Background
With the rapid development of world economy, more and more passengers choose to travel on board an aircraft. In the flight process of the civil airliner, the cabin is a closed environment, passengers and crews are exposed to the environment with higher personnel density, and air flow is realized by an air conditioning ventilation system. When a passenger carrying the virus takes an airplane, the virus is infected with breath, mouth water and mucus on the surface of an object or directly enters the air. Healthy people may become infected by touching the surfaces of these contaminated objects or by inhalation of viruses.
COVID-19 virus particles can be considered as a coronavirus different from SARS virus, and the particle size in air is about 60-140nm, belonging to inhalable ultrafine particles, slightly smaller than the particle size of 80-220nm of SARS virus. Researches show that COVID-19 viruses can be transmitted in a relatively airtight space and a specific place in an aerosol mode, and the space in the civil aviation cabin is smaller, so that the research on the method for transmitting and diffusing the viruses in the civil aviation cabin is significant for protecting the health of passengers and crewmembers.
Since COVID-19, SARS and several influenza events occurred through the transmission of civil airliners, the study of cross-transmission of pathogens within a relatively closed environment has become increasingly important, where viruses can be carried by infectious agents taking aircraft from one city and transmitted to passengers in the same aircraft and to people in another city. The research shows that the civil aviation passenger cabin is a suitable environment for transmitting pathogens carried by passengers or crewmembers, and the transmission mode and path of the viruses in the cabin mainly comprise direct contact transmission, indirect contact transmission and air transmission, and the method for researching the transmission and the diffusion of the viruses in the cabin mainly comprises a simulation experiment measurement method, a CFD numerical simulation method and a probability analysis method.
CFD has the unique advantages of low cost, high speed, complete data, capability of simulating various working conditions and the like, and is gradually favored by people. Hao Lei et al show that aisle passengers have a higher exposure rate in short flights. The method of combining simulation experiments and CFD numerical simulation is adopted by Wei Yan and the like, so that the propagation characteristics of air pollutants in an aircraft cabin are researched, and the pollution source position has an important influence on the propagation of the pollutants in the aircraft cabin.
The domestic scholars have few researches on the aspect, and examples prove that pollutants such as viruses in cabins can be transmitted in cabins, the particle size of the viruses is tiny, the viruses belong to inhalable particles, the transmission characteristic is extremely strong, and the influence on human population health is extremely great. Therefore, it is very necessary to invent a research method for virus transmission in the cabin of a civil aircraft based on a CFD model.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide an analysis method for virus transmission in a civil aircraft cabin based on a CFD model.
The invention adopts the following technical scheme. The method for analyzing the virus transmission in the cabin of the civil aircraft comprises the following steps:
collecting parameters of a civil aircraft, and constructing a cabin physical model of a selected space by utilizing three-dimensional modeling software;
The simulation path of virus diffusion, the diffusion speed field and the concentration field are determined according to the simulation result;
based on a mathematical model of virus propagation in the cabin of the civil aircraft, the probability of risk of infection of passengers in the cabin under different states of the personalized ventilation opening above the sick passengers is calculated.
Further, the parameters of the civil aircraft include overall cabin size, interior seat, body size, doorway position, doorway number and doorway size.
Further, the simulating of the cabin physical model after grid division specifically includes the following steps:
The divided grids are imported into FLUENT software for grid inspection, if the grid volume is negative, the grids are divided again, a turbulence model is set, an RNG k-epsilon model is selected, boundary condition setting is carried out on the inlet and outlet speed, flow and temperature, iteration times are selected, and a simulation result is obtained when the result is not converged any more.
Further, the formula of the mathematical model for virus propagation in the cabin of the civil aircraft is as follows:
Wherein P is the infection probability, D is the number of infected people, S is the number of people easy to be infected, I is the number of sick people, Q is the release rate of virus units, P is the pulmonary ventilation rate, Q is the ventilation rate of a passenger cabin, alphai is the I-th degree of opening the personalized ventilation opening above the sick passenger seat, Q0 is the maximum ventilation amount of the personalized ventilation opening above the passenger seat, and t is the exposure time.
Still further, the magnitude of the personalized vent opening above the diseased passenger seat, αi, is denoted as αi＝{α1,α2,α3},α1, α2, a specific proportion of the openings, and α3, a full opening.
Further, the method includes analyzing effects of cabin passenger activity and cabin service movement on cabin virus transmission under non-steady state conditions by setting the moving mesh size and the movement speed of cabin passengers and crewmembers.
The beneficial technical effects obtained by the invention are as follows:
The invention researches an analysis method of virus transmission and diffusion in a civil aircraft cabin, explores the virus diffusion condition of a virus source when the cabin is at different positions and the virus diffusion condition when personnel move in the cabin, and visualizes the transmission path of the virus in the civil aircraft cabin by using a numerical simulation method.
The invention can provide treatment advice for crew members and airline operators when virus transmission events such as COVID-19, SARS and the like occur in the cabin, and proper measures are taken to reduce the exposure risk of passengers and crew members, thereby contributing to scientific protection of passengers and crew members in the cabin of the civil aviation passenger plane and blocking epidemic diseases.
Detailed Description
The present invention will be described in further detail with reference to examples below in order to make the objects, techniques and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The method for analyzing virus propagation in the civil aviation passenger cabin provided by the embodiment comprises the following steps in sequence, wherein the implementation steps are shown in figure 1:
and S1, building a physical model of a cabin of the civil aircraft.
The interior of the passenger cabin is simplified to a certain extent, and only the interior space of the luggage rack of the passenger cabin is reserved. Because the total size of the cabin model unit is more, the number of the subsequent required grids is larger, and when public health safety events such as virus transmission and the like occur in the civil aviation passenger cabin specified by the civil aviation bureau of China, front and rear three rows of passengers should be isolated, in order to facilitate calculation, the cabin interior is simplified to a certain extent, and a 7-row cabin physical model is constructed by using periodic boundary conditions.
In this embodiment, the overall dimensions of the 7 rows of physical models (length 6.3m, width 3.7m, height 2.26 m) and the positions and dimensions of the roof air supply opening, the ceiling air supply opening and the air outlet are designed according to the dimensions of the cabin a320 and output IGS documents, as shown in fig. 2, 3 and 4.
In this embodiment, the Solidworks modeling software is used to construct the physical model of the cabin, and in other embodiments, other modeling software such as CAD and UG may be used to perform modeling.
In step S2, in this embodiment, an ICEM CFD preprocessor is used to perform meshing of the physical model.
Step S201, first, detailed understanding of CFD model features, principles, implementation process, etc. will be described. The appropriate model is selected for improvement, and the influence of various cabin activities on the virus transmission and diffusion path, such as jolt experienced by the aircraft, personnel activities in the cabin and the like, is considered.
Step S202, the IGS file obtained in the step S1 is imported into an ICEM CFD preprocessor, a solid model is restored first, each part size is defined, the solid model (namely, a constructed cabin physical model) is subjected to grid division by adopting an unstructured grid division method, the total number of 7 rows of cabin grids is about 480 ten thousand, three views of grid division results are shown in fig. 5, 6 and 7, an. Msh file is output, and grid division can be performed by adopting a GAMBIT and other preprocessors.
And step S3, performing numerical simulation calculation by using FLUENT, wherein FLUENT is a calculation software of CFD and has wide application in the aspects of aerospace, automobile design, petroleum and natural gas, turbine design and the like. In the embodiment, the divided grids of the physical model obtained in the step S2 are imported into FLUENT software, and numerical simulation is performed on virus propagation in the cabin of the civil aircraft by using the FLUENT software to obtain a numerical simulation result of virus propagation in the cabin of the civil aircraft.
Step S301, opening FLUENT software, inputting the msh file in step S2 into FLUENT and checking grids, and re-dividing the grids if the grid volume is negative;
step S302, a turbulence model selects an RNG k-epsilon model;
Step S303, setting parameter conditions and boundary conditions, wherein in the embodiment, parameter condition setting, entrance, exit speed, temperature and pathogen release speed boundary conditions of sick passengers are performed in FLUENT software according to a simulation scene of a civil aviation passenger cabin and a virus release state;
Step S304, setting convergence conditions and defining initial conditions;
Step S305, after the relevant parameter setting, starting the iteration number setting and performing the iterative calculation, when the residual is seen in the residual map to be no longer declining, the operation is considered to be converged,
Stopping operation to obtain an operation result;
step S306, the result is saved.
And S4, analyzing and evaluating a virus propagation numerical simulation result in the passenger plane cabin. And (5) analyzing and researching the results of the numerical simulation by utilizing the FLUENT self-contained post-processing software. And a simulation path of virus transmission and diffusion, a speed field, a concentration field and the like of diffusion are obtained through FLUENT simulation calculation, and the diffusion rule of virus transmission in the cabin is analyzed, so that the exposure risk of passengers and crewmembers is reduced.
And S5, constructing a virus propagation mathematical model in the cabin of the civil aircraft. When the personalized vent above the sick passenger seat is opened and closed, different effects can be caused on the air flow in the civil aircraft cabin. According to the invention, through correcting the Wells-Riley model, the probability of infection risk of passengers in the cabin under different states of the personalized ventilation opening above the sick passengers is calculated. The Wells-Riley model is as follows:
Wherein P is the infection probability, D is the number of infected people, S is the number of people easy to infect, I is the number of sick people, Q is the release rate of virus unit (quanta/h), P is the lung ventilation rate, Q is the ventilation rate of a passenger cabin, r is the infection initiating capability, and t is the exposure time.
The modified Wells-Riley model formula is as follows:
Where αi is the degree to which the personalized vent above the diseased passenger seat is opened. In this example, αi＝{α1,α2,α3},α1 represents unopened, α2 represents opened 50%, α3 represents fully opened, and Q0 is the maximum ventilation of the personalized vent above the passenger seat.
And S6, analyzing the virus transmission in the cabin under the unsteady state condition. The path of viral transmission may be altered by the movement of passengers and crewmembers in the cabin. According to the invention, the passenger and crew movable grid model is constructed, the size and the movement speed of the movable grid are set, and the influence of the passenger activity and cabin service in the cabin on the virus transmission in the cabin is analyzed.
When virus transmission events such as COVID-19 (Corona Virus Disease 2019, novel coronavirus pneumonia) and SARS (Severe Acute Respiratory Syndromes, severe acute respiratory syndrome) occur in a passenger cabin, suggestions are provided for a crew member and passengers to reasonably arrange cabin activities and use personal protection articles, the infection risk of other passengers is reduced, infected persons are isolated as much as possible, and virus transmission is blocked.
According to the invention, a virus propagation and diffusion mode in the civil aircraft cabin is researched, a mathematical model is established by using a CFD calculation method, the numerical simulation is carried out by using FLUENT software, a simulation path of virus propagation in the civil aircraft cabin is obtained, finally, a simulation result is analyzed, the virus propagation and diffusion rule in the civil aircraft cabin is analyzed, and the occupational exposure risk of a crew member is reduced from the aspect of occupational health. And provide the suggestion to crew and passenger's reasonable arrangement cabin activity and use personal protection articles for use, reduce other passengers and infect the risk, keep apart the infectious agent as far as possible, block virus transmission, have important meaning to cabin passenger and crew's human health.
The foregoing has shown and described the basic principles and main features of the present invention and the advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.