Determine the required stochastic-model parameters from physical flow inputs

Determine rigorous estimates of the Taylor microscale \(\lambda_{T}\), aerodynamic roughness length \(z_{0}\), friction velocity \(u_{\tau}\), and boundary-layer thickness \(\delta\) from the given surface geometry and undisturbed flow velocity, rather than relying on scaling relationships and reasonable guesses.

Background

The stochastic framework requires λT\lambda_{T}, z0z_{0}, uτu_{\tau}, and δ\delta as baseline inputs for generating uniform momentum zones, vortices, and the correlated two-dimensional velocity field. The paper notes that these quantities are not generally available a priori for a target rough-wall flow and that existing scaling and empirical relationships provide only approximate values.

A rigorous procedure for inferring these parameters from surface geometry and undisturbed flow conditions would make the generative framework more predictive and reduce its dependence on externally prescribed or fitted quantities.

References

The required modeling parameters \lambda_{T}, z_{0}, u_{\tau}, \delta are not known a priori. Scaling and empirical relationships exist to place reasonable guesses, e.g., elaborating on \lambda_{T}=(15\nu\overline{u{\prime 2}/\epsilon){1/2}, but rigorous estimates based on given surface geometry and undisturbed flow velocity are not strictly possible.

A stochastic modeling framework to generate 2-D rough-wall high-Reynolds-number turbulent boundary layers  (2609.10236 - Ehsani et al., 9 Sep 2026) in Section 6, “Limitations,” item 1