Viscous Force Constant for a Closed Cylinder

The viscous force constant of a moving cylinder closed at the ends has been calculated including first-order effects in width (2b)/length (2a). Experimental results, obtained for macroscopic models, are in essential agreement with this. For a/b20 the discrepancy is about 8%, for shorter cylinders near 20%. With the force on a cylinder moving sideways given by F=8πηav/(σ—γ), where σ=log2a/b, it is found that γ(σ2)=0.35–4(1/σ—0.43)2±0.25. For a translation lengthwise, with F=4πηav/(σ—γ), the relation γ(σ2)=1.30–8(1/σ—0.30)2±0.25 holds.