![]() ℹ️About GitHub Wiki SEE, a search engine enabler for GitHub WikisĪs GitHub blocks most GitHub Wikis from search engines.Experiments on crater formation in the strength regime were conducted using projectiles of various shapes with an aspect ratio of ~ 1, including both solid and hollow interiors. ⚠️ ** Fallback** ⚠️ □️ Page Index for this GitHub Wiki The figures below show (1) a time series of the propagation of the shock wave in air and its decay (in black you see the envelope of the region with 1.1 bar or higher note the reflections from the ground at ~0.1 s) and (2) the maximum overpressure versus the range in comparison with experimental data. PARRAY_N number of arrays : 1Īs we treat the air as an inviscid fluid we can deactivate the deviatoric stress model. The first probe in the array is in the first column of cells ( PARRAY_O = 0) and the probes are spaced two cells apart ( PARRAY_S = 2) until the last probe in the 400th column ( PARRAY_B = 400). We use a single probe array PARRAY_N = 1, vertically located in the bottom row of cells in the mesh PARRAY_V = 1. Here we use an array of Eulerian probes (fixed in space PARRAY_T = EULER) to record the pressure in the air as a function of range. Instead we use a no normal flow (free-slip) boundary condition on all sides. If any boundary is open the atmosphere will slowly flow out of it. so that the centre is at 100-m altitude Shift the bottom of the sphere down from top of mesh (layer) To move the airburst object to the appropriate altitude we offset it downwards. OBJENER specific internal energy : 2.1085023D7īy default, objects are placed above the top 'layer'. This is calculated by dividing the desired airburst energy (1 kTon) by the mass of the air in the object. To do this we need to define the specific internal energy in the object, which is distributed uniformly. The airburst is initiated by depositing internal energy in the object. Set pressure at the top of the mesh appropriateĪs we are using a very low-density material, we must turn off the density cutoff: - Make sure density cut-off is zero to retain all matter For this reason, in this case defines the pressure at the top of the model, not the surface. The atmosphere is treated like any other layer in the model, so the pressure (and density) gradient in the air is computed from the top down. The images, which should be identical to those shown below, will be output to the directory In addition, you will find the pdf document “MaxOverpressureVsRange” that includes a plot of the maximum overpressure as a function of range from the model in comparison with experimental data described by Glasstone and Dolan (1964). Then call python Plotting/pressure_snapshots.py ![]() The probe array is defined in the asteroid input file. To extract the data from the “PROBES”-file in the Airburst example directory. ![]() First you call python Plotting/blast_decay.py The simulation will take several hours, so this should be run in the background./iSALE2D &įrom this directory you can produce images of the simulation to visualise the expansion and decay of the shock wave. Go to the relevant example directory cd /share/examples/Airburst It also demonstrates the use of "probes" to record the state of parcels of material or places in the mesh at every tilmestep during the simulation. The example demonstrates how to set-up iSALE2D for problems involving the static release of energy instead of a kinetic impactor. The simulation ends after 3.8 s when the shock wave nearly has reached the lateral boundary. In the case of an ideal gas, iSALE interprets the specific heat capacity as the specific gas constant Rs. The Tillotson EoS is reduced to the ideal gas equation by setting all Tillotson parameters to zero, except the density at reference pressure (TL_RHO0), the specific heat capacity (TL_CHEAT) and a Tillotson parameter that reduces to the Grüneisen parameter for an ideal gas (TL_THERMA). The air is represented by a material model with an ideal gas equation of state (using a simplified Tillotson model) and an inviscid constitutive model. ![]() The model is a low-resolution model of a 1kT (TNT energy equivalent) airburst at 100m altitude. ![]()
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