CFX 5.5 V5.5.1H
? 2001AEA Technology
3-1
Geometry
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-2
Introduction
? Main Objective,Build a viable domain (B-rep
solids,cutout solids,simple solids)
? B-rep (Boundary Representation) solids are
composed of simple and/or trimmed surfaces
? Simple (Parametric) solids have cubic topology
? Multiple solids must connect at whole faces
? Surface and face congruency and
parameterization must be kept in mind or the
mesh quality will suffer
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-3
Global Model Tolerance
? The Global Model tolerance is the criterion used to
evaluate if there is a gap between two geometric
entities.
? Default tolerance is 0.005.
? This is an absolute geometric value (i.e,1 m cube is
accurate to 0.5 cm).
? A sensible override depends on model size and units.
For roughly unit geometry the default is reasonable.
For large geometry in mm a larger value is
recommended,and vice versa.
? A sensible guide is 1/100 the length of the shortest edge
length.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-4
Geometric Entity,Point
? Geometry is constructed from the following entities:
Point (Cyan).
> CFX-Build creates points automatically when constructing
curves,surfaces,and solids.
N.B,It is not necessary to construct higher order entities
starting with lower order entities.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-5
Geometry Entity,Curve
? Curve (Yellow)
A Curve is a general vector function of a single
parametric variable,It can have many types of
mathematical forms
x1
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-6
Geometry Entity,Parametric Surface
? Parametric surface (Green)
A parametric surface is a general vector function of two
parametric variables,It can have many types of
mathematical forms
Parametric surfaces typically have 4 sides
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-7
? Trimmed surface (Magenta)
A trimmed surface may have any number of outer
bounding edges and can have any number of inner
boundaries (holes)
Geometric Entity,Trimmed Surface
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-8
Geometric Entity,Parametric Solid
? Parametric solid (Blue)
Parametric solids are general vector functions of three
parametric variables
Parametric solids are topologically hexahedral
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-9
Geometric Entity,B-rep Solid
? B-rep solid (White)
General solid defined by a set of parametric or trimmed
surfaces,which completely enclose it
Typically,in CFX-5 the final geometry will be a B-rep solid
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-10
Geometric Entities
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-11
Geometry Form
? Methodology.
ACTION (What do you want to do?).
> Create,Edit,Delete,Transform,..
OBJECT (What do you want to do it to?).
> Point,Curve,Surface,Solid,Coordinate,..
METHOD (How do you want to do it?).
> XYZ,Revolve,Translate,Scale,Extrude,..
? Object options change depending on action.
? Method options change depending on object.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-12
Geometry Creation
? Geometry can be created in several
ways:
CREATE,Construct entities from either
nothing,or existing lower order entities
> create points by specifying coordinates
> create curves by rotating points
TRANSFORM,Construct objects from
existing entities of the same order
> copy/move
> transform surfaces by translating
existing surfaces
> transform solids by rotating existing
solids
EDIT,Modify existing objects
> edit a curve by breaking it into two
curves
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-13
Implicit and Explicit Entities
? Entities are identified as either implicit or explicit by their identifiers
EXPLICIT
> Points,Point 1
> Curves,Curve 12
> Surfaces,Surface 9
> Solids,Solid 1
IMPLICIT
> Points,Solid 1.1.2.1,Surface 1.1.2,Curve 1.1
> Curves,Solid 2.2.2,Surface 2.2
> Surfaces,Solid 1.1
? Selection filter can be used to pick different types of entities
Selection
filter
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-14
Commonly Used Methods
? Commonly Used Methods
POINTS
> Create,XYZ,Extract
CURVES
> Create,Point,Revolve,Project,Extract,Chain
> Edit,Break
SURFACES
> Create,Edge,Curve,Extrude,Trimmed,Extract
> Edit,Break,Sew,Edge Match
? ACTION = Show is the measurement command
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-15
Creating a Point
? Create/Point/XYZ
Creates a point at the specified
coordinate
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-16
Creating a Surface
? Create/Surface/Curve
Create surfaces from a list of 2 or more
curves
Curve 5
Curve 6
Curve 7
Curve 8
Before After
Curve 13
Curve 17
13 17 13
171
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-17
Creating a Surface
? Create/Surface/Edge
Create a new surface by using 4 curves
Can build 3 or 4 sided surfaces
7
8
6
5
Curve 5
Curve 6
Curve 7
Curve 8
Before
7
8
6
5
1
After
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-18
Creating a Chain Curve
? Create/Curve/Chain
Create a composite curve from two or
more existing curves or edges
To create trimmed surfaces,existing
curves must be chained to form a closed
loop
Curve 5
Curve 6
Curve 7
Curve 8
Before After
7
8 6
5
10
9
4
3
11
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-19
Trimmed Surface Construction
? Both planar and trimmed surfaces have the following
characteristics:
N-sided outer boundary
Possibly several inner boundaries (inner loops)
? A trimmed surface may not be trimmed again
? Two types of Trimmed Surfaces can be created:
Planar surface -
Requires an outer loop
and inner loops which
all lie in a 2D plane
3D surface - Possibly
created with an explicit
surface,an outer loop,
inner loops,or a
combination
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-20
Trimmed Surface Construction
? Create construction curves
? Chain curves to form closed outer (and
inner if required) loops
Construction curves
Outer loop
Inner loop
Planar
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-21
Trimmed Surface Construction
? Create trimmed surface from chained curves
Use edge vertices
alters the number of
surfaces edges the
trimmed surfaces has
Planar
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-22
Trimmed Surface Construction
? Create underlying manifold
surface of curvature
Construction curves
Manifold Surface
Surface
? Create construction curves
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-23
Trimmed Surface Construction
? Chain construction curves to
form inner and outer loops as
needed
Outer Loop
Manifold
Surface
Surface
Inner Loop
Use edge vertices
alters the number of
surfaces edges the
trimmed surfaces has
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-24
Trimmed Surface Construction
? The finished trimmed surface
Surface
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-25
B-rep Solid Construction
Curve 5
Curve 6
Curve 8
Create / Solid / B-rep.
? Select the set of surfaces and/or solid faces
which form a closed volume.
? All edges of adjacent surfaces must be
geometrically congruent.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-26
B-rep Solid Construction
? In order to create a B-rep solid,all edges must be
topologically congruent
? There are two situations where this rule can cause
problems
The geometry was not built with this rule in mind
If gaps,larger than the global model tolerance,were
unintentionally created
? Note,When creating geometry,if two points are within
a distance of the global model tolerance,then CFX-
Build only creates the first point and not the second
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-27
Topological Congruency
? When meshing adjacent surfaces or solids,geometry
must be topologically congruent so that coincident
nodes are created along the common boundary
1 2
3
Topologically Incongruent
Adjacent surfaces or solids
must share common edges,
as well as vertices
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-28
Topological Congruency
? Another type of incongruency is shown below,A gap
between a pair of surfaces is greater than the global
model tolerance
? Three recommendations for closing surface gaps:
EDIT/SURFACE/SEW
CREATE/SURFACE/MATCH
EDIT/SURFACE/EDGE MATCH
Gap>Global Model Tolerance
Incongruent Surfaces
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-29
Face Parameterization
? The surface mesher meshes in parametric space then
converts to geometric space
? Poor parameterization can cause high skew that cannot
be fixed with mesh controls
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-30
Face Parameterization
? Break the bounding edges into at least 5 bounding curves
? Chain into one curve
? Create a trimmed surface with the chained outer curve
? For non-planer surface use the manifold surface option
? To fix:
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-31
Face Parameterization
? Another example:
Wrong
Right
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-32
Summary
? Geometric entities
Parametric entities
Trimmed surfaces
B-rep solids
? ACTION/OBJECT/METHOD
Actions,create,transform,edit,delete
Objects,points,curves,surfaces,solids
Methods,XYZ,revolve,extrude,trimmed,B-rep
? Implicit and Explicit entities
? Global model tolerance and topological congruency
? 2001AEA Technology
3-1
Geometry
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-2
Introduction
? Main Objective,Build a viable domain (B-rep
solids,cutout solids,simple solids)
? B-rep (Boundary Representation) solids are
composed of simple and/or trimmed surfaces
? Simple (Parametric) solids have cubic topology
? Multiple solids must connect at whole faces
? Surface and face congruency and
parameterization must be kept in mind or the
mesh quality will suffer
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-3
Global Model Tolerance
? The Global Model tolerance is the criterion used to
evaluate if there is a gap between two geometric
entities.
? Default tolerance is 0.005.
? This is an absolute geometric value (i.e,1 m cube is
accurate to 0.5 cm).
? A sensible override depends on model size and units.
For roughly unit geometry the default is reasonable.
For large geometry in mm a larger value is
recommended,and vice versa.
? A sensible guide is 1/100 the length of the shortest edge
length.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-4
Geometric Entity,Point
? Geometry is constructed from the following entities:
Point (Cyan).
> CFX-Build creates points automatically when constructing
curves,surfaces,and solids.
N.B,It is not necessary to construct higher order entities
starting with lower order entities.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-5
Geometry Entity,Curve
? Curve (Yellow)
A Curve is a general vector function of a single
parametric variable,It can have many types of
mathematical forms
x1
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-6
Geometry Entity,Parametric Surface
? Parametric surface (Green)
A parametric surface is a general vector function of two
parametric variables,It can have many types of
mathematical forms
Parametric surfaces typically have 4 sides
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-7
? Trimmed surface (Magenta)
A trimmed surface may have any number of outer
bounding edges and can have any number of inner
boundaries (holes)
Geometric Entity,Trimmed Surface
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-8
Geometric Entity,Parametric Solid
? Parametric solid (Blue)
Parametric solids are general vector functions of three
parametric variables
Parametric solids are topologically hexahedral
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-9
Geometric Entity,B-rep Solid
? B-rep solid (White)
General solid defined by a set of parametric or trimmed
surfaces,which completely enclose it
Typically,in CFX-5 the final geometry will be a B-rep solid
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-10
Geometric Entities
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-11
Geometry Form
? Methodology.
ACTION (What do you want to do?).
> Create,Edit,Delete,Transform,..
OBJECT (What do you want to do it to?).
> Point,Curve,Surface,Solid,Coordinate,..
METHOD (How do you want to do it?).
> XYZ,Revolve,Translate,Scale,Extrude,..
? Object options change depending on action.
? Method options change depending on object.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-12
Geometry Creation
? Geometry can be created in several
ways:
CREATE,Construct entities from either
nothing,or existing lower order entities
> create points by specifying coordinates
> create curves by rotating points
TRANSFORM,Construct objects from
existing entities of the same order
> copy/move
> transform surfaces by translating
existing surfaces
> transform solids by rotating existing
solids
EDIT,Modify existing objects
> edit a curve by breaking it into two
curves
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-13
Implicit and Explicit Entities
? Entities are identified as either implicit or explicit by their identifiers
EXPLICIT
> Points,Point 1
> Curves,Curve 12
> Surfaces,Surface 9
> Solids,Solid 1
IMPLICIT
> Points,Solid 1.1.2.1,Surface 1.1.2,Curve 1.1
> Curves,Solid 2.2.2,Surface 2.2
> Surfaces,Solid 1.1
? Selection filter can be used to pick different types of entities
Selection
filter
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-14
Commonly Used Methods
? Commonly Used Methods
POINTS
> Create,XYZ,Extract
CURVES
> Create,Point,Revolve,Project,Extract,Chain
> Edit,Break
SURFACES
> Create,Edge,Curve,Extrude,Trimmed,Extract
> Edit,Break,Sew,Edge Match
? ACTION = Show is the measurement command
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-15
Creating a Point
? Create/Point/XYZ
Creates a point at the specified
coordinate
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-16
Creating a Surface
? Create/Surface/Curve
Create surfaces from a list of 2 or more
curves
Curve 5
Curve 6
Curve 7
Curve 8
Before After
Curve 13
Curve 17
13 17 13
171
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-17
Creating a Surface
? Create/Surface/Edge
Create a new surface by using 4 curves
Can build 3 or 4 sided surfaces
7
8
6
5
Curve 5
Curve 6
Curve 7
Curve 8
Before
7
8
6
5
1
After
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-18
Creating a Chain Curve
? Create/Curve/Chain
Create a composite curve from two or
more existing curves or edges
To create trimmed surfaces,existing
curves must be chained to form a closed
loop
Curve 5
Curve 6
Curve 7
Curve 8
Before After
7
8 6
5
10
9
4
3
11
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-19
Trimmed Surface Construction
? Both planar and trimmed surfaces have the following
characteristics:
N-sided outer boundary
Possibly several inner boundaries (inner loops)
? A trimmed surface may not be trimmed again
? Two types of Trimmed Surfaces can be created:
Planar surface -
Requires an outer loop
and inner loops which
all lie in a 2D plane
3D surface - Possibly
created with an explicit
surface,an outer loop,
inner loops,or a
combination
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-20
Trimmed Surface Construction
? Create construction curves
? Chain curves to form closed outer (and
inner if required) loops
Construction curves
Outer loop
Inner loop
Planar
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-21
Trimmed Surface Construction
? Create trimmed surface from chained curves
Use edge vertices
alters the number of
surfaces edges the
trimmed surfaces has
Planar
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-22
Trimmed Surface Construction
? Create underlying manifold
surface of curvature
Construction curves
Manifold Surface
Surface
? Create construction curves
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-23
Trimmed Surface Construction
? Chain construction curves to
form inner and outer loops as
needed
Outer Loop
Manifold
Surface
Surface
Inner Loop
Use edge vertices
alters the number of
surfaces edges the
trimmed surfaces has
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-24
Trimmed Surface Construction
? The finished trimmed surface
Surface
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-25
B-rep Solid Construction
Curve 5
Curve 6
Curve 8
Create / Solid / B-rep.
? Select the set of surfaces and/or solid faces
which form a closed volume.
? All edges of adjacent surfaces must be
geometrically congruent.
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-26
B-rep Solid Construction
? In order to create a B-rep solid,all edges must be
topologically congruent
? There are two situations where this rule can cause
problems
The geometry was not built with this rule in mind
If gaps,larger than the global model tolerance,were
unintentionally created
? Note,When creating geometry,if two points are within
a distance of the global model tolerance,then CFX-
Build only creates the first point and not the second
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-27
Topological Congruency
? When meshing adjacent surfaces or solids,geometry
must be topologically congruent so that coincident
nodes are created along the common boundary
1 2
3
Topologically Incongruent
Adjacent surfaces or solids
must share common edges,
as well as vertices
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-28
Topological Congruency
? Another type of incongruency is shown below,A gap
between a pair of surfaces is greater than the global
model tolerance
? Three recommendations for closing surface gaps:
EDIT/SURFACE/SEW
CREATE/SURFACE/MATCH
EDIT/SURFACE/EDGE MATCH
Gap>Global Model Tolerance
Incongruent Surfaces
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-29
Face Parameterization
? The surface mesher meshes in parametric space then
converts to geometric space
? Poor parameterization can cause high skew that cannot
be fixed with mesh controls
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-30
Face Parameterization
? Break the bounding edges into at least 5 bounding curves
? Chain into one curve
? Create a trimmed surface with the chained outer curve
? For non-planer surface use the manifold surface option
? To fix:
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-31
Face Parameterization
? Another example:
Wrong
Right
CFX 5.5 V5.5.1H
? 2001AEA Technology
3-32
Summary
? Geometric entities
Parametric entities
Trimmed surfaces
B-rep solids
? ACTION/OBJECT/METHOD
Actions,create,transform,edit,delete
Objects,points,curves,surfaces,solids
Methods,XYZ,revolve,extrude,trimmed,B-rep
? Implicit and Explicit entities
? Global model tolerance and topological congruency
