PIV Experimental Study Of The Multi-scale And Unsteady Airflow Characteristics In A Passenger Aircraft Cabin Mockup

The dynamic and multi-scale feature of airflows,which are common in aircraft cabins,significantly influence the thermal sensation of passengers and contaminant transmissions.How to quantify the complex airflow inside the cabin is not only the key to optimal air distribution but also an important step to build an idea cabin environment.For this purpose,a full-scale partially transparent 7-row cabin mockup and a single-occupancy transparent microclimate chamber were built to facilitate using particle image velocimetry(PIV)to quantify the air distribution inside.By the cross time between pulses splicing PIV method,both the multi-scale interaction between high speed personalized Gasper jet and the airflow distribution from main ventilation with lower velocity was obtained.Using the long-term continuously PIV method with large sampling size,the large-scale dynamic behaviors of airflow were revealed.By introducing the pre-seeding PIV method,the unsteady thermal convection flow of a passenger inside a limited space was obtained.Main findings were detailed below:1.This study introduced the cross time between pulses splicing method to solve the problem of PIV measurement of the flow field over a large velocity span,which not only provided high-quality data for validating the numerical simulation models but also revealed airflow characteristics of gasper jets in a realistic cabin environment.In a cabin environment,the decay of gasper jets was accelerated by the influence of the main ventilation.The jets from the diffusors of the main ventilation deflected the gasper jets to a similar degree under both isothermal and cooling conditions,and the empirical equations for jet deflection were summarized.At larger scales,the higher flow rates can cause draught for the user of gasper and influence the adjacent passenger.Thus,gaspers should be used at low flow rates.2.To analyze the large-scale dynamic characteristics in aircraft cabins,a series of long-term large-scale PIV measurements were performed in an aircraft cabin mockup to provide necessary basic data.In collision zones of two lateral jets,the temporal characteristics of the swing motions were presented via proper othogonal decomposition(POD)method,and the swing periods were nearly 30 s.By analyzing the occurrence probability of swings,the swing-induced contaminant transmission regularity was presented.In jet zones,the dynamic behavior of large-scale circulation was revealed by identifying the circulation center of each instantaneous flow field.However,the center oscillated in a small range near the breath zone of the passenger seating in the middle of one side,which explained the lock-up phenomenon founded in contaminant transmission studies in the cabin.3.The experimental procedure of pre-seeding PIV method to quantify the air distribution of thermal convection flow of passenger was built.Two different types of 2D-PIV and TR 2D-PIV systems were used to quantify thermal convection flow with both high temporal and spatial resolution.As limited by the space of cabin,the rising convection flow reached a maximum velocity of 0.179 m/s at a height of 0.068 m above the head.The vortexes of the thermal convection flow were identified by the ?ci criterion,which indicated increasing size and intensity in the region alongside the rising plumes.Multi-scaled characteristics of thermal plumes were revealed by POD,and the period of ascending plumes was estimated as 5 s.