As seen in Figure 3, the boundary layer can be divided into three regions and they are viscous sublayer
, log layer, and defect layer.
The S-shaped curves show that the two SST models consider the viscous sublayer
and buffer layer.
For traditional CPB, solid-liquid high-mud SUT is the turbulent viscous sublayer
which will produce big resistance loss under the continuous shearing force provided by the pipe wall.
In 2010, Neopane claimed that the k-e model is valid for the free flow region but tends to fail in the viscous sublayer
, despite being the most used in the industry due to its stability and numerical robustness.
The control over the entire surfaces to force viscous sublayer
resolution was computationally expensive and judged unnecessary.
The particle velocity profiles coincide very well in the viscous sublayer
for channel and pipe.
The turbulence is used to break the viscous sublayer
at the absorber surface.
It can be believed that the upper bound of the viscous sublayer
corresponds to the point A, below which the viscous stress is dominant in the total stress.
For the high Prandtl numbers, the grid resolution which captures the viscous sublayer
can be inadequate and insufficient for the thermal conduction region.
However, with the roughness reduced on the inner wall, the small convex parts are all completely submerged in the viscous sublayer
and the gas pipeline becomes "hydraulic smooth pipe" That means even though the coating surface is smoothed further, the wall friction is difficult to further reduce.
The boundary layers that cover airfoil are divided into viscous sublayer
, buffer layer and log-low region (MA, 20009).