Thread by @RamisOrlu, The Fluctuating wall-shear stress (FWSS), a thread. A solid body exposed to [...]

Ramis Örlü

RamisOrlu

The Fluctuating wall-shear stress (FWSS), a thread. A solid body exposed to flow experiences a shear force on its surface due to the viscosity of the fluid. This shear force is of primary importance in aero/hydrodynamic designs since it constitutes a major part of drag.

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The FWSS in canonical wall-bounded flows is known to increase with Reynolds number (Re) due to the influence of outer-layer structures as convincingly shown by Direct Numerical Simulations (DNS) of channel and boundary layer flows

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A recent study by Gubian et al (PRF, 2019, https://doi.org/10.1103/PhysRevFluids.4.074606),">https://doi.org/10.1103/P... using a flush-mounted cavity probe, came to the surprising conclusion that the FSWW becomes Re-independent already at a low Re contrary to DNS studies.

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4/7: In our Comment on their work, Örlü & Schlatter (PRF, 2020, https://journals.aps.org/prfluids/accepted/5b075ScfUc8X7b1110af03c13ce2b26360d432a4d)">https://journals.aps.org/prfluids/... we argue that their observation may be an artifact of insufficient spatial resolution and speculate about other effects that might have been neglected.

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4/7: In our Comment on their work, Örlü & Schlatter (PRF, 2020, https://journals.aps.org/prfluids/... we argue that their observation may be an artifact of insufficient spatial resolution and speculate about other effects that might have been neglected. 4/7

For our #apsdfd2020 talk (E08.15: http://meetings.aps.org/Meeting/DFD20/Session/E08.15)">https://meetings.aps.org/Meeting/D... we replicated their study experimentally & numerically and show that a cavity of only 3 viscous units depth, drastically affects the flow field also above/around the cavity.

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For our #apsdfd2020 talk (E08.15: https://meetings.aps.org/Meeting/D... we replicated their study experimentally & numerically and show that a cavity of only 3 viscous units depth, drastically affects the flow field also above/around the cavity.5/7

Our results show that a hotwire even in a small cavity does not measure the correct flow field, and thus should not be used in these situations. However, even “normal” resolution effects are present, and both together lead to the reported values in the aforementioned study.

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See/watch our slides/talk via: #apsdfd2020 @APSMeetings

https://apsapp.bravuratechnologies.com/APS-WEB/?event=DFD2020#!/aposters/33715661">https://apsapp.bravuratechnologies.com/APS-WEB/...

Do you agree with us?

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See/watch our slides/talk via: #apsdfd2020 @APSMeetings https://apsapp.bravuratechnologies.com/APS-WEB/... Do you agree with us?7/7

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