Fluid Simulation Method

Abstract

A fluid simulation method is provided that can realize analysis in accordance with the property mechanisms of fluids such as blood. [Solution] A fluid simulation system that executes a fluid simulation method includes a shape evaluation unit (10), a velocity evaluation unit (20), a shear rate evaluation unit (30), a volume calculation unit (40), an optimization unit (50), and a flow path / fluid database (DB).

Description

[Technical Field]

[0001] The present invention relates to a fluid simulation method for analyzing a fluid flowing in a channel. [Background technology]

[0002] As a fluid simulation method of this type, as shown in Patent Document 1 below, a system is known in which, in a medical system including a data acquisition unit that acquires data from a patient's fundus using at least one optical method, and a data processing unit that processes the data acquired by the data acquisition unit to generate information about the patient's circulatory system, the system processes information indicating the distribution of blood flow velocity within blood vessels, which is information about thrombosis symptoms, as information about the circulatory system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-54784 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in reality, analyzing the distribution of blood flow velocity within blood vessels is insufficient to detect the formation of thrombi, which are blood coagulation events, and there is a need to establish an analytical method that is in line with the mechanism of thrombus formation.

[0005] In view of the above circumstances, an object of the present invention is to provide a fluid simulation method that can realize an analysis that is in line with the property mechanisms of fluids such as blood. [Means for solving the problem]

[0006] The fluid simulation method of the first invention comprises: A fluid simulation method for analyzing a fluid flowing in a flow path, comprising: a shape evaluation step of creating a 3D model of the internal space shape of the flow channel and dividing the model into a large number of cells; a velocity evaluation step of calculating a flow velocity of the fluid in the flow channel for each cell; a shear rate evaluation step of calculating the shear rate of the fluid in the flow channel for each cell; Equipped with 、 a volume calculation step of calculating a total volume of cells in which the shear rate for each cell calculated in the shear rate evaluation step is equal to or less than a first predetermined threshold value; characterized by comprising .

[0007] According to the fluid simulation of the first invention, as a premise, the shape evaluation step makes it possible to create a 3D model of the internal spatial shape of the channel with a resolution suited to the fluid flowing within the channel and divide it into a large number of cells.

[0008] By calculating the flow velocity of the fluid in the flow path in cell units of this resolution in the velocity evaluation step and calculating the shear rate of the fluid in the flow path in the shear rate evaluation step, the properties of the fluid can be grasped in cell units, and analysis can be performed that is in line with the fluid property mechanisms.

[0009] In this way, according to the fluid simulation method of the first aspect of the invention, it is possible to realize an analysis that is in line with the mechanism of fluid properties.

[0011] Also, No. 1 According to the fluid simulation method of the invention, when the flow velocity of the fluid in the flow path is calculated on a cell-by-cell basis by the velocity evaluation step and the shear rate of the fluid in the flow path is calculated on a shear rate evaluation step, the total volume of cells where the shear rate between adjacent cells is equal to or less than a first predetermined threshold is highly related to blood coagulation, such as thrombus in blood, for example. Therefore, by calculating this total volume, the properties of the fluid can be grasped from a cell-by-cell basis as a volume value which is an aggregate of the cells.

[0012] In this way, 1According to the fluid simulation method of the present invention, analysis based on the mechanism of fluid properties can be realized in terms of a volume value, which is an aggregate of cells, rather than in units of cells.

[0013] No. 2 The fluid simulation method of the present invention is 1 In the invention, an optimization step of optimizing the shape of the flow path so as to minimize the total volume calculated in the volume calculation step; The present invention is characterized by comprising:

[0014] No. 2 According to the fluid simulation method of the invention, by minimizing the total volume of cells where the shear rate between adjacent cells is equal to or less than a first predetermined threshold, it is possible to optimize the properties of the fluid, for example, by eliminating blood clots such as blood clots.

[0015] In this way, 2 According to the fluid simulation method of the present invention, it is possible to optimize the properties of a fluid through analysis based on the mechanism of the fluid properties.

[0016] No. 3 The fluid simulation method of the present invention is 2 In the invention, The optimization step is characterized in that cells whose flow velocity in the velocity evaluation step exceeds a second predetermined threshold are excluded.

[0017] No. 3 According to the fluid simulation method of the invention, when minimizing the total volume of cells where the shear rate between adjacent cells is equal to or less than a first predetermined threshold, cells where the flow rate exceeds a second predetermined threshold are excluded. This makes it possible to, for example, exclude parts where the shear rate is equal to or less than the first predetermined threshold and may lead to blood clotting such as thrombus in the blood, but where the flow rate is high and blood clotting is not actually possible, thereby enabling better optimization in accordance with the properties of the fluid.

[0018] In this way, 3 According to the fluid simulation method of the present invention, it is possible to further optimize the properties of the fluid through analysis based on the mechanism of the fluid properties.

[0019] No. 4 The fluid simulation method of the present invention includes the first to second 3 In any of the inventions, In the case where the fluid is blood and the flow path is an artificial blood vessel that is deformed by an external force, the size of the cell in the cross-sectional direction of the flow path is 4% or more of the flow path diameter, excluding the vicinity of the flow path wall of the flow path.

[0020] No. 4 The fluid simulation method of the present invention is suitable for the case where the fluid is blood, as described above, and is particularly suitable for an artificial blood vessel in which the flow path is deformed by an external force. Furthermore, the size of the cell in the cross-sectional direction of the flow path is 4% or more of the flow path diameter, excluding the vicinity of the flow path wall.

[0021] In this way, 4 According to the fluid simulation method of the present invention, when the fluid is blood, it is possible to realize an analysis of an artificial blood vessel in accordance with the properties and mechanisms of blood. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a block diagram showing the overall configuration of a fluid simulation system that executes a fluid simulation method according to an embodiment of the present invention. [Figure 2A] FIG. 10 is an explanatory diagram showing the processing content of a velocity evaluation step in the fluid simulation method according to the embodiment of the present invention. [Figure 2B] FIG. 10 is an explanatory diagram showing the processing content of a shear rate evaluation step in the fluid simulation method according to the embodiment of the present invention. [Figure 3] FIG. 10 is an explanatory diagram showing the processing content of a volume calculation step in the fluid simulation method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The configuration of a fluid simulation system for executing a fluid simulation method according to one embodiment of the present invention will be described below with reference to FIG.

[0024] As shown in FIG. 1, the fluid simulation system includes a shape evaluation unit 10, a velocity evaluation unit 20, a shear rate evaluation unit 30, a volume calculation unit 40, an optimization unit 50, and a channel / fluid database DB.

[0025] The shape evaluation unit 10 executes a shape evaluation step of creating a 3D model of the internal spatial shape of the flow channel and dividing it into a large number of cells.

[0026] The velocity evaluation unit 20 executes a velocity evaluation step of calculating the flow velocity of the fluid in the flow channel for each cell.

[0027] The shear rate evaluation unit 30 executes a shear rate evaluation step of calculating the shear rate of the fluid in the flow channel for each cell.

[0028] The volume calculation unit 40 mainly executes a volume calculation step of calculating the total volume of cells whose shear rate is equal to or less than a first predetermined threshold value.

[0029] The optimization unit 50 performs an optimization step of optimizing the shape of the flow path so as to minimize the total volume. Execute.

[0030] The channel / fluid database DB stores and holds various parameter values ​​according to the characteristics of various channels and fluids.

[0031] The above is the configuration of the fluid simulation system of this embodiment. In the above configuration, each of the processing units 10 to 50 is configured with hardware such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and functions as an arithmetic device (sequencer) for executing various processes by storing and holding programs for executing various processes described below in memory (not shown) and executing the programs. Also, some or all of the processing units 10 to 50 may be configured with other servers (external servers), and the fluid simulation system may be realized by distributed processing.

[0032] Next, the details of the processing content of the fluid simulation method by the fluid simulation system will be explained. The liquid simulation of this embodiment uses a fluid simulation technology that visualizes the flow of liquid or gas using CFD (Computational Fluid Dynamics) on a computer.

[0033] First, the fluid simulation system sets the target flow path and fluid by appropriately referencing the flow path / fluid database (DB). For example, the flow path is set to an artificial blood vessel that is deformed by an external force, and the fluid is set to blood, and various parameters are set.

[0034] Specifically, the various parameters are set such that the flow path diameter of the artificial blood vessel is set to 3.0 mm to 4.0 mm, and specific parameters such as viscosity and coagulation conditions corresponding to blood components are set as parameters of the blood properties.

[0035] Next, the shape evaluation unit 10 executes a shape evaluation step to create a 3D model of the internal spatial shape of the channel with a resolution suited to the fluid flowing in the channel, and divide the model into a large number of cells.

[0036] In this embodiment where the fluid is blood, the thickness is specifically set to approximately several tens of microns to several hundreds of microns, taking into consideration the artificial blood vessel diameter of 3.0 mm to 4.0 mm.

[0037] (Once the cell size is determined by executing the shape evaluation step), the velocity evaluation unit 20 then executes a velocity evaluation step to calculate the flow velocity of the fluid in the flow path for each cell.

[0038] Specifically, when the flow path is an artificial blood vessel and the fluid is blood, the velocity is calculated to be approximately 0.1 to 0.4 m / s on a cell-by-cell basis, as shown in Figure 2(A), and this is displayed on the 3D model in accordance with the blood vessel shape.

[0039] Moreover, the shear rate evaluation unit 30 executes a shear rate evaluation step to calculate the shear rate of the fluid in the flow channel for each cell.

[0040] Specifically, when the flow path is an artificial blood vessel and the fluid is blood, as shown in Figure 2(B), the overall flow rate is calculated to be 30 [ / s] or higher on a cell-by-cell basis, and the parts that are below 30 [ / s] are displayed on the 3D model according to the blood vessel shape.

[0041] Then, the volume calculation unit 40 executes the volume calculation step to calculate the total volume of adjacent cells in which the shear rate for each cell calculated in the shear rate evaluation step is equal to or less than the first predetermined threshold value.

[0042] Specifically, in this embodiment where the flow path is an artificial blood vessel and the fluid is blood, by setting the first predetermined threshold to, for example, 20 [ / s], the central part of the artificial blood vessel and the clip part of the artificial blood vessel shown in the enlarged partial view in the upper right of the figure become the extraction targets for calculating the total volume.

[0043] Here, the volume calculation unit 40 (and the optimization unit 50) excludes cells whose flow velocity in the velocity evaluation step exceeds a second predetermined threshold.

[0044] Specifically, in this embodiment where the flow path is an artificial blood vessel and the fluid is blood, by setting the second predetermined threshold to, for example, 0.1 [m / s], the central part of the artificial blood vessel has a high flow velocity and is therefore excluded from the calculation of the total volume (and optimization process).

[0045] In this way, as shown in Figure 3, the volume calculation unit 40 calculates the total volume of the clip portion of the artificial blood vessel that satisfies the conditions that the shear rate is equal to or less than the first predetermined threshold value of 20 [m / s] and the flow rate is equal to or less than the second predetermined threshold value of 0.1 [m / s]. In other words, the total volume is calculated by integrating the volumes of adjacent cells that satisfy the conditions.

[0046] Next, the optimization unit 50 executes an optimization step to optimize the shape of the flow path so as to minimize the total volume calculated in the volume calculation step.

[0047] Various optimization methods can be used, such as a parametric study or an adjoint method.

[0048] For example, in a parametric study, calculations are repeatedly performed while changing many parameters of the blood vessel diameter.

[0049] Here, if each mesh (cell, equivalent to a voxel in 4D MRI) is too small, the total number of cells increases dramatically, making it impractical to perform computational processing. Therefore, it is preferable to set the cell length to 1 / 25 or more of the cross-section of the blood vessel diameter (0.2 mm for a 5 mm diameter). In addition, the boundary layer located on the blood vessel wall is thin, so it is excluded. In other words, by setting the size of the cell in the cross-sectional direction of the flow channel to 4% or more of the flow channel diameter, excluding the area near the flow channel wall, it is possible to perform optimization processing with a further reduction in computational load.

[0050] The Adjoint method minimizes the objective function (volume of the region with low shear rate) in the same way as a parametric study, but does not parameterize the blood vessel diameter or the width of the depression caused by clipping the blood vessel diameter, and instead directly modifies the shape that is highly sensitive to the objective function.The calculation then ends when the optimal shape is found.

[0051] The above is the processing content of the fluid simulation method by the fluid simulation system, and this fluid simulation method makes it possible to realize analysis that is in line with the mechanism of fluid properties. [Explanation of symbols]

[0052] 10...shape evaluation unit, 20...velocity evaluation unit, 30...shear rate evaluation unit, 40...volume calculation unit, 50...optimization unit, DB...flow path / fluid database.

Claims

1. A fluid simulation method for analyzing a fluid flowing in a flow path, comprising: a shape evaluation step of creating a 3D model of the internal space shape of the flow channel and dividing the model into a large number of cells; a velocity evaluation step of calculating a flow velocity of the fluid in the flow channel for each cell; a shear rate evaluation step of calculating the shear rate of the fluid in the flow channel for each cell; Equipped with a volume calculation step of calculating a total volume of cells in which the shear rate for each cell calculated in the shear rate evaluation step is equal to or less than a first predetermined threshold value; A fluid simulation method comprising:

2. 2. The fluid simulation method according to claim 1, an optimization step of optimizing the shape of the flow path so as to minimize the total volume calculated in the volume calculation step; A fluid simulation method comprising:

3. 3. The fluid simulation method according to claim 2, In the optimization step, cells for which the flow velocity in the velocity evaluation step exceeds a second predetermined threshold are excluded.

4. 4. The fluid simulation method according to claim 1, A fluid simulation method characterized in that, when the fluid is blood and the flow path is an artificial blood vessel that is deformed by an external force, the size of the cell in the cross-sectional direction of the flow path is 4% or more of the flow path diameter excluding the vicinity of the flow path wall of the flow path.

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