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A comment on Glass viscosity calculations debunk the myth of flow in medieval windows (2017). Parent comment

Re:Glass viscosity calculations debunk the myth of flow in m... by ThenAsNow on Thursday October 29, 2020 @10:46PM (#24938600)
I can't make sense of your claim. Compression could be done adiabatically, or not, but that doesn't mean it's isothermal or somehow inherently adiabatic. In fact, for it to be isothermal would require the transport away of compression heat, which would be decidedly non-adiabatic.

The parent is correct.

[ Parent | on HN ]
Re:Glass viscosity calculations debunk the myth of flow in m... by pfdietz on Thursday October 29, 2020 @10:59PM (#24938676)
I didn't say the compression was isothermal.

The parent is not correct. Compression occurs at a shock, but this is not heating due (solely) to adiabatic compression. This is clearly seen by considering the case where mach number goes to infinity: in that limit, the fraction of heating due to compression goes to zero (as the gas density remains below some finite limiting value.) What is causing heating is a dissipative process in the shock itself. This dissipative process is more akin to friction than it is to compression.

[ Parent | on HN ]
Re:Glass viscosity calculations debunk the myth of flow in m... by ThenAsNow on Thursday October 29, 2020 @11:19PM (#24938784)
Parent just said "compression heating" which no one takes as a claim of isentropic compression. Shock-driven compression still qualifies as compression.
[ Parent | on HN ]
Re:Glass viscosity calculations debunk the myth of flow in m... by pfdietz on Thursday October 29, 2020 @11:22PM (#24938802)
This has just defined shock heating as compression heating. But as I argued elsewhere, that makes no sense, since the compression at a shock is bounded by a finite maximum value regardless of the mach number.
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Re:Glass viscosity calculations debunk the myth of flow in m... by bollu on Friday October 30, 2020 @06:42AM (#24940906)
This is very interesting, is there a textbook for this?
[ Parent | on HN ]
Re:Glass viscosity calculations debunk the myth of flow in m... by bernulli on Friday October 30, 2020 @06:27PM (#24947465)
I haven't seen any of pfdietz' arguments in a book.

But ThenAsNow already recommended the excellent "Modern Compressible flow" by J.D. Anderson, and, in extension, I can recommend "Hypersonic and High-Temperature Gas Dynamics" by the same author.

[ Parent | on HN ]