MCQ's: Fluid & Pressure

Question 1

Rotameters:

1. How do they prevent static?
2. Type of flowmeter?
3. Laminar or turbulent flow at low flow?

Answer 1

1. Lined with gold to be antistatic
2. Variable orifice, constant pressure
3. Laminar at low flow

Question 2

Reynolds number at which flow becomes turbulent?

Answer 2

> 2000 turbulent flow.

Question 3

What is the ‘critical velocity’?

Answer 3

The critical velocity is the gas velocity at which laminar flow changes into turbulent flow

Question 4

How does density affect Reynolds number?

Answer 4

Lower density will reduce Reynolds number, therefore gas more likely to be laminar.

Ie. adding Helium to inspired gases lowers density.

Question 5

Pneumotachograph:

1. type of flowmeter?
2. lumen expands into….?
3. works on the principle of?
4. can be affected by what feature of a gas?

Answer 5

1. Pneumotachograph - Constant orifice, variable pressure.
2. Lumen expands into many small tubes
3. Works on the principle of hagen-poisueille principle (ONLY laminar flow)
4. Affected by gas VISCOSITY

Question 6

What is does the Poiseuille equation describe?

Answer 6

According to the Poiseuille equation:
1. Flow is proportional to the pressure difference and 4th power of the radius

2. Inversely proportional to viscosity and the length of the tube.

Question 7

How does warming a gas affect its flow?

Answer 7

Warming a gas makes it less dense,
reducing Reynolds number,
therefore more likely to be laminar flow.

Question 8

How does gas flow through an orifice?

Answer 8

Always turbulent and therefore influenced by gas density.

Question 9

How does resistance vary between laminar and turbulent flow?

Answer 9

LAMINAR: Resistance is constant and independent of flow.

TURBULENT: flow resistance increases with flow in an exponential manner.