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Adaptive Meshing, Adaptive Physics, Advanced Numerics for Reacting-LES Computations Nathan Mundis ERC, Inc. & AFRL/RQRC 2015 AFRL/RQR Basic Research Review UCLA Jan 20, 2015 VAFTC PA Release# 15012, 16 Jan 2015 Distribution A

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Adaptive Meshing, Adaptive Physics, Advanced Numerics for Reacting-LES Computations

2015 AFRL/RQR Basic Research Review UCLA Jan 20, 2015

Nathan Mundis ERC, Inc. & AFRL/RQRC

VAFTC PA Release# 15012, 16 Jan 2015

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Combustion Dynamics

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Reacting-LES

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Unstructured Mesh

  • Rarely automated
  • Very inefficient
  • Usually limited to 2nd
  • rder
  • Difficult to adapt
  • Good at capturing geom
  • Very good for boundary

layers

Cartesian Mesh

  • Automatic generation
  • Highly efficient
  • High-order accuracy

– Usually 5th or 7th order

  • Amenable to adaption
  • Poor geometry defn
  • Poor for boundary layer
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Dual-Mesh Paradigm

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Combine unstructured near-body with Cartesian off-body Use domain connectivity to exchange data between two mesh systems

CREATE-AV Infrastructure

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Goals

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Develop dual-mesh algorithms for reacting-LES

  • 1. Extend existing automated strand-Cartesian

gridding techniques for internal flows

  • 2. Develop off-body Cartesian adaptive meshing

strategies for turbulent reacting flows

  • 3. Devise adaptive physics approach for combustion
  • 4. Employ optimal numerics for reacting-LES

Project is part of the AFOSR/Test and Evaluation Portfolio

  • Dr. Michael Kendra as Program Officer
  • Dr Terrance Dubreus - AEDC - as tech transition advisor
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Strand Grids and Internal Flows

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Automated volume grid High-order accuracy Enhanced scalability

Strand Grids

Protypical Internal Geometries

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Adaptive Meshing

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Adaptive Algorithms

  • Current methods

– New grid level based

  • n vorticity detection

– Refinement terminated based on Richardson extrapolation

  • Reacting-LES

– Is vorticity suficient? – Use other detection & termination methods? – Heat release, temperature gradients, etc.

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Adaptive Physics

  • Combustion calculations are extremely expensive

– Detailed combustion kinetics

  • Large number of species and reaction steps

– Turbulent combustion closures

  • Linear Eddy Model involves sub-grid solutions
  • Silver Lining

– Detailed chemistry & closures needed only locally – Most of the flowfield has unburnt or burned propellants

  • Devise adaptive physics approach

– Apply detailed models only in local blocks – Block-based solver structure is ideally suited to adaptive physics implementation

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Modular Physics

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Different grid blocks can use different physics Domain connectivity provides data transfer between blocks

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Advanced Numerics

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High-Order Time Schemes

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Phase error for high-

  • rder spatial schemes

without accounting for temporal discretization Phase error for high-order temporal schemes

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Summary

  • New LRIR project awarded in FY15

– Research in technologies for the next-gen CFD solver for reacting LES for rocket propulsion

  • Focus areas

– Dual mesh paradigm for internal flows – Cartesian adaptive meshing for reacting-LES – Adaptive physics for kinetics and turbulent combustion – Optimal numerics for minimal dissipation/discretization

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