News for hackers. Stuff that matters.

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 bernulli on Friday October 30, 2020 @06:23PM (#24947443)
Well, but the gas does not reversibly expand again between the shock and the stagnation point. So clearly it is heating up, even if it were compressed isentropically.

The position is far from incoherent. Temperature rise during isentropic compression is well understood, as is the temperature rise and total pressure loss through a shock.

[ Parent | on HN ]
Re:Glass viscosity calculations debunk the myth of flow in m... by pfdietz on Friday October 30, 2020 @10:39PM (#24948727)
No, it is quite incoherent. Specifically, it fails to even offer what any physical theory must: a quantitative prediction. Compression, in your view, can be allowed to produce variable amounts of heating, for the same change in density. Since you aren't making a quantitative prediction, how is what you are saying even testable?

(The answer is that compression produces a specific amount of heating when it is adiabatic, and additional heating comes from dissipative processes that are occurring alongside the compression, but that are not themselves compression.)

[ Parent | on HN ]