AUTODYN Euler Blast Solver

Chapter 6 Euler Blast (Ideal Gas) Solver

ANSYS AUTODYN

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February 27, 2009 Inventory #002665

Euler Blast (Ideal Gas) Solver

Overview

Training Manual

• Efficient and accurate solution of blast problems – Multi-dimensional implementation of the explicit FCT (Flux Corrected Transport) formulation of Boris & Book

• Rectangular cells aligned with coordinate directions – Grid can be graded

• Hydrodynamic inviscid flow – Single ideal gas per Part • No void regions • Unused regions can model rigid structures

• In-flow and Out-flow boundaries • Joined Parts • Coupling to Lagrange solvers • Extensive Remapping options ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.

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Euler Blast (Ideal Gas) Solver

Example: Urban Blast

Training Manual

• Detonation and expansion of 1000kg charge initially modelled as a 1D spherical calculation using the AUTODYN 2D multi-material Euler solver – Models the detonation of the explosive accurately – Uses a very high resolution mesh

• Results are remapped into an AUTODYN 3D Ideal Gas Solver mesh as initial conditions – At large expansions, detonation products behave like air, so HE and Air can be combined into a single material (Air)

• Allows assessment of the effects of building confinement on the propagation of blast waves

ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.

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Euler Blast (Ideal Gas) Solver

Example: Urban Blast

Training Manual

1D Spherically Diverging Detonation Wave (AUTODYN 2D Multi-material Euler Solver)

Initial material locations

Final pressure profile

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Final material locations

Final pressure contours

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February 27, 2009 Inventory #002665

Euler Blast (Ideal Gas) Solver

Example: Urban Blast

Training Manual

Urban Blast

ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.

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February 27, 2009 Inventory #002665

Euler Blast (Ideal Gas) Solver

Example: Explosion in a Building

ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.

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Training Manual

February 27, 2009 Inventory #002665

Euler Blast (Ideal Gas) Solver

Example: Explosion in a Building

ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.

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Training Manual

February 27, 2009 Inventory #002665

Euler Blast (Ideal Gas) Solver

Refine and Block Remap

Training Manual

• Refine lets you refine a rectilinear 3D mesh by subdividing existing cells into multiple cells – You specify the number of subdivision to be used in the I, J and K directions – Primarily used for Euler FCT meshes, but can also be used for Lagrange, ALE and MM Euler

• Block Remap performs a fast remap from a refined mesh to the unrefined mesh

Before Refinement ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.

After Refinement

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Euler Blast (Ideal Gas) Solver

Fill Block

Training Manual

• Imports a meshed and filled Euler Ideal Gas Solver Part from an external file – External file includes: • The (I,J,K) range spanned by the data • The (X,Y,Z) dimensions for a single cell (all cells are the same size) Data source: Risk Management Solutions and Sanborn Map Co.

• A flag for each cell: 0 – Cell is part of a structure (unused) 1 – Cell is filled with air 2 – Cell is filled with air and assigned a gauge

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Euler Blast (Ideal Gas) Solver

Staged Blast Calculations

Training Manual

• Fill Block, Refine and Block Remap can be used together to perform large range staged blast calculations

Stage 1

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Stage 2

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Stage 3

February 27, 2009 Inventory #002665

Euler Blast (Ideal Gas) Solver

Multi-dimensional Remapping

Training Manual

• Accuracy can be maximized, by remapping blast solutions from 1D to 2D to 3D

1D (spherical)

2D (axial) 3D ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.

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Euler Blast (Ideal Gas) Solver

Workshop 5: Urban Blast

Training Manual

Goal: Model a Explosive blast in an urban environment

Procedure: Start AUTODYN standalone Set up and solve a problem using 2D Axial Symmetry to model the initial spherical blast Set up a 3D problem to model the urban area of the blast Remap the results from the 2D model into the 3D model as initial conditions Run the 3D solve

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