Types of Flow Flashcards
What is the volumetric flow rate (Q)?
Pressure difference / resistance to flow
What is the flow resistance formula?
8 x L x (n (poise) / (pi x r^4))
What type of flow occurs at the entrance of a vessel?
Plug flow
In what type of flow is the average flow speed across the vessel is equal to one half the maximum flow speed (center)
Parabolic
Where does disturbed flow typically occur?
Regions of stenosis or at bifurcation
What is the continuity rule equation?
Q (flow) = velocity x area
As the diameter of the stenosis INCREASES, what happens to flow speed?
Increase to maintain flow (vessel diameter decreases as stenosis builds up)
Where does turbulence occur in relation to stenosis?
DISTAL
What is known as a change in frequency caused by the motion of a sound source, receiver, or reflector?
Doppler effect
What are the important factors of the doppler effect?
- Relative motion
- Motion direction
- Velocity
- Angle
- Transmitting frequency
- Propagation speed
In what type of doppler is speed and direction now calculated and used in very small vessels?
Power Doppler
What is the doppler shift equation?
Received frequency - transmitted frequency
If the transmitted frequency is 3MHz and the received frequency is 2.98 MHz, is the reflector moving towards or away from the transducer?
AWAY - negative doppler shift
What is the doppler shifted frequency equation F (DS) ?
2 x F x V / propagation speed (c)
What is the doppler angle also called?
Insonification angle
