Learning Forum

[Joe_Roxburgh]

So I've made some test simulations of an explosion within a tube that have various locations of venting ports. However, when I plot pressure at points along each of the tubes, they always seem to be the same value despite adding venting locations? My process of finding pressure is as follows:

BINARY_BLSTFOR, History, Segment, Incident Pressure (or effective pressure), plot

However the pressure values don't change for each of the models? When I run them there are different deflection values so I would have assumed pressure would've changed also? Attached are two photos showing pressure, one a tube with no vents and the other a tube with three vents, showing no pressure change differences. Am I doing something wrong when it comes to plotting pressure?

[tslavik]

*LOAD_BLAST_ENHANCED applies blast pressure to the segments of *LOAD_BLAST_SEGMENT. Those pressures are recorded in the BLSTFOR database. The blast pressure for a given segment is computed and applied regardless of other segments subjected to the blast pressure. For example, if the load is applied to Segment A, the pressure on Segment A will always be the same, whether it is the only blast segment in the model or one of many blast segments. That is to say, Segment A knows nothing about the rest of the structure and what else might be loaded in that structure. In your case, the segments of *LOAD_BLAST_SEGMENT are unaware of the holes you created for venting - each receives the blast pressure from the source without regard to the pressures applied to other segments identified in *LOAD_BLAST_SEGMENT. The response and behavior you are seeing is expected for this empirical blast model. nIf you want to include the effects of venting, then you must model the air confined within the tube and probably some of the air surrounding the tube. The most common way to do that is with a multi-material ALE treatment. Other less common approaches would involve *DEFINE_PARTICLE_BLAST, SPH or CESE.n