Turbulent flow

Turbulent Flow

Turbulent flow is a type of fluid dynamics where the flow is characterized by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time.

Overview

Unlike laminar flow, where fluid travels smoothly in parallel layers, turbulent flow is characterized by swirling eddies and vortices. These chaotic flow patterns can mix the fluid more effectively and increase the shear stress on the boundaries of the fluid.

Characteristics

Turbulent flow is typically characterized by the following features:

• Irregularity: Turbulent flows are always highly irregular. For this reason, they are best studied statistically rather than deterministically.

• Diffusivity: The property of turbulent flow that enhances mixing and increased rates of mass, momentum and energy transports.

• Large Reynolds number: Turbulent flows are often described as high Reynolds number flows. Reynolds number is a dimensionless quantity that describes the ratio of inertial forces to viscous forces.

• Three-dimensionality: Turbulent flows have strong three-dimensional characteristics.

• Vorticity: Turbulent flows are characterized by the presence of coherent structures, such as vortices, streaks, and waves.

Reynolds Number

The Reynolds number (Re) is a dimensionless quantity that is used to predict the onset of turbulence. It is defined as the ratio of inertial forces to viscous forces and is used to determine whether a flow will be laminar or turbulent.

Turbulence Modeling

Turbulence modeling is a procedure to predict turbulent flow using mathematical models. These models can be divided into four types: Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), Reynolds-Averaged Navier-Stokes (RANS) equations, and Detached Eddy Simulation (DES).

Applications

Turbulent flow is found in many scientific and engineering contexts, such as weather forecasting, aerodynamics, and oil pipeline transport. Understanding and predicting turbulent flow is crucial in these fields.

See Also

• Fluid dynamics
• Laminar flow
• Reynolds number
• Turbulence modeling