\left(q_h\right)
- := \sum_{K \in \mathbb{T}} \int_K f \, q_h^\circ \;\mathrm{d}x
+ \dealcoloneq \sum_{K \in \mathbb{T}} \int_K f \, q_h^\circ \;\mathrm{d}x
- \sum_{\gamma \in \Gamma_h^N} \int_\gamma u_N q_h^\partial \;\mathrm{d}x,
@f}
The key point is that here, we have replaced the gradient $\nabla p_h$ by the
2. If $\varepsilon=0$ then this is the stationary advection equation solved in
step-9.
-3. Define the <i>Peclet number</i>: $\mathcal{P}\:=\|\boldsymbol{\beta}\|
+3. Define the <i>Peclet number</i>: $\mathcal{P} \dealcoloneq \|\boldsymbol{\beta}\|
\cdot L/\varepsilon$. If $\mathcal{P}>1$, we say the problem is
<i>advection-dominated</i>, else if $\mathcal{P}<1$ we will say the problem is
<i>diffusion-dominated</i>. Here $L$ is the length scale of the domain.