The characteristic length is the maximal length of a straight, untapered, column of the material that can support its own weight. However, for the shorter case of less than 100 km, it reduces to being exponential in the ratio of the height to the characteristic length. The formulas are complicated for the general case where you have to consider the variation of gravity with altitude and centrifugal forces when the tower or elevator may extend thousands of kilometers into space. In section 3 are given formulas for the taper of the tower and for the tower mass. ġ.)Theoretical Range and Trajectory of a Water Jet.Ģ.)An analysis of superhydrophobic turbulent drag reduction mechanisms using direct numerical simulation. In this case simulations and experiments show the drag can be reduced 50%. Recent research has been on materials extremely low on this measure called superhydrophobic. Materials low in this measure are called hydrophobic.
In extending the results of the published report on helium gases to water another effect needs to be taken into account, the stickiness of water on surfaces. Then the natural question that needs to be investigated is how much better would the effect be for microscale and nanoscale piping.
The experimenters noted the effect is much better for small straws as for example coffee stirrers compared to larger straws as used for example sodas. In the case of laminar flows in amateur experimenters, they were produced by using multiple small straws placed within the pipe to produce multiple small streams. The flatness at atomic scales would likely reduce drag and turbulence for macroscale pipes, and therefore also improve the laminar flow effect on exiting the pipe.īut an aspect of how laminar flow streams are produced suggests the nanoscale piping in itself would also improve laminar flow. One, is that the surface is atomically flat, the other is that the channels are at nanoscopic widths. Note this would be important not just for inducing low turbulence and laminar flow for a pipe-free approach but also for the approach using piping to reduce drag and pressure loss.Īctually, there are two effects involved in this report that need to be investigated separately. The reported anomalously-high flow is due to a phenomenon called 'specular surface scattering', which allows a gas to pass through the channel as if it were not there at all. This will not only be important for fundamental studies on molecular flows at nanoscale but also for applications such as desalination and filtration. Published in Nature, this new research shows that the channels allow gas through them at rates that are orders of magnitude faster than expected from theory. Gas flow through tiny atomically flat walls: Atomic-scale ping-pong.
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