Effect of Hydrophobic Surface on Velocity Profile of Pipe Flow

The branch of fluid mechanics is also familiar with biomechanics recently. The combination of hydrodynamic and mechanical specification of the flow can reach the complex description of the liquid flow in the hydraulic system. The hydraulic system can represent the airways and ventilation system, and external blood circulation. An important role in the study of hemo-transport has its interaction with walls. Contribution of fluid mechanics can imagine the equivalent of flow in arteries as the pipe flow, hence the Poiseuille's flow, with appropriate viscoelasticity and wettability against Newtonian liquids. The initial condition is the flexible wall and hydrophobic surface of the model. The simplification of the system leads to primary setup focused in one direction. It is the hydrophobic surface in our case. Here we present the study based on four various set of samples. We worked with hydrophobic surfaces, with contact angle (CA) above 90°, and with ultra – hydrophobic surfaces with CA above 120°. Increasing the contact angle leads from bubbles conglomeration to uniform air film. The existence of symmetrical air film close to hydrophobic surface has an effect on the character of the velocity profile and its boundary slip condition. The resulting velocity profiles give us information of velocity disturbance close to the wall and contribution of vorticities in the flow. Key-Words: hydrophobic surface, particle image velocimetry, boundary condition, slip effect, pipe flow