# Fluid Dynamics and Hemodynamics Flashcards

Fluid dynemics

Study of fluid through a flow system

what are some variables associated with fluid dynamics

Power Work Energy Potential/kinetic energy Pressure Volumetric flow Resistance Capacitance Compliance Velocity Viscosity

Power

rate at which energy is transferred. Power describes how fast work is being performed (WATTS=joules/sec)

Work

the amount of energy transferred (AVERAGE POWER X TOTAL TIME) - JOULES

Energy

quantities such as mass energy, kinetic, potential, heat, radiation

Potential energy

energy which is stored which can be converted to other forms of energy

Energy

Must be concerved

Kinetic energy

Represents energy related to movement and is proportional to the velocity squared of the movement

Pressure

force per unit area

Volumetric Flow

– volume of fluid per time which moves past a point (Litres/min…etc.)

Resistance

ratio of the pressure drop across a vessel per volumetric. Measured of the impediment that must be overcome for flow to occur.

Capacitance

the ability to hold a change in volume per change in tome (dv/dt) V is volume and t is time

Velcoity

speed with which a fluid moves in a specific direction

Viscosity

measure of the resistance of the fluid to flow due to the attraction of the molecules

Energy can occur from a

Higher to lower enrgy level

Energy is converted from what to what in ultrasound?

Electropotential energy is converted into acoustic mechanical energy and transmitted into the body – absorption is mainly the conversion of the acoustic energy into heat energy

Reflected waves are then converted back into electropotential energy

Fundamental rule #1 of energy

Energy is always conserved – energy is never lost, only converted between forms

Energy within the cardiovascular system is

Converted back and forth between kinetic and potential energy

Pressure that represents force exerted on the vessel walls

Potential energy

force of flow direction in the vessels

Kinetic energy

Increase in blood velocity=

Increased kinetic energy and therefore decreased potential energy

As flow accelerates

Decrease in potential energy and an compsentory increase in kinetic energy

Key concept Kinetic/potential energy

If we make the assumption that little or no energy is lost to heat, conservation of energy requires that a change in kinetic energy must equal a change in potential energy.

Since kinetic energy is related to velocity and since velocity can be measured by Doppler, a change in potential energy (pressure) can be determined by performing Doppler

hydrostatic pressure is a form of what

Potential energy

Hydrostatic pressure is what

is the pressure that results from the force of the fluid (gravity) which results from a column of fluid.

what is hydrostatic pressure proportional to

The hydrostatic pressure is proportional to the density of the fluid, the height of the fluid, and gravity

Any factors affecting weight will affect

hydrostatic pressure

A taller column will create higher/lower hydrostatic pressure

High hydrostatic pressure

A more dense fluid will create a higher/lower hydrostatic pressure

Higher hydrostatic pressure

clinically what affects hydrostatic pressure

Height and patient position

For normal density of blood, each inch of blood in a vertical column results in a pressure of….

2mmHG

Volumetric flow

Flow is defined as the amount or volume of a quantity which moves past a point per unit time

Doppler does not measure FLOW, it measures velocity

Velcoity

Speed

Speed

Velocity, flow and pressure are all related

Can not assume that high flow represents a high velocity

Capactiance

Capacitance is defined as a change in volume per time. Is a measure of the ability to hold a change in volume per change in time

Compliance

Is the measure of the ability to hold a change in volume per change in pressure

High compliance

implies that there is a large increase in volume for a small increase in pressure

Fluid viscoisty

Measure of the internal resistance of a fluid to flow

Fluid viscosity is caused by

Caused by molecular cohesive forces

Attraction of molecules

what does the resistance equation state

States that the resistance is directly proportional to the vessel length and the fluid viscosity and inversely proportional to the radius of the vessel to the 4th power

If the length increases

The resistance increases

More energy is required to transport the same flow in the longer pipeline

Resistance is inversely proportional to

Radius

Radius affects resistance faster then

Length

Radius is affected by

4th power

Resistance is inversely proportional to

r4

Resistance is proportional to

Viscosity