International Shipbuilding Progress - Volume 14, issue 151

Authors: Wu, T. Yao-Tsu

Article Type: Research Article

Abstract: The method of matched singular perturbation expansions is applied to calculate the asymptotic solution of a steady two-dimensional free surface flow past a body of an arbitrary form for large values of the Froude number. The expansion parameter is β = gℓ / U 2 (ℓ being the body dimension, U the free stream velocity, g the gravity constant) which is assumed small. The zeroth order inner solution near the body is based on the free streamline theory with no gravity effect; and the higher order terms give rise to the gravitational correction. The …outer solution contains in the order β -term a train of gravity waves on the downstream side, the nonlinear correction appears in the terms of order higher than β . The two expansions are matched to obtain a solution uniformly valid throughout the flow field. Show more

DOI: 10.3233/ISP-1967-1415101

Citation: International Shipbuilding Progress, vol. 14, no. 151, pp. 88-97, 1967

Authors: Solomon, Louis P. | Plesset, Milton S.

Article Type: Research Article

Abstract: Numerical solutions have been obtained for the motion of a gas bubble in an incompressible liquid when harmonic pressure oscillations are imposed. The mean pressure in the liquid was taken to be 1 atm and the ratio of oscillating pressure amplitude, A, to the mean pressure was given the values 0.2, 0.5, 1.0 and 2.0. The equilibrium bubble radius was chosen to be R o = 10 − 2 , 10 − 3 and, 10 − 4 cm , and …the angular frequency of the pressure variations was ω = 0.2 × 10 5 , 0.7 × 10 3 , and 1.2 × 10 5 per sec. The phenomena of bubble ‘explosion’ or ‘collapse’ were found for large A, i.e., 1.0 and 2.0. For the smaller values of A, the bubble radius varied with time within well-defined limits, but nonlinear effects were evident. Show more

DOI: 10.3233/ISP-1967-1415102

Citation: International Shipbuilding Progress, vol. 14, no. 151, pp. 98-103, 1967

Authors: Hsieh, Din-Yu

Article Type: Research Article

Abstract: A brief critical survey on the hydrodynamic formulations of the superfluid helium is given first. For the irreversible process, three major formulations, i.e. those due to Gorter-Mellink, Lin, and Hall-Vinen, Bekarevitch-Khalatnikov, are described, discussed and compared. Then some results of analyses based on the Gorter-Mellink formulation are presented. The paper concludes with some interesting findings resulting from the assumption that rotons are vortex rings.

DOI: 10.3233/ISP-1967-1415103

Citation: International Shipbuilding Progress, vol. 14, no. 151, pp. 104-119, 1967

Authors: Venezian, Giulio

Article Type: Research Article

Abstract: A survey of observational and theoretical work pertaining to the origin of planetary magnetic fields is given with special emphasis on the dynamo theory which attempts to explain these fields as arising from magnetohydrodynamic regenerative action. Some points are raised regarding what a satisfactory theory should contain. It is suggested that reversals may occur without a drastic change in the internal flow. A method of using one model of dynamo action to obtain information about the structure of the flow in the core of the earth is proposed.

DOI: 10.3233/ISP-1967-1415104

Citation: International Shipbuilding Progress, vol. 14, no. 151, pp. 120-126, 1967