Expansion Formulae for the Forces acting on Two Equal Circular Cylinders placed in a Uniform Stream at Low Values of Reynolds Number

As a continuation of a previous paper 1) , a further discussion is made on the steady slow motion of a viscous fluid past two parallel circular cylinders of equal radius with their axes in a plane perpendicular to a uniform flow, confining ourselves to the case when the two cylinders are in close proximity to each other. Expansion formulae in powers of Reynolds number R for the drag and lift acting on one of the cylinders are obtained correct to the lowest order of Reynolds number R . The coefficients of each term are expressed in power series of a /2 h and obtained as far as terms of ( a /2 h ) 4 where a denotes the radius of the cylinders and 2 h the distance between their centres. Up to the order of ( a /2 h ) 2 , the results are found to be in complete agreement with expansion formulae for the drag and lift acting on the one cylinder placed near the other, which has been obtained directly by expanding the formulae useful for the case when the distance between the cylinders is great.