Slamming Events of a Planing Hull and Wedge Water Entry Experiment: Comparisons and Insights on Fluid-Structure Interaction

Both towing tank experiments and wedge drop experiments are used to experimentally study slamming events on planning craft. The work presented in this paper shows a unique comparison between these two experiments. The first experiment was a towing tank test of a rigid hull in waves conducted at the U.S. Naval Academy. The second experiment was a series of free-falling water entry tests on a wedge conducted at Virginia Tech. In this paper, comparisons are drawn between the two experiments by using non-dimensional analysis and isolating similar slamming events. The non-dimensional impact velocities are chosen to be identical.

An Interactive Numerical-Experimental Approach for Predicting the Vortex Induced Motion of Floating Production Systems

The Vortex Induced Motion (VIM) phenomenon is one of the well-known and important behavior experienced by all Floating Production Systems (FPSs) in operation under the effect of uniform current. In this phenomenon, under the effect of the formed vortices around the FPS hull, the platform oscillates primarily in a direction perpendicular to the flow resulting in a significant fatigue damage to the risers and the station keeping mooring system. Scale towing tank test has been the standard industry tool for predicting the VIM response, but it has its own limitations and has showed to significantly overpredict the VIM response when compared to the field measurements. In this paper, an interactive numerical-experimental approach has been developed to more accurately predict the VIM response and avoid the shortcomings of the model tests to bridge the gap between the model test predictions and the field measurements. Numerical and experimental data are presented to demonstrate the application and advantages of the proposed approach

THE EXPERIMENTAL METHOD AND CFD STUDY OF THE BARE HULL FORM OF UNDERWATER VEHICLE AT NEAR SURFACE CONDITION

Hull form selection, resistance and powering are important in designing underwater vehicle. An underwater vehicle bare hull form is based on the five parameters due to the interaction between the propeller and the hull. When they are running on the surface condition, there will be problems likely as surface vessel, but the main hull of the underwater vehicle is below the waterline with low freeboard. The underwater vehicles are operating with high speed at a high Froude Number. Therefore, the wave making component becomes important in surface resistance. The wave making resistance of the underwater vehicle model at surface condition is analyzed by using CFD tools. Friction component of resistance is calculated by using ITTC’57 correlation line. The flow around the ship’s hull is complicated, so that model experiments are still the most reliable data source on ship resistance determination. The bare hull form of underwater vehicle resistance is based on the model experiments and CFD results. The towing mechanism arrangement should be considered at model. Therefore, towing mechanism is designed for model testing. This paper discusses the towing method and result between model test and CFD. This paper also makes comparison of wave formation Towing tank test and CFD at various speeds. The model was tested with bare hull form of underwater vehicle in the Ship Model Towing Tank at Marine Hydrodynamics Centre, Myanmar Maritime University. CFD analysis is also carried out and the results are compared for surface condition. The three software packages XFLOW, XMESH and XPAN are used for CFD simulations. The comparison of results shows that the coefficient differences are less staggered based on the speed.

Investigation of Environmental Effects of High Speed Boats

Luxury high-speed boats are increasingly being used for entertainment purposes. However, not only humans, but also animals are negatively affected by high-speed boats, and time is running out fast for people to do something about it. This study presents a review of current negative effects of high-speed boats to the environment. In this study, the flow around a benchmark planing Fridsma boat is simulated by CFD and resistance values for different non-dimensional Froude number (Fn) conditions are validated from the experimental results obtained from the literature. Using the same CFD methodology, a catamaran model in which the towing tank test results are available, is simulated for different Fn conditions and resistance values are predicted. In the CFD analysis, unsteady flow around the Fridsma hull model and catamaran model is simulated using overset meshing technique and turbulence is modeled by Reynolds Averaged Navier Stokes (RANS) with SST (Menter) k-omega turbulence model. Resistance values are compared with the experimental data and required propulsion powers are estimated for different Fn conditions. Then, total resistance of the catamaran for full-scale vessel is calculated using an extrapolation method and required propulsion power predictions are conducted. Noise prediction, corresponding to the required propulsion power are presented. In particular, the change of noise level and harmful gases released into the environment, when the speed of the vessel increases are examined and discussed. Consequently, it is believed that this study would lay an important foundation for the widespread investigation for the negative effects of the high-speed boats in the future.

Manoeuvring Prediction of KVLCC2 with Hydrodynamic Derivatives Generated by a Virtual Captive Model Test

This paper describes the application of computational fluid dynamics rather than a towing tank test for the prediction of hydrodynamic derivatives using a RANS-based solver. Virtual captive model tests are conducted, including an oblique towing test and circular motion test for a bare model scale KVLCC2 hull, to obtain linear and nonlinear hydrodynamic derivatives in the 3rd-order MMG model. A static drift test is used in a convergence study to verify the numerical accuracy. The computed hydrodynamic forces and derivatives are compared with the available captive model test data, showing good agreement overall. Simulations of standard turning and zigzag manoeuvres are carried out with the computed hydrodynamic derivatives and are compared with available experimental data. The results show an acceptable level of prediction accuracy, indicating that the proposed method is capable of predicting manoeuvring motions.

Comparison of Selected Parametric Methods for Prediction of Inland Waterways Ship Hull Resistance in Towing Tank Test

In the paper selected approximate methods for calculation of inland waterways ship resistance and their verification by towing tests, compared on the example of a small urban ferry, are presented. The test results are made for both the bare hull and the hull with appendages (skeg, azimuthal propeller). Significant differences between results of the theoretical methods and experimental ones, especially in the case of the model with skegs and propulsion, are pointed out. The purposefulness of using several parametric methods and the use of average results at the preliminary design stage were also discussed.

Influence of hull entrance angle “Perintis 750 DWT”, toward ship resistance: the case study for design development “Perintis 750 DWT.”

Geographically Indonesia which most of its territory consists of the sea, causing the necessity of strengthening maritime facilities and infrastructure to conduct activities of distribution of goods and sea transportation facilities, especially ships as a vehicle of sea transportation to maintain inter-island connectivity. Indonesian government builds national connectivity (sea tolls) by the development of pioneer ship design “Kapal Perintis.”. In this study, the vessel Perintis 750 DWT is still lacking in the EEDI (Energy Efficiency Design Index) aspect as required by IMO, so it is necessary to modify the hull part of the vessel to reduce the resistance. The modified hull is carried out by varying the angle of entrance bow of the ship ± 12° in step of 3°. Modifications were made using Delftship software, Computational Fluid Dynamic, called TDyn and verified by towing tank test at Indonesian Hydrodynamics Laboratory (IHL) Surabaya. Every change of the angle of entrance bow in 3 degrees, the ship's resistance will change more and less 3.5%. The smaller angle of entrance bow of the vessel the smaller ship's resistance.

Gaya Hambat Saat Hidro Planing dan Gaya Angkat Aerodinamika Saat Cruise di Efek Permukaan pada Pesawat Wing in Surface Effect

Perhitungan komputasional dinamika fluida pada model 3 Dimensi pada pesawat Wung In Surface Effect sangat penting untuk mengetahui data hasil uji towing tank dan uji terbang. Konfigurasi Lippisch mempunyai sayap berbentuk inverse delta dan punuk di atasnya menggunakan airfoil jenis Clark Y yang telah dirancang untuk memenuhi karakteristik efek permukaan. Piranti lunak pertama Maxsurf digunakan untuk membandingkan hasil uji model towing tank saat fase hydro planing. Piranti lunak kedua ANSYS CFX digunakan untuk menghitung gaya hambat air dan gaya angkat aerodinamika dari pesawat Wing In Surface Effect kapasitas 8 orang model 3 Dimensi dengan konfigurasi Berat Maksimum saat take off sebesar 32000 Newton pada kecepatan cruise 80 knots pada ketinggian terbang 2.5 meter. Aspek eksperimen pada uji model towing tank dan data uji terbang pada prototipe pesawat Wing In Surface Effect kapasitas (1-2) orang saat hydro planing dijelaskan dengan menggunakan teori gelombang hidrodinamika dan porpoising efek. [The Hump Drags During Hydro planing and Aerodynamic Lift During Cruise in Surface Effect Altitude Of Wing in Surface Effect Craft] The computational fluid dynamics of 3 Dimensions model of Wing in Surface Effect craft is very important to proof the model towing test and flight testing data. The inverse delta wing and shoulder airfoil is by using Clark Y of Lippisch configurations have been designed for the surface effect characteristics. The first Maxsurf software are used to compared the towing test results during hydro planing phase. The second ANSYS CFX software is used to calculate the hump drags and aerodynamic lift of Wing In Surface Effect craft 8 seaters 3 Dimensions model to verified the Design Requirement and Objectives. The forces equilibrium on the body axis during hydro planing are very important to fulfill the take off phase on the water surface. And, the aerodynamic lift for Maximum Take off Weight of 8 seaters configuration is 32000 Newton during cruise speed at 80 knots on the 2.5 meter altitude. The experimental aspects of towing tank test model and Wing In Surface Effect craft (1-2) seaters prototype during hydro planing test have been proposed by using the hydrodynamic wave and porpoising effect theory.

Study on Application of CFD and FEM Coupling Method to Evaluate Dynamic Response of Ship Under Severe Wave Condition

In this study, a series of validations of a weakly one-way CFD-FEA coupling method for the estimation of the dynamic response of a container ship under severe wave condition is made. By comparing the prediction with linear/non-linear strip method, 3D panel method and towing tank test results under various wave conditions in terms of rigid body motions and structural loads, the effectiveness of the CFD-FEA coupling method is confirmed. Furthermore, the hydro-elastic behavior obtained by 3D panel method and the CFD-FEA coupling method are validated regarding the whipping moment by comparing the experiment.