### 5.1.4. Solving the Mesh Displacement Equations and Updating Mesh Coordinates

During each outer iteration or timestep, the mesh displacement equations are solved to the specified convergence level and the resulting displacements are applied to update the mesh coordinates. This occurs before proceeding to solve the general transport (for example, hydrodynamics, turbulence, and so on) equations.

Unlike other equation classes, the convergence level (that is, controls and criteria) applied to mesh displacement equations is unaffected by changes made to the basic settings for all other equations. The default convergence controls and criteria for the mesh displacement equation are tabulated below, and are changed by visiting the Mesh Displacement entry in the Equation Class Settings tab under Solver Control.

Setting | Value
--- | ---
Maximum Number of Coefficient Loops | 5
Minimum Number of Coefficient Loops | 1
Residual Type | RMS
Residual Target | 1.0E-4

Mesh folding occurs and is detected when the displacements are used to update the mesh coordinates. Folded meshes can occur if the displacement equations are incompletely solved. In this case, the unconverged displacement solution field does not vary smoothly enough to ensure that adjacent mesh nodes move by similar amounts.

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