Stern Planes Research Articles

Numerical prediction for vertical dynamic anti-sinking performance of underwater vehicle

Computational fluid dynamics (CFD) simulations of an underwater vehicle (UV) during self-propulsion and dynamic anti-sinking maneuvers are presented. A generic submarine, Joubert BB2, was selected as the test model, which was modified by the Maritime Research Institute, Netherlands (MARIN). Different recovery maneuvers for improving the anti-sinking ability were performed when the UV bow cabin was broken. The overset mesh method was used to simulate the deflection of the rudder and stern planes, and a body-force propeller represented by an actuator disk incorporating predetermined propulsion properties provided the thrust and torque for self-propulsion. Extra vector forces of inflow water forces and recovery buoyancy forces were proposed to simulate the flooding of a bow cabin and recover buoyancy by emptying the ballast. Numerical simulations were performed for 20 different combinations of vertical anti-sinking maneuvers, including stern control surfaces, increasing ship speed, and emptying the ballast water. The pitch angle and depth characteristics of UV self-propelled motion were analyzed based on the pre-set anti-sinking criterions. The results indicated stern control surfaces combined with accelerating could effectively maintain the UV's depth and pitch angle, and discharge ballast water could always make it surface quickly. We hope that this study will provide ideas for further research on anti-sinking abilities.

Numerical simulation of near-surface turn maneuver of a generic submarine

Aiming at the actual demand of improving the numerical simulation of the unsteady motion of submarines in maneuvering conditions, the overset grid is used to model six degrees of freedom coupling motions of the submarine and the independent motion of each control plane, and the sliding grid is used to simulate the rotation of the propeller, to carry out the research on the numerical simulation approach of a generic submarine in near-surface maneuvering condition. The VOF method is utilized to capture the free surface. By comparing the submerged turn maneuver numerical simulation results of typical dynamics parameters with the experiment's results, the practicability of the approach for engineering prediction is verified. Then the simulations of near-surface maneuvers under different submergence depths are conducted, and the influence of submergence depth on kinematics and dynamics parameters of Joubert BB2 in maneuvering conditions are analyzed. Results demonstrate that the control performance of the stern planes will be sharply degraded when maneuvering too close to the free surface, resulting in a significant increase in the tactical diameter of the turn maneuver. The research can guide the prediction and evaluation of submarine maneuverability and seaworthiness. It is beneficial for the improvement of free running submarine model tests.

Effects of pitch angle on a near free surface underwater vehicle

Simulations of an underwater vehicle were conducted to investigate the effects of steady pitch angle, Froude number, and submergence depth. A shallow submerged (D* = 1.1) to a deeply submerged (D* = 6.6) SUBOFF was investigated over a range of steady pitch angles and Froude numbers. Results show that proximity to the free surface causes increased resistance, heave and pitch moment and that free surface effects diminish rapidly with increased submergence depth. Even though D* = 3.3 is typically quoted as being the deeply submerged threshold, free surface effects can still be observed especially at large pitch angles. At pitch angle, asymmetry can be seen between the pressure distribution of the upper and lower surfaces of the SUBOFF, with a phase shift of the hydrodynamic forces and moments. At smaller pitch angles, the changes in hydrodynamic forces and moments stay relatively linear at an offset from zero degrees. At larger pitch angles, the hydrodynamic forces and moments become non-linear due to crossflow separation and air entrainment over the bow/stern. Additionally, the potential of the stern planes to cope with free surface effects were investigated, showing the safety threshold with respect to Froude number, submergence depth, and hull pitch angle.

Experimental study of the submarine's wake improvement by displacement of stern planes

ABSTRACT An experimental investigation is conducted to describe the effects of the location of the stern planes on the wake flow entering the submarine propeller. By mounting the stern planes in three longitudinal positions on the stern, the formed wake flow at the propeller position is measured by using a five-hole pressure probe. The optimised position of the stern planes is selected to improve the wake flow entering the propeller in terms of width, size, and non-uniformity reduction. Moving the control surfaces on the stern from X / L = 0.89 to X / L = 0.95, decreases the average velocity value of the wake formed at the end of the submarine model at the radius while at the radius , , it increases. Moving the control surfaces from X/L = 0.89 to the X/L = 0.95 under maneuvering conditions leads to an increase in the average velocity at radius .

Numerical Study on Multiple-Blade-Rate Unsteady Propeller Forces for Underwater Vehicles

_ The unsteady propeller forces of an underwater vehicle were numerically simulated using computational fluid dynamics to investigate the effects of the axial location of the stern planes. A benchmark study was undertaken using a three-bladed propeller; experimental results of the nominal inflow wake profile were analyzed and the unsteady propeller forces were measured. The numerical method was applied to predict the unsteady propeller forces in the SUBOFF model’s wake by varying the axial locations of the stern planes. Several remarks were made on the primary harmonics of the hull’s wakes and blade-rate propeller forces. Introduction The hydroacoustic noise, which matches multiples of the number of propeller blades and its rotational speed, known as “blade-rate (BR) noise,” has been increasingly used to manage hydroacoustics for naval vessels. BR noise can be caused by alternating blade loads owing to fluctuations in the angle of attack of the blades because marine propellers are operated in the nonuniform wake of ships’ hulls. The unsteady blade load produces unsteady propeller forces that are transmitted via the propeller shaft and bearing, thus producing undesirable vibration and noise. Although the resultant BR noise is a common issue for marine vessels, in particular, submarines and other underwater vehicles deployed for undersea defense systems and oceanographic survey systems require strict specifications for the acoustic signature. Therefore, the unsteady propeller forces must be improved for reduced detectability, because the vehicles should be able to operate without being discovered while sonar detection technology continues to improve.

Numerical investigation of the effect of the location of stern planes on submarine wake flow

Numerical investigation of the effect of the location of stern planes on submarine wake flow

Vertical zigzag maneuver of a generic submarine

A study of a 10/10 vertical zigzag maneuver of the generic submarine Joubert BB2 is presented. CFD simulations, involving moving planes and rotating propeller using a dynamic overset technique, are performed at constant propeller rotational speed in model scale on four systematically refined grids and compared against experimental data for depth, pitch, pitch rate, vertical drift, vertical velocity, absolute velocity, and propeller thrust and torque coefficients. A grid study is also performed for the self-propelled approach condition before starting the maneuver, used to obtain the propeller rotational speed, controller vertical and horizontal commands, and boat attitude. The maneuver is also analyzed in full scale at 6, 10 and 15 knots. Results indicate that CFD matches very well the experimental data, even for the coarsest grid, with the propeller RPS converging slowest in grid. By comparing model and full scale results, it can be concluded that model scale simulations are a good surrogate for full scale for parameters related to motions, but as expected forces are strongly affected by scale and the propeller operational point changes considerably. Analysis of forces and moments affecting vertical control from hull, sail and stern planes, propeller and hull help understand the response of the vehicle.

CFD Simulations and Experiments of a Submarine in Turn, Zigzag, and Surfacing Maneuvers

We present simulations and experiments of the generic submarine Joubert BB2 performing standard turn, zigzag, and surfacing maneuvers in calm water at depth. The free-sailing experiments, performed at Maritime Research Institute Netherlands (MARIN), are unique in that they present an open dataset for the community to benchmark maneuvering prediction methodologies. Computations were performed with explicitly gridded sailplanes, tail planes, and propellers using a dynamic overset technique. This study analyzes a 20-degree turning maneuver with vertical control commanding the stern planes and a 20/20 zigzag maneuver with vertical control commanding both sail and stern planes, both of them at a nominal speed of 10 knots, and a 20-degree rise maneuver with horizontal control at 12 knots. The results show that computational fluid dynamics can predict well motions and speeds for free-sailing conditions, but controller commands are harder to replicate. Computations of the rise maneuver with surfacing compare well with experiments, including a crashback maneuver to stop the submarine. Introduction Simulation of free-running submarine maneuvers is demanding in terms of computational fluid dynamics (CFD) capabilities and computational resources. Full 6-DoF motions, moving appendages, control algorithms, and scalable performance are some of the requirements to execute free-running maneuvering simulations. Open literature data for validation of submarine maneuvers are very limited and consist mostly of static conditions (see for instance rotating arm [Toxopeus et al. 2012] and static drift [Roddy 1990; Toxopeus 2008] data for Defense Advanced Research Projects Agency (DARPA) Suboff and static drift [Quick & Woodyatt 2014] for the Joubert hull form [Joubert 2006]). A new dataset has been recently made available to the research community for the generic submarine model BB2 (Overpelt et al. 2015), based on the Joubert hull form.

An adaptive fault-tolerant robust controller with fault diagnosis for submarine’s vertical movement

In this paper, an integrated design of fault diagnosis and adaptive fault-tolerant robust control for a submarine with bow and stern plane faults is proposed. Considering the disturbance coming from waves when a submarine operates near sea surface, a simplified linear system of submarine’s vertical movement with both wave disturbance and bow and stern plane faults is presented. An unknown input observer is designed to decouple the wave disturbance and the bow and stern plane faults. Then a fault parameter tracking law is designed to estimate the bow and stern plane fault parameters without any prior fault information. Based on the estimated fault parameters, an adaptive robust fault-tolerant controller is designed. Simulation results show that the proposed control scheme has a satisfactory effect in the both pitch and depth control when the bow and stern planes suffer from unknown faults.

Submarine Maneuvers Using Direct Overset Simulation of Appendages and Propeller and Coupled CFD/Potential Flow Propeller Solver

This article presents two approaches to simulate maneuvers of a model radio-controlled submarine. In the direct simulation approach, rudders, stern planes, and propellers are gridded and treated as moving objects using dynamic overset technology. The second approach couples the overset computational fluid dynamics (CFD) solver and a potential flow propeller code, with both codes exchanging velocities at the propeller plane and wake, body forces, and propeller forces and moments, whereas rudders and stern planes are still explicitly resolved. It is shown that during the maneuvers, the range of advance coefficients does not deviate much from the design point, making a coupled approach a valid choice for standard maneuvering simulations. By allowing time steps about an order of magnitude larger than for the direct simulation approach, the coupled approach can run about five times faster. The drawback is a loss of resolution in the wake as the direct propeller simulation can resolve blade vortical structures. Open water propeller curves were simulated with both the direct propeller approach and the coupled approach, showing that the coupled approach can match the direct approach performance curves for a wide range of advance coefficients. Simulations of a horizontal overshoot maneuver at two approach speeds were performed, as well as vertical overshoot and controlled turn maneuvers at high speed. Results show that both CFD approaches can reproduce the experimental results for all parameters, with errors typically within 10%.

Submarine Maneuvers Using Direct Overset Simulation of Appendages and Propeller and Coupled CFD/Potential Flow Propeller Solver

This article presents two approaches to simulate maneuvers of a model radio-controlled submarine. In the direct simulation approach, rudders, stern planes, and propellers are gridded and treated as moving objects using dynamic overset technology. The second approach couples the overset computational fluid dynamics (CFD) solver and a potential flow propeller code, with both codes exchanging velocities at the propeller plane and wake, body forces, and propeller forces and moments, whereas rudders and stern planes are still explicitly resolved. It is shown that during the maneuvers, the range of advance coefficients does not deviate much from the design point, making a coupled approach a valid choice for standard maneuvering simulations. By allowing time steps about an order of magnitude larger than for the direct simulation approach, the coupled approach can run about five times faster. The drawback is a loss of resolution in the wake as the direct propeller simulation can resolve blade vortical structures. Open water propeller curves were simulated with both the direct propeller approach and the coupled approach, showing that the coupled approach can match the direct approach performance curves for a wide range of advance coefficients. Simulations of a horizontal overshoot maneuver at two approach speeds were performed, as well as vertical overshoot and controlled turn maneuvers at high speed. Results show that both CFD approaches can reproduce the experimental results for all parameters, with errors typically within 10%.

Hydrodynamic performance of distributed pump-jet propulsion system for underwater vehicle

A type of distributed pump-jet propulsion system (DPJP) is developed with two or four specially designed pump-jet pods located around the axisymmetric underwater vehicle body symmetrically. The flow field is numerically simulated by solving the RANS equations with the finite volume method. The computational method is validated by comparing the calculated hull resistances of the SUBOFF AFF-3 model and the open water performance of a ducted propeller with experimental data. The hydrodynamic performances of the DPJP with different axial or radial positions and numbers of pump-jet pods are obtained to analyze the interactions between the hull and the pump-jet pods. It is shown in the calculated results that the decrease of the distance between the pods and the hull leads to an increase both in the efficiency of the pods and the thrust deduction factor due to the effect of the stern wake. And, a negative thrust deduction factor can be obtained by locating the DPJP at the parallel middle body near the aftbody of the vehicle to improve the hydrodynamic performance of the DPJP. Besides, the increase of the number of pods will cause a remarkable decrease of the total propulsive efficiency of the DPJP with the pods mounted on the stern planes, while a small decline of the total propulsive efficiency of the DPJP is observed with the pods mounted on the parallel middle body.

Submarine propeller computations and application to self-propulsion of DARPA Suboff

Simulations of the submarine propeller E1619 using the overset flow solver CFDShip-Iowa V4.5 are presented. Propeller open water curves were obtained for two grids for a wide range of advance coefficients covering high to moderately low loads, and results compared with available experimental data. A verification study was performed for one advance coefficient (J=0.71) on four grids and three time step sizes. The study shows that grid refinement has a weak effect on thrust and torque but very strongly affects the wake. The effect of the turbulence model on the wake was evaluated at J=0.4 comparing results with RANS, DES, DDES and with no turbulence model, showing that RANS overly dissipates the wake and that in the solution with no turbulence model the tip vortices quickly become unphysically unstable. Tip vortex pairing is observed and described for J≤0.71, showing multiple vortices merging for higher loads. The wake velocities are compared against experimental data for J=0.74, showing good agreement. Self-propulsion computations of the DARPA Suboff generic submarine hull fitted with sail, rudders, stern planes and the E1619 propeller were performed in model scale and the resulting propeller performance analyzed.

Overset simulation of a submarine and propeller in towed, self-propelled and maneuvering conditions

Simulations of the free running submarine model DARPA Suboff in a horizontal overshoot maneuver are presented. To perform the simulations, the fully appended hull was fitted with the conceptual submarine propeller E1619. The overset flow solver CFDShip-Iowa v4.5 was used to perform the computations, including coupling with the propeller code PUF-14. Propeller open water curves were obtained for two grids over a wide range of advance coefficients covering high to moderately low loads, with results compared to available experimental data. The open water curves were also simulated with the coupled CFDShip-Iowa/PUF-14 approach. While computations are performed with delayed detached-eddy simulation (DDES), simulations with Reynolds-averaged Navier–Stokes (RANS), detached-eddy simulation (DES) and with no turbulence model were also performed. Results show that RANS overly dissipates the wake while the solution with no turbulence model shows unphysical instability in the tip vortices. Overall, open water curves are predicted well by the discretized propeller and by the coupled CFDShip-Iowa/PUF-14 approach. The towed DARPA Suboff hull fitted with sail, rudders and stern planes was simulated and results were compared against experimental data, showing satisfactory results. Self-propulsion computations of the DARPA Suboff fitted with the E1619 propeller were performed and the resulting propeller performance analyzed, both using a rotating gridded propeller and the CFDShip-Iowa/PUF-14 approach. A 20/10 overshoot maneuver is demonstrated with both approaches, showing that the results are similar when the propeller remains close to straight-ahead conditions, but trends between approaches tend to diverge for large wake distortions and low advance ratios. A more complex simulation of a surfacing maneuver of the submarine in waves is demonstrated showing the potential of the approach to tackle simulations including massive free surface deformations in a realistic environment.

Designing a sensitive and quantifiable nanocolloid assay with dielectrophoretic crossover frequencies

Dielectrophoretic nanocolloid assay is a promising technique for sensitive molecular detection and identification, as target molecule hybridization onto the probe-functionalized nanocolloids can change their surface conductance and consequently their dielectrophoretic crossover frequencies. Thus, instead of relying on surface charge density increase after hybridization, as in many capacitive and field effect transistor impedance sensing techniques, the current assay utilizes the much larger surface conductance (and dielectrophoresis crossover frequency) changes to effect sensitive detection. Herein, we present a Poisson-Boltzmann theory for surfaces with finite-size molecular probes that include the surface probe conformation, their contribution to surface charge with a proper delineation of the slip and Stern planes. The theory shows that the most sensitive nanocolloid molecular sensor corresponds to a minimum in the dielectrophoretic crossover frequency with respect to the bulk concentration of the molecular probes (oligonucleotides in our case) during nanocolloid functionalization. This minimum yields the lowest number of functionalized probes that are also fully stretched because of surface probe-probe interaction. Our theory provides the surface-bulk oligonucleotide concentration isotherm and a folding number for the surface oligonucleotide conformation from the crossover frequency, the zeta potential, and the hydrodynamic radius data.

Manta형 무인잠수정의 동안정성 향상을 위한 부가물의 설계 변경에 관한 연구

Proposed Manta-type Unmanned Undersea Vehicle(UUV) turned out to have the tendency of dynamic instability in vertical plane, and moreover to have that of so strong dynamic stability in horizontal plane as to cause another problem in turning motion due to negative value of sway damping lever. The authors discussed the changes in appendage design for improvement of dynamic stability of UUV in vertical and horizontal planes. As a result, the dynamic stability in vertical plane was improved by increasing the area of horizontal stern planes. and the dynamic stability in horizontal plane was also improved by removal of lower vertical plate and by adjusting the area and position of upper vertical plate simultaneously.

Underwater vehicle design using integrated plant-controller optimization methods

This paper addresses the problem of integrated design of autonomous underwater vehicle (AUV) plant parameters and feedback controllers to meet mission performance requirements with minimum energy expenditure. This research topichas been motivated by the fact that significant energy savings and increased dynamic performance can in principle be obtained if the process of control system design is integrated with the design of the vehicle itself, thus departing considerably from the classical approach whereby the plant structure is essentially fixed a priori. As a first step towards the solution of this general problem, the following simpler problem is addressed and solved: given an AUV (with a fixed baseline configuration) that is required to operate over a finite set of representative trim conditions in the vertical plane in the course of a given mission scenario, determine the optimal size of the bow and stern planes so that the average propulsion power required to execute that mission is minimized. The minimization process is subjectto open-loop stability requirements, and to theexistence of stabilizing feedback controllers that can meet time and frequency closed-loop requirements about each trim condition. The paper introduces a methodology to solve this combined plant controller optimization problem in the framework of convex optimization theory and describes its application to theselection of the optimal size of bow and stern planes for a prototype autonomous vehicle.

Optimal AUV Control Surface Sizing Using Convex Optimization Methods ⋆

This paper addresses the problem of integrated design of AUV plant parameters and feedback controllers to meet mission performance requirements with minimum energy expenditure. Given an AUV that is required to operate over a finite set of representative trim conditions in the vertical plane in the course of a given mission scenario, the objective is to determine the optimal size of the bow and stern planes so that the average propulsion power required to execute that mission is minimized. The minimization process is subject to open loop stability requirements, and to the existence of stabilizing feedback controllers that can meet time and frequency closed loop requirements about each trim condition. The paper introduces a methodology to solve this combined plant/controller optimization problem in the framework of convex optimization theory, and describes its application to the selection of the optimal size of bow and stern planes for a prototype autonomous vehicle.

Variation of the potential of the stern plane with interaction of dissimilar flat electrical double layers

The potential, Ψ δ , of the Stern planes of dissimilar double layers were calculated as a function of the separation distance. Also the surface charges, the Stern layer charges, and the diffuse layer charges were computed under the assumption of constant surface potentials. The dependence of Ψ δ on the parameter κ d (κ is the Debye reciprocal length parameter, d is half distance of separation) is distinct when κd < 1, particularly when the specific adsorption potential, φ, ∼0. As φ increases to ∼5 kT the dependence of Ψ δ on κ d is less distinct. It was found that the linear approximation is allowed for the system of high specific adsorption potential and high value of κ.

Estimating Stem Plane Effectiveness on a Body of Revolution

N order to estimate the static stability derivatives of streamlined bodies of revolution with attached stern planes, ' it is useful to have a way of calculating the lift-curve slope of low-aspect-ratio control surfaces taking into account fin-body interaction factors. Dempsey measured the lift and deduced the lift-curve slopes of a body of revolution with stern planes. These measurements were taken for a family of symmetrical stern planes intersecting the axis of the body of revolution. Dempsey found that the stern plane effectiveness can be correlated on the basis of a partial span factor K in the following manner. Let C,, be the lift-curve stope coefficient of a stern plane without the body present and C,, be the effective lift-curve slope coefficient of the stern plane mounted on the body. Let A be the total projected area of the stern plane, extended to the body centerline. Let p be the density of the fluid, U the freestream velocity, and a the angIe of attack of the plane. Then for any force F acting on the plane, the force coefficient slope is defined by Cm =F/ ( ?+AU2a) at a =O. Now suppose that the span of the stern plane is 2b and that d is the maximum diameter of the body. Dempsey computed CLu based on integrating an elliptic lift distribution over the entire span of the stern plane and C, based on integrating the elliptic lift distribution from the stern plane tips inward to the point a distance of Kb from the centerfine of the body. The value of the ratio C,/C,, is then only a function of K. Dempsey finds experimentally that the value of (2b/d)K for each stern plane deviates less than 2% from the average value of 0.4 for the entire family of stern planes. This indicates that the body interference effects on the stern planes causes a defect in the stern plane span of about 2Kb =50.4d. It would be useful to have a method for computing estimates of the interference factor K in order to avoid relying on experimental data to estimate the value of C, /C,, . This Note presents a very simple method for relating the value of K to the bare body axisymmetric momentum boundary-layer thickness.