What is the effect of increased viscosity?

What is the effect of increased viscosity?

• A. increased flow rate
• B. flow rates become unpredictable
• C. no change in flow rate
• D. decreased flow rate

Answer: (D)

Higher viscosity means more internal friction in the fluid, which increases resistance to flow. In laminar flow through a vessel, flow rate is governed by a relationship where, with the pressure difference, radius, and vessel length held constant, flow is inversely proportional to viscosity. So when viscosity increases, the flow rate decreases. This reflects why thicker blood doesn’t move as readily through the same vessels under the same driving pressure. The other ideas don’t fit this idea: increasing viscosity doesn’t make flow rates more unpredictable in a straightforward laminar model, and it certainly doesn’t cause a higher flow rate or no change when the driving conditions are unchanged.

Higher viscosity means more internal friction in the fluid, which increases resistance to flow. In laminar flow through a vessel, flow rate is governed by a relationship where, with the pressure difference, radius, and vessel length held constant, flow is inversely proportional to viscosity. So when viscosity increases, the flow rate decreases. This reflects why thicker blood doesn’t move as readily through the same vessels under the same driving pressure.

The other ideas don’t fit this idea: increasing viscosity doesn’t make flow rates more unpredictable in a straightforward laminar model, and it certainly doesn’t cause a higher flow rate or no change when the driving conditions are unchanged.