VALIDATION AND EVALUATION OF KNOPP ROUGHNESS MODELING FOR TURBULENT FLOW AND HEAT TRANSFER UNDER VARYING ROUGHNESS REGIMES

S. Jeong; S. Han; B.J. Lee

doi:10.6112/kscfe.2025.30.4.019

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Original Article

VALIDATION AND EVALUATION OF KNOPP ROUGHNESS MODELING FOR TURBULENT FLOW AND HEAT TRANSFER UNDER VARYING ROUGHNESS REGIMES 다양한 거칠기 구간에서의 난류 유동 및 열전달에 대한 Knopp 거칠기 모델의 검증 및 평가

31 December 2025. pp. 19-31

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Abstract

Accurate modeling of surface roughness effects is critical for predicting turbulent flow and heat transfer characteristics in practical engineering systems. This study investigates the performance and applicability of the Knopp roughness model coupled with the k-ω SST turbulence model implemented in CRUNCH CFD, validated against two benchmark experimental datasets: the incompressible turbulent pipe flow experiments by Nikuradse and the transcritical heat transfer experiments in supercritical hydrogen flow by Niino. To comprehensively assess the model’s predictive capability, two different near-wall treatment strategies, the wall-function approach and the wall-resolved approach, were systematically applied and compared. For the Nikuradse cases, the wall-function approach demonstrated stable and accurate predictions of velocity profiles and friction factors across hydraulically smooth to fully rough regimes. Conversely, the wall-resolved approach exhibited high accuracy in smooth and fully rough conditions but encountered increased deviations in the transitionally rough regime, attributed to the model’s inherent reliance on the single nondimensional roughness parameter (ks+), thus lacking sensitivity to Reynolds number variations. In the Niino cases involving supercritical hydrogen flows, characterized by significant near-wall property gradients and thermal spikes, the wall-resolved approach consistently yielded accurate predictions of thermal behavior and pressure drop, whereas the wall-function approach showed limitations in accurately capturing thermal spike phenomena under high heat flux conditions. The findings highlight the effectiveness of the Knopp model combined with wall-resolved methods for complex, thermally sensitive conditions, while suggesting further model improvements incorporating additional flow variables to enhance predictions in transitionally rough regimes.

Keywords

Roughness model

Turbulence model

Supercritical flow

Heat transfer

Computational fluid dynamics

키워드

거칠기 모델

난류 모델

초임계 유동

열전달

전산유체역학

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Information

Publisher :Korean Society for Computational Fluids Engineering
Publisher(Ko) :한국전산유체공학회
Journal Title :Journal of Computational Fluids Engineering
Journal Title(Ko) :한국전산유체공학회지
Volume : 30
No :4
Pages :19-31
Received Date : 2025-08-18
Revised Date : 2025-12-02
Accepted Date : 2025-12-04
DOI :https://doi.org/10.6112/kscfe.2025.30.4.019

Journal of Computational Fluids Engineering ISSN:1598-6071(Print) 3022-6252(Online) 한국전산유체공학회지

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