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Issue 18, 2018
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Do hydrodynamic interactions affect the swim pressure?

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We study the motion of a spherical active Brownian particle (ABP) of size a, moving with a fixed speed U0, and reorienting on a time scale τR in the presence of a confining boundary. Because momentum is conserved in the embedding fluid, we show that the average force per unit area on the boundary equals the bulk mechanical pressure P = pf + Π, where pf is the fluid pressure and Π is the particle pressure; this is true for active and passive particles alike regardless of how the particles interact with the boundary. As an example, we investigate how hydrodynamic interactions (HI) change the particle-phase pressure at the wall, and find that Πwall = n(kBT + ζ(Δ)U0l(Δ)/6), where ζ is the (Stokes) drag on the swimmer, l = U0τR is the run length, and Δ is the minimum gap size between the particle and the wall; as Δ → ∞ this is the familiar swim pressure [Takatori et al., Phys. Rev. Lett., 2014, 113, 1–5].

Graphical abstract: Do hydrodynamic interactions affect the swim pressure?

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Article information

27 Jan 2018
08 Apr 2018
First published
10 Apr 2018

Soft Matter, 2018,14, 3581-3589
Article type

Do hydrodynamic interactions affect the swim pressure?

E. W. Burkholder and J. F. Brady, Soft Matter, 2018, 14, 3581
DOI: 10.1039/C8SM00197A

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