Elasticity Estimation of Thin Flap Using Optical PIV Velocity Fields

We estimate the elasticity of a thin, cellulose acetate flap using forcing data derived from optical particle imaging velocimetry (optical-PIV) velocity fields. The flap is fixed on one end to a stand submerged within a PIV tank and deformed using a water jet pulse. PIV is then performed at the interface between the thin sheet and water jet throughout the deformation cycle; the resulting velocity field allows the determination of instantaneous pressure measurements via Poisson's equation. An optimal estimation technique utilizing ensemble Kalman filtering is coupled with a finite element analysis program to determine the sheet's elasticity. Results show good agreement with actual elasticity measurements for both homogeneous and non-homogeneous elasticity sheets. In addition, we performed a quantitative study to determine the optimal vector density for a given element size to achieve an accurate elasticity estimation value. Considering the success of this technique using optical-PIV, it should also be possible for in-vitro elasticity estimates based on ultrasound-PIV measurements.