Sensitivity of Wave Drift Damping Coefficient Predictions to the
                    Hydrodynamic Analysis Models Used in the Added Resistance Gradient
                    Method

Hearn, Grant E.; Tong, K.C.; Lau, Siew Ming

doi:10.1115/1.3257071

Cited by 2 publications

(4 citation statements)

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“…Furthermore, these results were improved upon, over the whole frequency range, using full 3D near-field pressure integration based calculations (2). Hearn and S.Y.…”

Section: Ate 6223mentioning

confidence: 99%

“…The size and geometry of the tank was dictated by tank costs and availability, and the level of funding available to the experimental programme. Since good comparisons had been established between MARIN measurements of tanker and semi-submersible low frequency damping and our predictions (2,7) we were disappointed at the lack of good comparison between the measured and the predicted low frequency damping values for the semi-submersible model investigated in the Edinburgh University Wave Power tank. The latter objective was considered necessary because we had previously demonstrated that the excursions of moored structures in a random seaway were very sensitive to the predicted values of the low frequency damping (6).…”

Section: Ate 6223mentioning

confidence: 99%

“…The 'forward speed corrected' velocity potentials are determined from the 'speed uncorrected' velocity potentials, provided by solving the proposed formulation, using standard strip-theory relationships (2,6). The 'forward speed corrected' velocity potentials are determined from the 'speed uncorrected' velocity potentials, provided by solving the proposed formulation, using standard strip-theory relationships (2,6).…”

Section: Problem Formulation and Solutionmentioning

confidence: 99%

“…The mean second order forces and moments are then evaluated using the modified near-field pressure integration formula of Hearn et al (1,2). The mean second order forces and moments are then evaluated using the modified near-field pressure integration formula of Hearn et al (1,2).…”

Section: Situations Analysedmentioning

confidence: 99%

See 3 more Smart Citations

The Influence of Tank Walls and Bottom Upon Low-Frequency Damping

Hearn

Liou

1990

All Days

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Open-water and in-tank theoretical predictions of the low frequency damping of four distinct structures are presented to demonstrate the sensitivity of the damping coefficients to tank wall influences and/or finite water depth effects. To include these effects, and to solve the open-water situation, an eigenfunction expansion matching technique is used to predict the required first order velocity potentials. Added resistance force predictions are performed using the near-field pressure integration analysis. The added resistance gradient (ARC) method is then used to predict the low frequency damping coefficients of the structures in open-water and in in-tank situations. The results presented are discussed in some detail. NOMENCLATURE Alj complex expansion coefficients D hemisphere and cylinder diameter Hl Hankel function of the first kind H Vertical distance from sea-bed / tank bottom to lowest underside point of structure h water depth J highest evanescent mode KI modified Bessel function of the second kind k superscript, k=1,2,.., 6 denoting surge, sway, heave, roll, pitch & yaw L highest harmonic propagating mode, or barge waterline or semi-submersible pontoon length mo real root of the dispersion equation mj imaginary roots of the dispersion equation _n inward normal vector on mean surface S Nk direction cosine in kth direction associated with _n p, q field point, source point R radius of matching(radiation) boundary r hemisphere and cylinder radius, or distance between generic points p and q Sb sea-bed surface Se side wall surface of wave tank Sf free-surface Sr matching boundary between inner and outer domain Sw wetted surface of structure T draught of barge U forward speed of structure W width of wave tank ?k complex amplitude of first order displacement in kth direction ? wavelength of incident wave ?I, ?O inner, outer fluid domains ? wave frequency ?e encounter wave frequency ?I, ?D incident, diffraction wave velocity potential ?k, ?k first order radiation velocity potentials INTRODUCTION Previously (1,2,3)* the surge related low frequency or wave drift damping coefficients have been calculated assuming infinite water depth and open-water conditions. Therefore, when comparing the theoretical predictions with the experimentally measured values it has been implicitly assumed that model scale and tank dimensions were such that tank influences were not important. Kaplan et al (4) suggested, in the presentation of the paper, that the difference between their predictions and Wichers' (5)experimental measurements of the low frequency damping of a 200,000 dwt tanker, was due to finite water depth effects at the lower frequencies. Alternatively, it is possible to attribute the differences to the use of the far-field radiation energy analysis approach to calculating the second order forces used to predict the low frequency damping. Certainly the apparent shift of the whole predicted low frequency damping transfer function to the right in Figure 2 of reference 4, which effectively attributes calculated damping values to higher frequencies, is consistent with our own experiences(2) of using a full 3D far-field based method.

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“…Furthermore, these results were improved upon, over the whole frequency range, using full 3D near-field pressure integration based calculations (2). Hearn and S.Y.…”

Section: Ate 6223mentioning

confidence: 99%

Section: Ate 6223mentioning

confidence: 99%