Computer simulation of human respiratory droplets

Abstract

To provide a computer-aided technique, a computer system, and a preliminary computer program product for simulating human respiratory events.SOLUTION: A process 70 for conducting a multi-component fluid-flow simulation for a respiratory event originating at an entrance to the oropharynx is provided, the process comprising conducting (72) a geometrical analysis of a typical upper respiratory tract. A simulation engine produces (76) a respiratory event by combining exhalation rate profiles, particle distribution sizes, and concentration data. A boundary condition for the simulation of cough is established (74) assuming that the cough occurs deep inside the throat in or beyond the region of the oropharynx.SELECTED DRAWING: Figure 5

Description

[Background technology]

[0001] Human respiratory droplets are released when humans breathe, talk, sing, cough, and sneeze. The ability to predict how these particles disperse into the surrounding environment is useful for creating guidance for social distancing, making design changes to improve air quality, reducing the risk of infection, and producing effective personal protective equipment. [Overview of the project]

[0002] According to one embodiment, a computer implementation method performed by one or more computer systems includes accessing a model that includes a portion of a person's airway, modeling the airway as a volumetric region; initiating a respiratory event into the volumetric region, the respiratory event occurring at a certain depth inside the modeled airway in the accessed model; simulating the movement of elements of the respiratory event within the volumetric region, the elements representing particles of the respiratory event in an inlet boundary condition that represents an area of ​​the model at a threshold depth inside the airway; and obtaining a representation of the trajectory of the respiratory event particles from the simulation.

[0003] Embodiments of the computer implementation may include any one or more of the following or other features disclosed herein.

[0004] The airway representation includes a model of the pharynx. The airway representation includes a model of the oropharynx region of the pharynx. An initiation occurs in the region representing the oropharynx region of the pharynx, and the simulation further includes simulating the fluid flow of the respiratory event exiting the person's mouth through the oral cavity from the oropharynx region of the pharynx. An initiation occurs in the region representing the pharyngolaryngeal region of the pharynx, and the simulation further includes simulating the fluid flow of the respiratory event exiting the person's mouth through the oropharynx region of the pharynx, the oral cavity, and so on. The respiratory event being simulated is a cough.

[0005] In an additional embodiment, the computer system comprises one or more processor devices, memory coupled to one or more processor devices, and storage for storing executable computer instructions for performing a fluid simulation of a human respiratory event, wherein the instructions involve configuring one or more processors to perform: access a model including a portion of an airway, modeling the airway of a person as a volumetric region; initiating a respiratory event into the volumetric region, the respiratory event occurring at a certain depth inside the modeled airway in the accessed model; simulating the movement of elements of the respiratory event within the volumetric region, the elements representing particles of the respiratory event at an inlet boundary condition representing an area of ​​the model at a threshold depth inside the airway; and obtaining a representation of the trajectory of the particles of the respiratory event from the simulation.

[0006] Embodiments of a computer system may include any one or more of the following or other features disclosed herein.

[0007] The representation of the airway includes a model of the pharynx. The representation of the airway includes a model of the mid-pharyngeal region of the pharynx. Initiation occurs in a region representing the mid-pharyngeal region of the pharynx, and the instructions for simulation further include instructions for simulating the fluid flow of a respiratory event exiting the person's mouth through the oral cavity from the mid-pharyngeal region of the pharynx. The system is further configured to initiate in a region representing the laryngeal region of the pharynx, and the simulation is further configured to simulate the fluid flow of a respiratory event exiting the person's mouth through the mid-pharyngeal region and the oral cavity from the laryngeal region of the pharynx. The respiratory event is a cough.

[0008] According to a further aspect, a computer program product tangibly stored on a computer-readable non-transitory storage device storing executable computer instructions for simulating a human respiratory event, the instructions causing a computing system to access a model including a portion of an airway that models the airway of a person as a volumetric region, initiate a respiratory event within the volumetric region, where the respiratory event occurs at a certain depth inside the modeled airway in the accessed model, simulate the movement of elements of the respiratory event within the volumetric region, where the elements represent particles of the respiratory event at an inlet boundary condition representing an area of the model at a threshold depth inside the airway, and obtain a representation of the trajectories of the particles of the respiratory event from the simulation.

[0009] Embodiments of the computer program product can include any one or more of the following features or other features disclosed herein.

[0010] The airway representation includes a model of the pharynx. The airway representation includes a model of the mid-pharyngeal region of the pharynx. The instruction for starting occurs in a region representing the mid-pharyngeal region of the pharynx, and the instruction further includes an instruction for simulating a fluid flow of a respiratory event exiting from the mouth of a person through the oral cavity from the mid-pharyngeal region of the pharynx. The instruction further includes an instruction for starting in a region representing the laryngeal-pharyngeal region of the pharynx, and the instruction for simulation further includes an instruction for simulating a fluid flow of a respiratory event exiting from the mouth of a person through the mid-pharyngeal region and the oral cavity from the laryngeal-pharyngeal region of the pharynx. The respiratory event to be simulated is a cough.

[0011] One or more of the above aspects can provide one or more of the following advantages.

[0012] The simulation by the above method provides a realistic respirator droplet cloud generated by the simulation. These clouds are much more dispersed than those of other methods and represent experimentally imaged respiratory clouds. Other methods tend to underestimate the dispersion of droplets. By having an inlet boundary condition inside the throat, it is not necessary to set a conical angle or introduce artificial turbulence based on experimental results to achieve a realistic cough. In fact, these characteristics can be a measure to verify that the respiratory event is accurately simulated.

[0013] The above method is also applicable to the lattice Boltzmann method including the finite volume method, the finite element method, etc., and other computational fluid dynamics methods.

[0014] Other features and advantages of the present invention will become apparent from the following description and claims.

Brief Description of the Drawings

[0015] [Figure 1] It is a diagram showing a system for simulating a respiratory event. [Figure 2] It is an image showing an aspect of the upper airway of a person. [Figure 3] This figure shows a conventional model of respiratory events. [Figure 4] This figure shows alternative techniques for modeling respiratory events. [Figure 5] Figure 4 is a flowchart illustrating the process for modeling respiratory events. [Figure 6] This is a diagram showing simulated cough patterns. [Figure 7] This is a diagram showing simulated cough patterns. [Figure 8] This graph shows the relationship between cough flow rate and time. [Figure 9] This figure shows the velocity components of two LBM models (conventional technology). [Figure 10] This figure shows the velocity components of two LBM models (conventional technology). [Figure 11] Figure 1 is a flowchart showing the steps taken by the simulation system. [Figure 12] A perspective view of a microblock (conventional technology). [Figure 13A] Figure 1 shows the grid structure used by the system (conventional technology). [Figure 13B] Figure 1 shows the grid structure used by the system (conventional technology). [Figure 14] This diagram shows variable disassembly technology (conventional technology). [Figure 15] This diagram shows variable disassembly technology (conventional technology). [Figure 16] This diagram shows the regions affected by surface facets (conventional technology). [Figure 17A-B] This figure shows a simulated cough (conventional technique) based on the arrangement of boundary conditions for the outside and inside of the mouth. [Figure 18] This figure shows a simulated cough based on the arrangement of boundary conditions at the exit of the oropharynx. [Figure 19A-B] This figure shows the details of the cough cloud regarding the arrangement of boundary conditions at the exit of the oropharynx (Figure 18). [Modes for carrying out the invention]

[0016] Referring to Figure 1, a system 10 for simulating respiratory events is shown. Simulations can be performed for various purposes, such as creating social distancing guides, making design changes to improve air quality, reducing the risk of infection, and generating effective personal protective equipment. The focus of this discussion is on the simulation of coughing as a respiratory event. The cough simulation is initiated at a location within the person's airway.

[0017] Generally, the system 10 in this embodiment comprises a server system 12 implemented as a massively parallel computing system 12 (standalone or cloud-based) and a client system 14, based on a client-server or cloud-based architecture. The server system 12 comprises memory 18, a bus system 11, interfaces 20 (e.g., user interface / network interface / display or monitor interface, etc.), and processing devices 24.

[0018] In the cough simulation example, memory 18 contains a breathing engine 32 that acts on a digital representation 40' of the airway 40 (Figure 2), which digitally represents various spaces and objects within the person's airway 40 (Figure 2). The digital representation 40' of the user's airway 40 (Figure 2) also includes the person's throat. The digital representation 40' of the user's airway 40 (Figure 2) includes the person's throat, including the nasopharynx, oropharynx, and pharyngeal region (see Figure 2, described below). System 10 requires that the digital representation 40' of the person's airway 40 (Figure 2) includes the mouth and throat portions of the person's airway. Within the throat portion of the person's airway 40 (Figure 2), there are boundary conditions for initiating a respiratory event, such as coughing.

[0019] One method for providing a digital representation of a person's airway is to obtain a digital representation from a third-party generated model.

[0020] Memory 18 can also store other parameters such as fluid properties 33a, for example, the properties of oral fluids (e.g., saliva) that cover various objects in the mouth. Memory 18 also stores parameters such as mucous membranes that secrete mucus.

[0021] System 10 accesses a data repository 38 that stores 2D and / or 3D meshes, coordinate systems, and libraries that can be used for respiratory event simulations using computational fluid dynamics or any known computational technique such as the so-called lattice Boltzmann method.

[0022] The respiratory engine 32 initiates a cough, i.e., a respiratory event, in the pharynx, for example, in the pharyngeal portion of the airway. In one embodiment, the pharyngeal portion is limited to the prepharyngeal pharynx and pharyngolaryngeal portion. In other embodiments, the nasopharynx portion of the pharynx can be used to simulate sneezing and / or coughing.

[0023] Referring temporarily to Figure 2, a diagram of the upper airway 40 of a human being is shown. The diagram was adapted from an image obtained at https: / / en.wikipedia.org / wiki / Respiratory_tract. The diagram of the human airway 40 represents a living human being. Representation 40 is converted to a digital representation 40' of the human airway, which is used to perform the simulation. Major objects within the human airway 40 are labeled with names. Of these major objects, some are labeled with names and reference symbols and include the mouth 42a and lips 42b. Other major objects labeled with names and reference symbols are also shown, and these include the pharynx 52, which includes the pharynx, e.g., the nasopharynx 52a, the oropharynx 52b and the pharyngolarynx 52c. Other parts of the upper airway 40 include the hard palate, soft palate, teeth (unlabeled), fluid membranes, and oral cavity, which includes at least the oral cavity proper, and may include the vestibular portion of the oral cavity (unlabeled).

[0024] Referring here to Figure 3, as conventionally understood, the simulation event is modeled as occurring at the exit of the mouth 42a of the person 40, for example, at the lips 42b. That is, the so-called inlet boundary condition 45 occurs at the mouth exit, for example, at the person's lips 42b. Therefore, conventionally, in order to achieve a realistic cough simulation, the user of system 10 needs to set the cone angles 44(α), 46(β1), and 48(β2) based on experimental results and introduce artificial turbulence. Typically, the cough setting has an oval or spherical section as the inlet boundary condition 45. This inlet is located directly in front of or inside the mouth opening, as shown. The user specifies angles α, β1, and β2 so that the inlet boundary condition achieves the desired cone shape. This can be done by varying the inlet velocity condition or by controlling the radius and solid angle of the spherical section used for the inlet shape. For a more fidelity simulation, artificial turbulence needs to be introduced to generate the cough structure. However, this is often ignored. (For further information, please refer to the paper entitled "Flow Dynamics and Characterization of a Cough" by Jitendra K. Gupta et al., published in Indoor Air, 19, 517-525 (2009), which is incorporated herein by reference.)

[0025] Referring here to Figure 4, when used herein, a simulation event, such as a cough, is modeled as occurring within the throat or pharynx 52 of a person. More specifically, the simulation engine 34 initiates the modeled cough from at least a portion of the person's throat around the exit of the oropharynx 52b, e.g., the posterior corner of the oral cavity, so that the correct flow development is obtained. In some embodiments, the cough initiation occurs at the entrance of the oropharynx 52b or the entrance of the pharyngolarynx 52c of the pharynx 52. From the perspective of computer-generated simulation, the cough initiation point is a so-called "boundary condition 60".

[0026] By moving the inlet boundary condition 55 from the mouth to the inlet boundary condition 60 inside the pharynx 52, it is no longer necessary to specify a particular cone angle or solid angle at the inlet. The inlet becomes the mass inlet boundary condition. Furthermore, it is no longer necessary to introduce artificial turbulence, because the simulated flow through the shape of the pharynx and mouth generates these structures. Therefore, the angles α, β1, and β2 specified in the above paper are now the simulation results and can be used to verify the coughing results.

[0027] The boundary condition 60 for coughs deep within the airway allows the turbulent structure of the fluid flow to develop naturally during the simulation. This results in cough structures with more realistic intensity and length scales than those artificially generated.

[0028] The development of these cough structures can be captured using high-fidelity flow simulations such as PowerFLOW, available from Dassault Systems SIMUOLIA Corp. Accurate modeling of these cough structures improves the accuracy of respiratory droplet dispersion into the environment.

[0029] Referring here to Figure 5, a process 70 for performing a multi-component fluid flow simulation for respiratory events occurring at least at the entrance to the oropharynx 52b is shown. Process 70 uses a simulation of a person's upper airway as an example. Process 70 includes performing a general upper airway geometric analysis (72) using X-ray or other types of imaging to identify the various objects to be modeled in the upper airway under investigation.

[0030] The simulation engine generates respiratory events by combining expiratory velocity profiles, particle distribution size, and concentration data (76). One example is obtaining these data from the literature. These data are then used to approximate expiratory events.

[0031] Determining the location of boundary conditions for particle and airflow introduction, as derived from conventional literature, yields a histogram of particle size distribution, but does not specify the timing of the release of these different-sized particles. Furthermore, the initial velocity of the particles is not specified. The concentration data available from the literature are also averaged data, which do not contain information about the time variation of respiratory droplets during an event.

[0032] The method described herein establishes the boundary conditions for cough simulation as occurring deep within the pharynx, within or beyond the oropharynx region (74). The need for the entry point to be in such a deep location within the airway is so that the turbulent structure of the flow through the rest of the upper airway develops naturally according to the airway model. This results in a cough structure with a more realistic intensity and length scale than if it were artificially generated.

[0033] During the generation of respiratory events, the process performs a full simulation of the generated events by propagating them through a model of the upper airway of a person 40.

[0034] Figure 6 shows a velocity slice 80 of the cough generated in the oropharynx by process 76. This illustrates how the resulting flow interacts with the oral features to develop the output of the cough jet from the mouth 42a.

[0035] Figure 7 shows a volume visualization of droplet concentration 82, which illustrates how a cough jet disperses particles.

[0036] These images are compared with the results shown in Gupta, J., Lin, C.-H., and Chen, Q. 2009, "Flow dynamics and characterization of a cough," Indoor Air, 19, 517-525.

[0037] Thermal considerations are also included, and respiration is introduced at a temperature higher than the ambient temperature or close to the subject's internal temperature. The particle size distribution used in the model is a normal distribution centered at 0.3 μm, fitted to the diameter data of Zayas et al. (2012). This distribution was chosen because it captures smaller particles than other previous experiments, due to improvements in measurement techniques.

[0038] As shown in Figure 8, a cough can be two coughs with temporal flow fluctuations, as obtained from Gupta, Lin, and Chen (2009).

[0039] Simulation examples are described in the following discussion. Figures 9, 10, and 12-16 are labeled as "prior art" because these figures are found in other applications / patents of the assignee. However, the above discussion is not found in those applications. The following discussion is one method for simulating a cough event. Other simulation techniques may be used.

[0040] Referring to Figure 9, the first model (2D-1)100 is a two-dimensional model containing 21 velocities. Of the 21 velocities, one (105) represents a particle that is not moving; three sets of four velocities represent particles moving at normalized velocities (r) (110-113), twice the normalized velocities (2r) (120-123), or three times the normalized velocities (3r) (130-133) in either the positive or negative direction along either the x or y axis of the lattice; and two sets of four velocities represent particles moving at normalized velocities (r) (140-143) and twice the normalized velocities (2r) (150-153) along both the x and y lattice axes.

[0041] Similarly, as shown in Figure 10, the second model (3D-1)200 is a three-dimensional model containing 39 velocities, where each velocity is represented by one of the arrowheads in Figure 8. Of the 39 velocities, one represents a particle that is not moving; three sets of six velocities represent particles moving at a normalized velocity (r), twice the normalized velocity (2r), or three times the normalized velocity (3r) in either the positive or negative direction along the x, y, or z axis of the lattice; eight represent particles moving at a normalized velocity (r) along all three x, y, and z lattice axes; and twelve represent particles moving at twice the normalized velocity (2r) along two of the x, y, and z lattice axes.

[0042] More complex models may also be used, such as a 3D-2 model containing 101 velocities and a 2D-2 model containing 37 velocities. The velocities are more clearly represented by their components along each axis recorded in Tables 1 and 2, respectively.

[0043] For the 101 velocity 3D-2 models, one represents a stationary particle (Group 1), three sets of six velocities represent particles moving at a normalized velocity (r), twice the normalized velocity (2r), or three times the normalized velocity (3r) in either the positive or negative direction along the x, y, or z axis of the lattice (Groups 2, 4, and 7), and three sets of eight velocities represent particles moving at a normalized velocity (r), twice the normalized velocity (2r), or three times the normalized velocity (3r) along all three x, y, and z lattice axes. Groups 3, 8, and 10 represent particles in motion; 12 particles represent particles moving at twice the normalized velocity (2r) along two of the x, y, and z lattice axes (Group 6); 24 particles represent particles moving at the normalized velocity (r) and twice the normalized velocity (2r) along two of the x, y, and z lattice axes, but not moving along the remaining axis (Group 5); and 24 particles represent particles moving at the normalized velocity (r) along two of the x, y, and z lattice axes, and three times the normalized velocity (3r) along the remaining axis (Group 9).

[0044] For the 37 velocity 2D-2 two-dimensional model, one represents a particle that is not moving (Group 1); three sets of four velocities represent particles moving at a normalized velocity (r), twice the normalized velocity (2r), or three times the normalized velocity (3r) in either the positive or negative direction along either the x or y axis of the lattice (Groups 2, 4, and 7); two sets of four velocities represent particles moving at a normalized velocity (r) or twice the normalized velocity (2r) with respect to both the x and y lattice axes; eight velocities represent particles moving at a normalized velocity (r) with respect to one of the x or y lattice axes and twice the normalized velocity (2r) with respect to the other axis; and eight velocities represent particles moving at a normalized velocity (r) with respect to one of the x or y lattice axes and three times the normalized velocity (3r) with respect to the other axis.

[0045] The LBM model described above provides a specific class of efficient and robust discrete velocity motion models for numerical simulation of flow in both two and three dimensions. This type of model includes a specific set of discrete velocities and weights associated with these velocities. The velocities coincide with lattice points in Cartesian coordinates in velocity space, which facilitates the accurate and efficient implementation of discrete velocity models, particularly those known as lattice Boltzmann models. Using such models, flows can be simulated with high fidelity.

[0046] Referring to Figure 11, the physical process simulation system operates according to step 300 to simulate physical processes such as fluid flow resulting from coughing. Before the simulation, the simulation space is modeled as a collection of voxels using the cough setup in Figure 4 (step 302). Typically, the simulation space is generated using a computer-aided design (CAD) program. For example, a CAD program can be used to draw the upper airway of a person positioned in a room. Subsequently, the data generated by the CAD program is processed to add a grid structure with appropriate resolution and to account for objects and surfaces in the simulation space of the airway.

[0047] The resolution of the grid can be selected based on the Reynolds number. The Reynolds number is related to the flow velocity (v), the characteristic length of the object in the flow (L), and the characteristic velocity of the flow (u). Re = uL / ν Equation (I-3)

[0048] The characteristic length of an object within the airway represents the object observed within the airway. The resolution of the simulation event can be increased, or an area of ​​increased resolution can be used around the region of interest. The dimensions of the voxels decrease as the grid resolution increases.

[0049] The state space is f i It can be expressed as (x,t), where f i This represents the number of elements or particles per unit volume in state i at the lattice region indicated by the 3D vector x at time t (i.e., the particle density in state i). For a known time increment, the number of particles is simply f i This is referred to as (x). All combinations of states of the lattice region are represented as f(x).

[0050] The number of states is determined by the number of possible velocity vectors within each energy level. These velocity vectors consist of integer linear velocities in a space with three dimensions: x, y, and z. The number of states increases in the case of multiple types of simulations.

[0051] Each state i represents a different velocity vector at a specific energy level (i.e., energy levels 0, 1, or 2). The velocity c of each state i is shown using its "velocity" in each of the three dimensions as follows. c i =(c i,x , c i,y , c i,z ) Equation (I-4)

[0052] The energy level 0 state represents a stopped particle that is not moving in any dimension, i.e., c stopped =(0, 0, 0). The energy level 1 state represents a particle with a velocity of ±1 in one of the three dimensions and a velocity of 0 in the other two dimensions. The energy level 2 state represents a particle with a velocity of ±1 in all three dimensions or a velocity of ±2 in one of the three dimensions and a velocity of 0 in the other two dimensions.

[0053] By generating all possible permutations of the three energy levels, a total of 39 possible states (one energy 0 state, six energy 1 states, eight energy 3 states, six energy 4 states, twelve energy 8 states, and six energy 9 states) are obtained.

[0054] Each voxel (i.e., each lattice site) is represented by a state vector f(x). The state vector completely defines the status of the voxel and contains 39 entries. The 39 entries correspond to one energy 0 state, six energy 1 states, eight energy 3 states, six energy 4 states, twelve energy 8 states, and six energy 9 states. By using this set of velocities, the system can generate Maxwell-Boltzmann statistics for the achieved equilibrium state vector.

[0055] Referring to Figure 12, a microblock is shown. For processing efficiency, voxels are grouped into 2x2x2 volumes called microblocks. Microblocks are organized to enable parallel processing of voxels and minimize the overhead associated with the data structure. The abbreviated notation for voxels in microblocks is N i (n) is defined as (n), where n represents the relative position of a lattice part within the microblock, and n ∈ {0, 1, 2, ..., 7}.

[0056] Referring to Figures 13A and 13B, the surface S (Figure 13A) has facets F in the simulation space (Figure 13B). α It can be represented as a set of elements. S = {Fα} Equation (I-5) Here, α is an index that enumerates a particular facet. Facets are not constrained by voxel boundaries and are typically of the order of the size of adjacent voxels, or slightly smaller, so that a facet affects a relatively small number of voxels. Properties are assigned to facets for the purpose of performing surface dynamics. In particular, each facet F α is the unit normal (n α ) and surface area (A α ) and the central location (x α ) and the facet distribution function (f) that describes the surface dynamics properties of the facets. i (α)) has

[0057] Referring to Figure 14, different levels of resolution can be used in different regions of the simulation space to improve processing efficiency. Typically, the region 650 around object 655 is of the greatest interest and therefore simulated at the highest resolution. Since the effect of viscosity decreases with distance from the object, decreasing resolution levels (i.e., expanded voxel volume) are used to simulate regions 660, 665 that are spaced at increasing distances from object 655.

[0058] Similarly, as shown in Figure 15, a lower resolution level can be used to simulate region 770 around less important features of object 775, while the highest resolution level is used to simulate region 780 around the most important features of object 775 (e.g., the front and back surfaces). The off-center region 785 is simulated using the lowest resolution level and the largest voxels.

[0059] Identifying voxels affected by facets Referring again to Figure 11, once the simulation space is modeled (step 302), voxels affected by one or more facets are identified (step 304). Voxels may be affected by facets in multiple ways. Firstly, voxels that intersect one or more facets are affected in that the voxel has a reduced volume compared to non-intersecting voxels. This results from the fact that the facets, and the underlying material of the surface represented by the facets, occupy a portion of the voxel. Fractional factor P f (x) represents the portion of the voxel that is not affected by the facets (i.e., the portion that can be occupied by the fluid or other material whose flow is being simulated). For non-intersecting voxels, P f (x) is equal to 1.

[0060] A voxel that intersects one or more facets by transferring particles to or receiving particles from a facet is also identified as a voxel affected by the facet. All voxels that intersect a facet have at least one state in which they receive particles from the facet and at least one state in which they transfer particles to the facet. In most cases, additional voxels will also have such states.

[0061] Referring to Figure 16, the non-zero velocity vector c i For each state i having, facet F αThe particle is given a velocity vector c i and the unit normal n of the facet α The magnitude of the vector dot product (|c i n i The height is defined by |) and parallelepiped G iα Volume V iα The surface area A of the facets is equal to the following: α A parallelepiped G having a base defined by iα Receive from or transfer to the region defined by [the specified method / function]. V iα =|c i n α |A α Equation (I-6)

[0062] Facet F α When the velocity vector of the state is directed toward the facet (|c i n i |<0), Volume V iα When a particle is received from and the velocity vector of the state is pointed away from the facet (|c i n i (>0), the particle is transported to the region. As will be discussed below, this representation is such that another facet is a parallelepiped G iα When it occupies a portion of something, it must be modified. This is a condition that can arise in the vicinity of non-convex features such as interior angles.

[0063] Facet F α Parallelepiped G iα A facet can overlap with part or all of multiple voxels. The number of voxels or parts of voxels depends on the size of the facet relative to the size of the voxels, the energy of the state, and the orientation of the facet relative to the lattice structure. The number of affected voxels increases with the size of the facet. Therefore, as mentioned above, the size of the facet is usually chosen to be of the order of the size of the voxels located near the facet, or smaller.

[0064] parallelepiped G iαThe part of voxel N(x) where they overlap is V iα It is defined as (x). Using this term, we have voxel N(x) and facet F α The flux Γ of particles in state i moving between and iα (x) is the density of particles in state i in the voxel (N i (x)) contains the volume (V) of the region that overlaps with the voxel. iα It is equal to multiplying (x) by the result of multiplication. Γ iα (x) = N i (x)V iα (x) Formula (I-7)

[0065] parallelepiped G iα When it intersects with one or more facets, the following condition is true: V iα =ΣV α (x) + ΣV iα (β) Equation (I-8) Here, the first sum is G iα Considering all overlapping voxels, the second term is G iα Consider all facets that intersect with it. Parallelepiped G iα When it does not intersect with another facet, this equation can be reduced to the following: V iα =ΣV iα (x) Formula (I-9)

[0066] Running the simulation Once voxels affected by one or more facets are identified (step 304), a timer is started to begin the simulation (step 306). During each time increment of the simulation, the movement of particles between voxels is simulated by an advection stage that takes into account the interaction between particles and surface facets (steps 308-316). Next, a collision stage (step 318) simulates the interaction of particles within each voxel. The timer is then incremented (step 320). If the increment timer does not indicate that the simulation is complete (step 322), the advection and collision stages (steps 308-320) are repeated. If the incremented timer indicates that the simulation is complete (step 322), the simulation results are stored and / or displayed (step 324).

[0067] Figures 17A and 17B show simulated cough jets with different boundary conditions set for the outside (Figure 17A) and inside (Figure 17B) of the mouth. In Figure 17A, the cough jet does not deflect sufficiently downwards and does not disperse correctly in accordance with experimental observations. In Figure 17B, the cough jet is improved compared to Figure 17A, but still does not deflect sufficiently downwards and does not disperse correctly according to experimental observations.

[0068] Figure 18 shows the simulated cough jet with boundary conditions set at the oropharynx exit. In Figure 18, the cough jet is deflected downwards here, which matches experimental observations, and the angle for the cough cloud is correct, as also shown in Figure 19B. The flow angle, velocity, and momentum of both the case phase and the particulate phase exiting the mouth are available for post-processing.

[0069] Figure 19A shows a side view and a front view of the cough jet with respect to the arrangement of boundary conditions at the mouth outlet of Figure 17A.

[0070] Figure 19B shows a side view and a front view of the cough jet regarding the arrangement of boundary conditions in the oropharynx region, as shown in Figure 17B (similar to Figure 7, but with angles indicated).

[0071] The subject matter and functional operating embodiments described herein can be implemented in digital electronic circuitry, tangibly embodied computer software or firmware, computer hardware (including structures disclosed herein and their structural equivalents), or one or more combinations thereof. Embodiments of the subject matter described herein can be implemented as one or more computer programs (i.e., one or more modules of computer program instructions encoded on a tangible non-primary program carrier for execution by a data processing device or control of the operation of a data processing device). Computer storage media can be machine-readable storage devices, machine-readable storage boards, random or serial access memory devices, or one or more combinations thereof.

[0072] A computer program, which may also be called, or written as, a program, software, software application, module, software module, script, or code, can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit appropriate for use in a computing environment. A computer program may, but is not required, correspond to a file in a file system. A program may be stored in part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document, a single file dedicated to the program in question, or multiple organized files, e.g., a file storing one or more modules, subprograms, or parts of code). A computer program can be deployed so that it runs on one computer, located in one place, or distributed across multiple computers connected to each other by a data communication network.

[0073] A computer suitable for running computer programs may be based on a general-purpose microprocessor, a dedicated microprocessor, or both, or any other type of central processing unit. Generally, the central processing unit receives instructions and data from read-only memory, random-access memory, or both. Essential elements of a computer are a central processing unit for executing or running instructions, and one or more memory devices for storing instructions and data. Generally, a computer also includes or is operationally coupled to one or more mass storage devices (including, for example, magnetic disks, magneto-optical disks, or optical disks) to receive data from them, transfer data to them, or both. However, a computer is not required to have such devices.

[0074] Computer-readable media suitable for storing computer program instructions and data include, for example, all forms of non-volatile memory and memory devices on a medium, including semiconductor memory devices (e.g., EPROM, EEPROM, and flash memory devices), magnetic disks (e.g., internal hard disks or removable disks), magneto-optical disks, and CD-ROM and DVD-ROM disks. Processors and memory can be complemented by or incorporated into dedicated logic circuits. [Explanation of symbols]

[0075] 10 Systems 11 Bus System 12 Server Systems 18 memory 20 Interfaces 24 Processing Devices 32 Breathing Engine 33a Fluid properties 34 Simulation Engines 38 Data Repositories 40 Airways 40' Digital Expression 42a mouth 42b lips 52 Pharynx 52a Nasopharynx 52b Oropharynx 52c Larynx

Claims

1. 1. A method executed by one or more computer systems for simulating a respiratory event, the method comprising: digitally processing, by one or more computer systems, one or more images of the person's airway to identify one or more objects in the person's airway that are modeled; generating, by the one or more computer systems, a model including a portion of the person's airway based on the one or more objects identified in the one or more digitally processed images, the airway being represented as a volumetric region including a plurality of voxels, the model having a higher resolution level for one or more regions of interest in the model than for one or more regions of the model outside the one or more regions of interest; initiating a respiratory event into the volumetric region by simulating a cough in the volumetric region by the one or more computer systems, the simulated cough occurring in the generated model at a depth within the modeled airway; simulating, with the one or more computer systems, movement of elements of the respiratory event within the volumetric volume, the elements representing particles of the respiratory event at an inlet boundary condition occurring at one or more voxels representing an oropharyngeal or laryngopharyngeal region of the person's airway; obtaining, by the one or more computer systems, a visual representation of particle trajectories of the respiratory event from the simulation; and displaying, by the one or more computer systems, the visual representation including the simulated movement of particles of the respiratory event within the volumetric region on a display device by displaying in a user interface one or more regions of the visual representation corresponding to the one or more regions of interest in the model having a higher resolution level than one or more regions of the visual representation corresponding to the one or more regions of the model outside the one or more regions of interest; A method comprising:

2. The method of claim 1 , wherein the representation of the airway includes a model of the pharynx.

3. The method of claim 2 , wherein the representation of the airway includes a model of the oropharyngeal region of the pharynx.

4. The start occurs in a region representing the mid-pharyngeal region of the pharynx, and the simulation 10. The method of claim 1, further comprising simulating fluid flow of the respiratory event from the oropharyngeal region of the pharynx through an oral cavity and out of a person's mouth.

5. The starting point occurs in a region representing the pharynx and the simulation 10. The method of claim 1, further comprising simulating fluid flow of the respiratory event from the laryngopharyngeal region of the pharynx, through an oropharyngeal region, an oral cavity, and out a person's mouth.

6. 1. A computer system comprising: one or more processor devices; a memory coupled to the one or more processor devices; 1. A storage medium storing executable computer instructions for simulating human respiratory events, the instructions comprising: digitally processing one or more images of the person's airway to identify one or more objects in the person's airway that are being modeled; generating a model including a portion of the person's airway based on the one or more objects identified in the one or more digitally processed images, the model modeling the airway as a volumetric region including a plurality of voxels, the model having a higher resolution level for one or more regions of interest in the model than for one or more regions of the model outside the one or more regions of interest; initiating a respiratory event into the volumetric region by simulating a cough in the volumetric region by the one or more computer systems, the simulated cough occurring in the generated model at a depth within the modeled airway; simulating movement of elements of the respiratory event within the volumetric volume, the elements representing particles of the respiratory event at an inlet boundary condition occurring at one or more voxels representing an oropharyngeal or laryngopharyngeal region of the person's airway; obtaining a visual representation of particle trajectories of the respiratory event from the simulation; and displaying the visual representation on a display device including the simulated movement of particles of the respiratory event within the volumetric region by displaying in a user interface one or more regions of the visual representation corresponding to the one or more regions of interest in the model having a higher resolution level than one or more regions of the visual representation corresponding to the one or more regions of the model outside the one or more regions of interest; 2. A computer system for configuring the one or more processors to perform the steps of:

7. The system of claim 6 , wherein the representation of the airway includes a model of the pharynx.

8. The system of claim 7 , wherein the representation of the airway includes a model of the oropharyngeal region of the pharynx.

9. The system comprises: and further configured to initiate a respiratory event in a region representative of an oropharyngeal region of the pharynx, the system comprising:

7. The system of claim 6, further configured to simulate fluid flow of the respiratory event from the oropharyngeal region of the pharynx through an oral cavity and out of a person's mouth.

10. The system comprises: The system is further configured to initiate in a region representative of a laryngopharyngeal region of the pharynx, the system comprising:

7. The system of claim 6, further configured to simulate fluid flow of the respiratory event from the laryngopharyngeal region of the pharynx, through an oropharyngeal region, an oral cavity, and out of a person's mouth.

11. 1. A computer program product tangibly stored on a computer-readable non-transitory storage device storing executable computer instructions for simulating a human respiratory event, the instructions comprising: digitally processing one or more images of the person's airway to identify one or more objects in the person's airway that are being modeled; generating a model including a portion of the person's airway based on the one or more objects identified in the one or more digitally processed images, the airway being represented as a volumetric region including a plurality of voxels, the model having a higher resolution level for one or more regions of interest in the model than for one or more regions of the model outside the one or more regions of interest; initiating a respiratory event into the volumetric region by simulating a cough in the volumetric region by the one or more computer systems, the simulated cough occurring in the generated model at a depth within the modeled airway; simulating movement of elements of the respiratory event within the volumetric volume, the elements representing particles of the respiratory event at an inlet boundary condition occurring at one or more voxels representing an oropharyngeal or laryngopharyngeal region of the person's airway; obtaining a visual representation of particle trajectories of the respiratory event from the simulation; and displaying the visual representation on a display device including the simulated movement of particles of the respiratory event within the volumetric region by displaying in a user interface one or more regions of the visual representation corresponding to the one or more regions of interest in the model having a higher resolution level than one or more regions of the visual representation corresponding to the one or more regions of the model outside the one or more regions of interest; A computer program product that causes

12. The computer program product of claim 11 , wherein the representation of the airway includes a model of the pharynx.

13. 13. The computer program product of claim 12, wherein the representation of the airway includes a model of the oropharyngeal region of the pharynx.

14. The command to trigger occurs in an area representing the oropharyngeal region of the pharynx, the command comprising:

12. The computer program product of claim 11, further comprising instructions for simulating fluid flow of the respiratory event from the oropharyngeal region of the pharynx through the oral cavity and out of a person's mouth.

15. The instruction: The method further includes instructions for starting in a region representative of a pharyngeal and laryngeal region of the pharynx, the instructions for simulating further comprising:

12. The computer program product of claim 11, further comprising instructions for simulating fluid flow of the respiratory event from the laryngopharyngeal region of the pharynx, through an oropharyngeal region, through an oral cavity and out a person's mouth.

16. The method of claim 1, wherein the simulated cough is based on a combination of exhalation velocity profile, particle distribution size and concentration data.

17. The method of claim 1, wherein the model including one or more smaller voxels in the one or more regions of interest and one or more larger voxels in the one or more regions outside the one or more regions of interest improves processing efficiency of initiating the respiratory event by the one or more computers and simulating movement of the elements by the one or more computers compared to a model including uniformly sized voxels.

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