# First cell height calculation

(Difference between revisions)
 Revision as of 06:46, 12 July 2006 (view source)Praveen (Talk | contribs)← Older edit Revision as of 22:47, 15 May 2007 (view source)Jasond (Talk | contribs) Newer edit → Line 1: Line 1: - While performing CFD simulations, it is critical that one capture boundary layer near the wall properly. In order to do that, mesh should be generated in such a manner that it captures boundary layer properly. Calculation of Y plus value helps in doing that. + {{Meshing table of contents}} + While performing CFD simulations, it is critical that one capture boundary layer near the wall properly. In order to do that, the mesh should be generated in such a manner that it captures boundary layer properly. For turbulent flows, calculation of the [[Dimensionless wall distance (y plus) | Y plus]] value of the first interior node/gridpoint helps in doing that.  This dimensionless distance is defined as + + :$y^+ := \frac{u_* \, y}{\nu}$ + + where $u_*$ is the friction velocity defined as + + :$u_* := \sqrt{\frac{\tau_w}{\rho}}.$ + + The [[Wall shear stress|wall shear]] $\tau_w$ can probably not be determined until after a simulation has been completed, so it is usually necessary to estimate a value, and then check after a simulation is complete. ==Related pages== ==Related pages== * [[Dimensionless wall distance (y plus)]] * [[Dimensionless wall distance (y plus)]] - + * [[Friction velocity]] - {{stub}} + * [[Wall shear stress]]

## Revision as of 22:47, 15 May 2007

 Introduction Mesh classification Structured mesh generation Unstructured mesh generation Special topics Mesh adaptation First cell height calculation

While performing CFD simulations, it is critical that one capture boundary layer near the wall properly. In order to do that, the mesh should be generated in such a manner that it captures boundary layer properly. For turbulent flows, calculation of the Y plus value of the first interior node/gridpoint helps in doing that. This dimensionless distance is defined as

$y^+ := \frac{u_* \, y}{\nu}$

where $u_*$ is the friction velocity defined as

$u_* := \sqrt{\frac{\tau_w}{\rho}}.$

The wall shear $\tau_w$ can probably not be determined until after a simulation has been completed, so it is usually necessary to estimate a value, and then check after a simulation is complete.