When running CFD simulations with turbulence on, I often need to specify inlet parameters such as the turbulent intensity, turbulent viscosity ratio and/or the turbulent length scale. If these parameters are already known for a given experiment, I have no problems validating experimental data.
But I'm curious to know how these parameters are measured experimentally. How can I directly measure the turbulent kinetic energy and turbulent viscosity from a single experiment? Due to the inherent randomness of turbulence, would I need a lot of repeated experiments to measure it or can it be done in a single experiment?
How is this typically done in practice? Knowing that there is a trade-off between accuracy and cost, what would be a low cost measurement technique that is minimally intrusive to the overall flow while providing accuracy to within an order of magnitude with the fewest number of repeated experiments?