TY - JOUR

T1 - Investigation of turbulence production and dissipation due to isotropic and anisotropic roughness components on real surfaces

AU - Ahrens, Jan

AU - Kurth, Sebastian

AU - Cengiz, Kenan

AU - Wein, Lars

AU - Seume, Joerg

N1 - Funding Information: The present work has been carried out in the subprojects B3 within the Collaborative Research Center (CRC) 871 “Regeneration of Complex Capital Goods” which is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – SFB 871/3–119193472. Acknowledgments: The authors thank the North-German Supercomputing Alliance (HLRN) for the HPC resources that have contributed to the development of the research results presented here.

PY - 2022/8/25

Y1 - 2022/8/25

N2 - Roughness generally consists of structures that are either oriented anisotropic in directions tangential to the surface or isotropic, or a superposition of both components. Interactions between the roughness elements exert a significant influence on the fluid mechanical losses. Cost-effective mainten-ance of the functionality of the surfaces of aerodynamically relevant components such as blades requires the quantitative prediction of the influence on the flow, which can be achieved through Reynolds-Averaged-Navier-Stokes Simulations (RANS). An established roughness parameter used to model the influence on the flow is the equivalent sand grain roughness ks. By contrast, the research presented here employs Direct Numerical Simulations (DNS) with Immersed Boundary Method (IBM) of channel flows over anisotropic, isotropic, and superimposed surfaces in order to investi-gate the aerodynamic losses, for example, due to turbulent production and dissipation. The simulation results show that the equivalent sand grain roughness does not correctly predict flow losses from anisotropic and superimposed surfaces, because in reality, the “angle of attack” with respect to the anisotropic structures changes the turbulence due to altered turbulent production and dissipation. A non-linear relationship between the flow resistance and this angle of attack is a result of local changes in pressure gradients.

AB - Roughness generally consists of structures that are either oriented anisotropic in directions tangential to the surface or isotropic, or a superposition of both components. Interactions between the roughness elements exert a significant influence on the fluid mechanical losses. Cost-effective mainten-ance of the functionality of the surfaces of aerodynamically relevant components such as blades requires the quantitative prediction of the influence on the flow, which can be achieved through Reynolds-Averaged-Navier-Stokes Simulations (RANS). An established roughness parameter used to model the influence on the flow is the equivalent sand grain roughness ks. By contrast, the research presented here employs Direct Numerical Simulations (DNS) with Immersed Boundary Method (IBM) of channel flows over anisotropic, isotropic, and superimposed surfaces in order to investi-gate the aerodynamic losses, for example, due to turbulent production and dissipation. The simulation results show that the equivalent sand grain roughness does not correctly predict flow losses from anisotropic and superimposed surfaces, because in reality, the “angle of attack” with respect to the anisotropic structures changes the turbulence due to altered turbulent production and dissipation. A non-linear relationship between the flow resistance and this angle of attack is a result of local changes in pressure gradients.

KW - anisotropic roughness

KW - direct numerical simulation

KW - equivalent sand grain roughness

KW - immersed bounday method

KW - turbulent dissipation

KW - turbulent production

UR - http://www.scopus.com/inward/record.url?scp=85136295118&partnerID=8YFLogxK

U2 - 10.33737/jgpps/151658

DO - 10.33737/jgpps/151658

M3 - Article

VL - 6

SP - 227

EP - 237

JO - Journal of the Global Power and Propulsion Society

JF - Journal of the Global Power and Propulsion Society

ER -