One of the most important quest that drives aviation development is the speed of an aircraft which is limited by the stiffness and damping of a structure associated with an aeroelastic responses such as static divergence and flutter, respectively. In literature, these aeroelastic responses of flat plate are available with an assumption that fluid viscosity and structural damping are negligible. However, these assumptions reflect significant difference between the numerical as well as experimental results. In this research, an effort has been made to include fluid viscosity and wake of flat plate for an aeroelastic response in time domain and make comparison with the results of frequency domain. Firstly, aeroelastic analysis is performed in frequency domain by using commercial code of MSC NASTRAN (Flight Load and Dynamic System Module) in which PK, K and KE methods are used. For this purpose, data available in literature for flat plate is used and the results showed that frequency based approach is very over-conservative and requires fluid viscosity and wake to be incorporated. Also, limited cycle oscillation, hard flutter as well as divergence are observed for different modes from damping and frequency versus velocity plot. Likewise, aeroelastic analysis is performed with the same set of conditions by incorporating fluid viscosity and wake in time domain. This higher order fidelity approach is implemented by using 2-way FSI with dynamic mesh settings using commercial software of ANSYS. FLUENT, Transient Structural and System Coupling are used with time step and simulation time calculated from CFL condition and settling time, respectively. It is concluded that the high fidelity approach is more accurate specially for flexible structures but it is computationally expensive. Hence, it will be a good choice to use time domain for detailed designing whereas frequency based approach is over- conservative and can be used in preliminary design for narrowing the spectrum of search for 2-way FSI.

Comparative Study of Aeroelastic Response of Flat Plate Using Frequency & Time Domain Methods

One of the most important quest that drives aviation development is the speed of an aircraft which is limited by the stiffness and damping of a structure associated with an aeroelastic responses such as static divergence and flutter, respectively. In literature, these aeroelastic responses of flat plate are available with an assumption that fluid viscosity and structural damping are negligible. However, these assumptions reflect significant difference between the numerical as well as experimental results. In this research, an effort has been made to include fluid viscosity and wake of flat plate for an aeroelastic response in time domain and make comparison with the results of frequency domain. Firstly, aeroelastic analysis is performed in frequency domain by using commercial code of MSC NASTRAN (Flight Load and Dynamic System Module) in which PK, K and KE methods are used. For this purpose, data available in literature for flat plate is used and the results showed that frequency based approach is very over-conservative and requires fluid viscosity and wake to be incorporated. Also, limited cycle oscillation, hard flutter as well as divergence are observed for different modes from damping and frequency versus velocity plot. Likewise, aeroelastic analysis is performed with the same set of conditions by incorporating fluid viscosity and wake in time domain. This higher order fidelity approach is implemented by using 2-way FSI with dynamic mesh settings using commercial software of ANSYS. FLUENT, Transient Structural and System Coupling are used with time step and simulation time calculated from CFL condition and settling time, respectively. It is concluded that the high fidelity approach is more accurate specially for flexible structures but it is computationally expensive. Hence, it will be a good choice to use time domain for detailed designing whereas frequency based approach is over- conservative and can be used in preliminary design for narrowing the spectrum of search for 2-way FSI. 

Comparative Study of Aeroelastic Response of Flat Plate Using Frequency &amp; Time Domain Methods

This paper comprehensively reviews the progress of static aeroelastic effect prediction and correction methods for aircraft, including the damage and protection of aeroelastic. It is significantly important to determine the similarity conditions and static aeroelastic scaling modeling in wind tunnel experiments to obtain accurate aerodynamic characteristics. Meanwhile, similar stiffness distribution, manufacturing materials, and processing technology are strongly associated with the simulation of aircraft structural dynamics. The structural layout of the static aeroelastic model, including plate type, beam type, bearing skin type, and full structural similarity type, are described in detail. Furthermore, the wind tunnel and test technique also play an important role in static aeroelastic experiments. It is worth noting that computational fluid dynamics (CFD) and computational structure dynamics (CSD) have attracted increasing attention from researchers for application in aeroelastic analysis of the flow field. The research status and key technologies of aeroelastic numerical simulation of aircraft are introduced in detail. Additionally, this paper briefly introduces the static aeroelastic prediction and correction method, especially the widely practiced K-value method. 

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The Prediction and Correction Method of Aircraft Static Aeroelastic Effects: A Review of Recent Progress

In any flutter prediction analysis, modal testing is necessary because flutter, a resonant like vibration occurs at a flutter frequency and adopts a mode shape akin to its structural natural modes. Modal testing can be performed computationally with knowledge of the mechanical properties of the structure. In the present work, computational modal analysis is first performed on a cantilevered hybrid composite thin plate and validated experimentally. Then, the computational procedure is demonstrated on a composite hollow wing model of same material. The concept of hollow wing is explored due to the superior mechanical properties of carbon/kevlar composite plate. It is observed that the natural frequencies of the hollow wing model are higher than thin plate due to stiffer configuration. A breathing mode was also observed at mode 4 for the hollow wing.

D. Raja Joseph

Papers

Review of Aeroelasticity Testing Technology