James W. Deardorff

James W. Deardorff was an atmospheric scientist whose numerical work helped establish large eddy simulation as a way to study turbulence. His 1970 study integrated three-dimensional equations for turbulent channel flow while representing subgrid effects through coefficients tied to resolved deformation. The primary paper identifies his affiliation as the National Center for Atmospheric Research.^[ref]

The calculation used 6720 uniform grid intervals and compared computed flow statistics with experimental measurements. The reported agreement ranged from good to marginal. This made the unresolved-motion model testable against quantities beyond the appearance of an evolving flow: the paper examined eddy structure and the kinetic energy balance as well as statistical averages.^[ref]

An elementary example explains why those separate statistics matter. Two equally likely velocities $U-a$ and $U+a$ have mean $U$ and variance $a^2$. A prediction that always returns $U$ has the correct mean but zero variance. Matching a mean velocity profile alone therefore cannot establish that a model captures turbulent fluctuations or their transport.

Deardorff's study illustrates a productive compromise: compute evolving resolved structures, model the missing influence with a subgrid-scale model, and compare predicted statistics with observations. Finer resolution and a different closure can change the prediction, so agreement remains a property of a specified calculation and test.