JP6138668B2 - Method, apparatus and computer program for displaying fluid flow around tire - Google Patents

Description

  The present invention relates to a method, an apparatus, and a computer program for displaying a fluid flow around a tire, which can be used for hydroplaning analysis, drainage analysis, and the like.

  Conventionally, the evaluation of hydroplaning performance and drainage has been carried out by actually making and experimenting with tires. In recent years, a simulation method using a computer has been developed because it takes a lot of time, cost, and labor to manufacture and test a prototype.

  For example, in Patent Documents 1 and 2, a tire, a water film, and a road surface are modeled using a finite element method and a finite volume method, and a tire model on a road surface having a fluid model on the surface based on a predetermined boundary condition. Performing a running simulation is disclosed. Specifically, a plurality of Euler elements are arranged in a space on a road surface covered with a fluid, and a running simulation calculation is executed using a tire model. The behavior of the fluid according to the tread surface and the groove shape of the tire is calculated for each Euler element, and the velocity, direction and interface position of the fluid are obtained. Then, from the calculation result of the simulation, an arrow (vector diagram) having a length corresponding to the velocity of the fluid is displayed, and the flow of the fluid is displayed.

JP 2002-14011 A JP 2000-141509 A

  However, since a large number of Euler elements are generally set in order to improve analysis accuracy, for example, when a vector diagram is displayed by averaging the flow velocity for each Euler element, a large number of fine elements are displayed. A vector line is drawn, which is not easy for an analyst to understand.

  As an effective means of displaying a vector diagram that is easy to understand for analysts, adjacent Euler elements are grouped to set a small region, and the flow velocity is averaged for each small region to create a vector diagram. It is possible to display. However, if the Euler elements are simply grouped into small areas, there may be a mixture of tire rubber and water areas in one small area. If averaged, the vector diagram may have contradictions that are not true. For example, in the simulation result, when the tire rubber occupies a small area despite the high flow velocity, a vector diagram is displayed so that the flow velocity is relatively slow by the averaging process, or the tire rubber has a flow velocity of 0. Because of the speed in the groove, it is conceivable that the direction of the vector diagram (direction that penetrates through the rubber, shear flow) is displayed in the direction of the vector diagram due to the averaging process.

  The present invention has been made paying attention to such problems, and the object thereof is an apparatus and method for displaying a fluid flow around a tire that displays an easy-to-understand vector diagram without any contradiction different from a phenomenon. And providing a computer program.

  In order to achieve the above object, the present invention takes the following measures.

  That is, the apparatus for displaying the fluid flow around the tire according to the present invention uses a plurality of Euler elements arranged in a space on a road surface covered with fluid and a tire simulation model having a groove on a tread surface. The fluid calculation unit that calculates the direction, velocity, and interface position of the fluid in each Euler element, and extracts the Euler element in which the fluid exists from all the Euler elements, and extracts the extracted Euler element of the fluid A closed region dividing unit that groups each closed region formed by the interface, a small region dividing unit that further divides the Euler element divided into each closed region into small regions of a predetermined size, and for each divided small region And a vector display unit for averaging the velocity and direction of the fluid in the Euler elements belonging to the small region and displaying a vector diagram.

  The method for displaying a fluid flow around a tire according to the present invention performs a running simulation calculation using a plurality of Euler elements arranged in a space on a road surface covered with a fluid and a tire model having a groove on a tread surface. And calculating the direction, velocity, and interface position of the fluid in each Euler element, extracting the Euler element in which the fluid exists among all Euler elements, and forming the extracted Euler element at the interface of the fluid A step of grouping for each closed region, a step of further dividing the Euler elements divided into the respective closed regions into small regions of a predetermined size, and a fluid in the Euler elements belonging to the small region for each divided small region And averaging the speed and orientation of the two and displaying a speed vector.

  In this way, the Euler elements in which the fluid exists are grouped for each closed region formed by the fluid interface, and the closed region is further divided into small regions that are units of the flow velocity averaging process. By considering the interface, it is possible to divide a small area that is the unit of velocity averaging processing along the groove shape of the tread surface, and display an easy-to-understand vector diagram without any contradiction different from the phenomenon Become.

  In order to ensure accurate analysis accuracy, the predetermined size is preferably a size including at least three Euler elements per coordinate axis in the analysis space.

  The present invention can be specified as a program that causes a computer to execute the steps constituting the method.

The block diagram which shows typically the apparatus which displays the fluid flow around the tire which concerns on this invention. The perspective view which shows the tire model, road surface model, and fluid model which are used for a fluid analysis. The figure which shows the water and tire tread which are fluid analysis results in piles. The figure which shows only the water which is a fluid analysis result. Explanatory drawing regarding grouping Euler elements for each closed region of fluid. Explanatory drawing regarding dividing a closed area into smaller areas. The flowchart which shows the fluid flow display process routine which an apparatus performs. Explanatory drawing regarding the vector diagram displayed by the conventional method. Explanatory drawing regarding the vector diagram displayed by the method of this invention. Explanatory drawing regarding the vector diagram displayed by the conventional method. Explanatory drawing regarding the vector diagram displayed by the method of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[Device to display fluid flow around tires]
The apparatus 1 for displaying the fluid flow around the tire according to the present invention shown in FIG. 1 displays the flow of fluid (liquid, water) around the tire in a vector diagram as schematically shown in FIGS. 8B and 9B. It is a device to do.

  Specifically, the apparatus 1 includes a setting unit 10, a fluid calculation unit 11, a closed region dividing unit 12, a small region dividing unit 13, and a vector display unit 14. These units 10 to 14 are realized by cooperation of software and hardware by executing a processing routine (not shown) stored in advance by the CPU in an information processing apparatus such as a personal computer having a CPU, memory, various interfaces, and the like. Is done.

  A setting unit 10 shown in FIG. 1 receives an operation from a user via a known operation unit such as a keyboard or a mouse, and sets a tire model (finite element model) in which a tire is modeled by a plurality of elements. Various settings necessary for tire rolling analysis using a finite element method (Finite Element Method) such as applied load value, internal pressure value, and traveling speed are received and stored in a memory. In the present embodiment, a tread pattern (groove) is formed on the tread surface of the tire. In addition, the setting unit 10 includes various settings necessary for simulating the Euler elements arranged in the space on the road surface necessary for fluid analysis, and the behavior of the fluid (including speed, direction, and interface position) in the Euler elements. And store these set values in the memory.

  The fluid calculation unit 11 shown in FIG. 1 executes a running simulation calculation based on the finite volume method using a plurality of Euler elements 21 and a tire model 20 as shown in FIG. 2, and the direction and speed of the fluid in each Euler element Calculate the interface position. In the analysis using the Euler element 21, the space on the road surface is divided into a plurality of Euler elements. Euler elements are fixed in space and do not deform over time. The tire rubber position in the Euler element is determined at every unit time by running analysis of the tire finite element model using the finite element method. Behavior (speed, orientation, interface position) is calculated based on the finite volume method. In the present embodiment, a hexahedral Euler mesh is used as the Euler element. However, the present invention is not limited to this, and various applications are possible. For example, an octahedral Euler mesh may be used.

  In the model shown in FIG. 2, the Euler elements are arranged along the road surface on which the tire travels, and the tire shaft is translated while giving a translation speed to the tire and rotating the tire model. Since speed is given to the tire, speed is not given to the liquid (water) as a boundary condition. In this case, the flow velocity obtained as the calculation result becomes the fluid velocity as it is. In addition to this, the following analysis method may be used. The Euler elements are arranged as much as necessary to rotate and analyze the tire model with the tire shaft fixed. The Euler element is disposed only in a region where the tire contacts the ground and its periphery. Since no speed is given to the tire, a translational speed is given to the liquid (water) as a boundary condition. In this case, since the translational velocity is included in the flow velocity obtained as the calculation result, the value obtained by removing the translational velocity is the fluid velocity. Since the latter method can reduce the number of Euler elements required as compared with the former method, there is an advantage that the calculation cost necessary for the analysis can be reduced.

  The closed region dividing unit 12 shown in FIG. 1 uses the calculation result of the fluid calculation unit 11 to extract the Euler elements in which the fluid exists from all the Euler elements, and the closed Euler elements formed by the fluid interface form the closed Euler elements. Group by area. FIG. 3 shows the water interface and the tire in the Euler element at the same time. In this figure, the Euler elements have a very fine lattice shape and are not shown. Referring to FIG. 3, it can be seen that the fluid flows between the tread surface of the tire and the road surface, and the fluid flows along the groove. As shown in FIG. 4, the closed region dividing unit 12 extracts Euler elements in which fluid exists. In the figure, only the water interface is shown, and the Euler element is not shown. As shown in the figure, the fluid interface forms several closed regions, and water exists in the closed regions. As an extraction method, the identification code of the object in the Euler element (for example, 1 for water, 2 for air, etc.) can be used. FIG. 5 shows a state in which Euler elements in which fluid (water) exists are grouped for each closed region. The dotted lines in FIG. 5 enclose grouped Euler elements (not shown). In the example of the figure, it is divided into two groups.

  The small area dividing unit 13 shown in FIG. 1 further divides the Euler elements divided into closed areas as shown in FIG. 5 by the closed area dividing unit 12 into small areas (dotted lines) of a predetermined size as shown in FIG. To do. The predetermined size is preferably a size including at least three Euler elements per coordinate axis in the analysis space. For example, when the size is set to include three Euler elements per coordinate axis, 3 × 3 = 9 Euler meshes exist in one small region in FIG. Thus, if there are at least three Euler elements per coordinate axis in the analysis space, it is possible to display the vector diagram while ensuring the analysis accuracy without impairing the accuracy of the flow velocity and the direction. In this embodiment, since one side of the hexahedral Euler mesh is 1 mm, the size of the small region is 3 mm or 5 mm per side.

  The vector display unit 14 shown in FIG. 1 averages the velocity and direction of the fluid in the Euler elements belonging to each small region divided by the small region dividing unit 13 as shown in FIG. 6 and displays a vector diagram. To do. The output destination of the vector display unit 14 may be an image file or may be displayed on a display (not shown). The vector diagram may be displayed using any figure or character as long as it displays the velocity and direction of the flow velocity.

  In this embodiment, the vector diagram is displayed on the plane focusing on the fluid velocity in the two-dimensional plane in the tire traveling direction and the width direction, but the present invention is not limited to this. For example, a vector diagram may be displayed in the three-dimensional space, focusing on the fluid velocity in the three-dimensional space obtained by adding the load direction (vertical direction) to the tire traveling direction and the width direction.

[Method of displaying fluid flow around tire]
A method of displaying the fluid flow around the tire using the device 1 will be described with reference to FIG.

  First, in step S100 of FIG. 7, the fluid calculation unit 11, which can be referred to as a fluid simulation unit, performs an analysis using the tire model and Euler elements shown in FIG. Thereby, the direction, speed, and interface position of the fluid in each Euler element are obtained every unit time.

  In the next step S101, the closed region dividing unit 12 extracts an Euler element in which a fluid exists. In the next step S102, the closed region dividing unit 12 performs grouping for each closed region formed by the fluid interface as shown in FIG. As a result, it is possible to obtain a region that does not contradict the phenomenon even if the flow velocity averaging process is performed.

  In the next step S103, the small area dividing unit 13 further divides the Euler elements divided into the closed areas into small areas of a predetermined size. As a result, the number of vector diagrams to be displayed becomes a number that is easy for an analyst to understand. If the predetermined size is at least three per coordinate axis in the analysis space, it can be set as appropriate.

  In the next step S104, the vector display unit 14 averages the flow velocity for each small region. In the next step S105, the vector display unit 14 displays a vector diagram such as an arrow having a length corresponding to the flow velocity and matching the direction of the fluid.

  For the example shown in FIG. 8A, conventionally, since a small region (dotted line) serving as a unit of the flow velocity averaging process straddles the tire rubber (shaded portion), a short flow is represented by the influence of the tire rubber region where the flow velocity becomes zero. It becomes an arrow. On the other hand, if the above apparatus and method are used, as shown in FIG. 8B, a small region (dotted line) is arranged along the groove shape, so that the influence of the tire rubber region where the flow velocity becomes zero is eliminated. Thus, it is possible to display a length arrow (vector diagram) representing the flow velocity consistent with the phenomenon.

  For the example shown in FIG. 9A, conventionally, since a small area (dotted line) that is a unit of flow velocity averaging processing straddles the tire rubber, a flow in a direction penetrating the rubber is displayed like the small area on the lower left, Shear flow is displayed. On the other hand, if the above apparatus and method are used, as shown in FIG. 9B, it is possible to display an arrow (vector diagram) having a direction consistent with the phenomenon.

  As described above, the device for displaying the fluid flow around the tire according to the present embodiment includes a plurality of Euler elements 21 arranged in a space on a road surface covered with fluid, and a tire model 20 having a groove on a tread surface. Is used to perform a travel simulation calculation, to extract the fluid calculation unit 11 that calculates the direction, velocity, and interface position of the fluid in each Euler element 21, and the Euler element 21 in which the fluid exists among all the Euler elements 21; A closed region dividing unit 12 that groups the extracted Euler elements 21 for each closed region formed by the fluid interface, and a small region that further divides the Euler element 21 divided into each closed region into small regions of a predetermined size. The dividing unit 13 and a vector for displaying a vector diagram by averaging the velocity and direction of the fluid in the Euler element 21 belonging to the divided small area for each divided small area. A display unit 14, a.

  The method for displaying the fluid flow around the tire according to the present embodiment is a driving simulation using a plurality of Euler elements 21 arranged in a space on a road surface covered with fluid and a tire model 20 having a groove on a tread surface. A step of calculating the direction, velocity, and interface position of the fluid in each Euler element 21 is executed (S100), and Euler elements 21 in which fluid exists are extracted from all the Euler elements 21, and the extracted Euler elements 21 are extracted. Grouping for each closed region formed by the fluid interface (S101, S102), and further dividing the Euler element 21 divided into each closed region into small regions of a predetermined size (S103), For each divided small area, the velocity and direction of the fluid in the Euler element 21 belonging to the small area are averaged and a velocity vector is displayed. Includes that the step (S104, S105), the.

  In this way, the Euler elements 21 in which the fluid exists are grouped for each closed region formed by the fluid interface, and the closed region is further divided into small regions that are units of flow velocity averaging processing. By considering the interface, it is possible to divide a small area, which is the unit of velocity averaging, along the groove shape of the tread surface, and display a vector diagram that is easy to understand without any contradiction different from the phenomenon Become.

  In averaging the flow velocities, if there are not at least three Euler elements per coordinate axis in the analysis space, the accuracy is lost in the averaging process. Therefore, in the present embodiment, the predetermined size is a size including at least three Euler elements 21 per coordinate axis in the analysis space. In this way, it is possible to ensure accurate analysis accuracy.

  The computer program according to the present embodiment is a program that causes a computer to execute the steps constituting the method. By executing this program, it is possible to obtain the operational effects of the above method. In other words, it can be said that the apparatus uses the method.

  As mentioned above, although embodiment of this invention was described based on drawing, it should be thought that a specific structure is not limited to these embodiment. The scope of the present invention is shown not only by the above description of the embodiments but also by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in this embodiment, the fluid to be analyzed is made liquid (water) and used for hydro analysis or drainage analysis, but the present invention is not limited to this. The analysis target may be gas (air) as a fluid. In this case, it can be used for acoustic analysis using air.

  Each unit 10 to 14 illustrated in FIG. 1 is realized by executing a predetermined program by a CPU of a computer, but each unit may be configured by a dedicated memory or a dedicated circuit.

  The structure employed in each of the above embodiments can be employed in any other embodiment. The specific configuration of each unit is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 11 ... Fluid calculation part 12 ... Closed area division part 13 ... Small area division part 14 ... Vector display part 20 ... Tire model 21 ... Euler element

Claims (5)

Running simulation calculation is performed using a plurality of Euler elements arranged in a space on a road surface covered with a fluid and a tire model having a groove on a tread surface, and the direction, speed, and interface of the fluid in each Euler element A fluid calculation unit for calculating a position;
A closed region dividing unit that extracts the Euler element in which the fluid exists among all the Euler elements, and groups the extracted Euler elements for each closed region formed by the interface of the fluid;
A small area dividing unit that further divides the Euler element divided into each closed area into small areas of a predetermined size;
For each divided small region, a vector display unit that averages the fluid velocity and direction in the Euler elements belonging to the small region and displays a vector diagram;
A device for displaying a fluid flow around a tire, comprising:   The apparatus according to claim 1, wherein the predetermined size is a size including at least three Euler elements per coordinate axis in the analysis space. Running simulation calculation is performed using a plurality of Euler elements arranged in a space on a road surface covered with a fluid and a tire model having a groove on a tread surface, and the direction, speed, and interface of the fluid in each Euler element Calculating a position;
Extracting the Euler elements in which the fluid is present among all the Euler elements, and grouping the extracted Euler elements for each closed region formed by the interface of the fluid;
Dividing the Euler element divided into each closed region into smaller regions of a predetermined size;
For each divided small region, averaging the velocity and direction of the fluid in the Euler elements belonging to the small region, and displaying a velocity vector;
A method for displaying a fluid flow around a tire, comprising:   The method according to claim 3, wherein the predetermined size is a size including at least three Euler elements per coordinate axis in the analysis space.   The computer program which makes a computer perform the method of displaying the fluid flow around the tire of Claim 3 or 4.