7/21/2023 0 Comments Laminar flow pipe![]() For laminar flow, you calculate the friction factor by dividing 64 by the Reynold’s number. ![]() This is seen by reviewing the equations to calculate both. Where, for turbulent flows, the primary friction loss is based on the friction between the fluid (our case water) and the pipe. For example:įor laminar flow, the primary friction loss is based on the viscosity of the fluid. Also, the description of the beginning of the turbulent regime is not reliable, because of its aleatory nature.Frictional factor does not directly relate to the friction loss of the pipe. The most interesting part is the central one, the transition regime, in which the friction factor is highly dependent on both the Reynolds number and the relative roughness.Fully turbulent flows are on the right side of the chart (where the curve is flat) and occur at high Reynolds numbers and/or high values of roughness, which perturb the flow.Shown on the left side, the laminar regime is linear and independent of the roughness.The relative roughness is a “local” factor, which indicates the presence of a region that behaves differently because of its proximity to the boundary. The behavior of the flow (described through the friction factor) depends both on the Reynolds number and the relative roughness\(^3\). In fact, other parameters may affect the flow regime locally.Īn example is a flow in a closed pipe, studied analytically through the Moody’s chart (Figure 3). This happens because the Reynolds number is a global estimator of the turbulence and does not characterize the flow locally. It occurs for a range of Reynolds numbers in which laminar and turbulent regimes cohabit in the same flow. The transition regime separates the laminar flow from the turbulent flow. Table 1: Reynolds number and different flow regimes Transition Regime Between Laminar and Turbulent Flows ![]() Problem Configurationįlow around a foil parallel to the main flowįlow around a cylinder whose axis is perpendicular to the main flow The following table shows the correspondence between the Reynolds number and the regime obtained in different problems. Different configurations of the same application may have different critical Reynolds numbers. The Reynolds number is a property of the application.For this reason, it is important to understand the physics of the flow to determine the accurate domain of application and the characteristic length. The Reynolds number describes the global behavior of flow, not its local behavior in large domains, it is possible to have localized turbulent regions that do not extend to the whole domain.It is interesting to notice that the Reynolds number depends both on the material properties of the fluid and the geometrical properties of the application. It is the threshold between the laminar and the turbulent flow. ![]() The mean value of Reynolds number in the transition regime is usually named “Critical Reynolds number”. Beyond that range, the flow becomes fully turbulent. This regime is usually referred to as the “transition regime” and occurs for a specific range of the Reynolds number. When the Reynolds number exceeds a threshold value, semi-developed turbulence occurs in the flow.
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