# MCQ's: Fluid & Pressure Flashcards

Rotameters:

- How do they prevent static?
- Type of flowmeter?
- Laminar or turbulent flow at low flow?

- Lined with gold to be antistatic
- Variable orifice, constant pressure
- Laminar at low flow

Reynolds number at which flow becomes turbulent?

> 2000 turbulent flow.

What is the ‘critical velocity’?

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

How does density affect Reynolds number?

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

Ie. adding Helium to inspired gases lowers density.

Pneumotachograph:

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

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

What is does the Poiseuille equation describe?

According to the Poiseuille equation:

1. Flow is proportional to the pressure difference and 4th power of the radius

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

How does warming a gas affect its flow?

Warming a gas makes it less dense,

reducing Reynolds number,

therefore more likely to be laminar flow.

How does gas flow through an orifice?

Always turbulent and therefore influenced by gas density.

How does resistance vary between laminar and turbulent flow?

LAMINAR: Resistance is constant and independent of flow.

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