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Simulation of the cold flow in a combustion
chamber using the THETA-code
R. Kessler
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Content

• Physical problem
• THETA-code
• Grid generation and adaptation strategy
• Results

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Physical problem

• Simulation of flow in model combustion chamber
• Complex geometry, many inlets
• Complex physics, 3-50 additional transport
  equations have to be solved
• Low Mach number flows
• c only the (simple) cold flow simulation are
  presented here

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TAU/THETA-Code (1)
Grid generation
TAU
THETA
Preprocessing
Solver incompressible
Solver compressible
Libraries
Adaptation
Postprocessing
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TAU/THETA-Code (2)

• Numerical algorithm is adapted to low Mach number
  flows
• Modified boundary conditions (wall, inflow,
  outflow)
• Flexible and modular model interface
• User defined functions

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Model geometry

• Combustion chamber with
• Swirl inlet
• 20 Cooling inlets

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Grid generation using CENTAUR (1)

• Standard settings
• Automatic clustering near panel intersections
• No clustering in the interiour
• c easy and fast grid generation
• c reasonable surface grids
• c Adaptation is needed

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Grid generation using CENTAUR (2)

• Coarsest Grid (33099 points)

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Adaptation

• Indicator is based on coarse grid solution
• The coarse grid solution does not (or not
  correctly) reproduce the relevant phenomana
• c no appropriate indicator may be available
• Solution a series of adaptation steps have to
  be applied

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Adaption indicator

• Based on vorticity
• Used sum of neighbouring points (rather than
  difference etc.)
• Indicator is computed by the user-defined
  functions of the solver
• Problems Vorticity is highest at inflow plane
  c a minimum h is essential c a properly
  choosen h-scaling power forces the refinement
  in regions with large cells (typical values
  1.7-2.1)

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Adapted Grids
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Contour plots of Velocity
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Velocity profiles
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Conclusions

• The adaptaion works well for the combustion
  chamber flow
• Using the vorticity as adaptation indicator
  requires
• - the setting of a proper lower limit for the
  edge length
• - an appropriate scaling of the indicator
  with the edge length