Static Drift Research Articles

Numerical Investigation of Underwater Vehicle Maneuvering Under Static Drift Conditions

The hydrodynamic behavior of underwater vehicles is crucial for achieving optimal maneuverability and energy efficiency in various underwater environments, thereby ensuring effective underwater operations. This research addresses the drift characteristics of an underwater vehicle by conducting Computational Fluid Dynamics (CFD) simulations. DARPA Suboff model was used to analyze its maneuvering characteristics under static drift conditions at a velocity of 3.34 m/s and drift angles ranging from 0 to 18 degrees with 2-degree intervals. The simulations replicate actual sea conditions using the Reynolds-Averaged Navier-Stokes (RANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. The computational domain and boundary conditions are carefully defined to optimize the computational cost. The results revealed a significant decrease in longitudinal force when the drift angle increased, while the lateral force and yaw moment showed substantial increases, indicating the complex interactions between drift angles and hydrodynamic performance. This research provides valuable insights into the hydrodynamic forces and moments acting on underwater vehicles, contributing to their design optimization for improved stability and efficiency.

Numerical PMM test in finite depth

This study conducted a numerical planar motion mechanism (PMM) test for a containership, considering the effects of finite depth. An OpenFOAM-based computational fluid dynamics (CFD) approach was employed to conduct the simulations. Before conducting a series of numerical computations, uncertainty analysis for the grid size and time step was performed to ensure the reliability of the computational results. Two PMM tests, static drift and pure yaw, were conducted, and the results were validated against experimental data. The comparison demonstrated good agreement between forces, moments, and hydrodynamic coefficients when compared with both experimental and other computational results. Furthermore, a comparison between a first- and second-order combination model and a first- and third-order combination model revealed that the latter showed better alignment with experimental data in deep water, while the former performed better in shallow water, emphasizing the role of crossflow. This study contributes to understanding the differences in maneuvering performance between deep and shallow water conditions.

Four-DOF Maneuvering Motion of a Container Ship in Shallow Water Based on CFD Approach

With the continuous increase in ship size combined with the generally slower increase in the sizes of waterways, the need for the prediction of ship maneuvering in shallow waterways continues to attract attention from the international scientific community. Ship behavior in shallow water is relevant in seabed effects that result in changing the hydrodynamic forces acting on a ship. In this study, the maneuvering characteristics of a container ship with four degrees of freedom in shallow water are analyzed. The Reynolds-Averaged Navier Stokes approach in Ansys Fluent code is used to produce the maneuvering coefficients through the simulations of forward running, static drift, static heel, circular motion, the combined motions, and the pure roll motion of the KRISO container ship. The maneuvering characteristics of the ship are estimated for evaluating the ship behaviors in shallow-water conditions. The obtained results show that the roll has a significant decrease and the ship’s turning diameter has a significant increase when the ship operates in a shallow waterway. The predictions of the maneuvering characteristics of the ship are in good agreement with those of free-running model tests, indicating that the numerical simulation based on the Computational Fluid Dynamics method has compromising capability to predict the maneuvering derivatives and the four-DOF ship maneuvering motion in shallow water as well.

Computational Study on Influence Factors and Vortical Structures in Static Drift Tests

This paper conducted a computational study on the KCS benchmark model at static drift conditions. At the first instance, the roles played by the grid size, turbulence model, and time step are qualitatively and quantitatively analyzed with the orthogonal experimental method (OEM). After the verification of simulated results compared with experimental data in a Static Oblique Towing Test (OTT), hydrodynamic performance is obtained with the employment of the SST κ-ω turbulence model. The grid size is set as 0.07 m while the time step as 0.01 s. The characteristics of the wake field are illustrated in different forms, such as contours of the free surface, distribution of pressure and hydrodynamic forces, variation of turbulent kinetic energy (TKE), and so on. For a deep insight into the physical mechanisms of the asymmetrical flow field, the Detached Eddy Simulation (DES) method is also utilized to capture vortical structures occurring around the hull, in comparison with results obtained through the Reynolds Averaged Navier Stokes (RANS) model. With the aim of a hydrodynamic derivative estimation or detailed flow characteristics analysis, corresponding selections of the computational method are disparate.

Power Prediction and Manoeuvring Study for an Inland Class Vessel

The paper explores the propulsive power requirements and manoeuvring capabilities of a popular class of inland bulk carriers in Bangladesh. After the initial verification study, model-scale CFD simulations are performed in calm, open waters at different speeds to assess hull resistance. The resistance results are then extrapolated to full scale for calculating propulsion power requirements. Subsequently, manoeuvring simulations are performed using PMM motions to evaluate static drift, pure sway, and pure yaw scenarios to calculate manoeuvring coefficients. Following this, model-scale resistance simulations in restricted waters are performed to estimate the minimum power needed for propulsion in heavy monsoon currents based on common inland waterway dimensions in Bangladesh. Finally, full-scale simulations are performed in open water to investigate the scale effect on resistance (thus power) prediction. The study confirms that the installed power in the vessel is adequate for safe navigation within Bangladesh’s inland waters. Although model-scale CFD studies are generally unsuitable for resistance prediction, the study suggests that extrapolated results often offer conservative estimates for power prediction. In cases of resource limitation, these simulations can prove beneficial since conservative estimations somewhat ensure the vessel’s propulsion and manoeuvrability in extreme conditions.

Research on the resistance and maneuvering characteristics of an amphibious transport vehicle and the influence of stern hydrofoil

Research on the resistance and maneuvering characteristics is a key requirement in amphibious vehicle design to ensure safety and efficiency. To tackle the challenges of evaluating amphibious vehicles' hydrodynamic performance, as well as the lack of research and systematic approaches, a comprehensive performance evaluation method based on the RANS method and MMG model is introduced in this study, and the influence of a stern hydrofoil is evaluated. Firstly, the numerical calculation model is established based on the RANS method and validated by towing tests. The resistance characteristics of vehicles with and without stern hydrofoil are evaluated. The hydrofoil has a 9.37% drag reduction rate under the rated condition. Then, the static drift tests, circular motion tests, and static heel tests are simulated to obtain vehicles' hydrodynamic coefficients. Subsequently, the four-degree-of-freedom MMG models are established to predict the vehicles’ maneuvering performance and evaluate the effect of stern hydrofoil. The results obtained from CFD and predictions are compared, confirming the capability of the MMG model. The stern hydrofoil can improve turning performance but affects course-keeping and yaw-checking abilities.

Estimation of linear hydrodynamic derivatives of a 37000 tdw chemical tanker using virtual captive model tests

Forecasting the hydrodynamic properties of a ship is crucial for assessing its maneuvering capabilities. This study presents the results of static drift and circular motion simulations conducted on a 37000 tdw chemical tanker. The calculations were carried out using the ISIS-CFD solver, accessible through the FineTM/Marine academic license provided by NUMECA. The flow solution was obtained by numerically solving the Reynolds-Averaged Navier Stokes equations, employing the k-ω Shear Stress Transport (SST) model to represent turbulence. The simulation results were used to determine the linear hydrodynamic derivatives, which were then compared with hydrodynamic derivatives estimated with empirical formulas proposed by Clarke et. al. [1] and Tribon Initial Design module in the absence of experimental results.

Numerical study on static drift tests for ship maneuvering in regular waves

This study is driven by the coupled seakeeping–maneuvering analysis, which predicts ship maneuverability in waves by combining seakeeping analysis with a mathematical maneuvering model. The traditional maneuvering model and its corresponding coefficients are developed based on calm sea conditions, where wave effects are typically disregarded as a temporary compromise. It is an inevitable need to revisit the mathematical maneuvering model or coefficients by considering wave effects. To this end, in this study, a series of static drift tests are employed in waves to investigate the influence of wave effects on the sway damping coefficients of ship maneuvering motion. These tests are conducted using a numerical tank, which overcomes spatial constraints and maintains a reliable wave field for ship–wave interactions. Three wave parameters, namely wavelength, wave steepness, and wave direction, are considered to assess their impacts on the wave-induced motions and forces. Furthermore, the wave effects on the maneuvering coefficients are summarized and discussed using direct observations of ship-turning motions in waves. Additionally, the benefits of computational fluid dynamics analysis are utilized to showcase the strong nonlinear phenomena of ship–wave interactions.

Four-dimensional particle tracking velocimetry measurements of unsteady three-dimensional vortex onset and progression for 5415 straight ahead, static drift, and pure sway

Large-scale towed system four-dimensional particle tracking velocimetry (4DPTV) implementation and measurements are presented for towing tank tests for a naval combatant 5415 ship model for straight ahead, static drift β = 10°, and pure sway βmax = 10° conditions. The results, for the first time, provide instantaneous volumetric flow field data around the ship model including near the hull surface, and a complete description of the sonar dome 3D unsteady vortex separation onset and progression due to the 4DPTV larger measurement volume and higher data rates in comparison with previous results using tomographic particle image velocimetry (TPIV); thereby, providing the essential data required for the assessment of current hybrid Reynolds-averaged Navier–Stokes/large eddy simulation turbulence modeling capabilities and guidance for the necessary modeling improvements. The 4DPTV system is summarized and compared with the previous TPIV, including the camera calibration procedures, trigger systems, and synchronization with the sway motion. Analysis procedures, including data reduction procedures and the 3D vortex core detection and voxel labeling techniques, are described. The identification of the complex vortex separations and breakdown is aided using complementary detached eddy simulations. The vortex–vortex interaction process is visualized from instantaneous volumetric datasets. The pros and cons of the 4DPTV vs TPIV, the comparison between the second- and third-generation vortex visualization technique, and the statistical convergence error analysis of sonar dome port vortex for β = 10° are discussed. Plans for increased spatial resolution of the 4DPTV system and additional data reduction techniques for detailed turbulence analysis are also discussed.

Numerical Investigation of the Maneuvering Forces of Different DARPA Suboff Configurations for Static Drift Condition

Numerical Investigation of the Maneuvering Forces of Different DARPA Suboff Configurations for Static Drift Condition

Non-dimensional Hydrodynamic Coefficients Determination of a Derived-Submarine Bare Hull Form

The hull of the marine vehicle can be optimized based on the target one or more purposes. One of the most frequent purposes is the form optimization to obtain the most suitable form in terms of resistance. When it comes to energy efficiency, optimizing the vessel's form in terms of resistance means less fuel consumption. However, it is thought that the effect of the optimized form on other dynamics in the marine vehicle should also be investigated. Resistance coefficients were obtained for this purpose by constructing various bow and stern forms for a simple submarine form. The resistance coefficients of both the submarine and the form derived from this submarine were validated again in this study since different software programs were used in the previous study. These dimensionless resistance coefficients obtained for various velocities were compared to each other and the experimental data. Furthermore, the static drift analyses are performed to obtain the sway force and yaw moment at various attack angles. The dimensionless hydrodynamic coefficients, such as Y_v' and N_v’, have been calculated with fitting a curve to the values of sway forces and yaw moments. The non-dimensional hydrodynamic coefficients differences calculated for the submarine and derived bare hull are close to each other when compared in terms of maneuvering derivatives.

Low-Pass Filters for a Temperature Drift Correction Method for Electromagnetic Induction Systems.

Electromagnetic induction (EMI) systems are used for mapping the soil's electrical conductivity in near-surface applications. EMI measurements are commonly affected by time-varying external environmental factors, with temperature fluctuations being a big contributing factor. This makes it challenging to obtain stable and reliable data from EMI measurements. To mitigate these temperature drift effects, it is customary to perform a temperature drift calibration of the instrument in a temperature-controlled environment. This involves recording the apparent electrical conductivity (ECa) values at specific temperatures to obtain a look-up table that can subsequently be used for static ECa drift correction. However, static drift correction does not account for the delayed thermal variations of the system components, which affects the accuracy of drift correction. Here, a drift correction approach is presented that accounts for delayed thermal variations of EMI system components using two low-pass filters (LPF). Scenarios with uniform and non-uniform temperature distributions in the measurement device are both considered. The approach is developed using a total of 15 measurements with a custom-made EMI device in a wide range of temperature conditions ranging from 10 °C to 50 °C. The EMI device is equipped with eight temperature sensors spread across the device that simultaneously measure the internal ambient temperature during measurements. To parameterize the proposed correction approach, a global optimization algorithm called Shuffled Complex Evolution (SCE-UA) was used for efficient estimation of the calibration parameters. Using the presented drift model to perform corrections for each individual measurement resulted in a root mean square error (RMSE) of <1 mSm-1 for all 15 measurements. This shows that the drift model can properly describe the drift of the measurement device. Performing a drift correction simultaneously for all datasets resulted in a RMSE <1.2 mSm-1, which is considerably lower than the RMSE values of up to 4.5 mSm-1 obtained when using only a single LPF to perform drift corrections. This shows that the presented drift correction method based on two LPFs is more appropriate and effective for mitigating temperature drift effects.

Numerical PMM test in shallow water using CFD method

This study aims to the estimation of the ship manoeuvrability in shallow water by using the numerical PMM approach, which analyses the hull hydrodynamic responses and manoeuvring performance from the viewpoint of coefficients. The test model is a scaled KVLCC2 tanker operating at a low Froude number of 0.0514. Static drift test and pure yaw test are considered, and the water depths vary from deep water to very shallow water of 20% under-keel clearance. The numerical tank is built based on an OpenFOAM+ package. The free surface is modelled by volume-of-fraction method, and the k-ω SST model associating with wall functions is applied for turbulence. After the convergence tests and validation works, the numerical tank is employed to investigate the wave-depth effect on hydrodynamic forces and manoeuvring coefficients. The present results show that the forces of static drift test, particularly sway force, can be significantly changed as the water depth decreases.

Design of Real-time Test System for Servo Stabilization System Based on Matlab/xPC

For the barrel and static drift problem in the working process of the servo-stabilization system of an unmanned firing module, a simulation test system is built by using the Matlab/xPC real-time platform. The CAN communication card is driven by the Simulink S-function, and communication between the test system and the servo stabilization system is realized. The fast Haar wavelet threshold processing method is used to de-noise the gyro speed signal, and the de-noising effect of the signal processor is simulated and verified in the physical system. The results show that the servo stability test system has strong real-time performance, and the performance of the Haar wavelet de-noising algorithm is good. The system has a broad application value.

SCALE EFFECT ON THE LINEAR HYDRODYNAMIC COEFFICIENTS OF DARPA SUBOFF

As well known, forces and moments acting on a ship are functions of Froude and Reynolds numbers. As a ship gets larger in size, these two numbers grow, which leads to different flow regimes around the hull. However, the state-of-the-art in maneuvering calculations is to consider the hydrodynamic coefficients as constants for model and full ship scales. For submerged bodies, the Froude number is insignificant due to the distant free water surface; therefore, these forces only depend on the Reynolds number. In this study, we consider the benchmark ‘DARPA’ Suboff form, which is extensively studied in the literature, and investigated the scale effects on the hydrodynamic coefficients with respect to the Reynolds number. Numerical studies are carried out on the bare hull form of the submarine. Captive motions of static drift and pure yaw motions are conducted utilizing the oblique towing and rotating arm tests via RANS-based CFD. Linear hydrodynamic coefficients are expressed with logarithmic equations as functions of the Reynolds number, explicitly showing the dependency on the ship’s model scale.

Towards the effects of load condition on ship manoeuvrability by a system simulation method with hydrodynamic derivatives from RANS computations

The effects of load condition on ship manoeuvrability are investigated by means of system simulation method. To this end, a MMG-type mathematical manoeuvring model is applied to simulate the standard turning and zigzag rudder manoeuvres for a KVLCC2 ship model in six load conditions (two drafts × three trims). In order to determine the needed hydrodynamic derivatives, the forces and moments on the hull in a range of combined static drift and circle motions are computed by using the own expanded RANS (Reynolds-Averaged Navier-Stokes) solver on OpenFOAM. However, the coefficients of hydrodynamic interaction among hull, propeller and rudder are obtained from available experiments. The computed surge forces, sway forces and yaw moments agree fairly well with the experimental data, suggesting a promising prospect for the used RANS solver in the application of ship manoeuvring prediction. By regressing the hydrodynamic forces and moments, the hydrodynamic derivatives are obtained. Turning and zigzag rudder manoeuvres are simulated by solving ship motion equations in line with the acquired derivatives and coefficients. Comparing the simulated results between the full and ballast load condition without trim, a small draft (i.e. the ballast load condition) improves turning performance, but weaken course stability. For the three full load conditions or ballast load conditions, trim by bow improves turning ability, but deteriorates yaw-checking ability. The simulated results for two load conditions show satisfactory agreement with available experimental data, which suggests that the present procedure for ship manoeuvring prediction is effective. The course stability indexes are analysed as well. The load condition will affect significantly the manoeuvrability of a ship, at least for KVLCC2. It may be quite necessary to evaluate the manoeuvrability of a ship in different load conditions at the initial design stage.

Theoretical model to predict the seismic drift concentration effect for self-centering-braced frame

This study is motivated to predict such drift concentration effects for SCB frames with the perfect flag-shape hysteretic behavior. Nonlinear time history analyses are conducted to compare and elucidate different deformation mechanisms between BRB and SCB frames. An elastic-plastic static model is established to predict the static drift concentration factor (DCFS) for the SCB frame under static lateral loads, where influential parameters include the column-to-frame stiffness ratios, α, and the SCB's post-yielding stiffness ratio, βk,2. To capture the dynamic loading effect, a regressive formula is further developed as the dynamic amplification factor by normalizing the dynamic drift concentration factor (DCFD) with the DCFS under static loads. The results show that unlike BRB frames with drift concentrated in the bottom story, SCB frames often feature peak story drifts in the top story. As opposed to BRB frames, the equivalent lateral loads do not feature an inverted triangle distribution but a parabolic distribution along the building height. The drift concentration effect for the SCB frame is reliably predicted by multiplying static DCFS with the corresponding closed-form formula for the dynamic amplification factor. The predicted DCFD is also utilized to identify a design range of βk,2 (i.e., 0.2–0.4) to effectively control the peak story drift and drift concentration for SCB frames.

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.

Overset RaNS simulations and validations for the effect of false bottom to the KCS under static drift and static rudder in shallow water

Overset RaNS simulations and validations for the effect of false bottom to the KCS under static drift and static rudder in shallow water

Noisy Surfaces: Vulnerability and Art in Human–Ocean Relations

At the shoreline, human and ocean activities often act in unproductive tension with one another. This article draws from encounters between the modernist architecture in the port city of Toamasina in Madagascar and the activities of the Indian Ocean at that location to sense how human–ocean binary lines might become more porous. The first part of the article sketches a material-discursive theory of the weathered hole in modernist architectural surfaces. It explores the hole as a vital collective of queer otherings to the specific land-centred individualistic subject-hood of modernist Man, a specific figuration of a human who draws binary lines to separate itself out from the “natural world”. The second part of the article argues that artistic inquiry is well positioned to sense into the activities of the hole. It looks to how the hole at the surface of modernist Man can co-shape the specific human–ocean relationship that forms at this shoreline. Such inquiry is explored through my solo exhibition titled Static Drift, held at the Wits Art Museum in Johannesburg in 2021. Sensing, the exhibition reveals, has the potential for listening to binary lines as they erect a surface that both pushes away yet also receives what has been pushed. In Static Drift, being vulnerable through human perceptions was highlighted as a critical mode for sensory attunement to the relationships that form at such surfaces. This article argues that the sonic is a useful sensory mode for opening perceptions toward what is not yet perceived in surface–hole relationships. The sonic opens sites for ontological thinking into human–ocean relations by sensing into the re-orienting potentials that noise offers for thinking about disrupting binaried surfaces.