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Validation - UNDEX

Introduction

This document presents validation of UNDEX simulations using the software.

Version control

The tests presented in this document are subjected to version control, meaning that the models are run and evaluated prior to release of a new solver. This document is updated in conjunction with official releases of the software.

Validation - UNDEX with quarter and half symmetry

UNDEX with quarter and half symmetry

The validation model consists of a submerged explosive charge surrounded by water. Following detonation, a shock wave propagates through the fluid domain while an expanding gas bubble forms and oscillates due to the surrounding hydrostatic pressure.

The benchmark consists of two equivalent simulations utilizing different symmetry conditions:

  • Quarter symmetry
  • Half symmetry

The physical setup, material definitions, loading conditions, and evaluation criteria are otherwise identical between the two models. The primary verification metric is the timing of the first bubble collapse after detonation. The bubble collapse is checked against an analytical result obtained using the *LOAD_UNDEX command.

General setup

Figure 1 shows the models at initiation. The lighter blue colour in the contour plot corresponds to a higher hydrostatic pressure.

initiation_half initiation_quarter
Figure 1. Models at initiation. At the center of both models the detonation point is shown.

Figure 2 shows the models with the bubble fully expanded. No contour quantities are shown.

bubble_peak_half bubble_peak_quarter
Figure 2. Simulations with the bubble fully expanded.

Results

Quantity Analytical Result [s] Half [s] Deviation [%] Quarter [s] Deviation [%]
Bubble collapse time 0.1355 0.1353 -0.01 0.1349 -0.4
internal_energy_half internal_energy_quarter
Figure 3. Internal energy from the CFD domain. Half symmetry to the left and quarter symmetry to the right.

In Figure 3 the internal energy from the CFD domain is presented. The bubble collapse is measured as the time at which the second energy spike occurs in the model.

Relevant energy levels within the model are also checked for version control.




Tests

This benchmark is associated with 2 tests.