[CIG-SHORT] How to mesh an interior small surface?

[tu xiang]

Hi,
I have constructed an ellipsoid magma chamber in a volume:
# -*- Python -*- (syntax highlighting)
# ----------------------------------------------------------------------
# ----------------------------------------------------------------------
# Set units to SI.
# ----------------------------------------------------------------------
#{Units('si')}
#
# ----------------------------------------------------------------------
# Reset geometry and turn undo off.
# ----------------------------------------------------------------------
reset
undo off
#
# ----------------------------------------------------------------------
# Create magma chamber.
# ----------------------------------------------------------------------
#{chamber_center_x=0.0*m}
#{chamber_center_y=0.0*m}
#{chamber_center_z=-380.0*m}
#{chamber_radius=50.0*m}
#{phi=250}
#{alpha=10}

# Create sphere, then move it to proper location.
create sphere radius {chamber_radius}
volume 1 move x {chamber_center_x} y {chamber_center_y} z {chamber_center_z}
volume 1 scale x 5 y 1 z 1
#rotate volume 1 about z {phi}
body all rotate {alpha} about y
body all rotate {phi} about z

# ----------------------------------------------------------------------
# Create box defining domain.
# ----------------------------------------------------------------------
#{domain_x=3.0*km}
#{domain_y=3.0*km}
#{domain_z=3.0*km}
#{domain_center_x=0.0}
#{domain_center_y=0.0}
#{domain_center_z=-0.5*domain_z}

# Create box, then move it to correct position.
brick x {domain_x} y {domain_y} z {domain_z}
volume 2 move x {domain_center_x} y {domain_center_y} z {domain_center_z}

# ----------------------------------------------------------------------
# Chop cylinder with sphere, then delete sphere.
# ----------------------------------------------------------------------
chop volume 2 with volume 1
delete volume 3

# ----------------------------------------------------------------------
# Imprint and merge all volumes.
# ----------------------------------------------------------------------
merge all

# ----------------------------------------------------------------------
# Compress ID's.
# ----------------------------------------------------------------------
compress ids all

I adopted the following two meshing methods to generate grid mesh.
First:

# ----------------------------------------------------------------------

# Assign sizes to different regions and define meshing scheme.

# ----------------------------------------------------------------------

#{min_size=10.0*m}

#{int_size=20.0*m}


surface 7 size {min_size}

volume all size {int_size}


volume all scheme tetmesh


# ----------------------------------------------------------------------

# Generate the mesh.

# ----------------------------------------------------------------------

mesh surface all

mesh volume all


Second:
${dx=15.0*m}
volume all size {dx}
volume all scheme tetmesh
mesh surface all
mesh volume all

Although I vary the values of min_size, int_size, dx, the trelis reports that:

Poor Quality Tet Generated!

(For example, the shape metric for Tet 1405 is 0.031918 .)

The threshold for a Tet is 0.200000

Deleting invalid mesh.
To retain the invalid mesh next time, set keep invalid mesh on.
ERROR:  Volume 1 (Volume 1) meshing unsuccessful.

I also failed to mesh the volume with  Sizing Functions (Skeleton Sizing).

I would like to know is there any methods to solve the problem?

Hope someone would give me some help.

Best regards,

Tu Xiang
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