Numberphile: Reynolds Number

The second of three videos I made with Numberphile on Fluid Mechanics. Reynolds Number is used to characterise a fluid flow and can lead to amazing results such as time-travelling fluids and the unsolved mystery of turbulence…

 

You can watch part one on the Navier-Stokes equations here.

Vortex Ring Collisions and Transition to Turbulence

Vortex ring collisions are incredibly beautiful and also incredibly complex. Ryan McKeown of Harvard University explains his amazing experiments visualising colliding vortex rings and their transition to turbulence.

Every year the Gallery of Fluid Motion video contest features the newest and most beautiful research in fluid dynamics. Watch all of the Gallery of Fluid Motion videos here: http://gfm.aps.org.

This video is part of a collaboration between FYFD and the Journal of Fluid Mechanics featuring a series of interviews with researchers from the APS DFD 2017 conference. Sponsored by FYFD, the Journal of Fluid Mechanics, and the UK Fluids Network. Produced by Tom Crawford and Nicole Sharp with assistance from A.J. Fillo.

Featuring:

R. McKeown et al. “The emergence of small scales in vortex ring collisions” https://doi.org/10.1103/APS.DFD.2017….

Physical Review Fluids publication: https://doi.org/10.1103/PhysRevFluids…

Climate Change will increase Turbulence on Flights

We’ve seen many recent extreme weather events – from mudslides in Columbia to flooding in Australia – which scientists say are a consequence of climate change; but it’s not just the weather that is affected. The Earth’s atmosphere is made up of several layers of air which all flow around each other in patterns known as jet streams and an increase in temperature will cause these to speed up. This is bad news for air passengers, including the 1 million people currently airborne at this very instant, because an increase in the speed of the jet streams will cause more turbulence making flying less comfortable and potentially more dangerous. I spoke to atmospheric scientist Paul Williams…

  • Climate change will cause a 59% increase in light turbulence, 94% increase in moderate turbulence, and 140%  increase in severe turbulence.
  • Turbulence is measured on a scale from 1 to 7 where 1 means light turbulence, 3 means moderate, 5 means severe, and 7 means extreme.
  • Light turbulence is a slight strain against the seat belt, moderate turbulence causes unsecured objects to become dislodged and makes walking around difficult, and severe turbulence results in anything that isn’t strapped down being catapulted around the cabin.
  • Turbulence is caused by wind shear – the higher you go up into the atmosphere the windier it gets – and instabilities within these layers of shear generate turbulence.
  • As the atmosphere is heated, the temperature increase causes the jet streams to move faster, creating more wind shear and thus more turbulence.
  • The researchers hope that results such as this will encourage us to think more carefully about our carbon footprint as there are likely many effects of Climate Change that we do not know about.

You can listen to the full interview for the Naked Scientists here.

JFM China Symposia: Beijing

Video highlights from the third and final stop of the JFM China Symposia in Beijing. We were hosted by Tsinghua University with further speakers from Peking University, Xidian University, Beihang University and the Chinese Academy of Sciences.

Ke-Qing Xia describes how water in the ocean travels the entire globe over the course of 1000 years

 

Colm Caulfield explains how to the shape of a hanging chain is related to turbulence

 

Charles Meneveau discusses wind energy and its future as the current cheapest form of energy in the US

 

Photo: Christian Steiness

 

WordPress.com.

Up ↑