Disentangling the origins of torque enhancement through wall roughness in Taylor–Couette turbulence

@article{Zhu2016DisentanglingTO,
  title={Disentangling the origins of torque enhancement through wall roughness in Taylor–Couette turbulence},
  author={Xiaojue Zhu and Roberto Verzicco and Detlef Lohse},
  journal={Journal of Fluid Mechanics},
  year={2016},
  volume={812},
  pages={279 - 293}
}
Direct numerical simulations (DNS) are performed to analyse the global transport properties of turbulent Taylor–Couette flow with inner rough wall up to Taylor number $Ta=10^{10}$ . The dimensionless torque $Nu_{\unicode[STIX]{x1D714}}$ shows an effective scaling of $Nu_{\unicode[STIX]{x1D714}}\propto Ta^{0.42\pm 0.01}$ , which is steeper than the ultimate regime effective scaling $Nu_{\unicode[STIX]{x1D714}}\propto Ta^{0.38}$ seen for smooth inner and outer walls. It is found that at the inner… 

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