Evaluation of dynamic correction of turbulence wall boundary conditions to simulate roughness effect in minichannel with rotating walls

Abstract

Purpose The purpose of this study is an assessment of the existing roughness models to simulate the flow in the narrow gap between corotating and rough disks. A specific configuration of the flow through the gap, which forms a minichannel with variable cross sections and rotating walls, makes it a complex problem and, therefore, worth discussing in more detail. Design/methodology/approach Two roughness models were examined, the first one was based on the wall function modification by application of the shift in the dimensionless velocity profile, and the second one was based on the correction of turbulence parameters at the wall, proposed by Aupoix. Due to the lack of data to validate that specific case, the approach to deal with was selected after a systematic study of reported test cases. It started with a zero-pressure-gradient boundary layer in the flow over a flat plate, continued with flow through minichannels with stationary walls, and finally, focused on the flow between corotating discs, pertaining each time to smooth and rough surfaces. Findings The limitations of the roughness models were highlighted, which make the models not reliable in the application to minichannel flows. It concerns turbulence models, near-wall discretization and roughness approaches. Aupoix’s method to account for roughness was selected, and the influence of minichannel height, mass flow rate, fluid properties and roughness height on the velocity profile between corotating discs in both smooth and rough cases was discussed. Originality/value The originality of this study is the evaluation and validation of different methods to account for the roughness in rotating mini channels, where the protrusions can cover a substantial part of the channel. Flow behavior and performance of different turbulence models were analyzed as well.

Analysis of open channel flow with various layered vegetation using CFD, considering different near-wall treatment methods

“…In spite of a multitude of numerical studies conducted to simulate flow-vegetation interaction and determine the hydrodynamic characteristics of vegetated channels, there are still substantial gaps in our knowledge. One of the crucial parameters in conducting numerical studies in turbulent flow conditions is accurately determining nearwall behaviour (Pahlavanzadeh et al, 2023). This near-wall behaviour plays an extremely critical role in successfully predicting flow characteristics at the interfacial contact surface between the plant and fluid using the roughness coefficient (De Marchis et al, 2016).…”

“…In spite of a multitude of numerical studies conducted to simulate flow–vegetation interaction and determine the hydrodynamic characteristics of vegetated channels, there are still substantial gaps in our knowledge. One of the crucial parameters in conducting numerical studies in turbulent flow conditions is accurately determining near-wall behaviour (Pahlavanzadeh et al. , 2023).…”