page_title: Boundary conditions in computational fluid dynamics
section_title: Physical boundary conditions
hierarchical_section_title: Boundary conditions in computational fluid dynamics / Physical boundary conditions
caption_attribution_description: English: v-cell at physical boundary j=NJ
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: Consider situation solid wall parallel to the x-direction:
  Assumptions made and relations considered-
  The near wall flow is considered as laminar and the velocity varies linearly with distance from the wall
  No slip condition: u = v = 0.
  In this we are applying the “wall functions” instead of the mesh points.
  Turbulent flow:
  .
  in the log-law region of a turbulent boundary layer.
  Laminar flow :
  .
  Important points for applying wall functions:
  The velocity is constant along parallel to the wall and varies only in the direction normal to the wall.
  No pressure gradients in the flow direction.
  High Reynolds number
  No chemical reactions at the wall
caption: Fig.8 v-cell at physical boundary j=NJ
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