@article{14341,
  abstract     = {Flows through pipes and channels are, in practice, almost always turbulent, and the multiscale eddying motion is responsible for a major part of the encountered friction losses and pumping costs1. Conversely, for pulsatile flows, in particular for aortic blood flow, turbulence levels remain low despite relatively large peak velocities. For aortic blood flow, high turbulence levels are intolerable as they would damage the shear-sensitive endothelial cell layer2,3,4,5. Here we show that turbulence in ordinary pipe flow is diminished if the flow is driven in a pulsatile mode that incorporates all the key features of the cardiac waveform. At Reynolds numbers comparable to those of aortic blood flow, turbulence is largely inhibited, whereas at much higher speeds, the turbulent drag is reduced by more than 25%. This specific operation mode is more efficient when compared with steady driving, which is the present situation for virtually all fluid transport processes ranging from heating circuits to water, gas and oil pipelines.},
  author       = {Scarselli, Davide and Lopez Alonso, Jose M and Varshney, Atul and Hof, Björn},
  issn         = {1476-4687},
  journal      = {Nature},
  number       = {7977},
  pages        = {71--74},
  publisher    = {Springer Nature},
  title        = {{Turbulence suppression by cardiac-cycle-inspired driving of pipe flow}},
  doi          = {10.1038/s41586-023-06399-5},
  volume       = {621},
  year         = {2023},
}

@article{10299,
  abstract     = {Turbulence generally arises in shear flows if velocities and hence, inertial forces are sufficiently large. In striking contrast, viscoelastic fluids can exhibit disordered motion even at vanishing inertia. Intermediate between these cases, a state of chaotic motion, “elastoinertial turbulence” (EIT), has been observed in a narrow Reynolds number interval. We here determine the origin of EIT in experiments and show that characteristic EIT structures can be detected across an unexpectedly wide range of parameters. Close to onset, a pattern of chevron-shaped streaks emerges in qualitative agreement with linear and weakly nonlinear theory. However, in experiments, the dynamics remain weakly chaotic, and the instability can be traced to far lower Reynolds numbers than permitted by theory. For increasing inertia, the flow undergoes a transformation to a wall mode composed of inclined near-wall streaks and shear layers. This mode persists to what is known as the “maximum drag reduction limit,” and overall EIT is found to dominate viscoelastic flows across more than three orders of magnitude in Reynolds number.},
  author       = {Choueiri, George H and Lopez Alonso, Jose M and Varshney, Atul and Sankar, Sarath and Hof, Björn},
  issn         = {1091-6490},
  journal      = {Proceedings of the National Academy of Sciences},
  keywords     = {multidisciplinary, elastoinertial turbulence, viscoelastic flows, elastic instability, drag reduction},
  number       = {45},
  publisher    = {National Academy of Sciences},
  title        = {{Experimental observation of the origin and structure of elastoinertial turbulence}},
  doi          = {10.1073/pnas.2102350118},
  volume       = {118},
  year         = {2021},
}

@article{7932,
  abstract     = {Pulsating flows through tubular geometries are laminar provided that velocities are moderate. This in particular is also believed to apply to cardiovascular flows where inertial forces are typically too low to sustain turbulence. On the other hand, flow instabilities and fluctuating shear stresses are held responsible for a variety of cardiovascular diseases. Here we report a nonlinear instability mechanism for pulsating pipe flow that gives rise to bursts of turbulence at low flow rates. Geometrical distortions of small, yet finite, amplitude are found to excite a state consisting of helical vortices during flow deceleration. The resulting flow pattern grows rapidly in magnitude, breaks down into turbulence, and eventually returns to laminar when the flow accelerates. This scenario causes shear stress fluctuations and flow reversal during each pulsation cycle. Such unsteady conditions can adversely affect blood vessels and have been shown to promote inflammation and dysfunction of the shear stress-sensitive endothelial cell layer.},
  author       = {Xu, Duo and Varshney, Atul and Ma, Xingyu and Song, Baofang and Riedl, Michael and Avila, Marc and Hof, Björn},
  issn         = {10916490},
  journal      = {Proceedings of the National Academy of Sciences of the United States of America},
  number       = {21},
  pages        = {11233--11239},
  publisher    = {National Academy of Sciences},
  title        = {{Nonlinear hydrodynamic instability and turbulence in pulsatile flow}},
  doi          = {10.1073/pnas.1913716117},
  volume       = {117},
  year         = {2020},
}