Towed ship motion test in directional spectrum waves in a long tank

Acharyya

1990

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Section: Discussionmentioning

confidence: 99%

Towed Ship Motion Test in Directional Spectrum Waves in a Long Tank (Part 3)

Takezawa

Acharyya

1990

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“…( 1 ) ( 2 ) Using this D(X), we can express wave spectrum as : S(w, X)= S(w)D(X) The followding distributions are considered to prepare input wave signals a) Using equation ( 1 ) with n=1 ; commonly known as cos-square distribution. b) Using equation ( 2 ) with s-parameter as 10 and as 25.…”

Section: Introductionmentioning

confidence: 99%

Towed Ship Motion Test in Directional Spectrum Waves in a Long Tank (Part 2)

Takezawa

Acharyya

1989

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As a continuation to our previuos report on tank testing results of ship motions in directional spectrum waves this paper presents further test results under 'following sea' condition. Uniform irregular waves with arbitrary directional spectrum have been generated in the whole area of towing tank of Yokohama National University by the newly installed snake type wave maker and running tests have been carried out at Froude numbers 0.2 and 0.275. The experimental data have been analyzed at encounter frequency base using both Fast Fourier Transformation (FFT) and Maximum Entropy Method (MEM) to obtain the power spectrum of motions and the results are presented along with the theoretical estimates. Directional transfer functions of motions have been calculated using well known New Strip Method (NSM) and analyzed directional wave spectra obtained from experimental data by Maximum Likelihood Method (MLM) have been used to estimate theorectical motion spectra. The compared results show fairly good agreement. This paper also presents short term prediction of motions calculated for both 'head sea' and 'following sea' conditions over venous range of wave periods.

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“…6, we could not get the point near the peak because the sampling time is 20 Hz. We should get data by higher sampling frequency like SHSS shown at ( 8 ) of Fig. 6.…”

Section: Transient Water Wavesmentioning

confidence: 99%

“…About the spectrum of Rw(t), we have : ( 8 ) Here, G1 corresponds to first order surge force transfer function and G2 corresponds to that of second order variable resistance. S means wave spectrum.…”

Section: Hsu's Assumptionmentioning

confidence: 99%

“…And it also can be used to obtain the added resistance in general irregular long crested waves. Even in directional spectrum waves7, 8,9), present method is available theoretically, but some techniques have not be resolved yet and will let it to next chance. We consider this method will also be used to estimate the added resistance coefficients indirectly from the ship in actual sea through speed reduction, if the sea waves could be obtained by any way.…”

Section: Introductionmentioning

confidence: 99%

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Simple Estimation of Wave Added Resistance from Experiments in Transient and Irregular Water Waves

Wang

1993

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