Prediction of planing hull side forces in yaw using slender body oblique impact theory

Morabito, Michael G.

doi:10.1016/j.oceaneng.2015.04.014

Cited by 30 publications

(16 citation statements)

References 12 publications

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“…In Eqs. (6) and 7, subscripts w and a refer to the water and the air, respectively. Moreover, a is the volume fraction of water in each cell which is governed by the equation:…”

Section: Governing Equationsmentioning

confidence: 99%

“…Accurate prediction of the forces acting on the sections entering water helps engineers design a better and safer structure, especially in the rough waters [1]. Furthermore, a good estimation of hydrodynamic pressure in such a phenomenon is an important key for accurately predicting the performance of high-speed crafts in steady [2], unsteady [3][4][5], and even maneuvering motions [6]. On the other hand, most of the researchers in this field have frequently considered the water entry with constant vertical speed, but when a section enters the water, its speed varies overtime.…”

Section: Introductionmentioning

confidence: 99%

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Numerical modeling of the freefall of two-dimensional wedge bodies into water surface

Izadi

Ghadimi

Fadavi

et al. 2018

J Braz. Soc. Mech. Sci. Eng.

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In the current paper, two-dimensional freefall of wedge water entry is investigated in 1 degree of freedom. The defined problem is numerically studied using the STAR CCM? software and by adopting an overset mesh approach. Three different chine wedges of 10°, 20°, and 30°deadrise angles are modeled. Kinematics of the considered wedges, impact loads, pressure, and the free-surface elevation around the considered wedges are presented. Based on the comparison of the computed vertical acceleration of the wedge of 20°deadrise angle against experimental data, it is determined that the proposed numerical method has relatively good accuracy in predicting the wedge response. The effects of deadrise angle and drop height on the kinematics of the wedges are also explored in different numerical simulations. Larger deadrise angle is found to yield lower and more transient vertical acceleration. It is demonstrated that impact force increases with an increase in depth, but finally approaches a constant value. Time histories of the pressure at three different points, located on the wedge wall, are also computed, indicating that an increase in the height leads to larger pressure at these points. However, when the mass is increased, the difference between the peak pressures at these points is strikingly reduced. Plots of the pressure distributions are also presented, which suggest that, as the submergence of the wedge increases, the pressure coefficient decreases. Furthermore, the pressure distributions indicate that, for the lighter wedge, the reduction in pressure coefficient is larger. Ultimately, the free surface elevation around a wedge during the freefall is presented. An increase in the pileup is observed when the submergence height is increased, but for the wedge of 30°deadrise angle, the difference between free-surface profiles at specific times is far less than that of wedges of 10°and 20°deadrise angles.

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“…In Eqs. (6) and 7, subscripts w and a refer to the water and the air, respectively. Moreover, a is the volume fraction of water in each cell which is governed by the equation:…”

Section: Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical modeling of the freefall of two-dimensional wedge bodies into water surface

Izadi

Ghadimi

Fadavi

et al. 2018

J Braz. Soc. Mech. Sci. Eng.

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“…Ghadimi et al [7] studied the running attitude of the warped planing hulls using a simple model based on the 2D + T theory. Morabito [8] used slender body theory and estimated side forces acting on planing hulls and compared the results with the experimental data. Ghadimi et al [9] also analyzed the roll motion in time domain and estimated its amplitude at different frequencies, based on 2D + T theory.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation of Stepped Planing Hulls in Finding an Optimized Step Location and Analysis of Its Porpoising Phenomenon

Sajedi

Ghadimi

2020

Mathematical Problems in Engineering

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Stability of a high-speed craft is an essential matter, and porpoising is one of the most critical instabilities that could occur in some planing hulls due to inappropriate design. In this paper, the porpoising phenomenon and variation of step location yielding resistance reduction are studied through experimental and numerical methods. The investigated models include a single-step model and a nonstep model with the same general shape, but with different step location. The nonstep model is previously tested, but the single-step model is examined in the present study. The nonstep model experiences porpoising at 8 m/s speed, but the single-step model remains stable at the same speed. A three-dimensional CFD analysis is conducted using the finite volume method (FVM). On the contrary, the volume of fluid (VOF) scheme is used for free surface modeling, and the overset mesh technique is implemented within StarCCM+ software. The CFD results of total hydrodynamic resistance and dynamic trim angle are compared against the experimental data. The numerical results are in good agreement with the experimental data. Subsequently, ten different stepped models are simulated to examine their effects. The longitudinal distance between steps and aft of these models are in the range of 19 to 50 percent of the length of models. The obtained results show that as steps are located farther than aft, the models become more stable, and resistance increases due to trim reduction. Finally, the optimum location of the step is extracted with the aim of minimizing the resistance through the design of experiment (DOE) method. Based on the DOE method, it is observed that the sensitivity of the drag value to the step location is higher than the speed.

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“…Accordingly, during the last decade, wide ranges of experimental studies have been devoted to study different characteristics of the planing hulls. Performance of these hulls [22][23][24][25][26][27], their seakeeping [28,29], roll motion [30], and even steady yawed [31,32] condition have been studied. The satisfactory, promising, and useful findings of these studies signal that experimental works can be considered as a very reliable alternative methodology for investigating the planing hull characteristics.…”

Section: Introductionmentioning

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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Prediction of planing hull side forces in yaw using slender body oblique impact theory

Cited by 30 publications

References 12 publications

Numerical modeling of the freefall of two-dimensional wedge bodies into water surface

Numerical modeling of the freefall of two-dimensional wedge bodies into water surface

Experimental and Numerical Investigation of Stepped Planing Hulls in Finding an Optimized Step Location and Analysis of Its Porpoising Phenomenon

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

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