FreeCASE - Free(dom) Computational AeroServoElasticity
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### Aileron buzz

In this section we present the numerical results of AeroFoam solver for a 2D aeroservoelastic test problem, such as the simulation of the inviscid buzz fluid structure interaction phenomenon on a NACA 65213 airfoil.

#### Problem definition

• Domain:
• Internal NACA 65213 airfoil subdomain with chord c = 1.4722 m
• External circular subdomain with radius Roo = 20 m >> c
• Material:
• Polytropic Ideal Gas (PIG)
• Specific heat ratio gamma = 1.4
• Gas thermodynamic constant R = 287.05 J/kgK
• Initial conditions:
• Thermodynamic pressure Poo = 101325 Pa
• Temperature Too = 288.15 K
• Mach number Moo = 0.839
• Angle of attack alpha = 0 deg
• Trailing edge control surface deflection delta = 0 deg
• Boundary conditions:
• Transpiration boundary conditions on internal subdomain to simulate, without  actually deforming the mesh runtime, the trailing edge control surface free motion
• Riemann boundary conditions on external subdomain
• CAE2D toolbox:
• Body reference frame to compute the aerodynamic loads
• Aerodynamic reference length La = c/2 = 0.7361 m
• Elastic axis dimesional coordinates xEA = 0.248 m and yEA = 0 m
• Hinge axis dimensional coordinates xHinge = 0.368 m and yHinge = 0 m
• Moment of inertia around the hinge axis I_dd = 0.55363 kg*m^2
• Structural damping C_dd = 0 Nms
• Structural stiffness K_dd = 0 Nm
• Steady-state solution with the CAE2D toolbox option solutionType = 0
• Unsteady trailing edge control surface free motion with the CAE2D toolbox option solutionType = 1 Figure: Problem definition.

#### Space and time discretization

• Space discretization:
• Mesh created with Gmsh
• # of triangular cells Nv = 8712
• # of nodes Nn = 9054
• Time discretization:
• Total simulation time for steady-state solution endTime = 0.3 s
• Total simulation time for unsteady solution endTime = 1 s
• Timestep deltaT = 4e-6 s
• Maximum Courant number maxCo = 1.95 Figure:
Computational grid.

#### Numerical results

• Comparison with FLUENT solver (many thanks to Edoardo Biganzoli) and NASA TP 3197 experimental results
• Single iteration CPUtime = 0.02 s on AMD64 3500+ desktop PC with AMD Athlon 64 2.2 GHz CPU, 1 Gbyte RAM, 512 Kbyte L2 cache Figure:
Trailing edge control surface free motion at Moo = 0.839. Figure: Pressure coefficient Cp contours.