page_title: Boundary conditions in computational fluid dynamics
section_title: Exit boundary conditions
hierarchical_section_title: Boundary conditions in computational fluid dynamics / Exit boundary conditions
caption_attribution_description: English: v-control volume at an exit boundary
context_page_description: Almost every computational fluid dynamics problem is defined under the limits of initial and boundary conditions. When constructing a staggered grid, it is common to implement boundary conditions by adding an extra node across the physical boundary. The nodes just outside the inlet of the system are used to assign the inlet conditions and the physical boundaries can coincide with the scalar control volume boundaries. This makes it possible to introduce the boundary conditions and achieve discrete equations for nodes near the boundaries with small modifications.
  The most common boundary conditions used in computational fluid dynamics are
  Intake conditions
  Symmetry conditions
  Physical boundary conditions
  Cyclic conditions
  Pressure conditions
  Exit conditions
context_section_description: Considering the case of an outlet perpendicular to the x-direction -
  In fully developed flow no changes occurs in flow direction, gradient of all variables except pressure are zero in flow direction
  The equations are solved for cells up to NI-1, outside the domain values of flow variables are determined by extrapolation from the interior by assuming zero gradients at the outlet plane
  The outlet plane velocities with the continuity correction
  .
caption: Fig. 13 v-control volume at an exit boundary
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