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 flow streamlines to favorite a better

convective discretization in the 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 unnecessary mesh clustering in fluid area of poor interest (far-field);



Conformance of the surface mesh to the geometric 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 the mesh generator software chosen for generation of the grids.

The software is able to generate meshes with different structures depending on the user

requirements, in a highly flexible environment, which allows high-resolution grids design.

Being mesh generation an inherently geometry dependent problem, the adaptability to the

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

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

method splits the fluid domain into large brick-shapes and forces the direction of grid lines

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

associated and projected onto the geometry.

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

goes from the far-field boundaries to the region closer to the wing-body, ensuring

homogeneity and lower cell density in the borderline regions of fluid domain.

In order to study the numerical sensitivity of the computational analysis, different

grids are evaluated and compared.

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37 Observing all the guidelines points, three structured hexa_mesh configurations has

been shaped on the same geometry by exploiting the multi-blocking method:



CASE 1;



CASE 2;



CASE 3;

The case 1 and case 2 meshes show an H-grid in the outer macro-block with

rectangular faces, see Figures 3-1 and 3-2 . Instead, the last tested grid presents a

semispherical far-field with O-grid configuration externally and a third intermediate

macro-block partitioning again to H-grid type. This configuration provides more control in

the transition from greater outer cells to finer mesh in the inner block.

Figure 3-1 H-grid outer macro-block configuration, far-field rectangular faces

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38

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: side view

The inner block is quite similar in each of the three mesh cases as an O-grid

configuration has been used in this region. It surrounds the wing-body geometry as a sort

of sheath, ensuring a good mesh alignment and a high density in the boundary layer. Edges

and faces are perfectly shaped on the control volume geometry by ensuring a good

conformance of the mesh to the aerodynamic surfaces and the possibility to change the first

layer height and orientation by parameters designed on CATIA environment.

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39

Figure 3-5 Inner macro-block, the sheath

Figure 3-6 Sheath blocks broken view

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40

3.3 Grids sensitivity comparison

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

but show different solutions for blocks development. The differences can be summarized

in terms of numerical features and design choices. In Table 3.1 the main numerical features

in the three cases are listed.

CASE 1

CASE 2

CASE 3

Total nodes

10,441,394

11,239,748

11,703,841

Total elements

10,625,791

11,427,602

11,873,379

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 Wing nodes x direction

82

74

74 Fuselage sheath nodes

41

30

30 Wing sheath nodes

45

45 Min angle

11.6069°

11.3425°

7.22697°

Min determinant

0.394468

0.379471

0.373736

Wall spacing

2.5109∙10

-5

m

2.5109∙10

-5

m

2.5109∙10

-5

m

Macro-blocks

2

3

Table 3-1 Numerical features of grid cases

The different design choices are developed starting from the CASE 1. This is the

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

later showing the improvements provided for CASE 2 and CASE 3.

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41

3.3.1 CASE 1

The reference mesh, CASE 1, presents an H-grid type in the far-field. The mesh lines

start from the nodes on the model in the O-grid region, then they reach the rectangular

faces in the far-field spreading over the central blocks split, bounded by edges black lines

in Figures 3-8, 3-9. However, due to smooth transition and cell skewness requirements, the

spread factor cannot be so high; therefore it remains a denser shadow region (Figures 3-10

and 3-11).

Figure 3-8 CASE 1 far-field blocks view from positive y direction

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42

Figure 3-10 CASE 1 mesh shell distribution in the far-field faces, isometric view

Figure 3-11 CASE 1 shell distribution in the symmetry plane

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

aircraft, while the edges that leave the geometry are almost perpendicular to the surfaces.

Another beneficial characteristic of the O-grid topology is the nodes saving in the external

macroblock region. Indeed all the nodes surrounding the model do not propagate to the

far-field, keeping higher density only in the more interacting regions. In this way, the

computational requirements in terms of times and memory usage are not “wasted” in lesser

interesting regions.

The fuselage, instead, is divided along the x direction in three macroblocks:



Tail region;



Nose region;

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43 O-grid ends respectively around the nose and tail in two vertices lying on the model

surface and two other placed on the intersection between geometry and symmetry plane.

Figure 3-12 Fuselage blocking CASE 1.

Figure 3-13 Fuselage mesh shell.

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44

Figure 3-15 Fuselage tail mesh shell

In the fairing region the edges are linked in shape to the local model geometry and

suitable splits allow the conformance of the mesh to the model.

Figure 3-16 Fuselage fairing mesh shell.

Also, to note is the O-grid which surrounds the root of the wing, ensuring the cells

alignment to the streamlines. The wing root region is very peculiar, because two different

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

sheaths do in an interconnecting belt region.

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45

Figure 3-17 Interconnecting belt isolated

Figure 3-18 Interconnecting belt leading edge view with wing and fuselage fairing

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46

Figure 3-20 Interconnecting belt blocking on leading side

Figure 3-21 Interconnecting belt blocking edges on trailing edge

The O-grid which covers the entire wing is split in 3 sections normal to the y direction.

The first one defines the end of interconnecting belt, while the two others are located at the

kink and tip sections.

One split passes through leading and trailing edges to divide the upper from the lower

wing.

Over the wing, along the spanwise direction, three splits allow a proper node

distribution on the upper and lower surfaces. Here it is very useful for example to control

the chordwise resolution in presence of shock waves development, thus capturing

non-linear phenomena with higher density nodes distribution.

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47

Figure 3-22 Upper view of wing splits

The finite thickness TE has two curves associated to the O-grid blocking edges, while

near the leading edge (LE) the O-grid is associated to the wing surface. The link shape

command provides good association to the deformed wing shape. The number of nodes

propagating out from the TE in the z direction, as listed in Table 3.1, are in excess of five

respect to the nodes entering the LE. This should seem strange, but the difference is due to

the presence of another O-grid leaving backward from tip TE surface. 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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48

Figure 3-24 Tip trailing edge detail of the O-grid type blocking

Figure 3-25 Tip trailing edge O-grid development

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49 The sheath blocking region ends at the tip where shells, similar to the fuselage one,

close the O-grid. The differences between the fuselage and tip sheaths lie in the location of

the nodes near trailing edge (TE). In the tip case, they are associated to the TE instead of

the surface, such as in the fuselage tail or nose or in the tip leading edge side.

Figure 3-27 Tip mesh shells, side view

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50

Figure 3-29 Tip trailing side

Figure 3-30 Tip leading side

3.3.2 CASE 2

The CASE 2 is derived from the previous one, changing some node distribution as

described in Table 3-1, with the differences in the blocking design in these regions:



Far-field split;



Fuselage middle region;



Cockpit.

The splits on the far-field edges are more uniformly spaced than the CASE 1, hence

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

density factor decreasing in the cross shaped central regions with subsequent improvement

of nodes distribution and mesh homogeneity in the far-field macro-block.

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51

Figure 3-31 Symmetry shell CASE 1.

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52 Another variation is in the fuselage middle region, where five splits over the wing are

extended in the fuselage sheat to better control cells quality and shape. Respect to the

CASE 1, the control on the node distribution increases, togheter with control of density

above the wing, where a relevant sonic region could be present.

Figure 3-33 CASE 2 fuselage blocking

The last difference lies on the cockpit. In CASE 2 the block edges are linked in shape

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

variations in the mesh are considered to be effective in the mesh quality improvement and

reducing numerical errors.

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53

3.3.3 CASE 3

The CASE 3 is the final stage of mesh optimization process. Starting from the CASE 2

the following changes have been included:



Three macro blocks configuration;



Semispherical far-field;

The three levels block configuration guarantees a greater nodes density in the

intermediate regions of fluid domain and a nodes saving in the far-field. The inner O-grid

macro-block, the sheath region, remains unchanged and preserves the same function. The

far-field macro-block is now split in two concentric macroblocks: one external comprises

the boundary faces of the fluid domain, the other at an intermediate region separates with

an H-grid configuration the far-field low density requirement from high density one in the

sheath. In this way the possibility of increasing nodes in the inner region of fluid domain

does not affect the nodes distribution in the outer portion, having a controlled transition.

The external macro-block 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 shape

provides more homogeneous cells to the border faces of domain.

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54

Figure 3-36 CASE 3 broken view of the blocking

Figure 3-37 CASE 3 symmetry plane mesh shell

3.4 Replay control

As described in previous sections, the need to test different curved wing planforms to

check the most efficient translates in an automated process design in order to reduce mesh

generation efforts. The replay function in ANSYS ICEM CFD allow to create script files

by performing operations CFD, so recording the equivalent Tcl/Tk commands in a Replay

file. Tcl, which stands for Tool Command Language, is a string-based programming

language, while Tk stands for Toolkit and contains the add-on Tcl commands that allow

graphical interfaces or windows of an application to be made. The user can write and

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55 modify this Replay file, then running the script file the manually written or command

recorded operations can be performed. The advantage of this function lies in the possibility

to analyze many different geometries with very similar meshes and to obtain a model

optimization in reduced times. Geometry and mesh elements are codified by numbers: in

particular, the CAD imported geometry has different numeration only replaced elements.

Therefore, if the elements are not replaced or deleted or added but only modified by

parameters in CATIA, 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 geometric

entities, the second associates the mesh blocking to the geometry and the last modifies the

nodes distribution.

3.4.1 Rename entities script

The exportation process from CATIA output files in .stp format to ICEM environment

represents an initial challenge: geometrical entities in the specification tree are named as

numbers (for example curve1203) attributed from ANSYS software, making very hard to

identify the elements on ICEM control tree. In order to avoid that, it is necessary to group

and rename the elements and that is what the first script does.

The entire file consists of a sequence of commands which generates parts bringing

together selected elements, renaming or deleting parts. Below are listed some examples.

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

curly braces:

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

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

one

:

ic_geo_rename_family PART1_11_1 KINK_TIP_VENTRE_1 0 ic_geo_rename_family PART1_11_1 KINK_TIP_VENTRE_1 1

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56 -Below FUSELAGE_INTERSECTION part is created, with the deletion of empty

parts showed.

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

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. This script works for the CASE3 mesh type

starting from a loaded reference block. The reference block file is designed and adapted to

the wing-body model in the swept wing configuration, that is with zero value to the airfoils

translation parameter defined in CATIA environment.

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57 Actually the first part of the script contributes to complete the grid generation, by

adding an external O-grid in the far-field, and adjusts the far-field shap

e.

ic_hex_ogrid 1 m FUSELAGE FUSOLAGE_OFFSET LATERAL OUTLET INLET TOP BOTTOM 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

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58 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

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

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

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

simply replacing the numerical value, it is possible to move the tip vertices to any desired

distance along the x direction

.

## trasla_tip set trasla_tip 6 ic_undo_group_begin

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 } { 469 } { 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, 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 in any direction.

Moreover, it becomes possible to change the spacing of the first cell normal to the model

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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60

Figure 3-38 Legend of variables in the 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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63

1029 r1 1.05 r2 1.3 lmax 0 default locked

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

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 association of mesh to geometry, 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, as specified in Chapter 2;



A disassociated mesh blocking designed on the reference geometry;



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 in

CATIA, by changing 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 variables 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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