Abstract
The aim of this paper is to present a new aeroelastic stability model taking into account the viscous effects for a supersonic nozzle flow in overexpanded regimes. This model is inspired by the Pekkari model which was developed initially for perfect fluid flow. The new model called the “Modified Pekkari Model” (MPM) considers a more realistic wall pressure profile for the case of a free shock separation inside the supersonic nozzle using the free interaction theory of Chapman. To reach this objective, a code for structure computation coupled with aerodynamic excitation effects is developed that allows the analysis of aeroelastic stability for the overexpanded nozzles. The main results are presented in a comparative manner using existing models (Pekkari model and its extended version) and the modified Pekkari model developed in this work.
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Abbreviations
- A :
-
Aerodynamic influence coefficient
- \(C_{\mathrm{f}}\) :
-
Friction coefficient
- \(F_\mathrm{k}\) :
-
Universal function of Chapman for the interaction zone
- \(\vec {f}_\mathrm{a} \) :
-
Aerodynamic loads
- {F} :
-
Force vector
- jp :
-
Number of elementary elements in the free interaction region
- [K], [\(K_{\mathrm{aero}}\)]:
-
Stiffness and aerodynamic rigidity matrices
- L :
-
Interaction length
- l :
-
Element length in the interaction region
- [M]:
-
Mass matrix
- M :
-
Mach number
- \(N_{i}\) :
-
Shape function
- \(\vec {n}\) :
-
Normal unit vector
- P :
-
Pressure
- \(R^{k}\) :
-
Dynamic influence coefficient
- s :
-
Curvilinear coordinate
- U :
-
Flow velocity
- t :
-
Time
- \(w_\mathrm{n} \) :
-
Normal displacement
- \(\{ V \}, \{ {\overline{{V}}}\}\) :
-
Natural and aeroelastic eigenmode vectors, respectively
- \(\{ W \}, \{ {\ddot{W}} \}\) :
-
Nodal displacement and acceleration vectors, respectively
- \(X_{i}\) :
-
coordinate along the axis of the nozzle
- \(X^{k}_{\mathrm{n}}\) :
-
Normal displacement of the mode k
- \(\gamma \) :
-
Specific heat ratio
- \(\sigma \) :
-
Heaviside function
- \(\rho \) :
-
Density of the fluid
- \(\omega ^k \) :
-
Structure natural frequency for mode k
- \(\Omega ^k \) :
-
Aeroelastic frequency for mode k
- \(\eta ^{x}, \eta ^{y}\) :
-
Normal unit vector components
- atm:
-
Ambient condition
- c:
-
Chamber condition
- k:
-
Relative to the interaction zone
- n:
-
Normal direction to the wall
- p:
-
Plateau
- sep:
-
Separation point
- w:
-
Wall
- \(\infty \) :
-
Isentropic flow condition at a given section of the nozzle
- 0:
-
Equilibrium state
- k :
-
Relative to mode k
- x, y :
-
Cartesian coordinates
- NPR:
-
Nozzle pressure ratio
- MPM:
-
Modified Pekkari model
- PVW:
-
Principle of virtual works
- TSP:
-
Theory of small perturbations
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The authors certify that no actual or potential conflict of interest including any financial, personal or other relationships with other people or organizations within three (3) years of beginning the work submitted that could inappropriately influence (bias) our work.
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Communicated by F. Lu.
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Bekka, N., Sellam, M. & Chpoun, A. Aeroelastic stability analysis of flexible overexpanded rocket nozzle. Shock Waves 26, 513–527 (2016). https://doi.org/10.1007/s00193-015-0575-2
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DOI: https://doi.org/10.1007/s00193-015-0575-2