3 Mesh generation and replay control 3.1 Grid guidelines

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36

3 Mesh generation and replay control

3.1 Grid guidelines

The generation of the mesh requires many considerations in order to cut down

discretization errors in the solution, as well as to avoid any potential divergence of

residuals. The main guidelines for the grids taken into account in this thesis can be

summarized as follow:

 Extension of fluid domain to about 200 times the wing reference chord.

 Mesh cells aligned as much as possible with streamlines to favorite a better

convective discretization solution of Navier-Stokes equations;

 High nodes density near the walls and hexahedral cells shape in order to better

capture the boundary layer physics;

 Avoid an unnecessary mesh clustering in fluid area of poor interest (far field);

 Conformance of the surface mesh to the geometry model;

 Successful evaluation of mesh quality (by meeting limits in 3x3 determinant,

maximum cell grow rate of 1.2, homogeneous adjacent cells).

3.2 ICEM CFD grids generation

ANSYS ICEM CFD is a software to generate meshes with different structures

depending on the user requirements, in a highly flexible environment, which allows

high-resolution grids. Because mesh generation is an inherently geometry dependent problem,

the adaptability to the complex geometry of an aircraft wing-body model is a requirement.

ICEM CFD is the mesh generator software chosen for generation of the grids.

Observing all the guidelines points, three structured hexa_mesh configurations has

been shaped on the same geometry by exploiting the method of blocking:

 CASE 56;

 CASE 64;

 CASE 73;

Hexa_meshes generation requires the blocks building in a first step, thus a top-down

method splits the geometry into large brick-shapes and shapes the direction of grid lines

with the arrangement of blocks themselves. Block entities (faces, edges, and vertices) are

then projected onto the geometry.

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37 The blocking structure can be thought of two macro-blocks. The first blocking zone,

goes from the far field to the near wing body region, ensuring homogeneity and lower cell

density in the borderline regions of fluid.

The first and the second mesh show an H-grid and a rectangular far field, as shown in

Figures 3.1 and 3.2 . The third tested grids presents an H-grid plus an O-grid configuration

with semispherical far field.

Figure 3-1 H-grid first macro-block configuration with rectangular faces in the far field

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Figure 3-3 H-grid plus O-grid configuration with semispherical far field

Figure 3-4 H-grid plus O-grid configuration with semispherical far field: view of symmetry plane

The second zone surrounds the wing-body geometry such as a sort of sheath, ensuring

a good mesh alignment and a high density in the boundary layer. Edge and faces are

perfectly shaped on the control volume geometry by ensuring a good conformance of the

mesh to the aircraft and the possibility to change the first layer by just replacing some

parameters on CATIA. An o-grid configuration has been used in this region.

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Figure 3-5 second macro_block. The sheath

Figure 3-6 Sheat witout the kink tip blocks

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3.3 Grid comparison

The three cases mesh are generated starting from the same macro blocking structure,

but show different blocks solutions developed from Case 56 to 73. The differences can be

summarized in terms of numerical features and design choices. In Table 3.1 are listed the

main numerical features of three cases.

Case 56

Case 64

Case 73

total nodes

10441394

11239748

11703841

total elements

10625791

11427602

11873379

fuselage nodes

232

261

261 root-kink nodes

134

100

100 kink-tip nodes

93

70

70 trailing edge nodes

21

21 leading edge nodes

16

16 x direction wing nodes

82

74

74 fuselage sheath nodes

41

30

30 wing sheath nodes

45

45 min angle

11,6069°

11,3425°

7,22697°

determinant>

0.394468

0.379471

0.373736

wall spacing

2.5109∙10

-5

m

2.5109∙10

-5

m

2.5109∙10

-5

m

Table 3-1 Numerical features of grid cases

The different design choices are developed starting from the CASE 56. This is the

reason why, the design comparison is carried out, firstly describing the reference mesh and

later showing the improvements provided for CASE 64 and CASE 73.

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3.3.1 CASE 56

The reference mesh CASE 56 presents the following choices.

H grid far field configuration with high density in “x” region. The nodes leaving the

aircraft o-grid region reaches the rectangular far field spreading over the central far field

split. However the spread factor is not so high, therefore the existence of “x” shadow

region (Figure 3.11).

Figure 3-8 CASE 56 far field view block y direction

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Figure 3-10 CASE 56 far field shell

Figure 3-11 CASE 56 symmetry shell

The O-grid sheath region guarantees a good density and homogeneity in the aircraft

nearness and a perpendicular exit direction of mesh edges from the geometry surfaces.

Another benefit is the nodes saving, indeed all the nodes circling the model geometry don’t

reach the far field keeping a high density only on high interest regions.

The fuselage is divided along the z direction in three macroblocks:

 Tail region;

 Nose region;

 Middle or fairing region.

O-grid ends At the nose and tail section with two nodes on the border line of geometry

and two lying down the surface.

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Figure 3-12 Fuselage blocking CASE 56.

Figure 3-13 Fuselage shell.

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Figure 3-15 fuselage tail

In the fairing region the edges link shape and the specific splits allow the conformance

of mesh to the geometry model. Also very interesting is the O-grid which surrounds the

root airfoil section ensuring the cell alignment to the x flux around the wing root.

Figure 3-16 fuselage fairing.

The root wing region it is very peculiar, because two different longitudinal

geometrical elements meet each other (fuselage and wing), such as their respective O-grid

sheaths.

The x axis fuselage O-grid blends with the y axis wing O-grid by means

interconnecting belt region.

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Figure 3-17 Interconnecting belt

Figure 3-18 Interconnecting belt leading side

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Figure 3-20 Interconnecting belt blocking on leading side

Figure 3-21 Interconnecting belt blocking on trailing side

The O-grid which covers the entire wing is split in 3 section along the y direction. The

first one defines the end of interconnecting belt, the next one is located at the kink section

and the last one at the tip.

Along the x direction there are 5 split, three of that allows a proper node distribution

on the upper wing surfaces (it is very useful for example in the region of shock wave

where an higher density allows a better CFD simulation). One is located along the leading

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47 edge and divides, together with the splits on the trailing edge, the wing in the upper and

lower wing.

Figure 3-22 View of wing splits

Two splits, placed on the wing edges, marks the region of leading edge. The number

of nodes, as visible in Table 3.1, are the same of leading edge plus five. The reason of this

difference is due to the O-grid located at the tip side edge which goes until the far field. It

has the following purposes:

 To avoid the degeneration of hexahedral elements into triangular cells;

 To support a particular focus on the vortex detached from tip.

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Figure 3-24 Tip side O-grid blocking

Figure 3-25 Tip side O-grid development

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49 The sheath, surrounding fuselage and wing, ends at the tip where shell similar to the

fuselage one close the O-grid. The differences between fuselage and tip sheath lie on the

location of the nodes near the trailing edge. In the tip case, they are associated to the

trailing edge instead to the surface, such as in the fuselage tail or nose or in the tip leading

edge side.

Figure 3-27 Tip shell

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Figure 3-29 Tip trailing side

Figure 3-30 Tip leading side

3.3.2 CASE 64

The CASE 64 is quite similar to the 56, it is possible to identified differences on:

 Far field split;

 Fuselage middle region;

 Cockpit.

The splits on the far field edge are more widely spaced than the CASE 56, hence the

nodes leaving the airplane surface are spread over a larger area. The major result is the

density factor decreasing in the “X” region and the subsequent improvement of nodes

distribution and mesh homogeneity in the far field macro block.

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Figure 3-31 Symmetry shell CASE 56.

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52 In the middel region the 5 splits over the wing are extended on the fuselage sheat. In

respect to the CASE 56, the control on node distribution increases, togheter with the

possibility of control the density above the wing, where a relevant sonic region could be

present.

Figure 3-33 Fuselage blocking CASE 64

The last difference lies on the cockpit. In CASE 64 the block edges are link shaped

with the geometry edges ensuring a better conformance of the mesh to the model.

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3.3.3 CASE 73

The Case 73 is the final stage of mesh optimization process. Starting from the CASE

64 the following changes have been included:

 Three macro blocks configuration;

 Semispherical far field;

The 3 stages block configuration guarantees a better nodes density in the inner regions

of fluid domain and a nodes saving in the far field. The second macro block with O-grid

remains the same and preserves the same function. The first one is now divided in two

macroblocks. One with H-grid configuration, splits in two side the portion of fluid domain

that before was not separated. In this way the possibility of increasing nodes only in one of

two remaining regions of fluid domain becomes feasible. The external zone of first stage is

characterized by an O-grid structure which save nodes on the far field by trapping a portion

of mesh line in a circular loop. The semispherical far field improve the node distribution

over the outer sheet and the normal approach of the mesh line to the border faces of

domain.

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Figure 3-36 CASE 73 entire blocking

Figure 3-37 CASE 73 symmetry shell

3.4 Replay control

This option helps to create script files by performing operations in ANSYS ICEM

CFD and recording the equivalent Tcl/Tk (Tcl, which stands for Tool Command Language,

is a string-based programming language, Tk stands for Toolkit and contains the add-on Tcl

commands that allow graphical interfaces or windows of an application to be made)

commands in a Replay file. The user can modify or run this Replay file as a script file and

in this way the write or recorder operation are performed. The advantage of this function

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55 lies on the possibility to analyze many different geometries with the same mesh and to

obtain a model optimization in reduced time. Geometry and mesh elements are codified by

numbers which changes only with the elements replacement. Therefore, if the elements are

not replaced or deleted or added but only modified, it is possible to generate a script useful

for different model configurations such as in this thesis.

The Replay scripts involved in the thesis are three, the first one renames the

geometrical entities, while the second associates the mesh to the geometries and the last

modifies the nodes distribution. The files are generated by recording the renaming and the

associating procedure between the original geometry and the created mesh blocking.

3.4.1 Rename entities script

During the exportation process between CATIA and ICEM, the names of geometrical

entities of specification tree changes randomly, generating chaos in the elements

identification

on ICEM control tree. In order to avoid that, it is necessary to group and

rename the elements and that’s what the first script does.

The entire file is compound by a sequence of sections which generates parts bringing

within the selected elements, renames parts and deletes parts. Below are listed some

examples.

ic_undo_group_begin

ic_geo_set_part curve {EDGEE29 EDGEE27 EDGEE28 EDGEE30} SYMMETRY 0 % edges incorporation % ic_geo_set_part surface FACEF1 SYMMETRY 0 % faces incorporation %

ic_geo_set_part point {VERT2028 VERT2017 VERT2006 VERT1995} SYMMETRY 0 % points incorporation % ic_delete_empty_parts

ic_undo_group_end

Here the SYMMETRY is the generated part and the elements included within are listed in the

curly braces.

ic_geo_rename_family PART1_11_1 KINK_TIP_VENTRE_1 0 ic_geo_rename_family PART1_11_1 KINK_TIP_VENTRE_1 1

Renaming of two elements. The first is the original name and the second is the new

one

.

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ic_geo_set_part curve {EDGEE1426 EDGEE1425 EDGEE1427 EDGEE1460 EDGEE1459 EDGEE1458 EDGEE1454 EDGEE1455 EDGEE1456 EDGEE1457 EDGEE1463 EDGEE1462 EDGEE1461 EDGEE1464 EDGEE1453 EDGEE1452 EDGEE1450 EDGEE1451} FUSELAGE_INTERSECTIONS 0

ic_geo_set_part point {VERT3592 VERT3588 VERT3589 VERT3584 VERT3585 VERT3580 VERT3596 VERT3593 VERT3724 VERT3577 VERT3725 VERT3572 VERT3721 VERT3564 VERT3720 VERT3556 VERT3717 VERT3500 VERT3716 VERT3497 VERT3700 VERT3508 VERT3704 VERT3701 VERT3712 VERT3709 VERT3708 VERT3705 VERT3713 VERT3505 VERT3732 VERT3729 VERT3736 VERT3733 VERT3741 VERT3740 VERT3737 VERT3513 VERT3728 VERT3516 VERT3696 VERT3544 VERT3697 VERT3552 VERT3692 VERT3540 VERT3693 VERT3536 VERT3688 VERT3685 VERT3689 VERT3528 VERT3684 VERT3524} FUSELAGE_INTERSECTIONS 0

ic_geo_delete_family PART1_57_1 ic_geo_delete_family PART1_58_1 ic_geo_delete_family PART1_59_1 ic_geo_delete_family PART1_82_1 ic_geo_delete_family PART1_83_1 ic_geo_delete_family PART1_84_1 ic_geo_delete_family PART1_85_1 ic_geo_delete_family PART1_86_1 ic_geo_delete_family PART1_87_1 ic_geo_delete_family PART1_88_1 ic_geo_delete_family PART1_89_1 ic_geo_delete_family PART1_90_1 ic_geo_delete_family PART1_91_1 ic_geo_delete_family PART1_92_1 ic_geo_delete_family PART1_93_1 ic_geo_delete_family PART1_94_1 ic_geo_delete_family PART1_95_1 ic_geo_delete_family PART1_96_1 ic_delete_empty_parts ic_undo_group_end

In this portion of script is visible the automatic erasing of empty parts. Sometimes,

after the incorporation process into other parts, it happens that the original ones remain

empty so they are deleted automatically.

3.4.2 Mesh-geometry association script

The run of this file replies the association procedure between the disassociated

imported blocking and the new geometry. Actually the first part of the scripts contributes

to complete the grid generation, by adding an external O_grid in the far field, and adjusts

the far field shap

e.

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KINK_TIP_DORSO_1 KINK_TIP_VENTRE_1 KINK_TIP_DORSO_2 KINK_TIP_VENTRE_2 KINK_TIP_DORSO_3 KINK_TIP_VENTRE_3 KINK_TIP_VENTRE_4 KINK_TIP_DORSO_4 KINK_TIP_DORSO_5 KINK_TIP_VENTRE_5 KINK_TIP_VENTRE_6 KINK_TIP_DORSO_6 ROOT_KINK_VENTRE_1 ROOT_KINK_DORSO_1 ROOT_KINK_VENTRE_2 ROOT_KINK_DORSO_2 ROOT_KINK_DORSO_3 ROOT_KINK_VENTRE_3 ROOT_KINK_VENTRE_4 ROOT_KINK_DORSO_4 ROOT_KINK_DORSO_5 ROOT_KINK_VENTRE_5 ROOT_KINK_DORSO_6 ROOT_KINK_VENTRE_6 QUASI_RADICE_INTERSECTIONS ROOT_KINK_INTERSECTIONS SYMMETRY UPPER_WING TRAILING_EDGE LOWER_WING FUSELAGE_INTERSECTIONS FUSELAGE_OFFSET_INTERSECTION TIP_OFFSET SCARTI TIP_OFFSET_INTERSECTIONS FLUID -version 50

ic_hex_mark_blocks unmark ic_undo_group_end ic_undo_group_begin ic_geo_new_family FAR ic_boco_set_part_color FAR

ic_point {} FAR pnt.06 VERT2028+(VERT2017-VERT2028)*(0.5) ic_undo_group_end

ic_set_global geo_cad 0.002 toler ic_undo_group_begin

ic_curve arc FAR crv.27 {pnt.23 pnt.06 pnt.08} ic_undo_group_end

ic_curve arc FAR crv.28 {pnt.08 pnt.07 pnt.23} ic_undo_group_end

ic_set_global geo_cad 0.002 toler ic_undo_group_begin

ic_geo_cre_srf_rev FAR srf.00 crv.27 pnt.08 {0 0 1} 0 180 c 1 ic_set_global geo_cad 0.002 toler

ic_set_dormant_pickable point 0 {} ic_set_dormant_pickable curve 0 {} ic_undo_group_end

The new O_grid requires nodes and spacing setup

.

ic_hex_set_mesh 129 39837 n 25 h1 0.0 h2 0.0 r1 2 r2 2 lmax 0 default unlocked ic_undo_group_end

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58 The association starts with the coupling of points, curves and faces to the far field.

Subsequently the vertices are displaced over the semispherical surfaces in order to achieve

the best nodes distribution.

ic_hex_set_edge_projection 69 163 -1 3 0 ic_hex_set_edge_projection 69 87 -1 3 0 ic_hex_set_edge_projection 87 843 -1 3 0 ic_hex_set_edge_projection 87 17391 -1 3 0 ic_hex_set_edge_projection 107 70 -1 3 0 ic_hex_set_edge_projection 107 17427 -1 3 0 ic_hex_set_edge_projection 70 17429 -1 3 0 ic_hex_set_edge_projection 70 166 -1 3 0 ic_hex_set_edge_projection 21 86 -1 1 crv.28 ic_hex_project_to_surface 21 86 ic_hex_set_edge_projection 21 157 -1 1 crv.28 ic_hex_project_to_surface 21 157 ic_hex_set_edge_projection 86 842 -1 1 crv.28 ic_hex_project_to_surface 86 842 ic_hex_set_edge_projection 106 37 -1 1 crv.28 ic_hex_place_node 39820 113.538383 319.779205 134.243317 ic_hex_place_node 39805 113.538383 38.5544967 -117.907745 ic_hex_place_node 39809 113.538383 115.15873 -117.907745 ic_hex_place_node 39811 113.538383 130.475891 -117.907745 ic_hex_place_node 39813 113.538383 319.779205 -117.907745 ic_hex_place_node 39814 113.538445 319.779205 -40.9352951

Before the association of blocking to the aircraft geometry, it is necessary to shift back

the tip vertices of a quantities equal to the tip translation of the curved wing geometry. By

replacing a value in the script it is possible to move the tip vertices of any desired distance

.

## trasla_tip set trasla_tip 6 ic_undo_group_begin

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ic_hex_set_node_location dx $trasla_tip -csys global node_numbers {{ 1214 } { 459 } { 460 } { 1430 } { 246 } { 288 } { 1431 } { 1222 } { 467 } { 468 } { 781 } { 782 } { 697 } { 698 } { 613 } { 614 } { 4 69 } { 470 } { 1727 } { 1728 } { 1438 } { 1756 } { 347 } { 430 } { 783 } { 784 } { 699 } { 700 } { 615 } { 616 } { 348 } { 438 } { 1731 } { 1732 } { 1439 } { 1758 } { …}

ic_undo_group_end

Finally, in order to improve the mesh quality, the link shape of edges is calibrated over

the region of new fluid domain, added to the old one, by the generation of the external

O_grid.

ic_hex_link_shape 348 561 ic_hex_link_shape 561 404 ic_hex_link_shape 479 404 ic_hex_link_shape 638 404 ic_hex_link_shape 625 561 ic_hex_link_shape 615 348 ic_hex_link_shape 469 348

3.4.3 Nodes and spacing setup script

Thanks to this script, it is possible to set up the node along any edge and in whatever

direction. Moreover becomes possible to change the spacing of the first cell over the entire

sheath. In the following file, firstly the variables, then the commands are listed. By

changing the value of a variable the corresponding command modifies the mesh.

1. ## variables setting 2. set node_dy_wing_root_tip_a 10 3. set node_dy_wing_root_tip_b 10 4. set node_dy_wing_root_tip_c 10 5. set node_tip 10 6. set node_dx_wing_lead_trail_a 10 7. set node_dx_wing_lead_trail_b 10 8. set node_dx_wing_lead_trail_c 10 9. set node_dx_wing_lead_trail_d 10 10. set node_dx_wing_lead_trail_e 10 11. set node_dx_wing_lead_trail_f 10

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Figure 3-38 Legend o-grid wing sections along x and z direction 12. set node_dz_fusolage_noogrid_center_out_a 10 13. set node_dz_fusolage_noogrid_center_out_b 10 14. set node_dz_fusolage_noogrid_center_out_c 10 15. set node_dx_fusolage_noogrid_nose_tail_a 10 16. set node_dx_fusolage_noogrid_nose_tail_b 10 17. set node_dx_fusolage_noogrid_nose_tail_c 10 18. set node_dx_fusolage_noogrid_nose_tail_d 10 19. set node_dx_fusolage_noogrid_nose_tail_e 10 20. set node_dx_fusolage_noogrid_nose_tail_f 10 21. set node_dx_fusolage_noogrid_nose_tail_g 10 22. set node_dx_fusolage_noogrid_nose_tail_h 10 23. set node_dx_fusolage_noogrid_nose_tail_i 10 24. set node_dx_fusolage_noogrid_nose_tail_l 10 25. set node_dx_fusolage_noogrid_nose_tail_m 10

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61

26. set node_ogrid_wing 10

27. set spacing_ogrid_wing_firstcell 2.5018e-005 28. set node_ogrid_fuso 10

29. set spacing_ogrid_fuse_firstcell 2.5018e-005 30. set node_far_intblock_upperfus 10 31. set node_far_intblock_lowerfus 10 32. set node_far_intblock_nosefus 10 33. set node_far_intblock_tailfus 10 34. set node_far_extblock 10 35. set node_far_tip_ext 10 36. ic_undo_group_begin

37. ic_hex_set_mesh 426 427 n $node_dy_wing_root_tip_a h1rel 0.0 h2rel linked 395 394 r1 1.2 r2 1.15 lmax 0 default locked

38. ic_undo_group_begin 39. ic_undo_group_end 40. ic_undo_group_end 41. ic_undo_group_begin

42. ic_hex_set_mesh 536 17509 n $node_dy_wing_root_tip_b h1rel linked 536 537 h2rel 0.0376282459867 r1 1.2 r2 1.2 lmax 0 default locked

47. ic_hex_set_mesh 17468 782 n $node_dy_wing_root_tip_c h1rel linked 17509 536 h2rel 439274669.665 r1 1.2 r2 1.3 lmax 0 default locked

52. ic_hex_set_mesh 637 639 n $node_tip h1rel 210116201609.0 h2rel linked 562 439 r1 1.2 r2 1.4 lmax 0 default locked

57. ic_hex_set_mesh 537 429 n $node_dx_wing_lead_trail_a h1rel 0.0548732975559 h2rel 0.0 r1 1.2 r2 1.2 lmax 0 default locked

62. ic_hex_set_mesh 427 537 n $node_dx_wing_lead_trail_b h1rel 0.0 h2rel linked 537 429 r1 1.2 r2 1.2 lmax 0 default locked

63. ic_undo_group_begin 64. ic_undo_group_end

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62

65. ic_undo_group_end 66. ic_undo_group_begin

67. ic_hex_set_mesh 429 803 n $node_dx_wing_lead_trail_c h1rel linked 429 537 h2rel linked 801 393 r1 1.5 r2 1.3 lmax 0 default locked

72. ic_hex_set_mesh 803 719 n $node_dx_wing_lead_trail_d h1rel linked 803 429 h2rel linked 717 633 r1 1.2 r2 1.2 lmax 0 default locked

77. ic_hex_set_mesh 719 635 n $node_dx_wing_lead_trail_e h1rel 0.0 h2rel linked 635 437 r1 1.2 r2 1.2 lmax 0 default locked

82. ic_hex_set_mesh 635 437 n $node_dx_wing_lead_trail_f h1rel linked 633 395 h2rel linked 436 1725 r1 1 r2 1.6 lmax 0 biexponential locked

87. ic_hex_set_mesh 717 27139 n $node_dz_fusolage_noogrid_center_out_a h1rel linked 717 719 h2rel 0.120760606032 r1 1.2 r2 1.2 lmax 0 default locked

92. ic_hex_set_mesh 27139 731 n $node_dz_fusolage_noogrid_center_out_b h1rel linked 27139 717 h2rel 0.0 r1 1.2 r2 1.2 lmax 0 default locked

97. ic_hex_set_mesh 729 731 n $node_dz_fusolage_noogrid_center_out_c h1rel 0.0 h2rel linked 731 27139 r1 1.2 r2 1.2 lmax 0 default locked

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1029 r1 1.05 r2 1.3 lmax 0 default locked 103. ic_undo_group_begin 104. ic_undo_group_end 105. ic_undo_group_end 106. ic_undo_group_begin

107. ic_hex_set_mesh 885 1029 n $node_dx_fusolage_noogrid_nose_tail_b h1 10000000000.0 h2 0.0 r1 1.2 r2 1.2 lmax 0 default locked

112. ic_hex_set_mesh 1029 1101 n $node_dx_fusolage_noogrid_nose_tail_c h1 linked 1029 885 h2 0.0 r1 1.2 r2 1.2 lmax 0 default locked

117. ic_hex_set_mesh 1101 1173 n $node_dx_fusolage_noogrid_nose_tail_d h1 linked 1101 1029 h2 0.0 r1 1.2 r2 1.2 lmax 0 default locked

122. ic_hex_set_mesh 1173 1245 n $node_dx_fusolage_noogrid_nose_tail_e h1 linked 1173 1101 h2 linked 1245 252 r1 1.2 r2 1.2 lmax 0 default locked

127. ic_hex_set_mesh 1245 252 n $node_dx_fusolage_noogrid_nose_tail_f h1 10000000000.0 h2 linked 252 813 r1 1.2 r2 1.2 lmax 0 default locked

132. ic_hex_set_mesh 294 1461 n $node_dx_fusolage_noogrid_nose_tail_g h1 linked 294 645 h2 0.0 r1 1.1 r2 1.2 lmax 0 default locked

137. ic_hex_set_mesh 1461 1533 n $node_dx_fusolage_noogrid_nose_tail_h h1 linked 1461 294 h2 0.0 r1 1.2 r2 1.2 lmax 0 default locked

138. ic_undo_group_begin 139. ic_undo_group_end

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64

142. ic_hex_set_mesh 1533 1605 n $node_dx_fusolage_noogrid_nose_tail_i h1 linked 1533 1461 h2 linked 1571 1643 r1 1.15 r2 1.2 lmax 0 default locked

147. ic_hex_set_mesh 1605 1677 n $node_dx_fusolage_noogrid_nose_tail_l h1 0.0 h2 linked 1677 189 r1 1.2 r2 1.2 lmax 0 default locked

152. ic_hex_set_mesh 1677 189 n $node_dx_fusolage_noogrid_nose_tail_m h1 0.0 h2 linked 188 329 r1 1.2 r2 1.2 lmax 0 default locked

157. ic_hex_set_mesh 610 612 n $node_ogrid_wing h1 0.497157 h2 linked 437 436 r1 1.2 r2 1.2 lmax 0 default locked

162. ic_hex_set_mesh 610 612 n $node_ogrid_wing h1 0.497157 h2 $spacing_ogrid_wing_firstcell r1 1.2 r2 1.2 lmax 0 default locked

167. ic_hex_set_mesh 694 696 n 45 h1rel 3.3284070974 h2rel linked 612 610 r1 1.2 r2 1.2 lmax 0 default locked 168. ic_undo_group_begin

169. ic_undo_group_end 170. ic_undo_group_end 171. ic_undo_group_begin

172. ic_hex_set_mesh 694 696 n 45 h1rel 3.32777918034 h2rel linked 612 610 r1 1.2 r2 1.2 lmax 0 default copy_to_parallel locked

173. ic_undo_group_begin 174. ic_undo_group_end 175. ic_undo_group_begin

176. ic_hex_set_mesh 718 719 n $node_ogrid_fuso h1 0.0 h2 linked 395 394 r1 1.2 r2 1.15 lmax 0 default locked 177. ic_undo_group_begin

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181. ic_hex_set_mesh 718 719 n $node_ogrid_wing h1 0.0 h2 $spacing_ogrid_fuse_firstcell r1 1.2 r2 1.15 lmax 0 default locked

186. ic_hex_set_mesh 634 635 n 30 h1rel 0.0 h2rel linked 395 394 r1 1.2 r2 1.15 lmax 0 default locked 187. ic_undo_group_begin

188. ic_undo_group_end 189. ic_undo_group_end 190. ic_undo_group_begin

191. ic_hex_set_mesh 634 635 n 30 h1rel 0.0 h2rel linked 395 394 r1 1.2 r2 1.15 lmax 0 default copy_to_parallel locked

196. ic_hex_set_mesh 129 39803 n $node_far_intblock_upperfus h1rel linked 129 189 h2rel 0.046098173744 r1 1.2 r2 1.2 lmax 0 default locked

201. ic_hex_set_mesh 39801 159 n $node_far_intblock_lowerfus h1rel 0.0489272696137 h2rel linked 159 188 r1 1.2 r2 1.2 lmax 0 default locked

206. ic_hex_set_mesh 39447 158 n $node_far_intblock_nosefus h1rel 0.0551617618667 h2rel linked 158 182 r1 1.2 r2 1.2 lmax 0 default locked

211. ic_hex_set_mesh 159 39823 n $node_far_intblock_tailfus h1rel linked 159 188 h2rel 0.0443895329481 r1 1.2 r2 1.2 lmax 0 default locked

216. ic_hex_set_mesh 39839 38 n $node_far_extblock h1rel linked 39505 164 h2rel 0.0 r1 1.2 r2 1.2 lmax 0 default locked

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221. ic_hex_set_mesh 39881 39889 n $node_far_tip_ext h1 linked 39881 39870 h2 0.0 r1 1.2 r2 1.2 lmax 0 default locked

222. ic_undo_group_begin 223. ic_undo_group_end 224. ic_undo_group_end

3.4.4 Automation procedure

One of the objectives of this thesis is the implementation of a procedure able to ensure

a fast and easy mesh-geometry association, as the latter changes, and the possibility to

modify the node distribution in an equally fast way. In order to make it possible there are

some requirements to be satisfied:

 A geometry model with particular prerequisites, specified in chapter 2;

 A disassociated mesh blocking shaped on the reference geometry, described in

chapter 3.  The replay script to rename geometrical entities (points, curves, surfaces);

 The replay script for mesh-geometry association (vertex, edges, faces).

 The replay script for node and spacing setup.

The automation procedure starts from the deformation of reference geometries on

CATIA, by modifying the design parameters. Once the deformed model is obtained, it is

imported on ICEM environment as a STP (step) file, together with the non-associated

blocking file. The Load Replay function is exploited, firstly to perform script of renaming

of geometrical entities, later to replying mesh-geometry association.

Actually two versions for the association procedure exist, according to the tip angle

chosen for the deformed model. Indeed for sweep angles higher than 53° degrees, the CAD

program generates some extra-points near the tip modifying the point numbering. This is

the reason why two different replay scripts are needed (hence two different automation

procedure) for angles higher than 53° and for angle between 53° and the original one. The

rest of the procedure remains the same.

The run of the third script is useful only if the user decides to change something in the

nodes distribution. In that case, firstly the value of corresponding variable has to change

and later the replay file can be run. In Figure 3.38 is depicted the flow chart of the

automation process starting from CAD model (aircraft plus control volumes) generation.

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