Captive Tests Research Articles

Low secondary risks for turkey vultures from a sodium nitrite toxic bait for wild pigs

AbstractAn acute and orally‐delivered toxic bait for wild pigs (Sus scrofa) containing sodium nitrite (SN) is being developed and tested for potential registration in the U.S. We evaluated oral toxicity of SN and risk of secondary consumption in a common avian scavenger, the turkey vulture (Carthartes aura), by 1) conducting an acute oral toxicity test (LD50) for turkey vultures by oral gavage, and 2) allowing turkey vultures to feed on whole carcasses and digestive tracts of wild pigs that died from consuming SN‐laden bait. Captive tests were conducted during fall 2016 and spring 2017 in the Wild Pig Research Facility at Kerr Wildlife Management Area, Hunt, Texas, USA. We estimated the LD50 of SN for turkey vultures at 659 mg/kg. None of the turkey vultures died or exhibited any symptoms of SN‐toxicity from consuming whole carcasses, or digestive tracts of wild pigs that were poisoned with SN. We concluded that the risks of secondary poisoning to turkey vultures are low, which agrees with previous work on another scavenger, the coyote (Canis latrans). Overall, we found no evidence to suggest that 2 common scavengers would be at risk of acute mortality from consuming wild pigs that were poisoned with SN.

A Numerical Study on Modeling Ship Maneuvering Performance Using Twin Azimuth Thrusters

A methodology of mathematical testing is proposed for a ship with twin azimuth thrusters based on numerical calculations. An unmanned surface vessel (USV) powered by two azimuth thrusters is considered, which is a model-scale configuration. The Ship Maneuvering Mathematical Model Group (MMG) model is introduced to describe forces on the hull and propellers. A set of captive tests (planar motion mechanism (PMM) and open-water tests) were simulated using STAR-CCM+ (16.06.008-R8) software to obtain hull hydrodynamic derivatives and azimuth thruster hydrodynamic coefficients. A maneuvering test of the model-scale ship with two azimuth thrusters is built based on numerical results, and numerical results are compared with the model-scale experimental data to validate the feasibility of numerical methods. The findings show that the usability of the developed mathematical test in predicting the maneuvering ability of ships with two azimuth thrusters is confirmed through numerical calculations.

Virtual PMM captive tests using OpenFOAM to estimate hydrodynamic derivatives and vessel maneuverability

This study reveals the significance of hydrodynamic derivatives derived at the different Froud number (Fr) in accurately predicting of a vessel's turning-circle maneuvers through solving the maneuvering modeling group (MMG) model. The computed turning-circle diameter showed a good agreement with the model test results, with less than 4% difference observed when using the hydrodynamic derivatives derived at Fr = 0.201. However, at Fr = 0.26, a significant difference was observed, which could be attributed to the use of lower values of maximum sway amplitude ymax and maximum yaw rate rmax′. The hydrodynamic characteristics of a maneuvering vessel may not be fully reflected, with the high displacement of the straight surging motion dominating the results. In this study, a set of virtual planar motion mechanism (PMM) captive tests is numerically conducted on a bare container ship hull model using an open-source code OpenFOAM. The virtual PMM captive test cases involve different maximum sway amplitude, maximum yaw rates, and Fr, achieved by varying sway amplitudes, heading angles, and the carriage speeds, respectively. The obtained numerical results are reconstructed as Fourier series (FS) equations to derive hydrodynamic derivatives employing the single run (SR) method. A system-based method is adopted to predict vessel's turning-circle maneuverability in calm water by employing the MMG mathematical model.

Study of Influencing Factors on CFD Method and Separated Flow by the Virtual Static Captive Test

In this paper, Computational Fluid Dynamic (CFD) methods are adopted to predict the manoeuvring behaviour of the KCS benchmark model. At first instance, the model is calibrated on the basis of three factors namely (a) turbulence model, (b) grid size and (c) time step. Secondly, a Static Oblique Towing Test (OTT) that utilises the SST K-ω turbulence model with a grid number of 1.64 million and a time step of 0.01 s is conducted. The maximum difference of the lateral force between the port and starboard ship sides is observed at x/Lpp = 0.055. Finally, application of Reynold Averaged Navier Stokes (RANS) and Dettached Eddy Simulation (DES) CFD models indicates that the latter may be preferable in terms of capturing the oblique flow field.

A numerical study on the added resistance and motion of a ship in bow quartering waves using a soft spring system

The prediction of resistance performance in oblique waves have been a key issue for the accurate estimation of added resistance of ships in the actual operating state. Therefore, in this paper, the added resistance of a large tanker in the bow quartering waves (180⁰, 150⁰, 120⁰) was studied by applying a computational fluid dynamics (CFD) solver based on the unsteady Reynolds-averaged Navier-Stokes equations. In addition, the forces and motion responses in bow quartering waves according to the captive test (heave, roll, and pitch free) and soft spring test (6 DOF) were investigated. To validate the CFD results, it was compared with the model test results showing good agreement. The maximum value of the added resistance was observed between 180⁰ and 150⁰, and it decreased sharply at 120⁰. The peak of the added resistance moved to a shorter wave region. The differences in added resistance, heave, and pitch motions in oblique wave according to the degree of freedom were insignificant. However, the discrepancy in roll motion occurred due to the forces and moments differences caused by the degree of freedom. The tendency of added resistance in the bow quartering waves and the forces and motion responses according to the degree of freedom were also investigated.

To study the effectiveness of stern appendages (Cruciform & X Shaped configurations) for maneuverability of autonomous underwater vessel using computational fluid dynamics

Maneuverability is one of the main aspects to be considered during the early design stage of Autonomous Underwater Vehicles. Several captive tests such as Planar Motion Mechanism (PMM), Oblique towing test, and Rotating Arm tests were conducted to obtain the hydrodynamic derivatives of the Autonomous Underwater Vehicle (AUV). In this research, the effectiveness of control surfaces with Cruciform and X configurations has been predicted for the maneuverability of the DARPA SUBOFF model. Computational Fluid Dynamics (CFD) technique was applied and the k- ω turbulence model was used to estimate the flow characteristics in the boundary layer region. The Straight-Line Towing Tank test has been used to calculate the hydrodynamic derivatives due to linear velocity, while the Rotating Arm test with a moving reference frame has been used to estimate the hydrodynamic derivatives. All the tests were conducted at a speed of 6.5 knots and three angles of incidence (10,30,50) for Straight-Line motion and three radii (13m,18m,24m) for Rotating Arm test were adopted. The simulation results of hydrodynamic coefficients have been compared with experimental results for the Cruciform configuration and the error was below 15%. So, the same procedure was adopted for the X-form configuration, and the stability index was calculated for both configurations.

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.

Prediction of the maneuvering behavior of a containership in a seaway

This study investigated the turning maneuver performance of a containership in regular waves using a two-time scale formulation. This article also presents a ship motion program, coupled with a 3-degree of freedom (3-DOF) maneuvering solver, whereby the seakeeping problem is solved with the forward speed considered in the computations. Captive tests were simulated in a computational fluid dynamics (CFD) environment to obtain the maneuvering derivatives. A near-field analysis was performed to obtain the effective wave force, which was the second-order mean drift force in this analysis. The proposed method was used to estimate the turning circle maneuver performance of the S-175 containership in both calm water and waves of different wavelengths. Ultimately, the simulation results showed high consistency with experimental data.

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.

Development and assessment of CFD methods to calculate propeller and hull impact on the rudder inflow for a twin-screw ship

The purpose of this study is to investigate the feasibility of a simple but robust approach for the identification of the main interaction effect of hull and propeller on the rudder inflow in a conventional manoeuvring simulator. The manoeuvring simulator adopts a modular/MMG based approach in which the hull, the rudders and the propellers are described by separate mathematical models which take into account the interaction phenomena. The propeller–rudder interaction factor is examined by means of a numerical model developed in OpenFOAM for the prediction of the performance of a rudder in behind propeller condition. Differently the hull–rudder interaction factor is numerically obtained by means of two different approaches. The proposed kinematic method shows the minimum additional computational cost without loss of accuracy. It is based on the analysis of rudder inflow fields (in a PIV fashioned), therefore It can be carried out in a post-processing phase of CFD simulations adopted to extract the hydrodynamic coefficients. This study validates the method by comparing it with the classical approach also used in the experimental campaign, based on the analysis of rudder forces from virtual captive tests. The approaches demonstrate to improve the overall accuracy of the main manoeuvring parameters with respect to the ones obtained by means of a calibrated semi-empirical model.

Assessment of the Manoeuvrability Characteristics of a Twin Shaft Naval Vessel Using an Open-Source CFD Code

The purpose of this study is to assess the quality of the manoeuvre prediction of a twin-shaft naval vessel by means of a time-domain simulator based on Computational Fluid Dynamics (CFD) hydrodynamic coefficients. The simulator uses a modular approach in which the hull, rudders, appendices and propellers are based on different mathematical models. The hydrodynamic coefficients of the hull in the bare and appended configurations are computed using virtual captive tests performed with an open-source CFD code: OpenFoam. This paper demonstrates that the application of the CFD hydrodynamic coefficients led to a good estimate of the macroscopic characteristics of the main IMO manoeuvres with respect to the experimental measures. The adopted test case is the DTMB 5415M frigate both with and without appendages. This test case has been investigated in several research studies and international benchmark workshops, such as SIMMAN 2008, SIMMAN 2014 and many CFD workgroups.

An initial evaluation of the free surface effect on the maneuverability of underwater vehicles

The present study aims to evaluate the free surface effect on the maneuverability of an axisymmetric underwater vehicle (UV) in the horizontal plane. Therefore, the hydrodynamic captive tests, including the straight-ahead resistance, drift and rotating arm tests, are performed over various submergence depths by using URANS equations with a Reynolds stress turbulence model available in the commercial code STARCCM+. To assess the maneuverability, the forces and moments generated by the velocity components, which are obtained from captive tests, are implemented in the maneuvering equations. Moreover, analytical equations are used to calculate the loads arising from the UV accelerations, thrust and rudder, which are all assumed to remain constant with respect to depth. The results show that the behavior of the lateral force and yaw moment generated by the UV stern region reduces significantly the UV stability over the entire range of depths. The results further show that, as the UV approaches the free surface, the behavior of the lateral force and yaw moment induced by the region between the UV midlength and aft shoulder increases the UV stability, which consequently decreases the maneuverability.

CFD evaluation and experimental comparison on the flow around fixed multi-column configurations

The flow-induced motion (FIM) of platforms is a vital phenomenon issue to be investigated to help the designers and to decrease the costs related to the mooring and/or riser systems. On this matter, when talking about multi-column configurations, captive tests (also called fixed or stationary tests) can be a methodology worth of examining the vortex detachments, the source for the oscillatory lift, the drag force, and the interference of the wake of the upstream column on the downstream ones. Computational fluid dynamics (CFD) evaluations on the flow around a fixed array of one, three, and four columns with low aspect ratio, $${\text{AR}} = H/L = 1.5$$ (the ratio between the column draft, $$H$$, and the column face dimension, $$L$$) were conducted. Three different shapes of the column sections were tested, namely, circular, square, and diamond. For the multi-column configurations, the spacing ratio tested was $$S/L$$ (where $$S$$ is the distance from center to center of each column). The Reynolds number tested was 100,000. Lift and drag forces were monitored in each column aiming at the integral quantities of the hydrodynamic to compare with the experimental results. Time averages of velocities and vorticity fields were also observed. The calculations were performed with the flow solver StarCCM+; the code solves the multi-phase incompressible Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations. Simulations were carried out with the Improved Delayed Detached Eddy Simulation (IDDES) method. The IDDES estimates the small turbulence scales near the body boundary with the Reynolds-Averaged Navier–Stokes (RANS) model and the large scales with the Large Eddy Simulation (LES) model. For the volume of fluid (VoF), an interface-capturing approach was used. The multi-column arrays presented no regular vortex shedding pattern when compared with the single-column case. The vortex shedding behavior was mainly determined by the column section. For the multi-column configurations, the number of columns, 3 or 4, was not the main issue. CFD calculations compared with the experiments showed good agreement for the circular and square cases and a significant difference for the diamond cases, which need to be further investigated.

Experimental and numerical studies on added resistance of ship in oblique sea conditions

In this paper, the added resistance of a large tanker is estimated experimentally and numerically in oblique sea. Experiments on ship motion response and added resistance in oblique sea are performed in the SSPA seakeeping basin. The experiments are conducted using the self-propulsion test for seven wave directions between 180° and 0°. In the self-propulsion test, the added resistance is estimated from the difference between the thrust of the propeller in calm water and waves. In the case of the head sea, the results are compared with those obtained from the captive test at the towing test of Seoul National University. As numerical method, two methods are selected: the strip method and the 3D Rankine panel method. The maximum value of the added resistance is observed between the incident wave directions of 180° and 150°. From 120°, the added resistance tends to decrease and the peak of the added resistance shifted to the short waves. Through the two numerical analysis methods, the tendency of added resistance and the cause of the change of the added resistance in the oblique sea are investigated.

Demonstration of Bipropellant Mode for Microsatellite-Friendly Multi-Purpose Propulsion System

Microsatellites are now in vogue and a lot of and a variety of missions using them are progressed in the world, some of them require propulsion system to realize a highly precise attitude control or orbit transfer. In order to satisfy the requirements, we are developing Microsatellite-Friendly Multi-Purpose Propulsion System, MFMP-PROP, with capabilities of both mono-propellant and bi-propellant modes to provide both of small impulse bit and large delta-V, under the policies of Safety First, Border Free, Effective COTS, and Easy Scalability, based on the techniques of 60wt% Hydrogen Peroxide. We conducted captive tests of a thruster for mono-propellant mode under bi-propellant mode to confirm its stable ignition and continuous operation, and obtained performances under its pre-heating temperature and mixing ratio of hydrogen peroxide and ethanol, of 160 seconds of specific impulse at the highest.

RANS simulation of the flow around a tanker in forced motion

This paper presents a study on simulating the flows around a tanker performing forced motions. The capacity of the original RANS solver in OpenFOAM has been extended for this purpose. The simulations of the flows around the tanker performing static drift, turning and dynamic pure sway motions in deep water are carried out. During the simulations, the free surface is not considered, i.e. double-body flow, due to the low Froude number. The k-ω SST model without wall functions is employed to approximate the eddy viscosity. This study shows that the extended solver can be used for the purpose of simulating forced ship motions of captive test, since satisfactory agreements are found between the computed results and measured data.

Effective field-based methods to quantify personality in brushtail possums (Trichosurus vulpecula)

Context There is growing recognition of the importance of animal personality in wildlife ecology and management. Individuals that differ consistently in their behaviours from others of the same population are considered to exhibit different personalities. Personality can be easily quantified with repeat tests on animals held in captivity. However, captive-based tests may not always be possible for logistical reasons and tests conducted in captivity can alter naturally occurring behaviours. Development of methods to assess personality in the field over short-term capture is an important alternative to long-term captive tests. Aims To develop and refine field-based tests that can be used to easily define personality traits of wild common brushtail possum (Trichosurus vulpecula), eliminating the need to bring individuals into captivity for an extended period of time. Methods We developed a series of short-term capture protocols to quantify personality traits of the common brushtail possum in the field, using handling-bag tests, modified open-field tests, trap-behaviour tests and release tests. Key results Personality traits of brushtail possums could be measured in several different ways, but refining methods was crucial to reveal traits efficiently. Behaviours related to several personality traits (boldness, docility and activity/exploration) could be measured rapidly in the field with our methods, and were repeatable over time. Conclusions Rapid, reliable and easy-to-perform quantification of personality of brushtail possums in the field is possible. This may sometimes be the only available option, and has advantages over long captive trials in terms of animal welfare and cost. Implications The present study provides a baseline for future research on the personality of common brushtail possums and its application to management and control strategies for the species.

Hydrodynamic modelling for the remotely operated vehicle Visor3 using CFD

Abstract: This paper addresses the hydrodynamic modelling of an inspection-class remotely operated vehicle using a viscous-flow solver for the accurate prediction of manoeuvring coefficients needed for control purposes. The 6-DOF differential nonlinear equation of motion for the ROV visor3 is first described with emphasis on hydrodynamic terms. Then, the hydrodynamic model of the ROV is assembled from data obtained using the Virtual Captive Test (VCT) approach, where experiments such as the Planar Motion Mechanism (PMM) are simulated using CFD. In this work, the Maritime Research Institute Netherlands’ viscous flow solver ReFRESCO is used to solve the steady-state and unsteady Navier-Stokes equations for single-phase turbulent incompressible flow, using a detailed geometry of the ROV. Three scenarios are considered: steady-state computations of forces and moments for different values of inflow velocity’s direction, steady-state computations of forces and moments for circular manoeuvres in the XY plane, and unsteady computations of forces and moments for rotation around the XYZ axes. The computation of manoeuvring coefficients using CFD allows one to develop a preliminary mathematical model for control purposes when there are limitations for performing physical tests.

Virtual simulation of maneuvering captive tests for a surface vessel

Hydrodynamic derivatives or coefficients are required to predict the maneuvering characteristics of a marine vehicle. These derivatives are obtained numerically for a DTMB 5512 model ship by virtual simulating of captive model tests in a CFD environment. The computed coefficients are applied to predict the turning circle and zigzag maneuvers of the model ship. The comparison of the simulated results with the available experimental data shows a very good agreement among them. The simulations show that the CFD is precise and affordable tool at the preliminary design stage to obtain maneuverability performance of a marine vehicles.

A numerical study on manoeuvrability of wind turbine installation vessel using OpenFOAM

In this study, a numerical prediction method on manoeuvrability of Wind Turbine Installation Vessel (WTIV) is presented. Planar Motion Mechanism (PMM) captive test for the bare hull of WTIV is carried out in the model basin and compared with the numerical results using RANS simulation based on Open-source Field Operation And Manipulation (OpenFOAM) calculation to validate the developed method. The manoeuvrability of WTIV with skeg and/or without skeg is investigated using the numerical approach along with the captive model test. In the numerical calculations, the dynamic stability index which indicates the course keeping ability is evaluated and compared for three different hull configurations i.e. bare hull and other two hulls with center skeg and twin skeg. This paper proves that the numerical approach using RANS simulation can be readily applied to estimate the manoeuvrability of WTIV at the initial design stage.