14th International Symposium on Particle Image Velocimetry – ISPIV 2021
August 1–5, 2021

PIV measurement of a jet from a gasper in an aircraft
cabin mockup

J. H. A. GOUVEIA1∗, J. I. YANAGIHARA1

1 University of São Paulo, Department of Mechanical Engineering, Polytechnic School, São Paulo, Brazil
∗ jhagouveia@usp.br

Abstract
The air conditioning system of most commercial aircrafts consists of a main system, which operates on the
principle of mix ventilation, and a personalized system called gasper. Field studies show that passengers
prefer to keep gasper parcially open or redirect it away from the head due to the discomfort. Therefore,
there is a demand to characterize the flow of this device for future improvements. In this way, the present
work aims to experimentally study the gasper jet inside a real cabin mockup using PIV. The results indicate
that passengers are subjected to a high speed jet and the air in their breathing zone is mostly supplied by the
mixed ventilation system due to the large entrainment ratio.

1 Introduction
A way to improve air quality inside aircrafts cabins is through personalized ventilation and the typical system
included in commercial aircrafts is the gasper, a small adjustable vent positioned above passengers’ head
that provides an air jet directly to passengers’ breath region (Li et al. (2018)). In previous studies focused on
the gasper airflow, particle image velocimetry (PIV) was used in mockups that did not faithfully represents
the complex geometry of a real cabin. Therefore, the present work is focused on the PIV measurement of the
gasper airflow under the influence of a mixing ventilation system to evaluate jet features as velocity decay
and entrainment ratio. Also, through measurement of multiple planes, a 3D airflow distribution of the gasper
jet was obtained. These results allow a proper understanding of the gasper jet behavior and an assessment
of its efficiency as a tool to increases passengers’ comfort and safety.

2 Materials and methods
A PIV system was used to measure the gasper jet velocity field. This system consists of a 200 mJ laser sheet
with a thickness of 2 mm. and a wavelength of 532 nm. provided by a double-cavity Nd:YAG laser with a
frequency of 7.4 Hz. The images were recorded using a Dantec FlowSense 4M MK II camera with 2048 x
2048 pixels. Three traverse were used to move the PIV system. The laser, the camera and all traverse devices
were mounted inside a fully functional mockup of an Embraer E-170 airplane, placed inside a low-pressure
chamber. In each run the cabin environmental conditions were kept constant: the temperature was 21°C, the
air flow in the main ventilation system was 1,050 m3/h and the mean flow rate in the gasper was 1.7 m3/h
(ASHRAE (2018)).The diethylhexyl sebacate (DEHS) particles with a mean diameter of 2 µm. were seeded
in the environment through the cabin main ventilation inlets.
For each measurement plane, a thousand of double-frame images from an area of 243.2 x 243.3 mm. was
recorded. Due to the cabin material and geometry, laser reflections caused a background noise in images;
therefore, the first image preprocessing step was the subtraction of a mean image from each image. Besides
that, a 3 x 3 Gaussian filter and in sequence a 3 x 3 Laplacian filter was applied to reduce noise and increase
the correlation peak (Raffel et al. (2018)). All PIV analysis presented in this work was made by a cross-
correlation algorithm with deforming interrogation window and grid refining that yielded a spatial resolution
of 1.9 mm. after vector validation through primary peak ratio (PPR) and universal outlier detection algorithm
(UOD) (Westerweel and Scarano (2005); Hain and Kähler (2007)).



3 Results
From the jet middle plane (Fig. 1(a)) was possible observe that the gasper produces an annular jet where
velocity increase until the reattachment point is reached and after that the velocity begins to decay in the
fully developed zone. In this way, in Fig. 1(b) is presented the fitting formula for centerline non-dimensional
velocity in the fully developed zone. The curve behaves in a similar way as presented in Dai et al. (2015)
despite gasper’s different physical characteristics.
Through PIV measurement of 20 planes separated by 2.5 mm. it was built a 3D representation of the gasper
jet (Fig. 1(c) and Fig. 1(d)). Considering that the cross-section has a circular shape, the local air flow
rate was calculated from the integral of the velocity profile for each axial position. It was notorious the
fast increase in flow rate inside the jet (Fig. 1(e)), meaning that the air in the passenger breath region is
essentially air from the cabin environment that merges into the jet.

Figure 1: Results summary

4 Conclusions
Although the gasper jet measured in the present work differs from previous studies in terms of its geome-
try and the cabin environmental conditions, the non-dimensional centerline velocity decay obtained in the
present study was very similar to the previous results. Also, it was demonstrated that due to its small outer
diameter (d0 = 10.5 mm in the present work), the gasper can provide a jet with a high-velocity that can
increase passengers’ draft sensation. For this reason, usually the passengers prefer to adjust the jet direction
to their trunk or lower limbs instead of their heads. From PIV data evaluation was also indicated that the
gasper is not an ideal barrier for virus and bacteria due to its high entrainment ratio.

References
ASHRAE (2018) ANSI/ASHRAE Standard 161-2018: Air quality within commercial aircraft. ASHRAE

Dai S, Sun H, Liu W, Guo Y, jiang N, and Liu J (2015) Experimental study on characteristics of the jet from
an aircraft gasper. Building and Environment 93:278–284

Hain R and Kähler J C (2007) Fundamentals of multiframe particle image velocimetry (piv). Experiments
in Fluids 42:575–587

Li J, Liu J, Dai S, Guo Y, Jiang N, and Yang W (2018) Piv experimental research on gasper jets interacting
with the main ventilation in an aircrat cabin. Building and Environment 138:149–159

Raffel M, Willert C, Wereley ST, and Kompennhans J (2018) Particle image velocimetry: A practical guide.
Springer

Westerweel J and Scarano F (2005) Universal outlier detection for piv data. Experiments in Fluids 39:1096–
1100


	Introduction
	Materials and methods 
	Results
	Conclusions