Research of Podded Propulsors with Varied Geometry in Viscous Flow

Based on the model test of podded propulsor in straight forward motion, the paper presents the results of the effects of geometric parameters on the propulsive characteristics of podded propulsors in viscous flow. Three main geometrical parameters, i.e. pod diameter, strut distance from the propeller plane, and the maximum thickness of strut are studied with systematically varied geometry while the parameters of propeller blades are fixed. The RANS approach is adopted to study the steady perfomaance using the Huent software package. While the interactions of the propeller blades with the pod and strut are time-dependent by nature, the mixing plane model is employed to predict the steady perfomlance. In considera- tion of the complexity, the research does not deal with the effects of the combination of such three main parameters.

An integral panel method for the hydrodynamic analysis of hybrid contra-rotating shaft pod propulsors

The present work is devoted to developing an efficient method for the analysis and design of hybrid contra-rotating shaft pod(HCRSP)propulsors.The geometry of contra-rotating propulsor(CRP)was then analyzed,and a steady integral panel method that treats the forward and aft propellers as a whole part is presented.During the study,the control equation of the steady integral panel method for CRP is derived in detail.From the experience of developing an integral panel method for CRP,the characteristics of panel singularity strength in HCRSP propulsor was analyzed.Based on this analysis,an integral panel method for HCRSP propulsor is developed and the wake model discussed.Then,the method is applied in the performance analysis of HCRSP propulsor.Comparison between experimental data and numerical results shows that the steady integral panel method has good accuracy in terms of open water performance.Regarding the latter,the error source in the steady integral panel method is discussed.

前置预旋定子泵喷推进器辐射噪声数值预报

The requirement of low radiated noise is increasing for underwater propulsors as the noise significantly affecting the comfort and quietness of ships,submarines,and vessels.To broaden the view of noise characteristics of pump-jet propulsors(PJPs),this paper considers the radiated noise of a pre-swirl stator PJP with the effects of the advance coefficient and rotor rotational speed.Radiated noise is obtained by the“hybrid method”approach,which combines a hydrodynamic solver with a hydroacoustic solver.The turbulence flow is obtained through improved delayed detached eddy simulation(IDDES),which show good agreement with the experiment,including the performance and flow field.The solver precision,permeable surface size,and sampling frequency notably affect the noise calculation.The spectra of thrust fluctuation and radiated noise are characterized by the tonal phenomenon around the blade passing frequency and its harmonics.The spectrum of radiated noise and overall sound pressure level(OSPL)are considerably affected by both the advance coefficient and the rotor rotational speed.Overall,the numerical results and analysis given in this paper should be partly helpful in deepening the understanding of the radiated noise characteristics of PJPs.

Piezoelectric Pump Used in Bionic Underwater Propulsion Unit

A new piezoelectric pump can pump liquid either forward or backward and adjust the flow rate. Thus an object can be driven forward or backward at different speeds. The driver of the pump, a circular piezoelectric plate, is modelled by Finite Element Method （FEM） in ANSYS and its performance is simulated and analyzed. The pump gives the best performance when the driving signals of the inlet and outlet valves have a bigger duty cycle and the plate has a higher voltage applied.

RANS Simulation of Podded Propulsor Performances in Straight Forward Motion

The Computational Fluid Dynamics （CFD） approach is adopted to study the steady and unsteady performances of the podded propulsor by the Fluent software package. While the interactions of the propeller blades with the pod and strut are time-dependent by nature, the mixing plane model is employed firstly to predict the steady performance, where the interactions are time-averaged. Numerical experiments are carried out with systematically varied mesh sizes to investigate the dependence of the predicted force values on the mesh sizes. Furthermore, the sliding mesh model is employed to simulate the unsteady interactions between the blades, pod and strut. Based on the numerical results, the characteristics of unsteady hydrodynamic forces are discussed, and the applicability of the mixing plane model is investigated for puller-type podded propulsor.

Numerical and Experimental Studies on the Propulsion Performance of A Wave Glide Propulsor

This paper introduces a newly developed Unmanned Wave Glide Vehicle （UWGV）, which is driven only by extracting energy from gravity waves, and presents a comprehensive study on the propulsion performance of the UWGV＇s propulsor-Wave Glide Propulsor （WGP） in a regular wave. By simplifying the WGP as six 2D tandem asynchronous flapping foils （TAFFs）, a CFD method based on Navier-Stokes equations was first used to analyze the hydrodynamic performance of TAFFs with different parameters of non-dimensional wave length rn and non-dimensional wave height n. Then, a series of hydrodynamic experiments were performed. The computational results agree well with the experimental results when n〈0.07 and both of them show the thrust force and input power of the WGP are larger at smaller m or larger n. By analyzing the flow field of TAFFs, we can see that a larger m is beneficial to the forming, merging and shredding of the TAFFs＇ vortices; as TAFFs are arranged in tandem and have the same motions, the leading edge vortex and wake vortex of the TAFFs are meaningful for improving the thrust force of their adjacent ones.

Flapping dynamics of a flexible propulsor near ground

The flapping motion of a flexible propulsor near the ground was simulated using the immersed boundary method. The hydrodynamic benefits of the propulsor near the ground were explored by varying the heaving frequency (St) of the leading edge of the flexible propulsor. Propulsion near the ground had some advantages in generating thrust and propelling faster than propulsion away from the ground. The mode analysis and flapping amplitude along the Lagrangian coordinate were examined to analyze the kinematics as a function of the ground proximity (d) and St. The trailing edge amplitude (\(a_\mathrm{tail}\)) and the net thrust (\(\overline{{F}}_x\)) were influenced by St of the flexible propulsor. The vortical structures in the wake were analyzed for different flapping conditions.

Influence of Ice Size Parameter Variation on Hydrodynamic Performance of Podded Propulsor

During ice-breaking navigation, a massive amount of crushed ice blocks with different sizes is accumulated under the hull of an ice-going ship. This ice slides into the flow field in the forward side of the podded propulsor, affecting the surrounding flow field and aggravating the non-uniformity of the propeller wake. A pulsating load is formed on the propeller, which affects the hydrodynamic performance of the podded propulsor. To study the changes in the propeller hydrodynamic performance during the ice podded propulsor interaction, the overlapping grid technique is used to simulate the unsteady hydrodynamic performance of the podded propulsor at different propeller rotation angles and different ice block sizes. Hence, the hydrodynamic blade behavior during propeller rotation under the interaction between the ice and podded propulsor is discussed. The unsteady propeller loads and surrounding flow fields obtained for ice blocks with different sizes interacting with the podded propulsor are analyzed in detail. The variation in the hydrodynamic performance during the circular motion of a propeller and the influence of ice size variation on the propeller thrust and torque are determined. The calculation results have certain reference significance for experiment-based research, theoretical calculations and numerical simulation concerning ice podded propulsor interaction.

Discretized Miller approach to assess effects on boundary layer ingestion induced distortion

The performance of propulsion configurations with boundary layer ingestion（BLI） is affected to a large extent by the level of distortion in the inlet flow field. Through flow methods and parallel compressor have been used in the past to calculate the effects of this aerodynamic integration issue on the fan performance; however high-fidelity through flow methods are computationally expensive, which limits their use at preliminary design stage. On the other hand, parallel compressor has been developed to assess only circumferential distortion. This paper introduces a discretized semi-empirical performance method, which uses empirical correlations for blade and performance calculations. This tool discretizes the inlet region in radial and circumferential directions enabling the assessment of deterioration in fan performance caused by the combined effect of both distortion patterns. This paper initially studies the accuracy and suitability of the semiempirical discretized method by comparing its predictions with CFD and experimental data for a baseline case working under distorted and undistorted conditions. Then a test case is examined,which corresponds to the propulsor fan of a distributed propulsion system with BLI. The results obtained from the validation study show a good agreement with the experimental and CFD results under design point conditions.

NUMERICAL SIMULATION OF A PODDED PROPULSOR IN VISCOUS FLOW

A podded propulsor in viscous flow is numerically simulated in this article. The region of fluid is divided into efficient calculation grids. The pressure and viscous force of blades, pod and strut are obtained as functions of an advance coefficient. The steady result is used as a base in the unsteady simulation to obtain a solution more quickly. The distributions of the thrust and torque fluctuations of the key blade in one revolution are obtained. The c^lculation results from the mixing plane on steady conditions are compared with those obtained from the sliding mesh model on unsteady conditions. The User-Defined Function （UDF） method is used to simulate the influence of ship hull on the non-uniform wake of the propeller.

Parametric Study of an Underwater Finned Propulsor Inspired by Bluespotted Ray

The performance ofbluespotted rays was emulated in the design ofa bioinspired underwater propulsor in the present work. First, the movement of a live bluespotted ray was captured for the swimming mode and useful information to the biomimetic mechanism design. By virtue of the modular and reconfigurable design concept, an undulatory fin propulsion prototype was developed. With a proper experimental set-up, orthogonal experiments were conducted to investigate the effect of various fin design parameters on the propulsion speed, thrust, and power of the fish robot. The controllable fin parameters include frequency, amplitude, wavelength, fin shape, and undulatory mode. The significance of these parameters was also determined by using the variance analysis. The results demonstrate that the designed propulsor, imitating bluespotted rays with large expanded undulatory fins, is able to propel itself by changing various kinematic parameters.

Numerical Prediction of the Pump jet Propulsor Tip Clearance Vortex Cavitation in Uniform Flow

Previous studies show that the tip clearance loss limits the improvement of pumpjet propulsor (PJP) performance,and the tip clearance flow field is the most complicated part of PJP flow.In this work,the non-cavitation and cavitation hydrodynamic performances of PJP with a tip clearance size of 1 mm are obtained by using the detached-eddy simulation (DES).At constant oncoming velocity,cavitation first occurs on the duct and then disappears with the decrease of the advance ratio.The rotor blade cavitation occurs at the low advance ratio and comprises tip clearance cavitation,tip leakage cavitation,and blade sheet cavitation.In the rotor region,the typical vortices include tip separation vortex,tip leakage vortex,trailing edge shedding vortex,and blade root horseshoe vortex.Combined with the pressure distribution,both the Q and λ2 criteria give reliable results of vortex identification.The cavitation causes an expansion of tip leakage vortex in the circumferential direction and decreases the intensities of tip separation vortex in the whole tip clearance area and tip leakage vortex in the cavitation area,and enhances the strength of tip leakage vortex in the downstream non-cavitation area.

Design, fabrication, and testing of a maneuverable underwater vehicle with a hybrid propulsor

Rapidity and agility are equally important to unmanned underwater vehicles(UUVs).In this study we developed a UUV equipped with a hybrid propulsor which consists of a screw propeller and four bio-inspired flippers.The bionic flippers rely on their flapping motion to generate both thrust and lateral forces,and the screw propeller provides additional thrust for fast cruise.The maneuverability is greatly improved while the capability of sailing fast is maintained.For the typical sailing requests,the flapping motions of the flippers were designed meticulously,and a control algorithm based on central pattern generators(CPGs)was built to produce rhythmic locomotor signals considering the motion periodicity.Simultaneously,a feedback control method was merged to correct the deviation of the course.A compact concentric-shafts transmission mechanism was employed to overcome the inadequacy of the inside space,and the vehicle was built.Finally,the sailing and maneuvering performance were tested.It was demonstrated that,the UUV’s overall sailing performance was enhanced significantly due to the combination of the flapping flippers and the screw propeller.The hybrid-propulsor vehicle is capable of sailing in multiplicate environments.

AN INTEGRATEDC METHOD FOR COMPUTING COMPUTING THE INTERNAL AND EXTERNAL VISCOUS FLOW FIELD AROUND THE DUCTED PROPULSOR BEHIND AN AXISYMMETRIC BODY

This paper presents an effective method for computing the internal and external viscous flow field around the ducted propulsor behind an axisymmetric they by using a new Navier-Stokes equations solver with primitive variable continuity equation formulation. In the present numerical method, the calculation equation for pressure with well-defined coefficient,which form is similar to the artificial compressibility method, is developed. A semi-staggered grid system is adopted. Not only the advantage of staggered grid system can be retained but the boundary conditions on the inner and outer surface of the duct can be also carried out easily. By using a special grid system and the programming technique for implementing the jump boundary condition on the duct surfaces, the internal and external viscous flow field around the ducted propulsor behind the axisymmetric they may be calculated integrally in an unified numbered grid system. Some configurations are calculated and compared with experimental date and numerical results of other methods. Illustrative calculations are also presented for a stern of axisymmetric body with the backstep fitted a duct to illustrate the capability of the present method. Beside that, the effect of axial distribution of they force is considered and discussed in order to extend the application range of the present method.