Cerebral Haemodynamics

Question 1

Measure of laminar flow

Answer 1

Reynolds number

Question 2

Assumptions for laminar flow

Answer 2

length of tube is greater than radius
flow must be steady in time and laminar in the velocity profile
newtonian fluid
tube must be rigid

Question 3

Reynolds number for laminar flow

Answer 3

<2000

Question 4

Reynolds number for laminar or turbulent flow

Answer 4

2000 < Re < 4000

Question 5

Reynolds number for turbulent flow

Answer 5

> 4000

Question 6

relationship between reynolds number and diameter of the tube

Answer 6

proportional

Question 7

Violations of the assumptions for pouiseuille’s law

Answer 7

high rate of branching of blood vessels
tube is not rigid
blood is non newtonian and only newtonian in at certain shear rates

Question 8

Why can pouiseuille’s law still be applied despite all the violations of the assumptions?

Answer 8

consider the vasculature
it works for a group of blood vessels

Question 9

Electrical equivalents of pouiseuille’s law

Answer 9

driving force: pressure vs voltage difference
current/flow: fluid flowing vs charge flowing
resistance: pouiseuille’s law vs resistance

Question 10

Flow (Q) formula

Answer 10

pressure difference / peripheral resistance