Linear Strip Theory Research Articles

Analysis Of Policy Has Been Established By The Minister On Opening The Export Of Lobster Seed In Indonesia

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by th Lobsters are animals that enter into crustaceans that have problematic skin. Adult lobsters can generally be found on a stretch of sand with coral spots with a depth of between 5-100 meters. This condition will cause a low number of young lobsters in the waters. This research was conducted with a case study regarding the policy of opening lobster seed export, which aims to find out how the policy is to open the export of lobster seed. The data obtained is done by reviewing the literature on the internet. Based on the analysis, the export profit of lobster seeds has continued to increase every month since it was again allowed by the government in May 2020. Based on data from the Central Statistics Agency (BPS), lobster seeds began to be re-exported in June 2020 at 32 kilograms, costing the US $ 112,990. The government can help with training and outreach on lobster cultivation. The government can offer Lobster a partnership package to help people start a freshwater crayfish business.

Analysis Of Wave Height To Ship Motion With Displacement Of 7,597 Tons By Finite Element Method

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by the ship.

Analysis Of Wave Height To Ship Motion With Displacement Of 7,597 Tons By Finite Element Method

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by the ship.

Analysis Of Policy Has Been Established By The Minister On Opening The Export Of Lobster Seed In Indonesia

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by th Lobsters are animals that enter into crustaceans that have problematic skin. Adult lobsters can generally be found on a stretch of sand with coral spots with a depth of between 5-100 meters. This condition will cause a low number of young lobsters in the waters. This research was conducted with a case study regarding the policy of opening lobster seed export, which aims to find out how the policy is to open the export of lobster seed. The data obtained is done by reviewing the literature on the internet. Based on the analysis, the export profit of lobster seeds has continued to increase every month since it was again allowed by the government in May 2020. Based on data from the Central Statistics Agency (BPS), lobster seeds began to be re-exported in June 2020 at 32 kilograms, costing the US $ 112,990. The government can help with training and outreach on lobster cultivation. The government can offer Lobster a partnership package to help people start a freshwater crayfish business.

NON LINEAR ANALYSIS OF SHIP MOTIONS AND LOADS IN LARGE AMPLITUDE WAVES

A non linear time domain formulation for ship motions and wave loads is presented and applied to the S175 containership. The paper describes the mathematical formulations and assumptions, with particular attention to the calculation of the hydrodynamic force in the time domain. In this formulation all the forces involved are non linear and time dependent. Hydrodynamic forces are calculated in the frequency domain and related to the time domain solution for each time step. Restoring and exciting forces are evaluated directly in time domain in a way of the hull wetted surface. The results are compared with linear strip theory and linear three dimensional Green function frequency domain seakeeping methodologies with the intent of validation. The comparison shows a satisfactory agreement in the range of small amplitude motions. A first approach to large amplitude motion analysis displays the importance of incorporating the non linear behaviour of motions and loads in the solution of the seakeeping problem.

On the High-Performance Hydrodynamics Design of a Trimaran Fishing Vessel

Trimaran hull form as multihull ship becomes more attractive these days in various ship types. It offers more advantages in terms of seakeeping performances, particularly on the application of a fishing vessel. However, thus far, the conventional design of fishing vessels is not favorable to ensure the safety of a vessel sailing in a rough sea. In conjunction with such issues, we discuss a trimaran fishing vessel design based on the seakeeping criterion to evaluate the dynamic stability, ship motion RAOs, and ship resistances at the initial design stages using linear strip theory. The intact stabilities are calculated to complement the seakeeping results. The analytical method based on the slender body method is used to evaluate the steady wave resistances. The results of heave, pitch, roll motions, and the ship resistances are discussed. At the zero speed and forward speed, the trimaran shows a favorable motion amplitude, although in forward speeds at the case of head seas there is no significant difference. The trimaran presents a favorable steady-resistance up to the ship speed of Fn=0.27, and it becomes deteriorating than the monohull at higher ship speeds. However, the added wave resistances of the wavelength range 1.0 – 3.0 shows significant added resistances at Fn=0.25 and Fn=0.35, respectively. The results of this study present promising seakeeping and resistance characteristics of the trimaran hull form. The trimaran hull form ensures the safety, reliability, and operation efficiency of ships sailing in broader ranges of violent-sea environment.

On the Comparative Seakeeping Analysis of the Full Scale KCS by Several Hydrodynamic Approaches

The main transport channel of the global economy is represented by shipping. Engineers and hull designers are more preoccupied in ensuring fleet safety, the proper operation of the ships, and, more recently, compliance with International Maritime Organization (IMO) regulatory incentives. Considerable efforts have been devoted to in-depth understanding of the hydrodynamics mechanism and prediction of ship behavior in waves. Prediction of seakeeping performances with a certain degree of accuracy is a demanding task for naval architects and researchers. In this paper, a fully numerical approach of the seakeeping performance of a KRISO (Korea Research Institute of Ships and Ocean Engineering, Daejeon, South Korea) container ship (KCS) container vessel is presented. Several hydrodynamic methods have been employed in order to obtain accurate results of ship hydrodynamic response in regular waves. First, an in-house code DYN (Dynamic Ship Analysis, “Dunarea de Jos” University of Galati, Romania), based on linear strip theory (ST) was used. Then, a 3D fully nonlinear time-domain Boundary Element Method (BEM) was implemented, using the commercial code SHIPFLOW (FLOWTECH International AB, Gothenburg, Sweden). Finally, the commercial software NUMECA (NUMECA International, Brussels, Belgium) was used in order to solve the incompressible unsteady Reynolds-averaged Navier–Stokes equation (RANSE) flow at ship motions in head waves. The results obtained using these methods are represented and discussed, in order to establish a methodology for estimating the ship response in regular waves with accurate results and the sensitivity of hydrodynamical models.

On operation capabilities analysis of a 100000 tdw tanker by seakeeping criteria

The operation capabilities of a maritime ship have to be assessed during the design, including the seakeeping criteria. In this study a 100000 tdw tanker is considered, with two loading conditions, cargo and ballast. The numerical analyses are developed with our own software DYN, module OSC, based on a linear hydrodynamic strip theory. The main oscillation components, heave, pitch and roll, are considered. The analysis includes an extended parametric study for the tanker speed up to 15 knots, different vertical positions of the gravity centre, a heading angle full range and irregular waves significant height up to 12m. Also the seakeeping limits have two sets of criteria. The results are pointing out the operation limits of the tanker on combined navigation parameters in irregular waves, by motions and acceleration short term seakeeping criteria.

ATLAS IV wing aerodynamic design: From conceptual approach to detailed optimization

In this paper, the aerodynamic design of the ATLAS IV, remote controlled aircraft, is summarized. A wing aerodynamic design methodology was established for a high lift-high efficient aircraft, which participated at the International Competition: Air Cargo Challenge 2013 (ACC 2013), Lisbon, Portugal. The conceptual approach includes the basic design considerations regarding the regulations, the power consumption for efficient take-off and the maneuverability during operational conditions. At the next step, the preliminary design is elaborated using an advanced numerical method based on Linear Strip Theory (LST). This numerical method evaluates the results from the conceptual approach, increases the numerical accuracy of the initial concept and the results are used for the Aircraft's Dynamic Stability analysis. At the final step, a full CFD model was developed and calibrated based on preliminary design results. During the detail design, the propeller effects, a gurney flap and a winglet design were also investigated, for the further increase of ATLAS IV prototype's aerodynamic efficiency. The wing aerodynamic design procedure was used for the Team's strategy plan for the ACC 2013, improving its rank during the Contest.

Effect of the nonlinear vertical wave-induced bending moments on the ship hull girder reliability

In the present paper the effect of the nonlinear vertical wave-induced bending moments on the ship hull girder reliability is evaluated. A chemical tanker for which the nonlinearity of the vertical wave-induced bending moments was found to be significant is adopted as case study. The nonlinear effects on the vertical wave-induced bending moments of the chemical tanker are accounted for in the reliability assessment problem through model correction factors, which are estimated using direct calculation methods based on linear and nonlinear strip theory formulations and the most likely response wave method. It is verified that the design formulation presently used to define the hull girder vertical wave-induced bending moments underestimates the magnitude of the nonlinear effects. The more accurate predictions provided by the direct calculations methods show that the actual hull girder reliability in sagging is significantly smaller. Possible modified design solutions for the midship cross-section of the chemical tanker are evaluated in order to demonstrate the impact of the increase of the nonlinear vertical wave-induced bending moment in sagging in terms of structural design criteria.

Assessing the Impact of a Slow Steaming Approach on Reducing the Fuel Consumption of a Containership Advancing in Head Seas

The slow steaming approach is increasing in popularity for commercial vessels, as it provides a method of reducing fuel use, and therefore operating costs, in the current economic climate. It is very important to be able to evaluate a ship's response to waves, because any added resistance or loss of speed may cause delays or course alterations, leading to financial losses. Potential flow theory based linear strip theory is still a widely used method among naval architects, due to its fast solutions with sufficient engineering accuracy. The key objective of this study is to predict the ship motions and added resistance of the S-175 containership, and to estimate the increase in effective power and fuel consumption due to its operation in regular and irregular head seas. The analyses were performed at design and slow steaming speeds, for a range of wave conditions in regular seas, and for three different sea states in irregular seas. The results obtained at a ship speed corresponding to Froude number 0.25 were compared to available experimental data and were found to be in good agreement with the experiments. The numerical analyses were carried out using VERES, which is based on potential flow theory.

Influence of ducted propeller on seakeeping in waves

It has been claimed that the use of a ducted propeller instead of an open propeller reduces the pitching motions of a ship, and the added resistance in waves. In addition, there is the potential benefit of smaller loss in propulsive efficiency when the propeller loading increases due to added resistance. Although little documentation for the validity of these claims is found, they look reasonable, since the duct has an effect similar to a passive foil, which is proven to reduce the vertical plane motions of high speed vehicles. This paper investigates the effect of a duct on the seakeeping of conventional ships. It is shown how the effect of the duct on the motions can be modelled by an equivalent flat foil. The effect of duct on motions and added resistance is investigated using linear strip theory. Results of model tests using a conventional 120m single screw cargo vessel with a ducted and an open propeller are presented. The model test results confirm the findings from the numerical calculations, which is that the duct needs to be much larger than what is typical for such a ship in order to have a significant influence on the seakeeping performance.

벌브를 가진 쌍동형 선박의 종동요 응답 스펙트럼 분석

In this study, a commercial seakeeping program Seakeeper, integrated into Maxsurf, which is based on the linear strip theory was employed to compare the effect of bulbous bow (with/without) on motion response characteristics in a 18-meter catamaran. The seakeeping analyses were conducted at several Beaufort wind conditions such as scale No. 3 (, =0.6m), No. 4 (, =1m) and No. 5 (, =2m) based on ITTC wave spectrum. Pitch motion response spectrum was calculated at Head sea, Head & bow sea and Beam sea as encounter angles. Hull form of a catamaran with bulb showed the maximum 20% decrease of pitch motion response as compared to that of hull form without bulb.

The influence of forward speed on ship motions in abnormal waves: Experimental measurements and numerical predictions

Ship encounters with abnormal waves are increasingly well documented and it is therefore important to be able to model such encounters in order to assess the risks involved and whether there is a requirement for more stringent design rules.This paper presents the results of an experimental investigation into the influence of abnormal waves on a vessel travelling with forward speed in irregular seas. The vessel studied in this case is a naval frigate travelling at a range of speeds. To put the motions measured in abnormal waves into context comparisons are made to those in random seas with a variety of significant wave heights, both non-severe and severe. A further objective is to compare experimental measurements with motion predictions from both a two-dimensional linear strip theory and a three-dimensional partly nonlinear seakeeping model.Results demonstrate that abnormal waves may not necessarily be the worst conditions that a ship can encounter. However, accelerations derived from the rigid body motions appear to be in excess of rules values. This has implications for design due to the unexpected nature of abnormal wave occurrence and the consequent likelihood of encountering such a wave at a higher speed (hence in a more severe operating condition) than a random sea of an equivalent height.The three-dimensional partly nonlinear model demonstrates improved agreement with experimental measurements of rigid body motions, compared to the two-dimensional strip theory. It is therefore considered to have greater potential as a design tool for abnormal wave encounters. Further validation with a wide range of sea states and vessel types is required.

Analysis of the forward speed effects on the radiation forces on a Fast Ferry

The paper presents an analysis of the radiation forces on a ship advancing with forced heave and pitch motions. This analysis is based on experimental data obtained with model tests and on numerical simulations with two codes, one based on 3D time domain Greens function method and the other is a 2D linear strip theory method. The case study consists of a hull shape from a Fast Ferry and several speeds are investigated between 0 and 40knot. The objective is to quantify the forward speed effects on the radiation forces and to verify the skill of the conventional strip theory and of a time domain panel methods in dealing with large forward speeds.The consequences of applying simplifications on the linear boundary conditions of the common seakeeping codes are investigated. It is concluded that forward speed has a large effect on the radiation forces, especially on the coupling terms, and thus it is important to consider the full linear interactions between the steady and unsteady flows in the numerical calculations as the speed of the ship increases and the time domain panel code is able to represent these effects.

상용코드를 이용한 다방향 불규칙파중 실습선의 종운동해석

본 연구에서는 실습선의 다방향 불규칙파중 종방향 운동응답특성을 선형 스트립이론에 기초한 상용코드(MAXSURF v.16)를 이용하여 해석하였다. 해석에 앞서 상용코드의 검증을 위해 파나막스급 컨테이너선에 대해 실험조건과 동일한 선형과 해석조건을 적용하여 계산한 결과와 기 계산된 결과(Flokstra, 1974)가 상호 유사한 경향을 얻어 해석의 신뢰성을 확보하였다. 계산조건으로는 Fn=0.257에서 파랑외력을 ITTC 파스펙트럼에 기초한 뷰포트 스케일 5(<TEX>$\bar{T}=5.46$</TEX>, <TEX>$H_{1/3}=2m$</TEX>)의 파스펙트럼을 산출하였고, 조우각은 선수사파(Head & bow seas, <TEX>$150^{\circ}$</TEX>)를 적용하여 상하동요(Heave)와 종동요(Pitch)의 선체운동응답스펙트럼을 해석하였다. 다방향 불규칙파에 대한 운동응답스펙트럼은 선수사파에서 상하동요의 경우는 미소하게 단파정파에서 높은 스펙트럼 분포를 보이고 종동요의 경우는 장파정파에서 높게 나타났다. This study gives the vertical motion analysis in multi-directional irregular waves using a commercial code(MAXSURF v.16) based on linear strip theory for a training ship. To verify the commercial code prior to the analysis, we guarantees the reliability of this paper's results using the commercial code by comparing with the results(Flokstra, 1974) of same hull and experimental conditions on a Panamax container. The analysis conditions are Beaufort wind scale No. 5(<TEX>$\bar{T}=5.46$</TEX>, <TEX>$H_{1/3}=2m$</TEX>) based on ITTC wave spectrum, encounter angle Head & bow seas(<TEX>$150^{\circ}$</TEX>) and Froude number Fn=0.257. Finally, we calculates heave RAO, pitch RAO and obtains the result of ship's response spectra for heave and pitch motions. In the motion response spectrum under the multi-directional irregular waves, heave motion reacts slightly high in short-crested waves and pitch motion reacts high in long-crested waves.

An efficient method for nonlinear aeroelasticy of slender wings

This paper aims the nonlinear aeroelastic analysis of slender wings using a nonlinear structural model coupled with the linear unsteady aerodynamic model. High aspect ratio and flexibility are the specific characteristic of this type of wings. Wing flexibility, coupled with long wingspan can lead to large deflections during normal flight operation of an aircraft; therefore, a wing in vertical/forward-afterward/torsional motion using a third-order form of nonlinear general flexible Euler–Bernoulli beam equations is used for structural modeling. Unsteady linear aerodynamic strip theory based on the Wagner function is used for determination of aerodynamic loading on the wing. Combining these two types of formulation yields nonlinear integro-differentials aeroelastic equations. Using the Galerkin’s method and a mode summation technique, the governing equations will be solved by introducing a numerical method without the need to adding any aerodynamic state space variables and the corresponding equations related to these variables of the problem. The obtained equations are solved to predict the aeroelastic response of the problem. The obtained results for a test case are compared with those of some other works and show a good agreement between results.

Numerical simulations of wave-induced ship motions in time domain by a Rankine panel method

A time domain prediction of wave-induced ship motions by a Rankine panel method is investigated. Linear boundary conditions on free surface and mean wetted body surface are adopted, while the numerical damping method is used for the radiation conditions. The motions of two ships in regular head waves are computed by the present method. The related numerical results are compared with the experiment data and those from linear strip theory. The comparison shows satisfactory agreements for pitch and heave transfer functions.

Fatigue Analysis of Structural Details of an Oceangoing LPG Ship

Structural details of ship structures are prone to fatigue damage mainly due to high-cycle wave load and low-cycle cargo loading/unloading. Full stochastic fatigue analysis of selected structural details on an oceangoing 6500 cbm LPG ship is presented. A critical Y-joint of longitudinal bulkhead and bilobe tank shell as well as double-bottom girder details are selected due to different reasons. The eccentricity of the Y-joint, leads to significant stress concentration. Saddle supports of gas tanks cause stress concentration in ship double bottom due to weight and dynamic loads. Wave load on ship structure is calculated using linear strip theory for ship in ballast condition and full ship. Wave load is transferred to ship finite element model and notch structural stresses are determined using finite element analysis. Stochastic fatigue analysis is then performed, taking into account sailing route and other ship operational parameters. Finally, fatigue damage summation is done and results are discussed.

다축선의 프로펠러 레이싱 추정에 관한 연구

This paper represents a basic statistical examination on the navigability of ocean-going ship from the point of estimating the time lasting period when propeller racing occurred by using the basic probability theory and the statistics. The propeller racing is one of the most important seakeeping qualities in relation to the safety of the main engine and shafting system. The trend of the racing has been mainly investigated in order to estimate allowable maximum propeller diameter, operation of ocean-going ships, etc.. In those studies, the propeller racing generally and mainly means the situation (propeller exposed) in which the relative motion amplitude between ship hull and wave surface would exceed a depth of point in rotary disk propeller. Therefore, it seems that the magnitude of the amplitude and its exceeding frequency of propeller racing have been examined as a principal subject of study as usual. However, the time during which the amplitude exceeds the depth of point, that is, the propeller exposes in the air, must be also one of most important factor affecting the trend of propeller racing. Then, this paper proposes a new practical method for estimating the time lasting of exposed propeller related to propeller racing in rough-confused seas on the basis of the linear strip theory and the statistics. And, numerical examples of estimating the propeller racing probability are given for four wide ship forms. Finally the usefulness of the proposed method for predicting propeller racing based on the time lasting period is discussed.