Wake fraction and thrust deduction are determined in closed-form expressions for a potential-flow case. The after body of a ship hull is represented by a sink distribution and the propeller by two superposed singularity systems. The first of these singularities simulates the uniform part (T1) of the thrust distribution and the second represents the nonuniform part (T2). A functional relationship between thrust deduction (f) and wake fraction (w) is obtained, which, when compared with the corresponding Dickmann expression, includes a correction term. The general expressions for t and w are reduced to a simpler form for the case of a body of revolution. Numerical results obtained from these reduced forms are in agreement with previous results obtained for the air-ship Akron. Additional computations are made for a hypothetical case where the body singularity distribution has a pronounced asymmetry. This computation demonstrates the important role of the nonuniform thrust distribution on the thrust-deduction fraction and confirms the belief that the nonuniform thrust could be the most decisive factor in the evaluation of the thrust deduction for the case of a very pronounced asymmetry. Since the hull is represented by discrete sources and sinks of known strength, which is a general method applicable to any form of a body, and since the thrust-loading variations, defined by T = T1 + T2 cos, represents well the important features of the propeller action, therefore, the developed analysis can be considered of general importance and applicable to most practical problems.
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June 01 1958
Analytical Expressions for Thrust Deduction and Wake Fraction for Potential Flows
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Tsakonas, Stavros. "Analytical Expressions for Thrust Deduction and Wake Fraction for Potential Flows." J Ship Res 2 (1958): 50–59. doi: https://doi.org/10.5957/jsr.19188.8.131.52
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