JP2009282748A - Design support device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration in the calculating precision of a model associated with execution of a morphing concerning a design support device. <P>SOLUTION: The node of each cell 32 of a mesh model 30 is moved by morphing according to the deformation amounts of the design variables of the mesh model 30 acquired by optimized retrieval. Then, a layer lamination and a cell group whose cell size is small in its neighborhood are discriminated and extracted from a cell region having a wall face boundary conditions, and interpolation morphing is executed so that the cell size in the mesh model 30 before shape change by morphing can be held concerning the layer lamination and the small size cell group in the neighborhood. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a design support apparatus for supporting the design of an intake port and the like by a computer.

  Conventionally, for example, Patent Document 1 discloses a technique related to a structure shape morphing method using CAD / CAE software. Here, morphing is a technique for transforming the shape of an object created on a computer into another shape using a computer.

JP 2003-108609 A JP 2003-178099 A JP-A-11-102382 JP 7-282105 A Japanese Patent Laid-Open No. 2004-272784

  When the shape of the mesh model of the structure is changed by morphing, each cell of the mesh model is stretched or contracted. As a result, the quality of each cell whose shape has been changed always changes.

  When performing computational fluid calculation using a mesh model, a cell region with a wall boundary condition that takes into account the friction term is provided. However, the calculation accuracy is significantly affected.

  More specifically, a cell region having the above-described wall boundary condition is generally provided with a high-quality layer layer (layer mesh) in order to accurately evaluate disturbance near the wall. The cell group in the vicinity of the layer is created finely so that the cell size becomes a predetermined value or less. When the quality of such a layer layer and its neighboring cell group changes due to shape change by morphing, turbulence near the wall surface cannot be expressed with high accuracy, and there is a concern that the calculation accuracy may deteriorate.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a design support apparatus that can avoid deterioration in the calculation accuracy of a model accompanying execution of morphing.

A first invention is a design support apparatus,
A design support device for obtaining an optimum shape of a structure that satisfies a target evaluation index by numerical fluid calculation,
Cell information acquisition means for acquiring a calculation result according to a predetermined rule for each of a plurality of cells constituting a structure model to be analyzed;
Cell deformation amount setting means for setting deformation amounts of the plurality of cells;
Morphing execution means for performing node movement of the plurality of cells based on the deformation amount set by the cell deformation amount setting means;
Among cell groups having a wall boundary condition among the plurality of cells, a specific cell group discriminating means for discriminating a layer mesh and a small size cell group having a cell size of a predetermined value or less,
Nodal movement restriction means for restricting nodal movement by morphing for the layer mesh determined by the specific cell group determination means and the small size cell group;
It is characterized by providing.

The second invention is the first invention, wherein
The node movement restriction unit allows the node movement by the morphing execution unit for the layer mesh and the small size cell group determined by the specific cell group determination unit, and then the layer after the node movement Interpolation morphing execution means for moving the nodes of the layer mesh and the small size cell group so that the size of the mesh and the small size cell group is the size before the movement of the node is included.

  According to the first invention, nodal movement due to morphing is restricted for a cell group having a large influence on calculation accuracy among a plurality of cells constituting a structure model, that is, a layer mesh and a small size cell group. Will be. As a result, the high quality of the original mesh model can be maintained with respect to such a cell group, so that deterioration of the calculation accuracy of the model accompanying execution of morphing can be favorably avoided.

  According to the second invention, the cell group having a large influence on the calculation accuracy can be effectively maintained in high quality even after morphing.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a hardware configuration of a design support system according to Embodiment 1 of the present invention. The design support system of this embodiment is a system for supporting the design of a structure (intake port here) that is a design target (analysis target), and a general-purpose computer 10 as shown in FIG. 1 is used as hardware. It is feasible.

  A computer 10 shown in FIG. 1 includes an input device 12 that receives input of predetermined design conditions (design variables, etc.), a CPU 14 that executes a predetermined program based on the input design conditions, and an output device that outputs a calculation result by the CPU 14. 16 and the basic components such as the storage device 18 in which various programs executed by the CPU 14 and various data necessary for arithmetic processing are stored.

  FIG. 2 is a diagram for explaining a software configuration of the design support system according to the first embodiment of the present invention. As shown in FIG. 2, the system of this embodiment includes a base mesh model creation unit 20, a condition setting unit 22, a calculation solver 24, an optimization search unit 26, and a morphing processing unit 28.

  Here, an example in which this design support system is applied as a system for optimizing the shape of the intake port of the internal combustion engine will be described. Specifically, as an index for optimizing the intake port, the in-cylinder tumble (longitudinal vortex) ratio TR and the intake port flow coefficient CF are used. The aim of this system is to search and obtain an optimal port shape that satisfies both the tumble ratio TR and the flow coefficient CF which are in a trade-off relationship.

  The storage device 18 stores three-dimensional shape data (CAD (Computer Aided Design) data) of the intake port created in advance by the user of the present design support system. The base mesh model creation unit 20 has a function of reading the CAD data from the storage device 18 and then dividing the CAD data into a plurality of cells (finite elements) to create a base mesh model. . The base mesh model is basically one that can be automatically created by the base mesh model creation unit 20, but one created by the user's hand may be used.

  In the condition setting unit 22, boundary conditions and calculation conditions (design variables) input from the user by the input device 12 are set. The boundary conditions here are the boundary conditions of the mesh model (intake port wall surface position and temperature information, etc.), and the calculation conditions are the various calculation conditions (intake port) required for the mesh model flow calculation. The diameter of each part, the port height, the flow velocity at the mesh model inlet, etc.). Although FIG. 2 shows a configuration in which condition setting is performed after execution of morphing, a configuration in which condition setting is performed before execution of morphing may be used instead.

  The calculation solver 24 performs flow calculation on the mesh model under the boundary conditions and calculation conditions obtained from the condition setting unit 22. FIG. 3 is a simplified view of the mesh model 30 of the intake port. As shown in FIG. 3, information on the flow velocity at each position is given to the center position of each cell 32 of the mesh model 30 in association with each cell 32. The calculation solver 24 calculates the flow velocity for each cell 32 of the mesh model 30.

  The calculation solver 24 calculates the in-cylinder tumble ratio TR and the intake port flow coefficient CF according to a predetermined relational expression based on the calculation result of the flow velocity for each cell 32. Here, the flow velocity information is given to the center position of each cell 32. However, the present invention is not limited to this, and the flow velocity information may be given to each node of each cell 32. The information given to each cell 32 may not be the gas flow velocity in the intake port, but may be the pressure in the intake port or the kinetic energy of the gas flowing in the intake port.

  In the system of the present embodiment, the above calculation is repeated while changing the shape of the mesh by the morphing processing unit 28 until both the tumble ratio TR calculated by the calculation solver 24 and the flow coefficient CF satisfy the target value. I am doing so. For such a purpose, the calculation result of the flow velocity by the calculation solver 24 is sent to the optimization search unit 26.

  Further, the optimization search unit 26 determines the amount of deformation (that is, the mesh by the morphing processing unit 28) of the design variables (the diameter of each part of the intake port, the port height, etc.) of the base mesh model 30 based on the calculation result of the flow velocity. The deformation amount of the model 30) is selected to be an optimal solution.

  In the morphing processing unit 28, processing for changing the shape of the mesh model 30 according to the deformation amount of the design variable selected by the optimization searching unit 26, that is, morphing is performed. More specifically, the shape of the mesh model 30 is changed so that the diameter and port height of each part of the intake port become values selected by the optimization search unit 26.

  The calculation solver 24 uses the optimization search unit 26 to morph the appropriate design variables into the morphing processing unit 28 until a calculation result is obtained that can determine that an optimal intake port shape that satisfies both the target tumble ratio TRm and the target flow coefficient CFm is obtained. In addition, the calculation is repeated on the mesh model 30 whose shape has been changed by the morphing processing unit 28.

  According to the above method of changing the shape of the mesh model 30 by performing morphing, the mesh model 30 can be acquired in a short time without having to recreate the mesh model 30 on the CAD one by one. Further, according to morphing, it is possible to change the shape of the mesh model 30 while maintaining the coarse and dense distribution of the entire mesh model 30 without largely changing from the base mesh model 30 before the shape change.

  As a result, the deviation amount of the model calculation result with respect to the actual machine evaluation does not change greatly every time the shape is changed, so that the model calculation result can be relatively evaluated. Furthermore, according to the above method, in addition to the automatic correction of the mesh model 30 by morphing and the evaluation of the result of the model calculation, the optimum shape according to the purpose can be automatically calculated by combining the optimization search described above. It becomes possible.

[Problems associated with morphing]
FIG. 4 is a diagram for explaining a portion provided in the base mesh model 30 in order to perform highly accurate calculation evaluation.
FIG. 4 shows a part of the mesh model 30 of the intake port (portion in the vicinity of the valve). When the base mesh model 30 is created, a cell region having a wall boundary condition considering the friction term is provided.

  More specifically, a high-quality layer layer (layer mesh) is generally provided in the cell region having the above-described wall boundary condition in order to accurately evaluate the disturbance near the wall. The cell group in the vicinity of the layer layer is intentionally finely created so that the cell size becomes a predetermined value or less. As the layer layer, hexacells are used when the surrounding cells are hexa (hexahedral elements), or prism cells are used when the surrounding cells are tetra (tetrahedral elements). .

  By the way, the morphing described above is a process for directly changing the node of each cell 32 of the mesh model 30. For this reason, when the shape of the mesh model 30 of the structure is changed by morphing, each cell 32 of the mesh model 30 is stretched or contracted. More specifically, when morphing is executed, the surface shape of the mesh model 30 is deformed according to the required deformation pattern, and accordingly, the internal space mesh is tangled and deformed. As a result, the quality of each cell 32 whose shape has been changed always changes.

  In the mesh model 30, the portion having a significant influence on the calculation accuracy is a cell group having a wall boundary condition considering the friction term, that is, a cell group having a small cell size in the layer layer or its vicinity. In order to maintain a good calculation accuracy of the model, it is not preferable to carelessly change the shape of such a layer layer or a cell group in the vicinity thereof.

  However, in order to perform morphing without generating mesh distortion in the internal space mesh, it is not possible to fix the cell layer in the layer layer and its vicinity, so depending on the required deformation pattern, The layer layer and the neighboring cell group are forced to be deformed. For this reason, if the shape of the cell layer in the layer layer and its vicinity is changed without any consideration due to execution of morphing, the turbulent flow in the vicinity of the wall surface cannot be expressed accurately, and there is a concern that the calculation accuracy may deteriorate. Is done.

[Characteristics of Embodiment 1]
Therefore, in the present embodiment, after identifying and extracting a layer layer and a cell group having a small cell size in the vicinity from the cell region having the wall boundary condition, the layer layer and the cell group in the vicinity thereof are extracted. In this case, the movement of the node of the cell 32 is limited so that the cell size in the base mesh model 30 before the shape change by morphing is maintained.

  Specifically, according to the required deformation pattern of the mesh model 30 selected by the optimization search unit 26, first, the shape of each cell 32 of the mesh model 30 including the layer layer and the neighboring cell group is changed by morphing. Later, only the layer layer whose shape was changed and its neighboring cells were discriminated and extracted. The cell size of the extracted layer layer and its neighboring cell group is held within the cell size ± β of the original layer layer and its neighboring cell group before shape change (β is a predetermined value). Interpolation morphing is applied in the same direction as the above morphing.

  FIG. 5 is a flowchart showing a design support program executed by the CPU 14 in the first embodiment in order to realize the above function. In the program shown in FIG. 5, first, the target tumble ratio TRm and the target flow coefficient CFm are selected as target values (the target performance value desired by the user is received by the input device 12), and the target is generated by the base mesh model creation unit 20 A base mesh model 30 is created (step 101).

  Next, after predetermined boundary conditions and calculation conditions are set by the condition setting unit 22, the flow velocity of each cell 32 in the base mesh model 30 is calculated by the calculation solver 24. As a result, the tumble ratio TR and A flow coefficient CF is calculated (step 102). More specifically, the flow velocity, the tumble ratio TR, and the flow coefficient CF are repeatedly calculated every predetermined calculation step (predetermined time).

  Next, the optimization search unit 26 determines the amount of deformation of the design variables (such as the diameter of each part of the intake port and the port height) using an experimental design (DOE) or an optimization algorithm (step 103). .

  Next, morphing is executed based on the required deformation amount determined in step 103 (step 104). Next, a process of assigning the boundary condition assigned to each cell 32 of the base mesh model 30 to each cell 32 after the shape change by morphing (after node movement) is executed (step 105).

  Next, a process for determining (extracting) a cell having a wall boundary condition from the cell group subjected to shape change by morphing is executed (step 106). More specifically, the cell having the wall boundary condition is determined (extracted) with reference to the information regarding the boundary condition assigned to each cell 32 in step 105.

  In step 106, a cell determined not to have a wall boundary condition (that is, a cell having a condition other than a wall boundary as a condition) is not subject to interpolation morphing according to the present embodiment. The subsequent shape is maintained (step 107). For the cell, as soon as other processing is completed, the analysis calculation in step 120 described later is executed.

On the other hand, for the cell determined to be a cell having the wall boundary condition in step 106, the distance R _i from the wall boundary surface (the surface of the mesh model 30) is set (step 108), and then interpolation is performed. An interpolation target area for extracting a cell group to be morphed is set (step 109). Further, in this step 109, the cell number of the interpolation target area is obtained as n _i.

FIG. 6 is a diagram showing a part of the mesh model 30 before and after the morphing. More specifically, FIG. 6 (A) is a diagram showing the shape of the mesh model 30 before morphing is performed, and FIG. 6 (B) is that morphing is performed in the morphing expansion direction shown in FIG. 6 (A). It is a figure showing the shape of the mesh model 30 after being done.
At step 109, as shown in FIG. 6, the cell area in the distance R _i from the surface of the mesh model 30 is set as the interpolation target area.

  In the program shown in FIG. 5, layer layer determination is performed in order to determine the cell group in the interpolation target region as a layer layer and other cell groups (step 110). When the base mesh model 30 is created, since the number of layers and the layer height are known, the layer height of the layer layer after deformation by morphing can be calculated from the deformation amount and deformation curvature by morphing. Therefore, in step 110, the layer layer is determined using a predetermined distance function that defines the layer height of the layer layer.

  The layer layer determination is not limited to the above method. That is, when cells around the layer layer are formed of tetra, the layer layer is a prism cell, and therefore the layer layer determination may be performed using a mesh type. Alternatively, the layer layer determination may be performed based on the aspect ratio (aspect ratio) of each cell 32 regardless of the mesh type.

The cell group is determined to be a layer layer in step 110, the cell number is held is obtained as L _i (step 111). On the other hand, for the cells (cell group) in the interpolation target area determined not to be a layer layer in step 110, the cell number _ni is obtained and the base mesh model is obtained for each cell. A cell size S _{i of} 30 is acquired (step 112).

Next, it is determined whether or not the cell size S _i acquired in step 112 is equal to or smaller than a predetermined threshold value α (step 113). As a result, the cell whose cell size S _i is determined to be larger than the threshold α is not a cell intentionally created in advance with a small cell size when the base mesh model 30 is created (that is, the flow is originally from Since it is not a cell in a severe area), it can be determined that there is no problem even if the cell is expanded by morphing. For this reason, such a cell is held in the shape after the morphing is performed in step 104 (step 107).

On the other hand, cells that are in the interpolation target area and for which the cell size S _i is determined to be less than or equal to the threshold value α in step 113 are intentionally small in cell size when the base mesh model 30 is created. It is determined that the cell has been created, and the number of the cell (small size cell) determined as such is acquired as C _i and held (step 114).

FIG. 7 is a diagram showing a part of the mesh model 30 before and after the morphing.
When morphing is executed, the node size of each cell moves from the base state shown in FIG. 7A to the state shown in FIG. 7B, and the cell size changes. In FIG. 5, each cell number _ni is not changed. Therefore, as in steps 112 to 114 above, the morphing is performed based on the cell size S _i of each cell other than the layer layer of the base mesh model 30 and the cell number n _i of each cell in the interpolation target region. A group of small-sized cells (cells intentionally created with a base cell size S _i equal to or less than a threshold value α) can be determined (extracted) from the mesh model 30.

Next, in the program shown in FIG. 5, the deformation amount ΔS _i due to the morphing in step 104 is calculated for the cells 32 (ie, the layer cell and the small size cell) 32 of the cell numbers L _i and C _i determined in the above processing. (Step 115).

Next, based on the deformation amount ΔS _i , an interpolation deformation amount ΔX _i necessary for returning each of the cells 32 having the cell numbers L _i and C _i to the original cell size before morphing is calculated ( Step 116). This interpolation deformation amount ΔX _i is a correction amount of the same direction component as the morphing direction in step 104. More specifically, when the morphing is performed in the height direction of the layer layer as in the examples shown in FIGS. 6 and 7, the target cell is set to the height of the interpolation deformation amount ΔX _i. It is calculated as a value that returns to the original cell size in the vertical direction.

  Here, the direction of correcting the cell size at the time of interpolation morphing is the deformation direction of the original morphing, but depending on each part of the analysis objective, depending on the shape of the intake port or the like that is the target of flow analysis, The direction of an arbitrary coordinate system vector may be used.

Next, based on the interpolation deformation amount ΔX _i , interpolation morphing is executed so that each of the cells 32 with the cell numbers L _i and C _i returns to the original size (step 117). Next, it is determined whether or not the aspect ratio A _i of each cell 32 after interpolation morphing is greater than or equal to a predetermined threshold value γ (step 118). Depending on the shape of the mesh model 30, there is a possibility that the mesh will break down if the original cell size is completely restored by interpolation morphing. Therefore, in this step 118, based on the aspect ratio A _i, and to perform the mesh distortions determined for each cell 32 after interpolation morphing.

  In addition to the above, as a method for determining mesh distortion, for example, a method for determining that mesh distortion has occurred in a cell 32 having a negative volume (Negative Volume), or a plurality of nodes For example, a method for determining mesh distortion by determining the overlap between the two can be used as appropriate.

If the determination in step 118 is not established, and it is determined that there is mesh distortion, the correction deformation amount k × ΔX _i calculated by multiplying the interpolation deformation amount ΔX _i by an arbitrary weighting factor k is used. The amount of correction by interpolation morphing is adjusted (step 119). The weight coefficient k is adjusted within a range satisfying the corrected deformation amount k × ΔX _i ≦ (S _i ± β). These processes of steps 118 and 119 are repeatedly executed until the mesh distortion is eliminated.

  On the other hand, if it is determined that there is no mesh distortion as a result of the determination in step 118, the boundary condition and the calculation condition are set, and the shape after morphing is executed for each cell 32. Is calculated (step 120).

  Next, the tumble ratio TRs and the flow coefficient CFs in a state where the tumble ratio TR is stable in the shape after execution of the morphing are obtained (step 121).

  Next, it is determined whether or not the tumble ratio TRs and the flow coefficient CFs acquired in step 121 are equal to or greater than the target tumble ratio TRm and the target flow coefficient CFm in step 101, respectively (step 122).

  As a result, when both the tumble ratio TRs and the flow coefficient CFs have not reached the target value, the processing after the above-described step 103 is repeatedly executed. On the other hand, both the tumble ratio TRs and the flow coefficient CFs have reached the target value. Then, the process of the design support program shown in FIG.

  According to the design support program described above, node movement due to morphing is restricted for the layer layer and the small-sized cell group in the vicinity thereof. Thereby, the layer layer having a large influence on the calculation accuracy of the model and the small size cell group in the vicinity thereof can be maintained with high quality like the base mesh model 30. For this reason, it is possible to ensure sufficient calculation accuracy even after execution of morphing.

Further, according to the above program, a sufficient aspect ratio A _i is ensured for the neighboring cells in the layer layer that are likely to generate many errors due to mesh distortion during morphing. Can be suppressed.

  The layer layer is a portion that is easily twisted or thinned by morphing. For this reason, a cell in which an error due to mesh distortion is likely to occur during morphing is a cell near the layer layer. According to the above program, the layer layer after execution of morphing and the small sized cells in the vicinity thereof are maintained at a high aspect ratio, so that the occurrence of mesh distortion can be suppressed.

  In addition, according to the method of the above program, the layer layer and its vicinity after morphing are compared with the conventional method in which the quality of the mesh model is kept high by changing the cell size or re-dividing the mesh. All you have to do is add adjustments for small cells. For this reason, the calculation accuracy of the model can be sufficiently secured without greatly extending the execution time of morphing.

  Further, according to the method of the above program, since the mesh is not subdivided, the density distribution of the entire mesh model 30 does not change, so that the relative evaluation of the calculation results of the model before and after the shape change of the mesh model 30 is performed. Is fully possible. Such a property is extremely effective in a system that performs an optimization search and determines a search value from a relative evaluation before and after shape deformation as in the system of the present embodiment.

In the first embodiment described above, the mesh model 30 corresponds to the “structure model” in the first invention. Further, when the CPU 14 executes the process of step 102 or 120 and 121, the “cell information acquisition means” in the first invention executes the process of step 103, thereby executing the process of the first invention. When the “cell deformation amount setting means” executes the process of step 104, the “morphing execution means” in the first invention executes the processes of steps 105, 106, and 108-114. The “specific cell group discriminating means” in the first invention realizes the “node movement restriction means” in the first invention by executing the processing of the above steps 115 to 119, respectively.
Further, the “interpolation morphing execution means” according to the second aspect of the present invention is realized by the CPU 14 performing the processing of step 104 and then performing the processing of steps 115 to 119.

It is a figure for demonstrating the hardware constitutions of the design support system in Embodiment 1 of this invention. It is a figure for demonstrating the software configuration of the design support system in Embodiment 1 of this invention. It is the figure which expressed the mesh model of the intake port simplified. It is a figure for demonstrating the site | part provided in a base mesh model in order to perform highly accurate calculation evaluation. It is a flowchart of the design support program performed in Embodiment 1 of this invention. It is a figure showing a part of mesh model before and after morphing execution. It is a figure showing a part of mesh model before and after morphing execution.

Explanation of symbols

10 Computer 12 Input device 14 CPU
16 output device 18 storage device 20 base mesh model creation unit 22 condition setting unit 24 calculation solver 26 optimization search unit 28 morphing processing unit 30 mesh model 32 cell A _i aspect ratio CF, CFm, CFs flow coefficient TR, TRm, TRs tumble Ratio k weighting factor C _i , L _i , n _i cell number R _i distance S _i cell size ΔS _i morph deformation amount ΔX _i interpolation deformation amount

Claims (2)

A design support device for obtaining an optimum shape of a structure that satisfies a target evaluation index by numerical fluid calculation,
Cell information acquisition means for acquiring a calculation result according to a predetermined rule for each of a plurality of cells constituting a structure model to be analyzed;
Cell deformation amount setting means for setting deformation amounts of the plurality of cells;
Morphing execution means for performing node movement of the plurality of cells based on the deformation amount set by the cell deformation amount setting means;
Among cell groups having a wall boundary condition among the plurality of cells, a specific cell group discriminating means for discriminating a layer mesh and a small size cell group having a cell size of a predetermined value or less,
Nodal movement restriction means for restricting nodal movement by morphing for the layer mesh determined by the specific cell group determination means and the small size cell group;
A design support apparatus comprising:   The node movement restriction unit allows the node movement by the morphing execution unit for the layer mesh and the small size cell group determined by the specific cell group determination unit, and then the layer after the node movement 2. The interpolation morphing executing means for moving the nodes of the layer mesh and the small size cell group so that the size of the mesh and the small size cell group becomes the size before the node movement. The design support apparatus described.

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