Swimming at low Reynolds number

Duration: 1 hour 31 mins

Share this media item:

Embed this media item:

<iframe width="_width_" height="_height_" src="https://sms.cam.ac.uk/media/1531181/embed" frameborder="0" scrolling="no" allowfullscreen></iframe>

Choose size:

About this item

Available Formats

About this item

Description:	Yeomans, J (University of Oxford) Thursday 01 August 2013, 15:00-16:30


Created:	2013-08-02 16:42
Collection:	Mathematical Modelling and Analysis of Complex Fluids and Active Media in Evolving Domains
Publisher:	Isaac Newton Institute
Copyright:	Yeomans, J
Language:	eng (English)


Abstract:	I shall introduce the hydrodynamics that underlies the way in which microorganisms, such as bacteria and algae, and fabricated microswimmers, swim. For such tiny entities the governing equations are the Stokes equations, the zero Reynolds number limit of the Navier-Stokes equations. This implies the well-known Scallop Theorem, that swimming strokes must be non-invariant under time reversal to allow a net motion. Moreover, biological swimmers move autonomously, free from any net external force or torque. As a result the leading order term in the multipole expansion of the Stokes equations vanishes and microswimmers generically have dipolar far flow fields. I shall introduce the multipole expansion and describe physical examples where the dipolar nature of the bacterial flow field has significant consequences, the velocity statistics of a dilute bacterial suspension and tracer diffusion in a swimmer suspension.

Abstract:

I shall introduce the hydrodynamics that underlies the way in which microorganisms, such as bacteria and algae, and fabricated microswimmers, swim. For such tiny entities the governing equations are the Stokes equations, the zero Reynolds number limit of the Navier-Stokes equations. This implies the well-known Scallop Theorem, that swimming strokes must be non-invariant under time reversal to allow a net motion. Moreover, biological swimmers move autonomously, free from any net external force or torque. As a result the leading order term in the multipole expansion of the Stokes equations vanishes and microswimmers generically have dipolar far flow fields. I shall introduce the multipole expansion and describe physical examples where the dipolar nature of the bacterial flow field has significant consequences, the velocity statistics of a dilute bacterial suspension and tracer diffusion in a swimmer suspension.

Available Formats

Format	Quality	Bitrate	Size
MPEG-4 Video	640x360	1.94 Mbits/sec	1.30 GB	View	Download
WebM	640x360	969.0 kbits/sec	645.85 MB	View	Download
iPod Video	480x270	523.03 kbits/sec	348.61 MB	View	Download
MP3	44100 Hz	250.41 kbits/sec	166.90 MB	Listen	Download
Auto *	(Allows browser to choose a format it supports)