RE: ALE and VF

[l...@schwer.net]

I believe what you are observing is the rebound of the detonation products.

 

As the detonation products initially expand into the air domain they cause a shockwave in the air that propagates ahead of the detonation products.

 

The detonation products expand rapidly and due to cooling of those gases and expansion, decrease in pressure rapidly.

 

At some instant the pressure in the detonation products is equal to the surrounding shocked air pressure and then immediately less than the shocked air pressure. The pressurized shocked air then compresses the detonation products back toward their origin, i.e. a sphere of detonation products being compressed to a “point.”

 

This recompression of the detonation products causes the pressure in the detonation products to increase and at some point exceed the ever decaying surrounding air pressure and the detonation products expand again – think of a vertical spring/mass that is released with the mass expanding the spring past its neutral position and then the mass traveling back toward its release point recompressing the spring.

 

                --len

 

From: Антон Савенков <a.save...@mail.ru>
Sent: Wednesday, May 20, 2026 10:27 PM
To: l...@schwer.net
Subject: ALE and VF

 

Hello! I can't figure out the secondary peaks that form in the explosion. I'm simulating the pressure at a point using VF, and my problem has symmetrical boundary conditions. Ideally, the wave should escape freely into the air, but secondary peaks are appearing out of nowhere, even though there's no reflection, as if it's breaking in a second time. Meanwhile, in other schemes, the secondary peak is often several times larger, as in the figure.This situation also occurs with explicit modeling of an explosive substance. Please help me figure this out! Thanks in advance!  

For example: first and immediately afterwards (you can see a secondary peak after the first wave).  

 

 

Savenkov Anton
т.: 8-916-356-52-01
e.mail: a.save...@mail.ru