TY - GEN A1 - Medina Méndez, Juan Ali A1 - Klein, Marten A1 - Peeters, Jurriaan W. R. A1 - Schmidt, Heiko T1 - Evaluating turbulent channel flows with rough walls : homogeneous roughness parameterization for use in a map-based turbulence model T2 - International journal of heat and fluid flow N2 - This work is focused on modeling the effects of homogeneous roughness on low-order velocity statistics in turbulent channel flows. Hydrodynamic effects due to the roughness are characterized on the basis of volume-averaging theory (VAT) and a discrete roughness element method. This theory exploits the homogeneous character of the roughness in order to reduce the complexity of the flow to its one-dimensional statistics. The formulated VAT-based roughness forcing is best suited for drag dominated surfaces. Turbulence modeling closure is achieved with a map-based turbulence model, the One-Dimensional Turbulence (ODT) model. This avoids the prescription of laws of the wall or other ad-hoc scalings, unlike in more traditional filter-based turbulence models. The modeling framework is applied on selected Reynolds number flows for likewise selected roughness topologies. Results are compared to direct numerical simulation (DNS) data available from the literature. Among others, model results are compared with those of a previously formulated parametric forcing approach (PFA) for roughness drag which involved a costly coefficient calibration linked to the roughness topology model. In ODT, the only calibration process required is the same one involved for the turbulence model parameters, i.e., similar to the ODT model application for smooth-wall flows. Despite all of the inherently implied shortcomings of a 1-D model, some appealing properties of ODT are discussed. Notably, the model is able to predict the roughness function, as well as the wall-normal profile of the Reynolds shear stress across the entire boundary layer thickness. KW - Turbulent channel KW - Roughness KW - ODT KW - Volume-averaging Y1 - 2026 UR - https://www.sciencedirect.com/science/article/pii/S0142727X25003716#d1e18585 U6 - https://doi.org/10.1016/j.ijheatfluidflow.2025.110113 VL - 117, Part B SP - 1 EP - 21 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Tsai, Pei-Yun A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Numerical simulation of turbulent concentric annular pipe flow using one-dimensional turbulence (ODT) : part 1 : momentum transfer T2 - International journal of heat and fluid flow N2 - Turbulent concentric coaxial (annular) pipe flow is numerically investigated using a stochastic one-dimensional turbulence (ODT) model as standalone 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 for a wide (radius ratio ) and a moderate () gap. Making use of the model’s predictive capabilities, radius ratio and Reynolds number effects are investigated, reaching bulk Reynolds numbers as large as . Despite the large 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. KW - Concentric coaxial annulus KW - Spanwise wall curvature KW - Stochastic modeling KW - Turbulence statistics KW - Turbulent boundary layer Y1 - 2026 U6 - https://doi.org/10.1016/j.ijheatfluidflow.2026.110281 SN - 1879-2278 VL - 119 SP - 1 EP - 13 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Joshi, Abhishek A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Non‐negligible influence of forcing mechanisms on turbulent mixing at low Reynolds numbers : a one‐dimensional turbulence study T2 - Proceedings in applied mathematics and mechanics : PAMM N2 - This study presents a numerical investigation of passive scalar mixing in homogeneous isotropic turbulence (HIT). Different volumetric forcing schemes have been used in the literature, but the side effects are rarely discussed, either because these are assumed irrelevant or because it is too costly to conduct such an analysis with a high‐fidelity model. In this study, we have used One‐Dimensional Turbulence (ODT) model to compare forcing schemes at low Reynolds numbers. Our analysis reveals critical flaws in the linear forcing model when applied to ODT. While both schemes exhibit spectral deviations from direct numerical simulation (DNS), the stochastic forcing scheme demonstrates superior dynamic fidelity, better capturing the turbulent energy cascade. In contrast, the linear forcing scheme suffers from a non‐physical energy deficit at large scales and is approximately 10 times more computationally expensive. These artefacts directly impact scalar mixing: The stochastic scheme produces classic, multi‐scale intermittency, whereas linear forcing generates extreme gradients confined only at the dissipative scales. These results demonstrate that the choice of forcing is a critical modelling decision in ODT, leading to fundamentally different model‐dependent artifacts in both turbulence dynamics and scalar mixing statistics, at least in low Reynolds number regimes. KW - Homogeneous isotropic turbulence (HIT) KW - Turbulent mixing KW - Stochastic modeling KW - One-dimensional turbulence KW - Forcing schemes Y1 - 2026 U6 - https://doi.org/https://doi.org/10.1002/pamm.70073 SN - 1617-7061 VL - 26 IS - 1 SP - 1 EP - 11 PB - Wiley CY - Weinheim ER - TY - CHAP A1 - Klein, Marten A1 - Glawe, Christoph A1 - Ehlert, Mark Simon A1 - Medina Méndez, Juan Alí A1 - Schmidt, Heiko ED - Dillmann, Andreas ED - Heller, Gerd ED - Krämer, Ewald ED - Breitsamer, Christian ED - Wagner, Claus ED - Krenkel, Lars T1 - Stochastic modeling of intermittent inflow turbulence in the atmospheric boundary layer T2 - New Results in Numerical and Experimental Fluid Mechanics XV : contributions to the 24th STAB/DGLR Symposium, Regensburg, Germany, 2024 N2 - Wind turbine predesign is challenged by the representation of site-specific wind conditions. A good deal of that challenge lies in the modeling of the inflow turbulence in the atmospheric boundary layer (ABL). A stochastic one-dimensional turbulence (ODT) model is applied to an idealized neutrally stratified ABL and evolves the instantaneous velocity profile with full-scale resolution. The model is able to reproduce the law of the wall consistently after an initial calibration with the surface drag law. Investigating turbulent time series of the horizontal velocity components it is demonstrated that the model generates physically justified intermittency features with increasing turbulence intensity. KW - Atmospheric boundary layer KW - Intermittency KW - Stochastic modeling KW - Turbulent inflow Y1 - 2026 SN - 978-3-032-11115-9 U6 - https://doi.org/10.1007/978-3-032-11115-9_63 SN - 1612-2909 SP - 684 EP - 693 PB - Springer Nature Switzerland CY - Cham ER - TY - CHAP A1 - Polasanapalli, Sai Ravi Gupta A1 - Klein, Marten A1 - Schmidt, Heiko ED - Dillmann, Andreas ED - Heller, Gerd ED - Heller, Ewald ED - Breitsamer, Christian ED - Wagner, Claus ED - Krenkel, Lars T1 - Investigating slip-velocity boundary conditions in turbulent thermal convection using a lattice Boltzmann method T2 - New Results in Numerical and Experimental Fluid Mechanics XV : contributions to the 24th STAB/DGLR Symposium, Regensburg, Germany, 2024 N2 - The present study investigates the impact of various surface boundary conditions on turbulent Rayleigh–Bénard convection within a cubic cavity configuration. Simulations are conducted with a characteristic-based off-lattice Boltzmann method (LBM) solver for mildly turbulent flow of water using a direct numerical simulation (DNS) approach. The current study considers different boundary conditions such as no-slip, free-slip, and Navier-slip conditions on the walls with variations in slip length and wall-slip anisotropy. Results are evaluated through mean isotherms, streamlines, root-mean-square fluctuations, and Nusselt number. The results obtained demonstrate that the selection of wall-boundary conditions has a significant influence on the flow organization within the cavity and on the heat transfer across it. KW - Rayleigh-Bénard convection KW - Navier-slip condition KW - lattice Boltzmann method Y1 - 2026 SN - 978-3-032-11115-9 U6 - https://doi.org/10.1007/978-3-032-11115-9_9 SN - 1612-2909 SP - 90 EP - 100 PB - Springer Nature Switzerland CY - Cham ER - TY - CHAP A1 - Naik Burye, Nishidh Shailesh A1 - Medina Méndez, Juan Alí A1 - Klein, Marten A1 - Schmidt, Heiko ED - Dillmann, Andreas ED - Heller, Gerd ED - Krämer, Ewald ED - Breitsamer, Christian ED - Wagner, Claus ED - Krenkel, Lars T1 - Revisiting near-wall modeling of fully developed turbulent flow in concentric annuli T2 - New Results in Numerical and Experimental Fluid Mechanics XV : contributions to the 24th STAB/DGLR Symposium, Regensburg, Germany, 2024 N2 - We report on a systematic study for Reynolds–Averaged Navier-Stokes (RANS) modeling and simulations of turbulent annular pipe flow. Several simulations were performed using the most readily-available RANS models in the open-source library OpenFOAM. A customized 1-D RANS solver was also developed for ease of analysis. The focus of the study is on the reproduction of the mean velocity profile, its maximum, and maximum radial location, as well as modeled low-order fluctuation statistics. The flow in the annular gap is characterized by a radius ratio of 0.1, and a friction Reynolds number equal to 600 that is based on a mean friction velocity. Deviations from the mean velocity profile are observed for all RANS models investigated when compared with Direct Numerical Simulation (DNS) reference data. The representation of the near-wall outer cylinder flow is better than that of the near-wall inner cylinder flow. KW - Annular pipe flow KW - HRN and LRN wall model formulations KW - Wall function KW - Reynolds-averaged Navier-Stokes (RANS) modeling Y1 - 2026 SN - 978-3-032-11115-9 U6 - https://doi.org/10.1007/978-3-032-11115-9_68 SN - 1612-2909 SP - 737 EP - 747 PB - Springer Nature Switzerland CY - Cham ER -