Relationship between boundary layer formation and surface roughness
When a fluid flows through Foamed Ceramic-Line Components, a boundary layer is formed near the wall. The boundary layer can be divided into a laminar bottom layer, a buffer layer, and a turbulent core. The effect of surface roughness on boundary layer characteristics begins to appear from the laminar bottom layer. For smooth surfaces, the laminar bottom layer is relatively thin and stable; however, when Foamed Ceramic-Line Components have a certain surface roughness, the roughness bumps will interfere with the fluid flow in the laminar bottom layer. These bumps will cause local velocity gradient changes in the originally stable laminar bottom layer, resulting in changes in the thickness of the laminar bottom layer, which may make the laminar bottom layer thinner. This is the starting point for surface roughness to affect boundary layer characteristics.
Effect on boundary layer velocity distribution
Surface roughness increases the interaction between the fluid and the wall. In terms of velocity distribution, a rough surface will increase the velocity gradient near the wall. In the case of a smooth wall, the velocity gradually increases smoothly from zero at the wall; but on a rough surface, due to the presence of roughness, the velocity changes of the fluid when flowing through bumps and depressions are more complex. The convex part accelerates the fluid, and the concave part may form a local low-speed area or even a vortex, thereby changing the velocity distribution curve in the entire boundary layer. This change in velocity distribution may further affect the transition position of the boundary layer from laminar flow to turbulent flow, making turbulence possible at a lower Reynolds number.
Impact on boundary layer resistance
Surface roughness will significantly increase the resistance of the boundary layer. The convexities and concavenesses on the rough surface cause more friction and collisions in the fluid during the flow process. In the laminar bottom layer, the viscous friction of the fluid under the smooth surface is dominant, but the rough surface makes this friction more complicated and adds additional body resistance. In the case of turbulence, the roughness makes the vortex motion in the boundary layer more intense and the energy dissipation increases, which leads to an increase in the pressure loss when the fluid flows through the Foamed Ceramic-Line Components, that is, the boundary layer resistance increases. This is an important influencing factor for application scenarios that require precise control of fluid pressure and flow.
Impact on boundary layer heat and mass transfer
In terms of heat and mass transfer, surface roughness changes the characteristics of the boundary layer and thus has an impact. From the perspective of heat transfer, the rough surface increases the contact area between the fluid and the wall, and due to the complex flow in the boundary layer, the heat transfer method is not only heat conduction, but also increases the heat mixing caused by convection and vortex. This increases the heat transfer coefficient and makes the heat exchange more sufficient. For mass transfer processes, the boundary layer changes caused by the rough surface will promote the exchange of substances between the fluid and the wall. For example, in applications involving chemical reactions or material separation, the effect of this surface roughness on boundary layer mass transfer may change the reaction rate or separation efficiency.
