Experimental And Numerical Study On Unsteady Airflow Around Passengers In The Aircraft Cabin

In the context of more and more passengers choosing to travel by air,the safety,health and comfort of the aircraft cabins are particularly important.While,the characteristics of airflows in aircraft cabins are the basis of the study of pollutant propagation and passenger comfort.The airflows in the cabin are affected by many factors and exhibits unsteady flow characteristics.Therefore,the unsteady airflows around passengers in aircraft cabin were studied in this thesis.Firstly,the factors influencing the unsteady airflow field of the aircraft cabin were optimized in the 7-row aircraft cabin mokcup.The cabin mockup ensured that the air supply was even,stable and controllable temperature boundary and reasonable heat dissipation characteristics of passengers.The full scale average airflow field of the cabin were obtained by experimental measurements,which made foundation for the study of unsteady flow fields in the cabin.After studying the averaged characteristics of the full-scale airflow of the cabin mockup,the characteristics of unsteady flow are studied in detail.The supply air jet characteristics were quantitatively analyzed by turbulence temporal scale and spatial scale.From the energy spectrum,the attenuation characteristics of jet and the energy characteristics of jet entrainment were analyzed.The high order turbulence parameters,kurtosis and skewness of the velocity time series were analyzed to reveal the law of jet airflow.It provides theoretical data support for numerical simulation of aircraft cabin airflow.The unsteady thermal plume of cabin passengers was studied by mini-PIV.For the first time,the frequency distribution of the thermal plume were shown to be a mixture of Gauss distribution,which qualitatively described the unsteady of thermal plume.The chaos theory was proposed to analyze the unsteady characteristics of human thermal plume,and it was found that the phase space distribution of thermal plume change from a single spindle to multi spindle shape.Moreover,the fractal dimension and flow entropy demonstrated the human thermal plumes was a kind of chaotic airflow.Then,the unsteady flow field in the jet collision region was measured by 400 Hz mini-PIV.The theoretical analysis of the turbulent scale can provide theoretical basis for the time step selection and mesh size of the unsteady flow field in the collision zone simulated by CFD method.The influence of unsteady airflow on passenger comfort was quantitatively described by power spectrum index.By wavelet analysis,the quasi periodic characteristics of the unsteady airflow in the collision region and the multiscale energy distribution characteristics were obtained.Finally,according to the characteristics of large-scale unsteady airflow in aircraft cabin,the concept of “dynamic airflow distribution” in aircraft cabin was put forward.To study the effects of Reynolds number,air supply direction and passengers thermal airflow factors for dynamic airflow evolution by numerical simulation method.It was found that with the increase of Reynolds number,the large scale flow of the aircraft cabin changed from stable symmetry to dynamic airflow.The different air supply angles affected the characteristics of jet attachment,which resulted in the different unsteady degree of the dynamic airflow distribution.The human thermal plumes had the effect of suppressing the dynamic airflow distribution of the aircraft cabin.