arXiv subjects

Pei-Yun Tsai

Publications and source records attributed to Pei-Yun Tsai.

3 recordsLinked to original sources

arXiv2026

Numerical Simulation of Turbulent Concentric Annular Pipe Flow using One-Dimensional Turbulence (ODT): Part 2: Heat Transfer

Turbulent concentric coaxial (annular) pipe flow with passive heat transfer is theoretically analyzed and numerically modeled in an extended parametric range using the stochastic one-dimensional turbulence (ODT) model. ODT provides predictive capabilities by fully resolving viscous, conductive, and turbulent advective transport processes along a representative radial coordinate within a dimensionally reduced and stochastic model formulation. Using a fixed model calibration for moderate and low Prandtl numbers, $Pr=0.71$ and $0.025$, effects of radius ratio, $η=R_{\rm i}/R_{\rm o}$ are investigated up to a highly turbulent flow regime. The analytical expression of the inner wall boundary layer yields a logarithmic law of the wall for the passive temperature. These results suggest that a conventional linear expression is inadequate for representing near-wall low-order statistics in the radial gap, in particular at the cylindrical inner wall. Additionally, the log-law region falls short if curvature and finite Reynolds number effects are not considered. Analytical boundary layer profiles fitting numerical predictions form the basis for heat transfer scaling relations. Heat transfer scalings are parameterized by a Nusselt correlation, which is extended to account for radius ratio effects. The findings demonstrate that the radius ratio has a significant impact on the thermal statistics over the two curved walls and should be considered even at high Reynolds numbers and low Prandtl numbers.

physics.flu-dyn↗

arXiv2025

Numerical Simulation of Turbulent Concentric Annular Pipe Flow using One-Dimensional Turbulence (ODT): Part 1: Momentum Transfer

Turbulent concentric coaxial (annular) pipe flow is numerically investigated using a stochastic one-dimensional turbulence (ODT) model as a stand-alone tool. The dimensionally reduced ODT domain enables fully resolved numerical simulations of the flow across the radial gap between the cylindrical inner wall and the cylindrical outer wall. The model is calibrated with available reference data at low bulk Reynolds number $Re_{D_h} = 8900$ for a wide (radius ratio $η= 0.1$) and a moderate ($η= 0.5$) gap. Making use of the model's predictive capabilities, radius ratio and Reynolds number effects are investigated, reaching bulk Reynolds numbers as large as $Re_{D_h}=10^6$. Despite the large $Re_{D_h}$ values reached, spanwise wall-curvature effects remain sensible in the momentum boundary layer. The effects are more pronounced for larger wall curvature and to leading orders restricted to the convex cylindrical inner wall. Wall-curvature corrections to the law of the wall are obtained for both the viscous and Reynolds-stress dominated regions by fitting analytically derived expressions for the flow profile to the stochastic simulation data, demonstrating physical compatibility with Reynolds-averaged Navier--Stokes flow. Second-order and detailed fluctuation statistics demonstrate the permeating and nonlocal influence of spanwise wall curvature on the turbulent boundary layer. Surrogate model output in terms of conditional eddy event statistics reveals that the disparity between the near-inner and near-outer wall turbulence increases with Reynolds number for small radius ratios, suggesting that annular pipe flows require wall-curvature-aware wall models even at very large Reynolds numbers.

physics.flu-dyn↗

arXiv2023

Stochastic modeling and large-eddy simulation of heated concentric coaxial pipe flow

Turbulent concentric coaxial pipe flows are numerically investigated as canonical problem addressing spanwise curvature effects on heat and momentum transfer that are encountered in various engineering applications. It is demonstrated that the wall-adapting local eddy-viscosity (WALE) model within a large-eddy simulation (LES) framework, without model parameter recalibration, has limited predictive capabilities as signalized by poor representation of wall curvature effects and notable grid dependence. The identified lack in the modeling of radial transport processes is therefore addressed here by utilizing a stochastic one-dimensional turbulence (ODT) model. A standalone ODT formulation for cylindrical geometry is used in order to asses to which extent the predictability can be expected to improve by utilizing an advanced wall-modeling modeling strategy. It is shown that ODT is capable of capturing spanwise curvature and finite Reynolds number effects for fixed adjustable ODT model parameters. Based on the analogy of heat and mass transfer, present results yield new opportunities for modeling turbulent transfer process in chemical, process, and thermal engineering.

physics.flu-dyn↗