Power Spectral Density: Atmospheric Turbulence & Aircraft Stability

[PujaSunil88]

Heya Everyone! I was going through topics on Atmospheric turbulence and their effects on stability of aircrafts...and I came across Power spectral density. I could'nt understand it properly. Could anyone please give me an idea of what it is an refer me some literatures / books on it or topics related with atmospheric turbulence and its effect of aircraft stability?

 

[RandomGuy88]

Power spectral density basically tells you how much power is in certain frequencies. For example consider measuring the air velocity at a single point in a turbulent flow for an arbitrary amount of time. You have measured the velocity in the time domain so you can plot velocity versus time. Using fast Fourier transforms you can convert this data to the frequency domain where the x-axis will be frequency and the y-axis will now be a measure of how much power is contained in a each frequency. So in a turbulent flow, a spike in the power spectral density at a certain frequency would likely indicate some kind of flow phenomena occurring at that frequency, for example vortex shedding from a cylinder which for certain Reynolds numbers occurs at a specific frequency.

I don't know too much about aircraft stability but I would imagine this would be important because flow phenomena at a particular frequencies could excite certain unstable modes of the aircraft.

 

[viscousflow]

RandomGuy is correct. I'll elaborate more on the uses in aircraft control.

The power spectral density is used to create a gust model to simulate random motion and/or certain maneuvers, such as pitch, yaw, roll, etc... Also it can be used to excite short period and long period modes. These models are used and applied as a disturbance model to simulate the desired gust frequency, shape or even strength to analyze the robustness of the model.

 

[PujaSunil88]

@Random Guy, Viscous low: Thanks a lot both of you! its been of great help!

 

[alphy]

Hello,

Power Spectral Density (PSD) is a mathematical tool used to analyze signals and their frequency content. In the context of atmospheric turbulence and aircraft stability, PSD can be used to quantify the intensity and characteristics of turbulence in the atmosphere that can affect the stability of an aircraft.

In simple terms, PSD is a way to represent how much power (or energy) a signal has at different frequencies. In the case of atmospheric turbulence, it can be used to analyze the fluctuations in air pressure, temperature, and velocity that can impact the flight of an aircraft.

There are many resources available on PSD and its applications in the field of atmospheric turbulence and aircraft stability. Some recommended literature includes "Atmospheric Turbulence and Mesoscale Meteorology" by J.C. Wyngaard and "Aircraft Dynamics: From Modeling to Simulation" by Marcello R. Napolitano.

I would also suggest looking into topics such as turbulence modeling, aerodynamic stability, and flight control systems, as they are closely related to the effects of atmospheric turbulence on aircraft stability.

I hope this helps and provides some direction for further research. Best of luck in your studies!