Aero-thermo-acoustic Simulations

PROJECT TITLE: MULTI-PHYSICS, COUPLED ANALYSIS OF SPATIALLY TAILORED AERO-THERMAL STRUCTURES

PARTICIPANTS: CHRIS OSTOICH (PHD), MAHESH SUCHEENDRAN (PHD), PROF. DANIEL BODONY (U. ILLINOIS) AND PROF. PHILIPPE GEUBELLE

SUPPORT: AFRL AIR VEHICLES DIRECTORATE THROUGH THE MIDWEST STRUCTURAL SCIENCE CENTER

PROJECT DESCRIPTION: A high-fidelity numerical approach is used to predict the response of aerospace structures in extreme environments where coupling between fluid, thermal, and structural physics is significant.  Previous work involved the prediction and comparison with experiment of the thermal response of a rigid thermal protection system geometry under a laminar boundary layer in a Mach 6.59 flow.

Temperature contours

Temperature contours on an the initially 300 K model. Maximum temperature 326 K after 5 seconds in Mach 6.59 flow.

 

Streamlines

Streamlines and surface heat flux contours highlighting heat load inducing vortex shed off of domed TPS panel.

 

Results are shown in Figure above.  Over most of the surface, an aerospace structure will be wetted with a fully turbulent boundary layer.  Currently, the response of a thermally and structurally compliant panel under a Mach 2.25 turbulent boundary layer is being studied.  A direct numerical simulation of the turbulent boundary layer takes place in the fluid domain in order to calculate the fluid loading and study the effect of coupling on the flow.  The thermal and structural solution of the panel is found using a finite strain thermomechanical finite element code.

 

Mach 2.25 turbulent boundary layer visualized by vorticity isosurfaces colored by span-wise velocity contours.

Mach 2.25 turbulent boundary layer visualized by vorticity isosurfaces colored by span-wise velocity contours.

 

Van Driest scaled turbulent boundary layer mean profile showing uc+=y+ in the viscous subregion and obeying the log law.

Van Driest scaled turbulent boundary layer mean profile showing uc+=y+ in the viscous subregion and obeying the log law.

 

Using a high-fidelity computational approach, the panel motion is computed for the geometry shown in figure above, where 140 dB amplitude sound waves from 75-500 Hz graze a 3 mm thick Aluminum panel backed by a small cavity.  To complement the numerical method, an analytical solution was formulated for the fully coupled response of the cavity-backed thin plate and compared its predictions against the numerical predictions.

Panel deformation (exaggerated)

Panel deformation (exaggerated)

Corresponding pressure field in the duct

Corresponding pressure field in the duct

Time-history of the panel deflection at (x,y) = (1/4,1/2)

Time-history of the panel deflection at (x,y) = (1/4,1/2)

 

The above set of results show an example for a sound wave which excites the (2,1) plate mode (left) and generates the pressure field (middle) and the measured response (right).  A key aspect of the coupled response is that the panel motion generates its own pressure field that adds to the incident sound field and creates a different loading condition.