Targeted Vibration Isolation of Aircraft Interior Cabins From External Disturbances

Stephanie Vavra Author

04/01/2021 Added

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Aircraft vibration is the cause of aircraft passenger discomfort, fear, and even injury. Research on how to mitigate the flow of energy from the outside of the aircraft (such as turbulence) to the inside aircraft cabin is discussed in this presentation.

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[00:00:01.000]Hello my name is Stephanie Vavra
[00:00:02.940]I'm a mechanical engineering student here
[00:00:04.860]at the University of Nebraska Lincoln.
[00:00:07.120]For the past year my research advisor
[00:00:09.250]Dr. Keegan Moore and I have been researching
[00:00:11.870]the topic of targeted vibration isolation
[00:00:14.850]of airline interior cabins from external disturbances.
[00:00:19.330]In this presentation, I will be discussing more
[00:00:21.500]about the progress we have made for this project.
[00:00:27.950]As a more specific introduction, this research involved
[00:00:30.850]a study of airplane cabin vibration
[00:00:32.910]caused by external disturbances.
[00:00:35.500]Types of disturbances include turbulence during flight
[00:00:38.550]engine vibration, other external noise
[00:00:40.990]or even internal noise or vibrations.
[00:00:44.170]And these vibrations are not desirable during commercial
[00:00:47.320]flight as they can cause passenger discomfort,
[00:00:50.420]fear or even injury.
[00:00:52.320]For instance, studies have shown that up
[00:00:54.060]to 25% of the general public fears aircraft travel
[00:00:57.890]due to the roughness from turbulence
[00:01:00.590]additionally, about 40 injuries in the US alone
[00:01:04.000]are recorded each year as a result of turbulence
[00:01:08.400]therefore there is a great desire to isolate passengers
[00:01:12.570]from these exterior aircraft disturbances.
[00:01:16.390]For this specific research a hypothesis has been developed
[00:01:19.540]for testing this hypothesis or claim states that
[00:01:24.350]the passengers themselves act as vibration absorbers
[00:01:27.550]so in other words, when external disturbances are translated
[00:01:32.740]from the outside to the inside of the cabin the passengers
[00:01:37.090]are absorbing that energy which is undesirable.
[00:01:40.810]So to further test this hypothesis, a method
[00:01:43.320]needs to be implemented such that there's a disruption
[00:01:46.500]in energy transfer from the outside of the aircraft
[00:01:49.390]to the inside cabin.
[00:01:51.560]To achieve this, we have introduced elements such as springs
[00:01:54.980]and dampers into the system shown here to disrupt the flow
[00:01:59.250]of energy with the springs being the main focus
[00:02:02.260]as there are linear and nonlinear springs incorporated
[00:02:06.640]which can greatly affect the overall translation
[00:02:10.840]of energy in the system.
[00:02:13.490]Then the response of the system will be able to help us
[00:02:16.130]determine how to more effectively create a system
[00:02:19.330]where the passengers are not not absorbing
[00:02:22.360]as much of the vibrational energy.
[00:02:26.460]So to test the first hypothesis, a reduced order model
[00:02:30.760]capable of testing the dynamics of the system
[00:02:33.160]with reduced dynamics was developed.
[00:02:36.250]The system includes the primary elements of the aircraft
[00:02:38.950]such as the airframe, otherwise known as a fuselage,
[00:02:42.370]floor and both the left and right rows of seats.
[00:02:46.240]Additionally sets of springs and dampers have been placed
[00:02:49.500]between the ground, airframe, cabin floor
[00:02:52.050]and the two sets of seats.
[00:02:54.200]The springs between the seats and the floor
[00:02:56.610]are modeled with nonlinear springs
[00:02:58.570]that incorporate a cubic nonlinearity.
[00:03:03.890]So next a computational non dimensionalised model
[00:03:08.200]of the system was derived and modeled
[00:03:10.760]using a program called MATLAB the non dimensionalised system
[00:03:14.610]allows us to simulate responses for not only the system
[00:03:18.050]but other systems as well such as other models
[00:03:21.170]or types of aircraft so here a low amplitude response
[00:03:25.790]was generated for the translational model that I just showed
[00:03:29.270]with the airframe having a non dimensionalised
[00:03:32.188]initial velocity of 0.1 or 0.01 and the plots here
[00:03:41.200]show the displacement of the airframe, cabin floor
[00:03:43.810]and both sets of seats as a function of time
[00:03:46.610]in each of the plots, the linear and nonlinear
[00:03:49.220]responses can be seen, for this case both linear
[00:03:52.720]and nonlinear cases behave nearly the same
[00:03:55.870]as you can see with the red and black lines
[00:03:58.770]which is expected at a pretty low initial velocity.
[00:04:04.610]However, as we start to continue to increase the initial
[00:04:08.420]velocity of the airframe to 0.03 you may now be able to
[00:04:13.730]notice more of the differences between the linear
[00:04:15.960]and the nonlinear displacements.
[00:04:18.120]Additionally, it should be noted that for the system
[00:04:20.410]the displacements of the seats are rather large
[00:04:23.060]for such a small initial velocity, this indicates how
[00:04:26.470]the seats and even the passengers in those seats
[00:04:29.290]are absorbing a lot of the energy transfer
[00:04:31.590]from the outside of the airplane cabin to the inside.
[00:04:37.690]So now increasing the initial velocity of the airframe
[00:04:42.750]to even higher value of 0.1, now the difference in
[00:04:47.310]nonlinearity and linearity are clearly seen
[00:04:49.990]in these displacement plots.
[00:04:52.430]Therefore, this is further proving how the lower mass system
[00:04:55.560]elements like the seats are absorbing the energy
[00:04:58.140]transferred through the aircraft.
[00:05:02.660]Lastly using MATLAB this generated plot shown
[00:05:06.790]on the screen shows how the transmissibility or the ability
[00:05:11.403]of energy to be translated through the system increases
[00:05:14.440]with an increased in increase in an external force
[00:05:18.670]so in other words, more energy is being translated
[00:05:21.110]from the outside of the aircraft to the inside
[00:05:23.050]with an increase in force proving again that the system
[00:05:27.000]masses are absorbing this energy.
[00:05:32.570]So after stimulating the amplitude responses
[00:05:35.330]and energy transmissibility of the aircraft,
[00:05:37.760]translational model the hypothesis that the passengers
[00:05:41.570]act as a vibration absorber was verified
[00:05:44.990]therefore, future work with more complex models
[00:05:48.070]are currently being investigated to further
[00:05:50.330]understand the dynamics of the entire model
[00:05:53.700]once more complex models are stimulated
[00:05:56.060]we will have a better of how to isolate the passengers
[00:06:00.920]in the aircraft from external vibrations.
[00:06:05.270]So this concludes my discussion on the isolation
[00:06:08.510]of airline cabins from external disturbances
[00:06:11.960]I would like to thank my research advisor for supporting me
[00:06:14.640]through this project and I would like to thank UCARE
[00:06:17.090]for sponsoring this research opportunity.
[00:06:19.470]Should there be any questions regarding this project
[00:06:21.650]please email me at the email provided.
[00:06:24.580]Thank you.

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Targeted Vibration Isolation of Aircraft Interior Cabins From External Disturbances

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