Reynoldsszámra

Reynoldsszámra, also known as the Reynolds number, is a dimensionless quantity in fluid mechanics used to predict flow patterns in different fluid flow situations. It is named after Osborne Reynolds, who introduced it in 1883. The Reynolds number quantifies the ratio of inertial forces to viscous forces within a fluid.

The formula for the Reynolds number is Re = (ρvL)/μ, where ρ is the density of the fluid, v is the flow velocity, L is a characteristic linear dimension (e.g., diameter of a pipe), and μ is the dynamic viscosity of the fluid. Alternatively, it can be expressed as Re = (vL)/ν, where ν is the kinematic viscosity (ν = μ/ρ).

A low Reynolds number indicates that viscous forces are dominant, leading to smooth, laminar flow. In this regime, fluid particles move in orderly layers, with little to no mixing between them. As the Reynolds number increases, inertial forces become more significant. At a critical Reynolds number, the flow transitions from laminar to turbulent.

Turbulent flow is characterized by chaotic, irregular fluid motion with significant mixing. The value of the critical Reynolds number depends on the specific geometry of the flow. For instance, in a pipe, laminar flow typically occurs for Reynolds numbers below approximately 2300, while turbulent flow is observed above approximately 4000. The region between these values is known as the transition regime.

Understanding the Reynolds number is crucial for various engineering applications, including the design of pipelines, aircraft wings, and pumps, as it helps predict energy losses, heat transfer rates, and the overall behavior of fluid flow.