The determination of boundary layer thickness can be done with a macro where you compute the parameter you want to use for determining boundary layer thickness everywhere then search along a ray that is orthogonal to the wall. Compute the normal vector as you would with the unit normal vector in I, J, or K depending on the orientation of the grid that provides the computational direction orthogonal to the wall. Then, using the local cell sizes, march along a vector from a point on the wall until you find where the criteria is satisfied. Chances are that you will simply hit a point where the criteria changes from true to false, and not an exact point. To find the point, a simple linear interpolation is sufficient to find a more exact point. Store each point into a zone that can later be used for integration. To do this, you need to know the number of points which means you either do this computation twice (once to find the number of points and a second time to store them from one zone to another), or you set the number of points and interpolate the points you create with the known data. Once a line is extracted, all remaining integrated quantities can be computed.
Aerospace Research Engineer
NASA Langley Research Center