Theory Manual Version 3.4
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Subsection 7.3.2: Gap Function Up Section 7.3: Biphasic-Solute Contact Subsection 7.3.4: Discretization

### 7.3.3 Penalty Method

Let the normal component of the contact traction be described by the penalty function, where is a penalty factor associated with . Similarly, let and where and are penalty factors associated with and , respectively. It follows that Given these relations, it can be shown that the directional derivatives of the various terms appearing in the integrand of are where .
Subsection 7.3.2: Gap Function Up Section 7.3: Biphasic-Solute Contact Subsection 7.3.4: Discretization