Study on calculation methods for acoustic radiation of axisymmetric structures in finite water depth

Experiments were conducted at the U.S. Naval Academy's Hydromechanics Laboratory to determine the effect of finite water depth on the resistance, heave, and trim of two different trimaran models. The models were tested at the same length to water depth ratios over a range of Froude numbers in the displacement speed regime. The models were also towed in deep water for comparison. Additionally, the side hulls were adjusted to two different longitudinal positions to investigate possible differences resulting from position. Near critical speed, a large increase in resistance and sinkage was observed, consistent with observations of conventional displacement hulls. The data from the two models are scaled up to a notional 125-m length to illustrate the effects that would be observed for actual ships similar in size to the U.S. Navy's Independence Class Littoral Combat Ship. Faired plots are developed to allow for rapid estimation of shallow water effect on trimaran resistance and under keel clearance. An example is provided.

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COMPARISON OF UNSTEADY REYNOLDS-AVERAGED NAVIER-STOKES PREDICTION OF SELF-PROPELLED CONTAINER SHIP SQUAT AGAINST EMPIRICAL METHODS AND BENCHMARK DATA

The International Journal of Maritime Engineering ◽

10.5750/ijme.v162ia2.1131 ◽

2021 ◽

Vol 162 (A2) ◽

Author(s):

Z Kok ◽

J T Duffy ◽

S Chai ◽

Y Jin

Keyword(s):

Water Depth ◽

High Speed ◽

Navier Stokes ◽

Container Ship ◽

Benchmark Data ◽

High Speeds ◽

Port Throughput ◽

Finite Water Depth ◽

Urans Cfd ◽

Effective Wake

The demand to increase port throughput has driven container ships to travel relatively fast in shallow water whilst avoiding grounding and hence, there is need for more accurate high-speed squat predictions. A study has been undertaken to determine the most suitable method to predict container ship squat when travelling at relatively high speeds (Frh ≥ 0.5) in finite water depth (1.1 ≤ h/T ≤ 1.3). The accuracy of two novel self-propelled URANS CFD squat model are compared with that of readily available empirical squat prediction formulae. Comparison of the CFD and empirical predictions with benchmark data demonstrates that for very low water depth (h/T < 1.14) and when Frh < 0.46; Barass II (1979), ICORELS (1980), and Millward’s (1992) formulae have the best correlation with benchmark data for all cases investigated. However, at relatively high speeds (Frh ≥ 0.5) which is achievable in deeper waters (h/T ≥ 1.14), most of the empirical formulae severely underestimated squat (7-49%) whereas the quasi-static CFD model presented has the best correlation. The changes in wave patterns and effective wake fraction with respect to h/T are also presented.

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Comparison of Unsteady Reynolds-Averaged Navier-Stokes Prediction of Self-Propelled Container Ship Squat Against Empirical Methods and Benchmark Data

10.3940/rina.ijme.2020.a2.604 ◽

2020 ◽

Vol 162 (A2) ◽

Author(s):

Z Kok ◽

J T Duffy ◽

S Chai ◽

Y Jin

Keyword(s):

Water Depth ◽

High Speed ◽

Navier Stokes ◽

Container Ship ◽

Benchmark Data ◽

High Speeds ◽

Port Throughput ◽

Finite Water Depth ◽

Urans Cfd ◽

Effective Wake

The demand to increase port throughput has driven container ships to travel relatively fast in shallow water whilst avoiding grounding and hence, there is need for more accurate high-speed squat predictions. A study has been undertaken to determine the most suitable method to predict container ship squat when travelling at relatively high speeds (Frh ≥ 0.5) in finite water depth (1.1 ≤ h/T ≤ 1.3). The accuracy of two novel self-propelled URANS CFD squat model are compared with that of readily available empirical squat prediction formulae. Comparison of the CFD and empirical predictions with benchmark data demonstrates that for very low water depth (h/T < 1.14) and when Frh < 0.46; Barass II (1979), ICORELS (1980), and Millward’s (1992) formulae have the best correlation with benchmark data for all cases investigated. However, at relatively high speeds (Frh ≥ 0.5) which is achievable in deeper waters (h/T ≥ 1.14), most of the empirical formulae severely underestimated squat (7-49%) whereas the quasi-static CFD model presented has the best correlation. The changes in wave patterns and effective wake fraction with respect to h/T are also presented.

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Critical assessment of hydrodynamic load models for a monopile structure in finite water depth

Marine Structures ◽

10.1016/j.marstruc.2020.102743 ◽

2020 ◽

Vol 72 ◽

pp. 102743 ◽

Cited By ~ 1

Author(s):

Loup Suja-Thauvin ◽

Erin E. Bachynski ◽

Fabio Pierella ◽

Michael Borg ◽

Jørgen Ranum Krokstad ◽

...

Keyword(s):

Water Depth ◽

Critical Assessment ◽

Hydrodynamic Load ◽

Load Models ◽

Finite Water Depth

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Wave Scattering From Multiple Horizontal Plates as a Breakwater

Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization, Parts A and B ◽

10.1115/omae2009-79276 ◽

2009 ◽

Author(s):

Guoyu Wang ◽

Yongxue Wang

Keyword(s):

Water Depth ◽

Plate Thickness ◽

Wave Theory ◽

Linear Potential ◽

Antisymmetric Part ◽

Transmission Coefficients ◽

Present Solution ◽

Relative Water ◽

Constant Coefficients ◽

Finite Water Depth

The multiple horizontal plates breakwater is proposed in this article, which mainly consists of several horizontal plates. The regular wave test results demonstrate that it has good performance of dissipating waves. Based on the linear potential wave theory, the scattering of waves normally incident on the multiple horizontal plates in a channel of finite water depth is investigated. The velocity potential is split to the symmetric and antisymmetric part, and the method of eigenfunction expansions is used to obtain the unknown constant coefficients determined from the matching conditions. The thickness of the plates is considered in the theoretical analysis. The present solution is compared with the existing theoretical, numerical and experimental results with good agreements. The parameters such as the relative water depth, relative plate width, relative plate thickness and number of plates, those identified with the performance of the breakwater are investigated and discussed. The variation of reflection and transmission coefficients alone with the above mentioned parameters are also presented.

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Nonlinear Crest Height Distribution in Three-Dimensional Ocean Waves

Volume 4: Ocean Engineering; Offshore Renewable Energy ◽

10.1115/omae2008-57944 ◽

2008 ◽

Author(s):

Felice Arena ◽

Alfredo Ascanelli

Keyword(s):

Water Depth ◽

Three Dimensional ◽

Ocean Waves ◽

Second Order ◽

Wave Crest ◽

Height Distribution ◽

Order Model ◽

Rayleigh Law ◽

Wave Trough ◽

Finite Water Depth

The interest and the studies on nonlinear waves are increased recently for their importance in the interaction with floating and fixed bodies. It is also well known that nonlinearities influence wave crest and wave trough distributions, both deviating from Rayleigh law. In this paper a theoretical crest distribution is obtained taking into account the extension of Boccotti’s Quasi Determinism theory, up to the second order for the case of three-dimensional waves, in finite water depth. To this purpose the Fedele & Arena [2005] distribution is generalized to three-dimensional waves on an arbitrary water depth. The comparison with Forristall second order model shows the theoretical confirmation of his conclusion: the crest distribution in deep water for long-crested and short crested waves are very close to each other; in shallow water the crest heights in three dimensional waves are greater than values given by long-crested model.

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