Turbulent Kinetic Energy

Turbulent Kinetic Energy (TKE) is the mean kinetic energy per unit mass associated with eddies in turbulent flow. It is a concept used to assess what contribution to buoyancy is brought by turbulence.

Additional recommended knowledge

Daily Sensitivity Test

Safe Weighing Range Ensures Accurate Results

Weighing the right way

The production of TKE equals the sum of mechanical/shear/frictional turbulence plus the buoyancy, and must match with the heat dissipated. Balancing the two, we get an equation and thus can make a budget about the TKE. ^[1]

In Computational Fluid Dynamics (CFD) it is common to hear of the k-epsilon (k-ε) model for turbulence. What is useful for users of CFD is a method by which to calculate reasonable values of turbulence kinetic energy, k and the turbulence dissipation rate, ε.

k = 1.5U²I²

Where I is the initial turbulence intensity [%] U is the initial velocity magnitude

ε = k^{3 / 2} / l

Where l is the turbulence or eddy length scale. This represents the largest eddies in the flow.

I = 0.16Re ^{− 1 / 8}

Where Re is the Reynolds number

l = 0.07L

Where L is the characteristic length. For internal flows this may take the value of the inlet duct (or pipe) width (or diameter) or the hydraulic diameter.

References

1. ^ Baldocchi, D. (2005), Lecture 18, Wind and Turbulence, Part 1, Surface Boundary Layer: Theory and Principles , Ecosystem Science Division, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA: USA.