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86 | 86 | vanish on <span class="math notranslate nohighlight">\(\Gamma\)</span>. The outflow condition is the “do nothing” condition which |
87 | 87 | is imposed simply by not including the surface terms created by integrating the |
88 | 88 | velocity equation by parts when formulating the weak form.</p> |
89 | | -<p>These equations are well posed so long as $Gammasetminus Gamma_D neq |
90 | | -emptyset$. That is to say, there must be some outflow boundary. If $Gamma |
91 | | -=Gamma_D$ then there will be a null space comprising all of the constant |
| 89 | +<p>These equations are well posed so long as <span class="math notranslate nohighlight">\(\Gamma\setminus \Gamma_D \neq |
| 90 | +\emptyset\)</span>. That is to say, there must be some outflow boundary. If <span class="math notranslate nohighlight">\(\Gamma |
| 91 | +=\Gamma_D\)</span> then there will be a null space comprising all of the constant |
92 | 92 | pressure functions. We will implement the two-dimensional case (<span class="math notranslate nohighlight">\(d=2\)</span>) and, for |
93 | 93 | simplicity, we will assume <span class="math notranslate nohighlight">\(\mu=1\)</span>.</p> |
94 | 94 | <p>The colon (<span class="math notranslate nohighlight">\(:\)</span>) indicates an inner product so:</p> |
95 | 95 | <div class="math notranslate nohighlight" id="equation-9-mixed-problems-1"> |
96 | | -<span class="eqno">(9.4)<a class="headerlink" href="#equation-9-mixed-problems-1" title="Link to this equation">¶</a></span>\[\nabla u:\nabla v = \sum_{\alpha\beta} \nabla_{\alpha} u_{\beta}\nabla{\alpha} v_{\beta}\]</div> |
| 96 | +<span class="eqno">(9.4)<a class="headerlink" href="#equation-9-mixed-problems-1" title="Link to this equation">¶</a></span>\[\nabla u:\nabla v = \sum_{\alpha\beta} \nabla_{\alpha} u_{\beta}\nabla_{\alpha} v_{\beta}\]</div> |
97 | 97 | <p>In choosing a finite element subspace of <span class="math notranslate nohighlight">\(V \times Q\)</span> we will similarly choose |
98 | 98 | a simpler to implement, yet still stable, space than was chosen in |
99 | 99 | <a class="reference internal" href="L6_stokes.html#stokes"><span class="std std-numref">Analysis Section 6</span></a>. The space we will use is the lowest order |
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