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  • 1
    Electronic Resource
    Electronic Resource
    Interaction of laminar far wake with a free surface (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 421-429 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wave disturbances caused by the uniform translatory motion of a submerged body on or beneath the free surface of a viscous fluid are investigated analytically. The submerged body is idealized as an Oseenlet or an Oseen doublet, and exact solutions in closed integral forms are obtained. Based on these exact solutions, asymptotic representations of the wave amplitude for large Reynolds numbers based on the deep-water wavelength at large distances downstream of the body are derived. The results obtained show explicitly the effect of the laminar wake on the amplitude and the phase of the surface waves thus created. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868796
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  • 2
    Electronic Resource
    Electronic Resource
    Trailing vortices in a free-surface flow (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 14 (2002), S. 827-838 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The free-surface effect on two-dimensional flow structures, especially on the trailing vortices, is investigated numerically in this paper. The solution procedure employs a higher-order semi-implicit projection method. The numerical results have been compared with experimental data on wave elevation disturbed by a submerged translating hydrofoil with a positive angle of attack. The schematic computations reveal some interesting and unique characteristics of the trailing-vortex development in a laminar flow beneath a free surface. Based on the computational data, an empirical Strouhal–Reynolds–Froude number relationship is proposed for the purely laminar vortex shedding in a free-surface flow. Moreover, the numerical findings also indicate that the presence of a free surface accelerates the Strouhal vortex frequency, yet delays not only the onset of a large-scale Kármán instability but also the occurrence of transitional behaviors. The shedding frequency downshifts drastically or even becomes discontinuous when the secondary vortex grows on the suction side. A metastable transition frequency emerges at the same time and becomes distinct with increasing Reynolds number. The variation of the vortex-shedding Strouhal number with respect to both Reynolds and Froude numbers is obtained. The power spectra of the trailing wake consist of harmonics of the vortex-shedding and transition frequencies (mfs,nft), as well as their combinations (mfs±nft). © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1432320
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  • 3
    Electronic Resource
    Electronic Resource
    An experimental study of nonlinear waves produced by an accelerating plate (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2456-2465 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The free-surface flow generated by an impulsively accelerating, surface-piercing, vertical plate has been studied experimentally in an open channel of constant depth. The flat vertical plate is fixed on a towing carriage that is set off by suddenly dropping a weight bucket through a connecting steel cable in a pulley system. The free-surface profile in front of the plate and the pressure distribution on the plate surface are measured for three different accelerations of the plate. A capacitance-type wave gauge is used to measure the variations of the water surface, while a variable reluctance pressure transducer is used to measure the pressure on the plate surface. The acceleration of the plate is obtained by means of an accelerometer. All response voltage outputs are recorded on an IBM PC-XT personal computer with a data-acquisition electrical board. Experimental measurements are compared with the numerical, viscous-flow results of Yang and Chwang (IIHR Report No. 332; Iowa Institute of Hydraulic Research, The University of Iowa, 1989) and the analytical, inviscid-flow solution of Chwang [Phys. Fluids 26, 383 (1983)]. The agreement of the free-surface profile and the pressure distribution between the numerical results and the present experimental measurements is fairly good. However, the inviscid-flow solution overpredicts the wave amplitude and the pressure distribution on the plate. In the physical experiments, the water surface is observed to rise in front of the vertical plate where the potential-flow theory becomes singular.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858434
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  • 4
    Electronic Resource
    Electronic Resource
    Scattering of surface waves by a semi-infinite floating elastic plate (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 3215-3222 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new inner product is developed based on the Fourier analysis to study the scattering of surface waves by a floating semi-infinite elastic plate in a two-dimensional water domain of finite depth. The eigenfunctions for the plate-covered region are orthogonal with respect to this new inner product. The problem is studied for various wave and geometrical conditions. Especially, the influence of different edge conditions on the hydrodynamic behavior is investigated and compared. The edge conditions considered in the present study involve (i) a free edge, (ii) a simply supported edge, and (iii) a built-in edge. The hydrodynamic performance of an elastic plate is characterized for various conditions in terms of wave reflection and transmission, plate deflection, and surface strain. It is observed that the hydrodynamic behavior depends on the wave conditions, the geometrical settings, and the edge conditions. The built-in edge condition induces the maximum wave reflection and the minimum wave transmission. The free edge condition leads to the maximum plate deflection. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1408294
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  • 5
    Electronic Resource
    Electronic Resource
    The development of a swirling round laminar jet (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 986-988 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The development of a swirling round laminar jet in an unbounded viscous fluid is investigated in this Brief Communication by applying the unsteady Stokes equations instead of the full Navier–Stokes equations. The solutions corresponding to a constant linear-momentum source, an impulsive linear-momentum source, and constant and impulsive angular-momentum sources are presented. Since the Stokes equations are linear, these results can be superimposed together. For a constant linear-momentum source and a constant angular-momentum source, the present results reduce to the Stokeslet and rotlet solutions, which are the singular solutions of the Stokes equations, respectively, as time approaches infinity. It is also found that the developing flow field due to a linear-momentum source at the initial stage is irrotational and has a dipolelike structure. However, the developing flow field due to an angular-momentum source is immediately rotational and the magnitude of the velocity is exponentially small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857977
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  • 6
    Electronic Resource
    Electronic Resource
    Rotation of a torus (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1309-1311 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to study the rotational motion of a vortex ring or the locomotion of bacteria, which propel their cells by rotating their long curved filaments called flagella, the low-Reynolds-number flow resulting from the rotation of a torus is studied. The velocity field is obtained by distributing uniform rotlets along a circle with the rotlet directions tangent to the circle. It is found that the effect of curvature of this ring distribution of uniform rotlets is to displace this rotlet ring from the center of the cross section toward the outside of the torus in the normal direction. The net force exerted on the surrounding fluid by the rotational torus is zero. The net torque acting on the fluid is also zero.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857580
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  • 7
    Electronic Resource
    Electronic Resource
    Numerical study of nonlinear shallow water waves produced by a submerged moving disturbance in viscous flow (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 147-155 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-dimensional solitary waves generated by a submerged body moving near the critical speed in a shallow water channel are studied numerically. The incompressible Navier–Stokes equations in a curvilinear free-surface-fitted coordinate system are solved by the finite difference method. The present numerical results are compared with the existing experimental data, and with the numerical solutions of two inviscid-flow models, i.e. the general Boussinesq equation and the forced Korteweg-de Vries equation. It is found that the viscous effect in the boundary layer around the body and on the bottom of the channel plays an important role in the generation of solitary waves on the free surface. Hence the Navier–Stokes solutions have a better agreement with the experimental data than those obtained from two inviscid-flow models. The effect of the submergence depth of the body on the waves generated is also investigated. It reveals that waves are insensitive to the submergence depth of the body, except for a small region quite close to the bottom of the water channel. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868822
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  • 8
    Electronic Resource
    Electronic Resource
    Ship waves on a viscous fluid of finite depth (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 940-944 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we are concerned with the wave generation by a singular forcelet in a viscous fluid of finite depth, where the singularity is located far from the bottom and not very near the free surface. In the first part of this work, the image system of an Oseenlet bounded by a no-slip wall, is considered. It is found that the resultant velocity field can be described by a planar distribution of vertical Oseen doublets and a negative Oseenlet located at the mirror point of the singularity with respect to the plane wall. In the second part of the work we deal with the generation of waves by these solutions. By imposing the linearized free-surface conditions on the solutions obtained from the first part, the wave generated is shown to exhibit the Kelvin ship wave pattern that agrees with observation. The effects of water depth and of submergence on the wave amplitude are also investigated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869189
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  • 9
    Electronic Resource
    Electronic Resource
    On nonlinear ship waves and wave resistance calculations (1999)
    Springer
    Journal of marine science and technology 4 (1999), S. 7-15 
    Details
    ISSN: 1437-8213
    Keywords: Key words: nonlinear waves ; wave resistance ; free-surface flow ; computational fluid dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract: A finite difference method based on the Euler equations is developed for computing ship waves and wave resistances. Time marching is carried out using a time-splitting fractional-step method. The second-order central difference is used to discretize the spatial differentials, while the convection terms are discretized by the QUICK scheme. A body- and free-surface-fitted grid system with a cell-centered stencil is used. A Poisson equation for the pressure increment at each time step is solved to enforce mass conservation. The method is validated by comparing the numerical results with the experimental data for a Wigley parabolic hull. The characteristics of ship waves, such as the wave profile along the hull, the wave pattern on the free surface, the pressure distribution on the hull surface, and the wave-making resistance are reasonably predicted. The calculated results are in good agreement with the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007730050002
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  • 10
    Electronic Resource
    Electronic Resource
    The swirling round laminar jet (1992)
    Springer
    Journal of engineering mathematics 26 (1992), S. 339-348 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract The swirling round laminar jet in an unbounded viscous fluid is investigated in this paper. The axisymmetric laminar jet with a swirling velocity is simulated by a linear-momentum source and an angular-momentum source, both located at the origin. The first-order and the second-order solutions in the far field have been obtained by solving the complete Navier—Stokes equations. It is found that the first-order solution is the well-known round-laminar-jet solution without the swirling velocity obtained by Landau [2] and Squire [3]. The second-order solution represents a pure rotating flow. The swirling velocity predicted by the present solution is compared with that obtained by Loitsyanskii [15] and Görtler [16], who solved the corresponding boundary-layer equations. It is found that the swirling velocity predicted by the present theory is smaller than that obtained from the boundary-layer equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042727
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