Planar Motion Mechanism Tests Research Articles

Evaluation of hydrodynamic coefficients and sensitivity analysis of a work-class remotely operated vehicle using planar motion mechanism tests

This paper presents a comprehensive analysis of the hydrodynamic forces and moments relating to the drag on an open-frame work-class remotely operated vehicle (ROV) AUTO-1000. We describe the results of planar motion mechanism experiments conducted with the aim of modeling and simplifying the mathematical maneuverability model for such an ROV. The scale of the model is 1:4. Various experiments are performed in a nonlinear wave channel. The flow speeds in the static drag tests range from ±0.2–±0.5 m/s and the angle in the drift tests is less than 10°. The motion frequencies of the dynamic tests range from 0.25 to 3.14 rad/s. The amplitude of the translation motions is 0.03 m and the largest angular amplitude in the rolling tests is 5°. The viscous and inertial hydrodynamic coefficients are estimated. Normalized sensitivity coefficients are used to investigate the sensitivity of both the viscous and inertial hydrodynamic coefficients considering the multi-degree-of-freedom motion and velocity effect. The drag, drift, and stationary random motions are used to examine the sensitivity. A comparison of the motion simulation results given by simplified and complete models shows that a threshold normalized sensitivity coefficient value of 0.01 is suitable for filtering the ROV coefficients.

The comparative research on the VPMM experiment and numerical simulation of the SUBOFF model

To ensure optimal maneuvering performance of underwater vehicles, it is essential to obtain highly precise hydrodynamic coefficients for constructing the equations of motion. The principal approach to acquiring these coefficients is through the Planar Motion Mechanism (PMM) test. The subject of this paper is the SUBOFF full appendage model. To obtain hydrodynamic coefficients related to maneuvering motion, a Vertical Planar Motion Mechanism (VPMM) test is conducted in the circulating water tank. In addition, a numerical simulation of the typical pure heaving and pure pitching maneuverability test is performed for the model by programming its motion UDF using Fluent’s dynamic mesh technology. The test results and calculated hydrodynamic coefficients are compared to the data obtained from the Key Laboratory of Underwater Robotics Technology of Harbin Engineering University. The calculation results show high credibility of the test results of the circulating tank VPMM test. The corresponding numerical simulation has a certain practical engineering accuracy, which can break through the limitations of the test and also provides valuable experience and technical reference for the hydrodynamic prediction of other underwater vehicles.

Analysis of turning ability of large tankers with and without bulbous bow in calm sea and waves

The present study introduces an experimental and numerical investigation of the turning ability of two ships with and without a bulbous bow: original and modified KVLCC2 hulls Experiments are performed via free-running model tests in a square basin, and a system-based simulation are performed. The maneuvering coefficients for the system-based solver are obtained via numerical planar motion mechanism (PMM) tests based on CFD computations, and other variables are obtained from reference ships. The effects of ship speed, wave direction, and wavelength are investigated. Results of a calm-water turning test obtained experimentally and numerically agree well. When the ship turns in the presence of incident waves, the overall behavior and evaluation parameters predicted in the simulation are similar to those obtained from experiments. However, the evaluation parameters show scattered values under severe turning-failure conditions. The most significant wave effects are observed in short waves. Additionally, the turning ability is compared between two ships, and slightly different maneuvering capabilities are observed. The time series for two hulls are further compared to investigate the reason for the difference showing the difference in the force and drift angle time series.

Effect of amplitudes and frequencies on Virtual Planar Motion Mechanism of AUVs: Part II 3DOF implementation, comparison with RANSE and field trials

Planar motion mechanism tests have been widely used in simulations, i.e, virtual environments for ocean craft, especially for underwater vehicles. These tests involve a pre-determined sinusoidal trajectory. While there are general guidelines for the choice of amplitude and frequency for such trajectories in existing literature, there are none for smaller submerged ocean craft. The direct application of the work presented in this paper is for autonomous underwater vehicles (AUVs). A series of two articles presents analysis of virtual planar motion mechanism (VPMM) specific to AUVs. An arbitrary selection of amplitudes and frequencies for VPMM can result in significant uncertainty in hydrodynamic derivatives. The results in this article explain the effect of frequencies and amplitudes of pure sway and pure yaw VPMM implemented in a lumped parameter maneuvering model (LPM) for the horizontal plane. This article shows that for typical AUV geometries that the use of non-dimensional frequency up to a value of 0.5 and a non-dimensional amplitude of up to 0.25 remains acceptable for pure sway and pure yaw VPMM despite fluid memory effects. For the first time, a detailed methodology to determine appropriate amplitudes and frequencies for any craft is presented, with the results of one craft shown as an example. Overall, this series of articles sheds light on the process to determine the amplitude and frequency for pure sway and pure yaw VPMM for an AUV in the early design stage.

Effect of amplitudes and frequencies on Virtual Planar Motion Mechanism of AUVs, Part I: Forces, moments and hydrodynamic derivatives

Planar motion mechanism tests have been widely used in the virtual form for ocean craft, especially for underwater vehicles. These tests involve a pre-determined sinusoidal trajectory for the AUV. While there are general guidelines for the choice of amplitude and frequency for such trajectories in existing literature, there are minimal to none for smaller submerged ocean craft such as autonomous underwater vehicles. This series of articles analyzes VPMM from the perspective of AUVs and the significance of variation in these parameters. The results in Part I of this series are discussed in terms of forces and moments reconstructed using hydrodynamic derivatives obtained through RANSE. This includes variation in forces and moments, and the possible non-linear effects that cause such variation. The resultant hydrodynamic damping derivatives show upto 50% variation based on parameters that signify pure sway and pure yaw simulations. The resultant added mass derivatives do not vary much among the various VPMM simulations attempted (<2%). The inflow angle to the craft is found to be significant in characterizing pure sway simulations.The results in Part II are discussed in terms of implemented dynamic maneuvers through RANSE and in field.

Characteristic of hydrodynamic derivatives for a multi-hull navigation vessel in dynamic positioning mode

The Quadmaran vessel is a maritime multi-hull vessel developed for water quality observation in aquaculture farms. The vessel’s dynamic positioning (DP) performance is essential for the accuracy of the collected data. The maneuvering characteristics in DP mode have been investigated in our previous research using a quasi-static motion prediction model based on static planar motion mechanism (PMM) tests. However, since the Quadmaran vessel has a unique hull arrangement, the motion characteristics need to be determined with greater accuracy. Therefore, in this study, the maneuvering equations are newly established with higher accuracy hydrodynamic derivatives determined through dynamic PMM tests. The higher order hydrodynamic derivatives are obtained from pure sway, pure yaw and pure yaw with a constant angle tests. Model scale experiments are conducted to establish an advanced mathematical model and compared with the quasi-static assumption results. The result shows significant improvements in the motion prediction under DP mode, and a more accurate motion prediction model is successfully established. This study is a new attempt to utilize the dynamic PMM tests method on a vessel with unique shape and motion characteristics. The advanced mathematical model deepens our understanding of the maneuverability of a multi-hull vessel in DP mode.

Experimental study of the hydrodynamic maneuvering coefficients for a BB2 generic submarine using the planar motion mechanism

In this study, a series of captive model tests were conducted to obtain the reference dataset of hydrodynamic coefficients and experimental data for the BB2 generic submarine model with a scale ratio of 35.1. A mathematical model was constructed using the dataset, and validated against a model scale free-running experiment conducted by MARIN for scale ratio of 18.341. The experiments used vertical planar motion mechanism equipment in the model basin at Pusan National University and included resistance, static drift, static control plane deflection, and dynamic tests. Horizontal planar motion mechanism tests were performed by rotating the model by 90° about the propeller shaft axis. Subsequent combination tests—horizontal static with rudder tests and pure yaw with rudder tests—were performed to evaluate the effects between the hull and control planes. The tests were performed under the model self-propulsion point to consider the effects of the propulsor on the maneuvering characteristics of the vehicle. The obtained results were compared with those of numerical studies owing to the absence of open-experimental captive test data for the scaled BB2 model.

Maneuverability prediction of the wave glider considering ocean currents

The wave glider powered by waves has a unique dual-body architecture and can perform long-duration operational tasks in the ocean. In this paper, to accurately predict its maneuverability, the horizontal plane 3-degree of freedom (DOF) dynamic models of the surface float and the submerged glider are established separately. The influence of ocean currents is considered, and the influence of the torsional moment of the umbilical cable is considered for the first time. The hydrodynamic coefficients of the submerged glider will vary with different rudder angles and angles of attack of incoming flow. The computational fluid dynamics (CFD) method is used to analyze and calculate added mass coefficients and damping coefficients corresponding to different rudder angles based on planar motion mechanism (PMM) test simulation and oblique navigation dynamic test simulation. The flow fields are analyzed under different working conditions. The structural parameters of the wave glider and the hydrodynamic coefficients obtained from the simulation are brought into the dynamic model. The rotary motion and the Z-shaped motion under different sea conditions and currents are numerically analyzed. The difference of the hysteresis of the surface float relative to the submerged glider in yaw motion are analyzed under different ocean currents and rudder angles. Sea trial and simulation results show that the established dynamic model and obtained hydrodynamic parameters can accurately basically predict the maneuvering performance of the wave glider.

구속모형시험을 통한 잠수함 선형의 수상 조건 조종성능 추정 연구

In this paper, the results of Planar Motion Mechanism (PMM) test for a 1/15 scaled model of the MARIN Joubert BB2 submarine is dealt with to derive the maneuvering coefficients for surface condition. For the depth of surface navigation, the top of the sail was exposed 0.46 m above the water surface in the model scale, and it corresponds to 6.9 m in the full scale. The resistance and self-propulsion tests were conducted, and the model’s self-propulsion point was obtained for 1.328 ㎧, which corresponded to 10 knots in the full scale. The maneuvering tests were performed at the model’s self-propulsion point, and the maneuvering coefficients were obtained. Based on the maneuvering coefficients, a turning simulation was performed for starboard 30 degree of stern fins. The straight-line stability and control effectiveness in the horizontal plane were analyzed using the maneuvering coefficients and compared with the appropriate range. For the analysis of the neutral fin angle of the X-type stern fin, the stern fin test with drift angles was carried out. As a result, the flow straightening effect at lower and upper parts of the stern fin was discussed.

Simulation of Turning Manoeuvre of Planing Craft Taking Into Account the Running Attitude Change in a Simplified Manner

Abstract The modelling and simulation of planing craft manoeuvres requires coupled six degrees of freedom (6 DOF) motion equations. A coupled 6 DOF motion equation needs hundreds of manoeuvring hydrodynamic coefficients (MHCs) that are mostly determined using the planar motion mechanism (PMM) test. The number of test runs is too high, unless a kind of simplification is imposed to the motion equations. This study modifies 6 DOF motion equations to 4+2 DOF motion equations in which heave and pitch equations are replaced by dynamic draught and trim (so-called running attitude), respectively. The method is applicable for a manoeuvre that commences in the planing regime and ends in the same regime. On that basis, the PMM test is conducted and the model is restrained in the vertical plane at a certain running attitude, determined by a resistance test. The 4+2 DOF method, together with MHCs from the PMM test, are employed for the simulation of turning manoeuvres of a 25° prismatic planing hull. The results of the simulation indicate that the 4+2 DOF method reasonably predicts the path of the craft during the turning manoeuvre and cuts the number of PMM tests required at the same time. The PMM test results show that MHCs are highly related to forward speed and wetted surfaces. The turning manoeuvre simulation shows that the non-linear terms of MHCs cannot be ignored. The STD/L (Steady Turning Diameter divided by Length of the craft) for a planing craft is very large, compared to ships.

1/42.0 KCS 모형선의 조종성능에 관한 연구

The emergence of new concept ships, such as autonomous ships, has drawn much attention on the manoeuvrability of ships because of the safe navigation and operation of ships. Although the manoeuvrability of KRISO Container Ship(KCS) has been frequently reported, there have been few documents of representative manoeuvre cases conducted in various methods by one institute. This paper presents the manoeuvrability of the ship in 1/42.0 model scale by 3 methods: free running model tests, horizontal planar motion mechanism tests, and computational fluid dynamics analysis. KRISO reports KCS manoeuvre data: 35° turning circle tests and 20/20(10/10) zigzag manoeuvring tests. In addition, a simple formula for integrating and comparing manoeuvre indices, Manoeuvrability Comparing Simple Index(MCSI), is proposed.

Study on numerical PMM test and its application to KCS hull

· A numerical moving tank was applied for the various PMM tests of the KCS model. · Numerical sensitivity of time window, grid resolution, and time step was systematically examined. · The wave patterns and vortices around ship was observed in various PMM test conditions. · A complete set of hull manoeuvring coefficients was obtained. · The manoeuvring coefficients were successfully applied for the prediction of turning tests. The planar motion mechanism (PMM) test is among the most popular methods to evaluate ship manoeuvrability due to its ability to generate manoeuvring coefficients through a series of captive tests. As a replacement for conventional towing tank facilities, the present work applies an open-source-based computational fluid dynamics (CFD) solver to conduct numerical tests, including the static drift, pure sway, pure yaw, and combined drift-yaw tests. The test model is the KRISO container ship (KCS), which has a highly-curved hull with sharp edges and extruded bulbous bow. The original k-ω SST turbulence model has been enhanced to stabilize the turbulence fields near the free surface as well as the hull, and the bow and stern vortices that occur during the ship's PMM motions are displayed in the present CFD analysis. For both the static and dynamic tests, the force and moment predicted by the present CFD solver agree well with the experimental measurements. The numerical PMM tests have generated a complete list of manoeuvring coefficients for the bare hull, and the further application to ship 35° turning circle test has demonstrated a reasonable agreement with the direct free-running experiments.

Experimental Study on the Wave Effect on Maneuvering Hydrodynamic Derivatives

Abstract For maneuverability in waves, all the current theoretical methods rely on an unverified hypothesis that the hydrodynamic derivatives in waves are consistent with those in calm water. Many scholars attribute the errors between the predicted motions using the theoretical methods and the experimental motions to this irrational hypothesis. To explore the rationality of the hypothesis and improve the theoretical methods, the planar motion mechanism tests of KVLCC2 in calm water and regular head waves were carried out in the towing tank. Different components of the hull forces are obtained by the fast Fourier transform technique. Then, maneuvering hydrodynamic derivatives in calm water and head waves are calculated to assess the wave effect on them quantitatively. The results reveal that the wave effect on Yv′, Nr′ and the high-order derivatives are obvious, and the influence on Nr′ and Yv′ is small. This finding sheds light on the error of the earlier hypothesis and is conducive to the improvement of potential flow methods in the future.

An efficient and accurate approach for zero-frequency added mass for maneuvering simulations in deep and shallow water

An overall increase in ship sizes in conjunction with a general decrease in ship powering has increased the relevance of reliably predicting a ship’s maneuvering performance. These predictions rely often on mathematical models based on modified Taylor series expansion, where nonlinear multivariate algebraic polynomials that require hydrodynamic coefficients are determined from physical or numerical planar motion mechanism (PMM) tests. The added mass coefficients are needed for a fast and accurate simulation. For maneuvering simulations, these added mass coefficients should be obtained for zero frequency. Despite the advance of high-performance computing, numerical PMM tests based on solving the unsteady Reynolds-averaged Navier–Stokes equations is time-consuming and often not suitable for practical design-related investigations. Furthermore, hydrodynamic coefficients obtained from PMM tests are frequency-dependent. An alternative to numerical PMM tests consists of steady numerical tests. This kind of analysis requires much less computing time and effort for the users. However, the acceleration-dependent hydrodynamic forces and moments cannot be derived from these steady computations. Here we introduced a fast and accurate procedure to obtain water depth-dependent zero-frequency added mass and added moment of inertia. Using Euler Equations, we impulsively accelerated the ship hull over only one time step. We validated our method against an analytical solution for an ellipsoid. We performed systematic computations of added mass and added moment of inertia for two benchmark containerships, a benchmark tanker, and a cruise ship, thereby demonstrating the effects of water depth on added mass for different hull shapes.

Numerical Study on Hydrodynamic Coefficient Estimation of an Underactuated Underwater Vehicle

Hydrodynamic coefficient estimation is crucial to the shape design, dynamic modeling, and control of underwater vehicles. In this paper, we conduct a numerical study on the hydrodynamic coefficient estimation of an underactuated underwater vehicle (actuated only in the surge, heave, and yaw degrees of freedom) by adopting the computational fluid dynamics (CFD) approach. Firstly, the mechanical structure of an underactuated underwater vehicle is briefly introduced, and the dynamic model of the underwater vehicle with hydrodynamic effects is established. Then, steady and unsteady Reynolds Averaged Navier–Stokes (RANS) simulations are carried out to numerically simulate the towing test, rotating arm test, and Planar Motion Mechanism (PMM) test of the underwater vehicle numerically. To simulate unsteady motions of the underactuated underwater vehicle, a sliding mesh model is adopted to simulate flows in the computational fluid domain that contain multiple moving zones and capture the unsteady interactions between the underwater vehicle and the flow field. Finally, the estimated hydrodynamic coefficients of the underwater vehicle are validated in a physical experiment platform, and the results show that the numerical estimates are in good agreement with the experimental data.

Dynamics Modeling and Hydrodynamic Coefficients Identification of the Wave Glider

The wave glider is an ocean-wave-propelled autonomous marine vehicle with unique dual-body architecture, which can converse the energy obtained from the ocean wave into the forward thrust. In this paper, the dynamic models of the submerged glider based on dynamic characteristics of tandem hydrofoils and the surface float were separately established. The pitching angles of the hydrofoils and the submerged glider and the angle of attack between hydrofoils and relative current were considered for dynamic models and hydrodynamic coefficients. The translational hydrodynamic coefficient term for high-angle-of-attack passive motion of the submerged glider was calculated from static test simulations by using Computational Fluid Dynamics (CFD). Moreover, the rotational damping coefficients and added mass coefficients varying with the pitching angle of hydrofoils were analyzed by the simulation of the vertical planar motion mechanism (VPMM) tests. Furthermore, the numerical simulation of longitudinal motion with the computed hydrodynamic coefficients was performed, and the simulation results were compared with the sea trial data. The analysis was performed, and conclusions were drawn, which would provide a theoretical reference for the design of the wave glider.

Research on accurate modeling of hydrodynamic interaction forces on AUVs operating in tandem

The hydrodynamic interaction force between autonomous underwater vehicles (AUVs) operating in tandem can adversely affect the hydrodynamic prediction of individual AUVs and the formation control of the tandem fleet. Accurate modeling of hydrodynamic interaction forces is crucial to the model-based controller design of AUVs. In this paper, we innovatively propose a modeling method that can describe the hydrodynamic interaction relationship accurately and continuously (when the spacing between adjacent AUVs changes). First, an accurate hydrodynamic model for individual AUVs in tandem fleets is established by modifying the typical model through the consideration of memory effects. Second, a model of hydrodynamic interaction forces is derived by subtracting hydrodynamic forces acting on a single AUV operating independently from those acting on an AUV operating in tandem. To enable this model to continuously describe the hydrodynamic interaction relationship when the spacing changes, this model is further derived by taking the spacing as an independent variable based on the parameter conversion method. Finally, planar motion mechanism (PMM) tests are carried out using the computational fluid dynamics (CFD) method to verify the accuracy and continuity of the proposed modeling method. The results show that compared with the typical model, the average error of hydrodynamic forces predicted by the proposed model is reduced by 5.36%, which verifies the feasibility and effectiveness of the proposed modeling method.

The estimation of hydrodynamic coefficients of an autonomous underwater vehicle by comparing a dynamic mesh model with a horizontal planar motion mechanism experiment

This study aims to establish a dynamic mesh model based on the horizontal planar motion mechanism (HPMM) test and provide a comprehensive database of hydrodynamic coefficients for the autonomous underwater vehicle (AUV) numerically and experimentally. A series of HPMM tests in National Cheng Kung University's towing tank validated the simulation results. The dynamic mesh model can be performed on oscillation motions of the yaw mode, the pitch mode, and the roll mode by adding a series of comprehensive user-defined functions (UDFs). The test of straight-line motion with constant drift angles, the pure surge test, the pure yaw test, the pure pitch test, the pure yaw test with a constant drift angle, and the pure pitch test with a constant drift angle are all available for the yaw and pitch modes. In addition, the pivot roll test is included in the roll mode. After measuring forces and moments from an individual HPMM test, the hydrodynamic coefficients can be derived by means of Fourier analysis and the least-square method. Since most numerical results are reasonably in good agreement with the experimental data, applying the proposed dynamic mesh model to the simulation of the HPMM tests in the towing tank can be demonstrated.

Numerical investigation of the influence of wave parameters on maneuvering hydrodynamic derivatives in regular head waves

To evaluate the wave effect on the maneuvering hydrodynamic derivatives in the research of maneuverability in waves, the experimental and numerical studies on the Planar Motion Mechanism (PMM) tests in regular head waves for the standard ship model KVLCC2 are carried out. The simulations are performed by an up-to-date Unsteady Reynolds Averaged Navier-Stokes (URANS) solver. Overset mesh technique and Euler Overlay method are adopted. The simulation results are validated using the experimental data obtained from the PMM tests in towing tank of Shanghai Jiao Tong University. The comparison of the hydrodynamic derivatives in waves and calm water conditions reveals that the wave effect on Yr′ can be ignored except for the extremely steep wave condition. However, Nr′ is significantly changed by the wavelength and wave steepness. This finding shows that there is an error in the previous assumption that the hydrodynamic derivatives in waves are the same as those in calm water. In addition, a simple modification for the wave effect on high-order hydrodynamic derivatives is hard to be proposed due to the random changing tendency of these parameters. The instantaneous flow field information is also obtained and indicates that the influence of waves on the free surface contour and dynamic pressure is more significant than that of low-frequency maneuvering motions.

SHIP MANOEUVRING PREDICTION BASED ON NUMERICAL TOWING TANK TECHNIQUE

A practical procedure is proposed in this paper to predict ship manoeuvrability. A three degrees of freedom MMG (Japanese Manoeuvring Mathematical Modelling Group)-type model is established to simulate rudder manoeuver. Propeller thrust and rudder loads are calculated by empirical formulas, whereas the hull forces as well as moment are determined with hydrodynamic derivatives which are derived from CFD (Computational Fluid Dynamics) computations. An own developed RANS (Reynolds-Averaged Naiver-Stokes) solver on the base of OpenFOAM is applied to simulate a range of PMM (Planar Motion Mechanism) tests and Fourier analyses of the computed results are carried out to obtain the required derivatives. In order to demonstrate the effectivity of the whole procedure and the RANS computations, the US (United States) combatant DTMB 5415 is taken as a sample for an application. Forced motions of surge, sway, yaw and yaw with drift for the bare hull with bilge keels are simulated. Thereafter, simulations of standard rudder manoeuvers, i.e. turning and zigzag, are performed by applying the computed derivatives. The results are compared with available measured data. It has been shown that the present procedure together with the RANS method can be used to evaluate the manoeuvrability of a ship since general good agreements between the simulated results and measured data are achieved.