A Practical Method for the Prediction of Planing Craft Motions in Regular and Irregular Waves

Proceedings of the Institution of Mechanical Engineers, Part M:

Tavakoli

Dashtimanesh

2016

Prediction of the roll motion is considered as an important problem in planing hull motion, since safety of the craft highly depends on it at high speeds. Accordingly, the main aim of the present study is to analyze this motion in time domain and estimate its amplitude at various frequencies. In many of the earlier works performed for predicting the motion of planing hulls, the 2d + t theory has been used. However, in all of these studies, water entry phenomenon was modeled without considering the asymmetric condition. In order to overcome this problem, a mathematical model is hereby proposed for prediction of the roll motion which is derived by applying an analytical model of the water entry in which asymmetric condition is taken into account. The suggested method may be used for the warped planing boats. Validity of the model is examined by comparing the obtained results against different experimental results. Another objective of the present study is to examine the effects of deadrise angle, longitudinal center of the gravity and the hullform on the amplitude of motion and hull response. The response is investigated at different conditions: (1) sinusoidal exciting moment, (2) a fixed existing moment and (3) an initial roll angle without any exciting moment. The proposed model is also used to evaluate the horizontal forces and moments acting on the hull during the roll motion.

Section: Amplitude Of the Roll Motionsupporting

confidence: 87%

An analytical procedure for time domain simulation of roll motion of the warped planing hulls

Proceedings of the Institution of Mechanical Engineers, Part M:

Tavakoli

Dashtimanesh

2016

“…Comparison of the predicted heeling moment for planing hull at different heel angles against experimental measurements of Judge 19 at Fn B = 4.3: (a) u = 5, (b) u = 10, (c) u = 15, and (d) u = 20.component in x-direction-see equations(15) and(21)). Reduction in both wetted surface and pressure force causes a reduction in the resistance.…”

mentioning

confidence: 99%

Steady performance prediction of a heeled planing boat in calm water using asymmetric 2D+T model

Proceedings of the Institution of Mechanical Engineers, Part M:

Tavakoli

Dashtimanesh

et al. 2016

This article presents a simple mathematical model for predicting the running attitude of warped planing boats fixed in a heel angle and free to trim and sinkage. The proposed model is based on asymmetric 2D + T theory utilizing a pressure equation which is previously introduced in the literature to compute the hydrodynamic force acting on a heeled planing hull. Integration of pressure distribution on the asymmetric wedge sections enables the suggested model to compute trim angle, center of gravity rise, resistance, and heeling moment acting on the heeled planing boat in calm water. The hydrostatic force in addition to two drag forces acting on the pressure area and spray area are also taken into account. Finally, a computational algorithm is introduced to find the running attitude of the heeled planing boats. The validity of the proposed model is examined by comparing the obtained running attitudes for two planing hulls series with zero heel angle and computed lift force and heeling moment of a heeled planing boat against available experimental data. Based on the comparisons, favorable accuracy is observed for both symmetrical and asymmetrical conditions. Moreover, it is shown that existence of a heel angle can lead to a decrease in trim angle and resistance, while it intensifies the center of gravity rise of planing boats. It is also observed that as the beam Froude number increases, the heeling moment of the heeled boat reduces.

“…The main aim of these studies have been the utilization of the results of these studies in motion prediction of planning hulls. Meanwhile, Sebastiani et al (2010) presented a method including heave, pitch and roll that separated the added mass to the left and right sides. Ghadimi et al extended this method to four DOF (2013a) and six DOF (2013b) motions.…”

Section: Introductionmentioning

confidence: 99%

Statistical Analysis of Wedge Effect on the Seakeeping of a Planing Hull in Irregular Waves at the Onset of the Planing Region

Sajedi

Taghikhani

2018

JAFM

In the current paper, different experiments are conducted on a high speed planing craft in irregular waves, with and without a wedge. Performance and seakeeping aspects of these planing hulls in the form of trim, rise-up, and resistance in regular waves and heave, pitch, bow, and center of gravity (CG) acceleration in irregular waves are extracted in time series. Irregular waves represent sea state 3 with 12cm height and peak period of 1.66. A model length of 2.63m and 1:5 scale is considered and all data for irregular waves are scaled, as well. The deadrise angle is constant and is taken to be 24 degrees. The targeted experimental tests are conducted for four longitudinal Froude numbers of 1.0, 1.18, 1.37, and 1.57, which are all in the planing regime. The results are analyzed for the mean height of wave, significant wave height, RMS, and spectrum. The comprehensive study of wedges' effects is also presented which indicates that a wedge can decrease the motions and accelerations, exceedingly. Ultimately, the obtained results are compared against those by Fridsma (1971) and Soletic (2010) and it is demonstrated that motions and accelerations are indeed reduced.