Asymmetric Water Entry of Twin Wedges with Different Deadrises, Heel Angles, and Wedge Separations using Finite Element Based Finite Volume Method and VOF

Shademani, Roya; Ghadimi, Parviz

doi:10.18869/acadpub.jafm.73.238.26185

Cited by 21 publications

(8 citation statements)

References 29 publications

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“…Through the same approach, Ghadimi et al 14 obtained the pressure distribution over a wedge-shaped cross section which enters the water with constant speed. Also, Shademani and Ghadimi 15 investigated the forces of the water entry phenomenon on wedges with a deadrise angle ranging from 10° to 80° using a two-dimensional (2D) finite-element-method-based finite-volume-method (FEM-FVM) code. The use of FEM-FVM to investigate the spray parameters, secondary impact and the turbulence effect of forces in the case of water entry problem of the wedges was followed by Shademani and Ghadimi 16,17 in some other papers, and the results of their extensive research via this method, in addition to determining the behavior of various parameters during the occurrence of wedge water entry, show the suitability of this numerical method for solving this problem.…”

Section: Background Literature Surveymentioning

confidence: 99%

Numerical simulation of the slamming phenomenon of a wave-piercing trimaran in the presence of irregular waves under various seagoing modes

Ghadimi

Nazemian

Sheikholeslami

2019

Proceedings of the IMechE

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Trimaran vessels have been of great interest to naval architects, due to their large deck space, low resistance at high speeds and stability. Meanwhile, determination of their slamming forces in the presence of highly nonlinear waves has always been a challenge for the structural designers. However, because of novelty and complexity of their hulls, there is insufficient information in this regard, which necessitates suitable effort in filling this gap. Accordingly, in this article, using Flow-3D, a commercial computational fluid dynamics code, seakeeping of a wave-piercing trimaran is simulated in the presence of irregular waves via standard Bretschneider spectrum in sea state 5 in various seagoing modes. These modes include two speeds and two waves with encountering angles of head sea and bow quartering sea. For validation purposes, seakeeping of a trimaran vessel and water entry of a wedge-shaped section are investigated and numerical results are compared against experimental and analytical data. Good compliance of the results confirms the accuracy of the proposed numerical model. In the slamming analysis of the considered trimaran, using the relative vertical velocity of the bow section from the seakeeping analysis, the water entry problem is investigated for the most severe slamming mode. Pressure distribution caused by water entry and instantaneous impact pressure, known as structural design pressure, is computed. The exerted slamming pressure on the bottom and bow flare region is determined to be 4300 and 2100 Pa, respectively. Results indicate that during slamming phenomenon, the maximum pressure exerted on the vessel’s floor occurs at the time of impact at which the pressure coefficient is 4.4. Accurate assessment of the vessel’s vertical velocity from the start of water entry until the water surface rise-up, and the utilized technique considered for slamming phenomenon in more realistic sea condition, can be considered as important features of this study.

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Section: Background Literature Surveymentioning

confidence: 99%

Numerical simulation of the slamming phenomenon of a wave-piercing trimaran in the presence of irregular waves under various seagoing modes

Ghadimi

Nazemian

Sheikholeslami

2019

Proceedings of the IMechE

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“…It is considered that the model passes through a transverse plane and the three dimensional problem can be reduced to a water entry of a solid body with wedge section, as shown in Figure 19. Dynamic pressure distribution over the wall of the wedge can be computed using analytical scheme, numerical methods [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] or experimental measurements [68][69][70][71][72][73][74]. Here, the Wagner solution [75] is used as in when the water has not drenched the chine.…”

Section: Longitudinal Force Distributionmentioning

confidence: 99%

Experimental Study of the Wedge Effects on the Performance of a Hard-chine Planing Craft in Calm Water

2018

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In this paper, effects of a wedge on the performance of planing craft in calm water are experimentally investigated. Experiments are carried out on three different cases distinguished by the wedge type. The model, built of fiberglass, is a prismatic planing hull with deadrise angle of 24 degrees. Towing tests are conducted at different Froude numbers ranging from 0.21 to 2.1. The total trim angle, resistance, rise up at the CG as well as stern and bow, keel wetted length, chine wetted length, stagnation angle, and the length of stagnation line are measured. They are used to study the effect of installing a wedge on the performance as well as the effect of height on the hydrodynamic characteristics. Based on the observations made, it is concluded that, when the wedge is applied to the hull, the risk of model exhibiting instability diminishes, while total trim angle largely decreases, keel wetted length is enlarged, wetted surface becomes thinner, CG rise up is lowered, and the resistance is reduced. Moreover, experimental measurements and theoretical 2D+T theory are combined to bring deeper insight about physics of the flow and pressure distribution when a wedge is installed on the bottom of a planing hull.

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“…The submerged behavior of high-speed craft is directly related to the pressure distribution on the bottom of the craft and thereby the pressure center at the bottom. Finding the pressure distribution on the planing hulls is very influential on their performance and has been studied separately in various research works through analytical, 2–4 numerical, 5–17 and experimental 18,19 approach, or simultaneous use of them. 20–22…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical analyses of wedge effects on the rooster tail and porpoising phenomenon of a high-speed planing craft in calm water

Sajedi

Ghadimi

Sheikholeslami

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part C:

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This paper presents experimental and numerical investigation of stability and rooster tail of a mono-hull high-speed planing craft with a constant deadrise angle. Initially, a one-fifth scale model was tested in a towing tank, which showed porpoising phenomenon at 8 m/s (equal to the speed of sailing). Subsequently, two wedges of 5 and 10 mm heights, based on the boundary layer calculations, were mounted on the aft section of the planing hull. These wedges were shown to increase the lift at the aft section. These experiments were carried out at different speeds up to 10 m/s in calm water. The experimental results indicated that the installed wedges reduced the trim, drag, and the elapsed time for reaching the hump peak, and also eliminated the porpoising condition. All these test cases were also numerically simulated using Star CCM+ software. The free surface was modeled using the volume of fluid scheme in three-dimensional space. The examined planing craft had two degrees of freedom, and overset mesh technique was used for space discretization. The obtained numerical results were compared with experimental data and good agreement was displayed in the presented comparisons. Ultimately, the effect of the wedge on the rooster tail behind the planing craft was studied. The results of this investigation showed that by decreasing the trim at a constant speed, the height of the generated wake profile (rooster tail) behind the craft decreases, albeit its length increases.

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Asymmetric Water Entry of Twin Wedges with Different Deadrises, Heel Angles, and Wedge Separations using Finite Element Based Finite Volume Method and VOF

Cited by 21 publications

References 29 publications

Numerical simulation of the slamming phenomenon of a wave-piercing trimaran in the presence of irregular waves under various seagoing modes

Numerical simulation of the slamming phenomenon of a wave-piercing trimaran in the presence of irregular waves under various seagoing modes

Experimental Study of the Wedge Effects on the Performance of a Hard-chine Planing Craft in Calm Water

Experimental and numerical analyses of wedge effects on the rooster tail and porpoising phenomenon of a high-speed planing craft in calm water

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