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U.S. Department of Health and Human Services

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Laboratory of Fluid Dynamics

Laboratory leader:   Laurence Grossman 301-796-2502 laurence.grossman@fda.hhs.gov

Fluid dynamics, as it applies to medical devices, can be broadly defined as the interaction of moving fluids with medical devices; both as the device affects the moving fluid and as the moving fluid affects the device.  Often the moving fluid is blood, as in the flow of blood through a heart valve or through the filters and pumps of a renal dialysis apparatus.  Damage to the flowing blood can result in serious clinical consequences, up to and including death.  Damage to a device, such as might be caused by cavitation in a heart valve, can lead to catastrophic device failure causing death.  Accordingly, the Laboratory of Fluid Dynamics, located in the Division of Solid and Fluid Mechanics, maintains a research program focused on the fundamental factors governing the interaction of flowing fluids with medical devices and the development of test methodologies to objectively characterize such interactions and their consequences.

The interaction between biological fluids, especially blood, and medical devices is complicated in part because blood is not an ideal fluid.  Rather, blood is a complex, living tissue consisting of deformable particulates (cells) suspended in a liquid phase (plasma) which itself has multiple constituents (ions, proteins, dissolved gases).  Accordingly the “mechanical” characteristics that describe fluids (e.g., viscosity) are (non linear) functions of shear rate, hematocrit, and the like.  As well, the extent to which the physiological functions (e.g., oxygen carrying capacity, ability to clot) of blood may be compromised by its passage through a medical device depend not only on physical factors describing the flow (e.g., shear rate) but also on time of exposure.  Similarly, whether the function of a medical device will be compromised by its interaction with flowing blood (e.g., cavitation damage to a heart valve, flow reduction by clot formation in a blood pump) is a complex function of the flow dynamics within the device.

Therefore, to fulfill our functions as regulators and as scientists and engineers Fluid Dynamics Laboratory staff members continue to develop and to assess analytical (computational fluid dynamics) and measurement (flow visualization, hemolysis, and platelet activation) techniques to better study the interaction of flowing fluids with medical devices.