Page 271 - Introduction to Computational Fluid Dynamics

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NV 3 NUMERICAL GRID GENERATION
NV
3
NV 2 NV 2
NE 2
NE 1
NE 2 NE 1
NV 4 NV 4
NV 1 NV 1
a) TYPE 1 b) TYPE 2
Figure 8.10. Construction of triangular elements from a quadrilateral element.
accomplished by a simple routine as follows:
C *** FOR NV (ODD), TYPE1 , FOR NV (EVEN), TYPE2 (IN, JN KNOWN)
NE1=0
DO 1 J=1,JN-1
DO 1 I=1,IN-1
NV=I+(J-1)*IN
NE1=NE1+1
NE2=NE1+1
M=MOD(NV,2)
NV1=NV
NV2=NV1+IN
NV3=NV2+1
NV4=NV1+1
IF(M.EQ.1)THEN
WRITE(6,*)NE1,NV1,NV3,NV2
WRITE(6,*)NE2,NV1,NV4,NV3
ELSE IF(M.EQ.0)THEN
WRITE(6,*)NE1,NV1,NV4,NV2
WRITE(6,*)NE2,NV4,NV3,NV2
ENDIF
NE1=NE2
1 CONTINUE

Figure 8.11 shows the element numbering for the grid shown in Figure 8.9. The
numbering is carried out using the routine given here.

8.5.3 Automatic Grid Generation

Automatic grid generation (AGG) is used to generate elements having desired
properties and desired density (i.e., clustering). For example, when 2D triangular
elements are generated, one may desire that each element has a prespecified area or