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Research Papers

# Multilaboratory Particle Image Velocimetry Analysis of the FDA Benchmark Nozzle Model to Support Validation of Computational Fluid Dynamics Simulations

[+] Author and Article Information
Prasanna Hariharan1

Food and Drug Administration, Silver Spring, MD 20993prasanna.hariharan@fda.hhs.gov

Matthew Giarra, Steven W. Day

Rochester Institute of Technology, Rochester, NY 14623

Varun Reddy, Keefe B. Manning, Steven Deutsch, Eric G. Paterson

Pennsylvania State University, University Park, PA 16802

Sandy F. C. Stewart, Matthew R. Myers, Michael R. Berman, Richard A. Malinauskas

Food and Drug Administration, Silver Spring, MD 20993

Greg W. Burgreen

Mississippi State University, Starkville, MS 39762

http://www.pivchallenge.org/

http://fdacfd.nci.nih.gov

http://fdacfd.nci.nih.gov

Available at http://fdacfd.nci.nih.gov

1

Corresponding author.

J Biomech Eng 133(4), 041002 (Feb 17, 2011) (14 pages) doi:10.1115/1.4003440 History: Received September 23, 2010; Revised January 08, 2011; Posted January 14, 2011; Published February 17, 2011; Online February 17, 2011

## Abstract

This study is part of a FDA-sponsored project to evaluate the use and limitations of computational fluid dynamics (CFD) in assessing blood flow parameters related to medical device safety. In an interlaboratory study, fluid velocities and pressures were measured in a nozzle model to provide experimental validation for a companion round-robin CFD study. The simple benchmark nozzle model, which mimicked the flow fields in several medical devices, consisted of a gradual flow constriction, a narrow throat region, and a sudden expansion region where a fluid jet exited the center of the nozzle with recirculation zones near the model walls. Measurements of mean velocity and turbulent flow quantities were made in the benchmark device at three independent laboratories using particle image velocimetry (PIV). Flow measurements were performed over a range of nozzle throat Reynolds numbers $(Rethroat)$ from 500 to 6500, covering the laminar, transitional, and turbulent flow regimes. A standard operating procedure was developed for performing experiments under controlled temperature and flow conditions and for minimizing systematic errors during PIV image acquisition and processing. For laminar $(Rethroat=500)$ and turbulent flow conditions $(Rethroat≥3500)$, the velocities measured by the three laboratories were similar with an interlaboratory uncertainty of $∼10%$ at most of the locations. However, for the transitional flow case $(Rethroat=2000)$, the uncertainty in the size and the velocity of the jet at the nozzle exit increased to $∼60%$ and was very sensitive to the flow conditions. An error analysis showed that by minimizing the variability in the experimental parameters such as flow rate and fluid viscosity to less than 5% and by matching the inlet turbulence level between the laboratories, the uncertainties in the velocities of the transitional flow case could be reduced to $∼15%$. The experimental procedure and flow results from this interlaboratory study (available at http://fdacfd.nci.nih.gov) will be useful in validating CFD simulations of the benchmark nozzle model and in performing PIV studies on other medical device models.

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## Figures

Figure 1

Benchmark nozzle model: schematic of the test section with dimensions

Figure 2

(a) Flow loop for sudden expansion configuration. Laboratory specific operating conditions are listed in Table 3. (b) Picture of the nozzle and the acrylic extenders.

Figure 3

Sensitivity of flow variables to the standard operating procedure. ((a) and (b)) Axial velocity as a function of radial distance for Rethroat=500 and 6500. ((c) and (d)) Viscous shear stress profile for Rethroat=500 and 6500. (○) Positive control (with SOP violations); (▲) final data (SOP followed).

Figure 4

Schematic of the test section showing the locations where velocity, shear stress, and Reynolds stresses were measured for the sudden expansion orientation

Figure 5

Uncertainty analysis comparing PIV software using the same 100 image pairs supplied by Lab-1. Interlaboratory comparison of (a) mean axial velocity, (b) viscous shear stress, and (c) Reynolds stress magnitude. Images for this comparison study were obtained for Rethroat=6500. PIV data obtained at z=0.008 m (Fig. 4).

Figure 6

Axial velocity profile at the entrance (z=−0.064 m in Fig. 4) for Rethroat=500, 3500, and 6500. The corresponding velocity profiles for the Poiseuille flow are also included.

Figure 7

Turbulence quantified by the rms of axial velocity fluctuations versus radial distance at the nozzle inlet (z=−0.064 m in Fig. 4) for Rethroat=6500. Mean velocity for this Reynolds number=0.6 m/s.

Figure 8

Sudden expansion orientation: (a) centerline velocity (normalized to the mean inlet velocity) versus axial distance for different flow conditions; (b) pressure difference (normalized to the mean throat velocity) versus axial distance. Pressure difference normalized based on Eq. 8. Mean and standard deviations were calculated from three Lab-1 trials (averaged) and one trial each from Lab-2 and Lab-3 (n=3).

Figure 9

Sudden expansion orientation: velocity profiles at different cross-sections for two Reynolds numbers (500 and 6500), normalized to the mean inlet velocity. Example recirculation regions are identified with arrows in (c).

Figure 10

Transitional flow data (Rethroat=2000): centerline velocity (normalized to the mean inlet velocity) versus axial distance

Figure 11

Transitional flow data (Rethroat=2000): velocity profiles at different cross-sections

Figure 12

Sensitivity of velocity profiles at z=0.06 m to Reynolds number uncertainty: (a) Rethroat=500 and (b) Rethroat=2000

Figure 13

Sensitivity of velocity profiles at z=0.06 m to upstream flow perturbations for Rethroat=2000

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