GambitCreateBoundaryLayer边界层

1、Create Boun dary LayerThe Create Boundary Layeoperation ( blayer create and blayer attach comma nds) defi nes thespac ing of mesh no des in the vici nity of an edge or face. The operati on requires the followi ngspecificati ons.仓U建边界层定义了边或者面邻近的网格节点间距。这个操作要求以下的输入参数。?Defin iti on?Tran siti on patter n

2、?Attachme ntThe Definition specifications include the algorithm type and dimension parameters that determine the shape of the boun dary layer, as well as opti ons that gover n the behavior of boun darylayers in corner regi ons.The Tran siti on patter nspecifies the arra nge璵ent of mesh no des in the

3、 boun dary layer region. TheAttachme nt parameters in clude the en tities towhich the boundary layer is attached and the entities that specify its directio n. Definition设置包括算法类型和尺寸参数来决定边界层的形状控制在角落区域边界层的行为.Transitionpattern设置指定网格节点在边界层区域的安排.Attachment参数包括边界层粘贴的实体和方向.Specify ing the Defin iti onTo def

4、i ne a boun dary layer, you must specify the followi ng parameters:?Algorithm?Dime nsions?Internal con ti nu ity opti on?Corner shapeopti onThe Algorithm specifies the method that GAMBIT uses to determ ine the general shape of theboundary layer. Thedimension parameters specifyfactors such as the num

5、ber of boundary layer rows and growth factor. The Internal con tin uityopti on specifies the behavior of the boun dary layer in regi ons where it overlaps adjoiningboun dary layers. TheCorner shapeoption deter璵ines the shape of the mesh in regions surroundingCorneror Reversaverti璫es that connect edg

6、es to which boundary layers are attached.Internalcontinuity选项指定在相邻边界层的overlaps区域边界层的行为。Corner shape决定在连接边界层attach到的边的corner或者Reversal顶点处周围区域的网格形状。Specifying the AlgorithmThe Algorithm specification determines the method that GAMBIT uses to establish the heightsof the elements in the first row of the

7、 boundary layer and compute the heights of all succeedingrows. GAMBITprovides the follow璱ng algorithm types. Algorithm参数决定GAMBIT用来确定第一行边 界层的高度和所有行的高度。?Uniformassigns a uniform height to all first-row elements and uses a universal growthfactor for succeeding rows第一行所有的元素使用一样的高度，并且对于后面的行使用一样的增长因子?Aspe

8、ct ratio (first)computes first-row element heights as a fixed per璫entage of themesh element widths on the attachment entity and uses a universal growth factor计算第一行元素的高度作为一个在attachment实体上网格元素宽度的固定比例来并且使用一个全局增长因 子。?Aspect ratio (last)assigns a uniform height to all first-row elements and uses individu

9、algrowth factors at each attachment-entity mesh node to determine the size ofsucceeding rows第一行元素使用相同的高度并且在每个attachment实体网格结点处使用各自的增长因子来决 定以后各行的size。Figure 3-1, Figure 3-2, and Figure 3-3 illustrate the differences between the Uniform, Aspectratio (firs,t)and Aspect ratio (lasta)lgorithms for a 2-D

10、boundary layer attached to one edge of asquare planar face. In each figure, the attachment edge meshincludes five intervals and agrading ratio of 1.25, and the boundary layer includes five rows.每幅图中，attachment边网个有5个interval并且grading ratio是1.25，边界层有5行。Figure 3-2: Aspect ratio (firslt)oun dary layer a

11、lgorithm (2-D)Figure 3-1:Uni formb oun dary layer algorithm (2-D)Figure 3-3: Aspect ratio (last)o un dary layer algorithm (2-D)For the Uni formb oun dary layer (Figure 3-1), the first row exhibits a uniform height across thespa n of the attachme nt edge, and the growth factor is con sta nt; therefor

12、e, each succeed ingrow of eleme nts also exhibits a uniform height. For theAspect ratio (firslt)oun dary layer(Figure3-2), the first-row heights vary in proportion to the edge mesh interval lengths. Consequently,the first row of the boundary layer grows thicker from left to right across the edge, be

13、cause theedge mesh in tervallen gthsin crease from left to right.For the Aspect ratio (last) oun dary layer (Figure3-3), the first row exhibits a uniform height across the span of the attachme nt edge, but thegrowth factor varies in proporti on to the edge mesh in tervalwidths. Con seque ntly, thesu

14、cceed ing rows grow thicker fromleft to right across the edge.对于Uniform边界层，第一行在整个attachment边上高度相同，并且增长因子为常数，因此，每行元素同样展示出 相同的高度。对于Aspect ratio(first)边界层，第一行的高度变化和边网格in terval长度成正比，结果，边界层第一行高度从左到右逐渐变厚，因为网格interval长度从左到右增加。对于Aspectiraito(last)边界层，第一行高度一样，但增长因子同边网格in terval宽度成正比，结果，随后的各行从左到右 逐渐变厚。NOTE:

15、If the attachme nt edge show n in Figure 3-1, Figure 3-2, and Figure 3-3, above, weregraded uniformly ( Ratio = 1), all three Algorithm options would produce boun dary layers ofuniform height across the spa n of theedge.注意，如果attachment边被均匀的grade，则左右的算法将会产生均匀 高度的边界层。If you attach a boundary layer to

16、a face (rather than an edge), GAMBIT applies the definitionalgorithm along the boundaries of the attachment face. For example, Figure 3-4 shows an Aspectratio (firstt)oun dary layer attached to one face of a cube. In this case, the boun dary edges of theattach璵ent face have been premeshed using five

17、 intervals and a grading ratio of 1.25.如果你是attach到一个面，GAMBIT应用这个算法沿着attachment面的边界。Figure 3-4:Aspect ratio (firslt)oun dary layer algorithm (3-D)Whe n attach ing a boun dary layer to a face, care must be take n to en sure that the boun darylayeris not disc ontinu ousat any vertices on the facebounda

18、ry. In Figure 3-4, above, the boundary edges of the attachment face are graded such thatthe mesh interval widths on either side of any corner vertex are equal to each other. As a result,the 3-D boun dary layer is continuous at all four corners of the attachment face. In Figure 3-5, theface boundary

19、edges are graded such that edge meshintervallengths differon either side of three of the four corner vertices (b, c, and d).Con seque ntly, the boun dary layer exhibits disc ontin uities at thosevertices.当attaching个边界层到一个面时， 必须保证边界层在这个面边界 的任何vertice处连续。如图3-4，attachment面的边界被graded使得在任何corner vertex的任

20、何一边的网格宽度都相等。结果，3维边界层在attachment面的四个corners处连续。Specifyi ng the Dime nsionsTo specify the dime nsions of any boun dary layer, you must in put three parameters that defi neits characteristics. The parameters to be specified vary accord ing to algorithm as follows.Uniform AlgorithmThe Un iformalgorithm

21、(see Figure 3-6) defi niti on parameters are as follows.?First row (a)?Growth factor (b/a)?RowsFigure 3-5: Effect of disc on ti nu ous grad ing at face boun dary verticesFigure 3-6: Boun dary layer dime nsionsUni formalgorithmThe First row (a)value specifies the height of the first row (a)that is,th

22、e absolute distanee between the entity to which the boundary layer is attached and the firstrow of mesh no des in the boun dary layer. (NOTE:_For the Uni formalgorithm, the first-row height,a, is un iform across thebou ndary layer.)First row (a决定第一行的高度，即attachec实体到边界层第一行网格节点的距离。The Growth factor (b/

23、a)value ( G represe nts the ratiowhere b is the dista nee betwee n the first and sec ond rows anda is theheight of the first row. The height of any row in the boundary layer (other than the first row) isequal to the height of the previous row times the Growth factor (b/a)value.边界层中任何一行的高度等于前一行的高度乘以G

24、The Rows value specifies the total nu mber of rows to be in cluded in the boun dary layer.NOTE: When youspecify the First row (a) Growth factor (b/a) and Rows values, GAMBITcomputes the total depth (D of the boun dary layer and displaysthe value in the non-editableDepth (D)field on the Create Boun d

25、ary Layerform.当你确定好上面三个参数值后，GAMBITS动计算边界层总的深度并且显 示在不可编辑的Depth (D)处。Aspect ratio (first) AlgorithmThe Aspect ratio (first)lgorithm (see Figure 3-7) defi niti on parameters are as follows.Db0?First perce nt (a/w)?Growth factor (b/a)?RowsFigure 3-7: Boun dary layer dime nsionsAspect ratio (first)lgorit

26、hmThe First perce nt (a/w)value specifies the height of any first row boun darylayer node (碍)as a percentage of mesh interval width at the associated node on the attach璵ent en tity. For in terior no des on the attachme nt entity, the general specification of first-rowheight can be expressed as First

27、 percent (a/w值确定第一行边界层节点ai的高度为在attachmen实体上相 应节点处网格宽度的百分比。对于内部节点，总的第一行高度的参数确定如下：where is the height of the firstrow at node i , F is the First percent (a/w)value, andand讥are the widths of the attachme nt-e ntity meshintervals on either side of nodei .For exterior no des on the attachme nt en tity (f

28、or example, no des located at edge en dpo in ts)the first-row heights can be expressed as夕卜部节点，如边的端点确定如下。andwhere % and are the heights of the first rows at the exterior no des.The Growth factor (b/a)value ( G represe nts the ratio(7 =切仏where - is the distanee between the first and second rows at ed

29、ge meshnode i and is the height of the first row at node i. (NOTE: For the Aspect ratio (first)algorithm, theGrowth factor (b/a)value is constant across the bound璦ry layer.) The height of any boundarylayer row at a given edge node is equal to the height of the preced璱ng row at that node timesthe gro

30、wth factor, G注意，G为常数。任何边界层在指定边界点处的高度等于前一行在 那个节点的高度乘以GThe Rows value specifies the total nu mber of rows to be in cluded in the boun dary layer.NOTE: When you specify the First percent(a/w,Growth factor (b/a)and Rows values, GAMBITcomputes the last perce nt value for the boun dary layer and displays

31、the value in thenon-editableLast perce nt (c/w)field on theCreate Boundary Layeiform. The Last percent (c/w)value represents the height of the boun darylayer top row at any give n node relative to the corresp onding mesh in terval widths on theattachme nt en tity. TheLastperce nt (c/w)value can be c

32、omputed from注意：当你指定了以上三个参数后，GAMBI将计算边界层的last percent值并且显示在不可编辑的Last percent(c/w)处，它代表了边界层顶层高度在任何给定节点出相对于相应网格宽度的值。L =阳 4】where F and L are theFirst percent (a/w)and Last percent (c/w)values, respect璱vely, Gis the Growth factor (b/a)value, and R is the number ofRows.Aspect ratio (last) AlgorithmThe As

33、pect ratio (last)lgorithm (see Figure 3-8) defi niti on parameters are as follows.First row (a)RowsLast perce nt (c/w)Figure 3-8: Boun dary layer dime nsionsAspect ratio (lasgigorithmThe First row (a)value specifies the height of the first row (a)that is,the absolute distanee between the entity to w

34、hich the boundary layer is attached and the firstrow of mesh no des in the boun dary layer. (NOTE:_For the Aspect ratio (lasOjlgorithm, the first-row height,a, is uniformacross the boun dary layer.)The Rows value specifies the total nu mber of rows to be in cluded in the boun dary layer.The Last per

35、ce nt (c/w)value specifies the height of the boun dary layer top row at any noderelative to the corresponding meshinterval widths on the attachme nt en tity.At any in teriormesh node on the attachme nt en tity (forexample, the en dpo ints of an attachme nt edge), the relati on ship betwee nthe top r

36、ow height (), the Last percent (c/w)/alue ( L), and the meshin terval widths (w) can be expressed as Last perce nt (c/w)值指定了边界层在任何界点处的顶行高度相对于attachment实体的网格宽度。在任何内部节点处，关系如下：where叫andJare the widths of the attachment-entity mesh intervals on either side of node i .NOTE: For the Aspect ratio (laslgori

37、thm, the growth factor varies across the boun dary layerand is computed at each mesh node on the attachme nt en tity.For mesh no des that arein terior to the en tity,the growth factorat any node i can be expressed as注意，对于Aspect ratio (last)增长因 子沿着边界层变化并且通过在attachment实体上的每个网格节点计算。内部节 点，计算如下，where : i

38、s the node-specific growth factor andBecause the growth factor is not con sta nt across the boun dary layer,GAMBIT does not display the Growth factor (b/a)field on theCreate Bou ndaryR is the nu mber ofRowsLayer form.Specifyi ng Internal Con ti nu ityWheryou attach a boundary layer to a face that co

39、nstitutes part of a volume, GAMBIT impri nts theboun dary layer on all adjoi ning faces that are also part of the volume (see Figure 3-9(a). If you attachboun dary layers to two or more adjoi ning faces of a volume, the boun dary-layer impri nts overlap onany faces that are commomeighbors to the fac

40、es to (see Figure 3-9(b).当你attach一个边界层到一个组成volume的一部分的面时，GAMBIT同样将边界层印在其他所有和这个面相邻的组成volume部分的面上。如果你attach一个边界层到两个或者更多的一个volume的面上，边界层将会在所有的公共的相邻面上印重叠。Figure 3-9: Boun dary-layer impri nts (with shaded attachme nt faces)The Internal continuityoption on the Create Boundary Layeform determines the mann

41、er in whichGAMBITmprints boundary layers on adjoining faces as well as the mesh pattern in regi ons of impri ntoverlap.In ternal con ti nuity选项决定了GAMBIT各边界层印在相邻面上的方式以及重叠区域的网格方式。?If you do not select theIn ternal contin uityopti on, GAMBIT impri ntsboun dary layers on adjoining faces in the manner de

42、scribed above (Figure 3-10(a).如果没有选择此选项，如图3-10bItnpnnt overlapsAttachment feceAttachment facesBoundary layer impruitsIf you select the In ternal continuity opti on, GAMBIT modifies the mesh patter ns in theoverlap regi ons such that the impri nts are dovetailed together (see Figure 3-10(b).如果你选择了此选项

43、，GAMBITS修改网格样式使得重叠区域吻合。如图3-10aThe effect of the Internal contin uityopti on depe nds, in part, on the values of two GAMBIT defaultvariables:In ternal c on tiuity选项部分的决定与GAMBIT勺两个默认变量值?MESH.BLAYER.ANGLE_SMOOTH_FACTOR?MESH.BLAYER.ADJUST_EDGE_BL_HEIGHTThe ANGLE_SMOOTH_FACTOR default variable specifies

44、whether or not the boun dary-layer an gli ngin the corner regi on is smoothed out across the adjace nt edges. The ADJUST_EDGE_BL_HEIGHTdefault variable specifies whether or not GAMBIT adjusts the boun dary layer heights along the adjacent edges to maintain con sta nt heights with respect to the edge

45、s.Each default variable can take the values 0 (off) and 1 (on).ANGLE_SMOOTH_FAC决定在corner区域的边界层是否沿着相邻变被smooth,ADJUST_EDGE_BL_HEIGH定GAMBIT1否调整沿着相邻边的边界层高度来保持 相应与边的常高度。0为off,1为onFigure 3-11 shows the effect of these default variables on the boun dary layer created using theInternal continuityoption. In

46、Figure 3-11(a), both variables are set to zero; therefore, the angling of theInternal contin uityopti onFigure 3-10: Effect of theboundary layeris confined to the corner region. In Figure 3-11(b), ANGLE_SMOOTH_FACTOR is set to 1; therefore,GAMBITspreads the boundary-layer angling acrossthe entire ed

47、ge. In Figure 3-11(c), ADJUST_EDGE_BL_HEIGHiaiso set to1; therefore, GAMBIT adjusts the boun dary-layer heights to main ta incon sta nt heights with respect to the edges adjace nt to the corner.(G = 0(b) ASF = 1(c) ASF = 1QAEEH 0AEBH 1ASF -ABH= ADTUST_EDGE_B1_HE IGHTFigure 3-11: Effect of default va

48、riables onInternal contin uity opti onIn addition to affectingthe meshpattern in the imprint overlap regions,the Internal continuityoption directly affects which types of meshing schemes are appropriate forvolumes to which boun dary layers have bee n applied.For example, the volume shown in Figure 3

49、-10(b) can be meshed using a Map meshingscheme-resulting in the meshshown in Figure 3-12(a). By contrast, the volume show n in Figure 3-10(a)cannot be meshed using aMapscheme,because the vertex located at the lower right corner of the front face(and impri nt overlap regi on) is n ecessarily treated

50、as aSidevertex. Tomesh the volume show n in Figure 3-10(a), it is most reas on able to apply a Pavemeshing scheme tothe front face, then apply a Coopermeshing scheme to the volume, using the front and back faces assource faces (see Figure 3-12(b).除了影响在重叠区域的网格方式外，In ternal con tiuity选项直接影响哪种meshing方法

51、合适于已经被贴了边界层的volume的，13-12(a)可以 使用map而13-12(b)不能使用map因为前面的一个面的右下角的vertex被当作side处理，为了mesh这个volume，应该合理的采用Pave方法mesh前 面，然后采用cooper方法，使用前后两个面为源面。Figure 3-12: Effect of Internal continuityoption on allowable meshing schemesSpecifyi ng the Wedge Corner ShapeGAMBIT allows you to con trol the shape of the m

52、esh in the regi onsurrounding a Corneror ReversaVertex that connects two edges to which boun dary layers areattached. To do so, you must select or un select(default ) the Wedge corner shape)ption on the Create Boundary Layeform. The Wedge cornershape)ption produces the followingeffects (see Figure 3

53、-13):GAMBIT允许你控制在围绕在边界层attach的两条边的连接处的corner和reversal vertex周围区域的网格形状。?If you select theWedge corner shape)pti on, GAMBIT creates awedge-shaped boun dary-layer regi on surro unding the connecting vertex (Figure 3-13(a).如果你选择此选项，则创建一个楔形型形状?If you un select theWedge corner shape)ptio n, GAMBIT creates

54、 ablock-shaped boun dary-layer regi on surro unding the conn ect ing vertex (Figure 3-13(b).如果取消此选项，则创建矩形形状。(a) Map volume meshSource feces(b) face tucshCo op er volume mesh.Wedge corner shapeopti onIf two edges meet at aCorneror ReversaVertex, and each edge possessesa separate boun dary layer, the

55、n to create a wedge-shaped boun dary layer at the corner, you mustselect the Wedge corner shapeoption when creating each separate boundary layer.女口果两条边载corner或者reversal顶点处相 遇，并且拥有各自分离的边界层，然后为了在corner处创造楔形边界层，你必须选择此选项。Specifying the Transition CharacteristicsThe boundary-layer transitioncharacteristi

56、csconsist of two components:?Tran siti on patter n?Number of tran siti on rowsSpecifyi ng the Tran siti on PatternThe tran siti on patter n determ ines the arra ngeme nt of mesh no des in the regi on n ear theoutermost row of the boun dary layer. Boun dary layer tran siti on patter ns are defi ned b

57、y the ratio过渡样式决定了网格节点在靠近边界层最外面一行区域的安排。过渡样式定义为如下比率(a) Wedge corner shape on(b) Wedge comer shape offFigure 3-13: Effect ofwhere B is the number of mesh intervalsin a given row and A is the numberof mesh intervals in the immediately preceding full row. GAMBIT allowsyou to specify any of four tran sit

58、i on patter ns1:1, 4:2, 3:1, or 5:1. B是在给定行的网格间距数，而A是先前完整行的网格间距数。Figure 3-14 shows four differe nt two-row boun dary layers represe nti ng each of the four tran siti onpatter ns listed above.NOTE: Edges can host any of the four tran siti on patter ns, but faces can host o nly the1:1 transition patte

59、rn.注意：使用所有的过渡样式，面只能使用1:1Specify ing the Number of Tran siti on RowsWhe n you specify any tran siti on patter n other tha n1:1, you must alsospecify the nu mber of tran siti on rowsthat is, the nu mber of outermost rows to which the tran sition pattern is applied. GAMBIT applies the1:1pattern to all

60、rows other than the transition rows. Figure-3-15 shows the effect of the nu mber of transiti on rows on a boun dary layer con sist ing of three rows with the transition pattern4:2当你选择了不是1:1的过渡层时，你必须选择过渡行的数量，即过渡样式应用于边界层最外面的层数。(a)Figure 3-14: Boun dary layer tran siti on patter nsFigure-3-15: Effect o