An expression is derived for the added mass of two equal circular cylinders (radius a) moving normal to the line of centers in an ideal fluid enclosed by a fixed cylindrical boundary (radius b). The two moving cylinders, with centers 2c apart, have velocities equal in magnitude but opposite in direction. Except for extreme cases, the added mass per unit length of each cylinder is given by M=πa2ρ[1−12γ2+8β4γ2(β4−γ4)2], where ρ is the fluid density, β = b/a, and γ = c/a. This expression is compared with the results of a torsion pendulum experiment in liquid helium II. For γ = 4.9 and 8.6 < β < 11, the predicted change in moment of inertia is in good agreement with that observed in liquid helium between 2.15° and 1.3°K. The observed damping is independent of boundary radius.
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Hussey et al. (1965) studied this question.
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