Velocity field measurements allow, in principle, the evaluation of the pressure field by integrating the equations of fluid motion. Unavoidable experimental uncertainty, however, may result in unreliable estimates. In this study, we use the Poisson pressure equation to estimate the relative pressure from experimental velocities, and investigate how pre-processing with smoothing and solenoidal filters affects this estimate. For diffusion dominated laminar flow or for turbulent flow modeled through an eddy viscosity, measurement noise significantly affects the results. In this case, solenoidal filtering provides superior performance over other smoothing approaches, as it preserves the second spatial derivatives of the velocity field. For laminar flows dominated by advection or acceleration components of the pressure gradient, the choice of the filter appears to have little effect under limited noise, while smoothing produces improved relative pressure estimates for higher noise intensities. The above statements are verified using idealized flow conditions, numerical fluid dynamics simulations, and velocity fields from in-vivo and in-vitro magnetic resonance velocimetry.
Bibliographical noteFunding Information:
The authors would like to thank the two anonymous reviewers for their comments and feedback that greatly contributed to improve the consistency and quality of the present contribution. This work was supported by the American Heart Association Grant #15POST23010012 (Daniele Schiavazzi), the Leducq Foundation as part of a Transatlantic Network of Excellence for Cardiovascular Research, and a National Science Foundation (Chemical, Bioengineering, Environmental, and Transport Systems) CAREER Grant #1453538 (Filippo Coletti). The authors would like to thank Gianluca Iaccarino, Javier Urzay Lobo, Gianluca Geraci, and Dante De Santis for the interesting and motivating discussions, and Jorge Bernate for providing the large eddy simulation results on the human airways model. We also acknowledge the open source SimVascular project at http://www.simvascular.org .
© 2017, Springer-Verlag Berlin Heidelberg.