Turbulencemalli

Turbulencemalli refers to a mathematical model used to describe and predict turbulent flow phenomena. Turbulence is a complex flow regime characterized by chaotic, irregular, and highly fluctuating velocities. Directly simulating all the scales of motion in a turbulent flow is computationally very expensive, especially for engineering applications. Therefore, turbulence models are employed to approximate the effects of turbulence without resolving all the fine details.

The fundamental approach of most turbulence models is to Reynolds-average the Navier-Stokes equations. This process separates the flow variables into a mean component and a fluctuating component. The averaging introduces new unknown terms, known as Reynolds stresses, which represent the effect of the turbulent fluctuations on the mean flow. The core task of a turbulence model is to provide a closure relation for these Reynolds stresses, meaning an equation or set of equations that relates them to the mean flow variables.

Common types of turbulence models include eddy viscosity models, such as the mixing length model, the k-epsilon (k-ε) model, and the k-omega (k-ω) model. These models assume that the turbulent stresses are proportional to the mean strain rate of the flow, with a turbulent viscosity as the proportionality constant. More advanced models, like Reynolds Stress Models (RSMs), aim to model each component of the Reynolds stress tensor individually, offering potentially greater accuracy for complex flows but at a higher computational cost. Large Eddy Simulation (LES) is another approach that directly resolves the larger, energy-containing eddies of the turbulent flow while modeling the smaller, sub-grid scale eddies. Direct Numerical Simulation (DNS) aims to resolve all scales of motion but is currently only feasible for low Reynolds number flows. The choice of turbulence model depends on the specific application, the desired accuracy, and the available computational resources.