There have been many investigations into the effect of restricted water on wave-making resistance. In numerical calculation of the wave-making resistance, however, ship forms were represented by source distributions obtained for the unbounded water instead of those for the restricted water. In the present study the authors consider the effect of restricted water to obtain source distributions and calculate the wave-making resistance to compare with the results derived from the source distributions in unbounded water. Numerical calculations are carried out on a ship in a canal with rectangular cross section. The ship is represented by stepped distribution of sources and sinks on the centre plane. The side walls aud the bottom of the canal are replaced by infinite series of image sources and sinks. Calculations are made on the following ship form and canal sizes. Ship form Parabolic water line and frame line L/B=L/T=10 Canal size W/L=0.25, 0.5, 0.75, 1.0, 1.5, 2.0 H/L=0.25, 0.5, 0.75, 1.0 where L=ship length, B=ship breadth, T=draft, W=canal width, H=canal depth From the results of the calculations, the following conclusions are derived. (1) The source density representing the same ship form increases with the presence of canal walls and decreases with the presence of canal bottom. (2) For practical purposes, the wave-making resistance in restricted water may be calculated by using the source distribution obtained in unbounded water. (3) When the canal is wider than 3/2・L and is deeper than 3/4・L, the efect of restricted water may be neglected in practical application.

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As the continuation of the previous paper with the same title (Journal of the Society of Naval Architects of West Japan No.40, 1970, p.71), the equations adapted for numerical calculations of propulsion performance of a thin ship are derived in this text. Furthermore, in the appendix the authors develope the method to evaluate the new self-propulsion factors which are defined by considering the propeller combined with the rudder as a propulsion device.

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Model experiments and theoretical calculations were carried out to obtain data about the seakeeping qualities of high speed single screw container ships in head waves, and to make clear how much extent can a theory predict that. The models selected for the experiments were wooden models of length 4m with block coefficient C_B≒0.56 and length beam ratio L/B≒6.8, one with small bulbous bow and the other with normal bow. The effect of length beam ratio on the seakeeping qualities were also investigated. From the investigation, the following conclusions were obtained. 1) The linear theory based on the Strip Method can predict seakeeping qualities with sufficient accuracy for practical use, except a few items such as vertical acceleration at stern, and resistance increment in irregular waves. 2) When we compare ship motions of two ships having similar body plan, similar displacement, same speed and different L/B, the heaving and pitching amplitude and the vertical acceleration of the large L/B ship are smaller than that of the small L/B ship. 3) Impact pressure on bottom and probability of deck wetness of the normal bow ship are smaller than that of the bulbous bow ship, but there are little differences in ship motions and resistance increment between both types of ships. Investigation on the impact wave load is hoped to be continued to make clearer the seakeeping qualities of ships.

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Equations of longitudinal motion of ACV_S of arbitrary planforms operating over oscillating surfaces of arbitrary shapes are derived with the assumption that the ACV has a transverse membrane which prevents the cross flow. Numerical calculations are then made assuming constant jet momentum flux, and the effect of the geometry and the operating conditions of ACV_S on stability derivatives is investigated. Numerical calculations of heave periods and response functions are made for some examples. Comparison with the experimental results shows that the calculation gives reasonable results.

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台風津浪が寄せて来る静穏な海面で測定された船舶動揺記録を解析すると,波峯の前面と後面に発生しつつある共振波の波高や周期が,すでにかなり異っている事実が判明している。海石上の境界層の高さは無風に近い5〜7m/secの恒風時には台風津浪の高さ約数十糎であるから,波峯部付近がこれを突破して恒風圧を受ける前後約数百米の範囲で,細微な白浪が群生することになる。そこで波浪萌芽の発生機巧を探索する目的で,岨度の異る三種の木製Stokes波模型を製作し,風洞実験によって表面の水平圧力と垂直圧力の分布状況を測定し,これから抵抗係数と揚力係数を算定した。その結果,岨度のほとんど無い模型についてだけ時には水平圧力積分値が負になる現象が観測されたので,改めて模型を種々の角度に傾斜させて同上の計測を行った。海面の基本波である台風津波のなめらかな起伏は,各波峯部に向って前面から吹き上げられ,背面から吸い上げられ次第に高くなって行く状況を理解する上に上述の成績は参考になると思われる。基本波の観念はDarbyshireが導入して初期波高が零ならば海洋波は永久に発達せず,もし細微なりといえども有限振幅の波高が存在すればこれを基礎に成長して行くのであるが,数分ないし十数分の周期を有する台風眼津浪に僅かな凹凸を与えるのは,数十秒ないし数分の台風壁津浪であって,両者の適当な組み合わせによって風浪,うねりがほとんど発生せぬ時と,瞬時に白泡となるのと千差万別になるようである。

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動揺状況を[numerical formula]で現わす時,この不規則度示数は[numerical formula][numerical formula][numerical formula][numerical formula]で定義される。この値は長時間の動揺記録全体を通じての平均値であって,一般にはε^2≒1というGauss-Laplace型分布に対応する値を示し易い傾向かおる。しかるに,動揺記録は波形がだいたい同一と見受けられる長短種々の時間間隔で区分し得る多数の波群から構成され,これが順に接続されている。もちろんその中には振幅の極端に大きい単一共振波動も存井し,また周期が一定なRayleigh型分布を呈している部分も混入している。したがって不規則度示数は上述二例のε^2=0から前述のε^2=1の範囲に入り,任意の時間区分域で自由な値をとり得るのであって,しかもN個の成分中一個或は任意の数個の組み合わせがこれまた自由に発現していることになるのである。不規則度がほぼ定常的に類似とみられる持続時間は意外に長く,台風津浪の周期と同じ数十秒以上十数分にも及び,この期間中に完全な同調動揺が十分考えられる。スペクトル分布から得られるε^2の値は,断片的に発現する共振の性質を直接には理解できぬことになる。ここでN=3すなわち台風津浪の上に共振波が載った例を選ぶと,_3C_3+_3C_2+_3C_1=7種の重複状況が記録のどこかに発現し得ることになり,動揺記録としては最も波面傾斜の小さい台風眼津浪を略すればN=2,_2C_2+_2C_1=3種の混合が出て来ることになる。共振成分の周期は数秒〜十数秒に対し誘振成分は数十秒〜数分であれば,基本波の波峯部には共振波が波底部には基水波自身が単独に発現し,その中間波面傾斜が最大となる平均水位の付近は,両者の混合状況を呈しているようである。海面に常時存在する基本波の成分数を調べると,風浪,うねりより長い周期を有する位置でスペクトルの山の数は数個であるから,音響学のいわゆるwhite noiseよりもむしろ音楽学のdrownに近く,これらの波動群はあたかも和音の如き比率を形成した時,その旋律に乗ったかの如く風浪やうねりが極度に発達するように考えられる。

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