FSAE | AERO-ELASTICITY & MASS OPTIMIZATION

Structures EngineerAug 2024 – Present

FSI - Star-CCM+ to AnsysAnsys ACPComposite Ply OptimizationAero-elasticity

"Implemented a one-way Fluid-Structure Interaction (FSI) workflow to map real CFD pressure fields onto composite FEA models for accurate deflection sizing. Iterated on ply schedules and internal layouts to hit a 5.86 lb assembly weight while minimizing aerodynamic performance loss."

My Journey

The Problem: Beyond Static Goals

Sizing the front wing assembly to an arbitrary target like "maximum deflection under 0.5 inches" is flawed when sizing aero structures. The wing deforms in 3D: surface deformation alters the airfoil shape itself, spanwise bowing physically closes down the slot gaps that are critically sized for aerodynamic performance, and torsional twisting basically changes the Angle of Attack. I'm not going to act like I know how exactly each of those things affect performance. We needed to understand exactly what loads were hitting where, and how twisting would kill our aerodynamic efficiency/goals.

The Methodology: The FSI Loop

To build a realistic physics model, I implemented a Fluid-Structure Interaction (FSI) workflow that could be used iteratively. We ran CFD in Star-CCM+ with all elements and endplates to get a baseline, then exported the pressure field data as a .csv file.

Pressure Mapping

I imported this into Ansys, defined the composite stack-ups using ACP (Ansys Composite PrepPost), and used pinball regions to map the pressures perfectly onto the skin.

Boundary Conditions

For a sanity check, I checked if the fixed-joint reaction forces equaled the CFD's total downforce and drag outputs. Finally, I solved the high-fidelity structural mesh, exported the deformed geometry, and ran it back through CFD to examine the actual C_l loss.

Iteration & The Sweet Spot

Considering we had a strict 7.5 lb mass limit for the entire assembly, I essentially tested about 6 different distinct internal architectures. I evaluated a 2 spar in each mainplane setup, a 1 spar in each mainplane, a complex cell-structure that was inspired from a youtube video (which was scrapped due to manufacturing concerns), and then with different material choices. We continuously tweaked the ply schedules, part by part, testing stiffness in different orientations to resist torsional twist vs flexural bending until we found the sweet spot. The output and design rationale for each part is mentioned below.

The Optimal Output

Component	Material	Ply Schedule	Design Rationale
Mainplane 1	Twill weave	[45, -45]	Torsional Stiffness
Mainplane 2	Twill weave	[45, -45]	Torsional Stiffness
Elements	Twill weave	[0, 0]	Flexural Rigidity
Spars	Twill weave	[0, 0, 0, 0, 0]	Flexural Rigidity
Ribs	Twill weave	1C1 [0.125" core]	Buckling Resistance
Mounting Inserts	6061 Al		Buckling Resistance
Endplates	Twill weave	[0, -30]	Flexural Rigidity

Results

We hit a final weight of just 5.86 lbs (including the aluminum struts), destroying the 7.5 lb constraint.

Kept wing deflection under 0.5" and strut deflection under 0.1" at 95 mph.

Successfully limited the Coefficient of Lift (Cl) loss to an acceptable margin.

Established a validated FSI workflow connecting Star-CCM+ directly to Ansys ACP.

Gallery

CONTACT

Let's Build Something Great

I'm currently looking for new opportunities in mechanical design and analysis. Whether you have a question about my work or want to discuss a project, my inbox is open.

advaitc2@illinois.edu LinkedIn

Champaign, IL