Multi-phase Fluid Flow (or Two-phase Fluid Flow).For fully developed laminar pipe flow, Vavg is half of the maximum velocity.įrom a practical engineering point of view the flow regime can be categorized according to several criteria.Īll fluid flow is classified into one of two broad categories or regimes.

Average velocity Vavg is defined as the average speed through a cross section. Mathematical analysis is very difficult.The average flow velocity is approximately equal to the velocity at the center of the pipe.The flow velocity profile for turbulent flow is fairly flat across the center section of a pipe and drops rapidly extremely close to the walls.Average motion is in the direction of the flow.The flow is characterized by the irregular movement of particles of the fluid.Therefore, unlike laminar flow, the friction factor in turbulent flow is a strong function of surface roughness. Any irregularity or roughness on the surface disturbs this layer and significantly affects the flow. Nevertheless laminar flow occurs at any Reynolds number near solid boundaries in a thin layer just adjacent to the surface, this layer is usually referred to as the laminar sublayer and it is very important in heat transfer.ĭespite the small thickness of the laminar sublayer (usually much less than 1 percent of the pipe diameter), since it strongly influences the flow in the rest of the pipe. Most industrial flows, especially those in nuclear engineering are turbulent. Since laminar flow is common only in cases in which the flow channel is relatively small, the fluid is moving slowly, and its viscosity is relatively high, laminar flow is not common in industrial processes. On the other hand turbulent flow tends to occur at higher velocities and low viscosity. Laminar flow tends to occur at lower velocities and high viscosity. When a fluid is flowing through a closed channel such as a pipe or between two flat plates, either of two types of flow (laminar flow or turbulent flow) may occur depending on the velocity, viscosity of the fluid and the size of the pipe. The term streamline flow is descriptive of the flow because, in laminar flow, layers of water flowing over one another at different speeds with virtually no mixing between layers, fluid particles move in definite and observable paths or streamlines. Therefore the laminar flow is also referred to as streamline or viscous flow. The fluid flows in parallel layers (with minimal lateral mixing), with no disruption between the layers. In fluid dynamics, laminar flow is characterized by smooth or in regular paths of particles of the fluid, in contrast to turbulent flow, that is characterized by the irregular movement of particles of the fluid.

Laminar flow airfoil