7 Lecture Notes on Fluid Dynamics and Blood Flow

  • Overview of Lectures

  • Focus on blood flow and fluid dynamics; considered complex but manageable.

  • Encourage questions and detailed review in tutorials.

  • Key Topics Covered

  • Density and Pressure

  • Pascal's Principle

  • Laplace's Law

  • Hydrostatic Pressure

  • Clinical Applications

  • Atmospheric Pressure and Manometers

  • Blood Pressure Monitoring Techniques

  • Fluids

  • Definition: Fluids are either liquids or gases.

  • Major focus is on:

    • Hydrostatics: Fluids at rest (Pascal’s principle)
    • Hydrodynamics (Hemodynamics): Fluids in motion, specifically blood flow

  • Density

  • Definition: Density (ρ) = mass/volume

  • Units: Kilograms per meter cubed (kg/m³)

  • Values:

    • Water: 1000 kg/m³
    • Blood: 1060 kg/m³

  • Not necessary to memorize aside from water density.

  • Pressure

  • Definition: Pressure = force/area

  • Unit: Pascal (Pa)

  • Example: Pressure from a small force (e.g., poke with a finger) vs large force (e.g., poke with a needle).

  • Pascal's Principle

  • Any change in pressure applied to a fully enclosed fluid is transmitted undiminished throughout the fluid and its enclosing walls.

  • Example: Hydraulic systems like car lifts demonstrate this principle.

  • Hydraulic Lift Example

  • If a 100N force is applied to a 1 cm² piston, the force at a 100 cm² piston can be calculated using:

    • P₁ = P₂
    • F₁/A₁ = F₂/A₂

  • Resulting larger force at the larger piston is much greater, demonstrates efficiency of hydraulic systems.

  • Clinical Applications of Fluid Dynamics

  • Glaucoma: Increased fluid pressure in the eye due to blocked aqueous humor flow can result in optic nerve damage.

  • Protection of Unborn Baby: Amniotic fluid buffers against impacts.

  • Bedsores: Pressure on bony areas from prolonged lying can cause necrosis due to pinched blood vessels.

  • Tumors: Increased volume in fixed spaces (e.g., skull) leads to increased pressure, indicating tumor presence through spinal tap analysis.

  • Laplace's Law

  • Relation of tension, pressure, and radius: Tension (T) = Pressure (P) x Radius (R) for cylindrical shapes.

  • Radius increases pressure; tension increases with radius for vessel walls.

  • Aneurysms

  • Weakness in blood vessels that leads to ballooning and risk of rupture.

  • Pressure Readings

  • Importance of measuring pressure using manometers, often with mercury due to its density and liquid state at room temperature.

  • Systolic (pressure during heartbeats) and diastolic (pressure between beats) values for blood pressure evaluation (e.g., normal is 120/80 mmHg).

  • Conclusion

  • Understanding of fluid dynamics essential for various medical conditions and devices.

  • Emphasize clarity in calculations and the significance of key variables in fluid mechanics.

  • Additional Resources

  • Encourage further review of practical applications through problems and practice questions as well as tutorial sessions for clarity.