Propeller Geometry Research Articles

A simple method for estimating transition locations on blade surface of model propellers to be used for calculating viscous force

Effects of inflow Reynolds number (Re), turbulence intensity (I) and pressure gradient on the transition flow over a blade section were studied using the γ-Reθ transition model (STAR-CCM+). Results show that the ReT (transition Re) at the transition location (PT) varies strongly with Re, I and the magnitude of pressure gradient. The ReT increases significantly with the increase of the magnitude of favorable pressure gradient. It demonstrates that the ReT on different blade sections of a rotating propeller are different. More importantly, when there is strong adverse pressure gradient, the PT is always close to the minimum pressure point. Based on these conclusions, the PT on model propeller blade surface can be estimated. Numerical investigations of pressure distribution and transition flow on a propeller blade section prove these findings. Last, a simple method was proposed to estimate the PT only based on the propeller geometry and the advance coefficient.

INFLUENCE OF BLADE AND PROFILE CHARACTERISTICS ON HYDRODYNAMIC EFFICIENCY OF MARINE PROPELLERS

Purpose.The study involves: 1) formation of 3D propeller models under study; 2) studying of the effect of profiling the blade of the propeller on its hydrodynamic characteristics; 3) development of a methodology for specifying optimal project parameters for modeling the operation of a propeller in free water, which in the future could be recommended when simulating similar tasks in the CFD package Flow Vision. Methodology. The technology of design of propellers of new series was developed. For the first time, the project methodology was proposed in the CFD package Flow Vision for studying the operation of a propeller in free water. Findings. On the example of solving a practical problem for studying the influence of blade profiling on the efficiency of a propeller, the expediency of developing the proposed methodology for setting a propeller design in the CFD package Flow Vision is justified. The using of this technique makes it possible to obtain reliable values of the propeller hydrodynamic characteristics for constructing its action curves, and also to reduce the estimated time. This approach makes it possible to optimize the process of designing propellers. Originality. Through numerous experiments and based on the analysis of the obtained results, it was found that the profiling of the propeller mainly affects its hydrodynamic characteristics. The choice and calculation of the propeller for the projected vessel occurs in the early stages of design. Therefore, the rationale for choosing one or another geometry of the marine propeller is a topical task. A method for specifying project parameters for conducting numerical experiments in studying the operation of propellers in free water was proposed and justified. Thus, it is possible to design not only the serial screws, but also the new series propellers, minimizing the costs of carrying out the research along with the reliability of the resulting calculation results. Practical value. Authors established that the influence of the propeller blade profiling on its hydrodynamic characteristics is greater than the influence of its other general and blade characteristics. The developed design methodology for the calculation of propellers in the CFD package Flow Vision can be used to design the marine propellers of both new series and existing ones, and also in the case of optimizing the shape of the propeller to ensure the greatest efficiency. The application of the technique will allow reducing the time for conducting a numerical experiment due to the convergence of the solution in a relatively short time.

Numerical prediction of effective wake field for a submarine based on a hybrid approach and an RBF interpolation

A hybrid approach coupled with a surface panel method for the propeller and a Reynolds averaged Navier-Stokes (RANS) model for the hull with the propeller body forces are presented for predicting the self-propulsion performance and the effective wake field of underwater vehicles. To achieve a high accuracy and simplicity, a radial basis function (RBF) based approach is proposed for mapping the force field from the blade surface panels to the RANS model. The effective wake field is evaluated in two ways, i.e., by extrapolation from the flat planes upstream of the propeller disk, and by direct computation in a curved surface upstream of and parallel to the blade leading edges. The hull-propeller system of a real propeller geometry is further simulated with the sliding mesh model to numerically verify the hybrid approach. Numerical simulations are conducted for the fully appended SUBOFF submarine model. The high accuracy of the RBF-based interpolation scheme is confirmed, and the effective wake fraction predicted by the hybrid approach is found consistent with that obtained by the sliding mesh model. The effective wake fractions predicted by the two methods are, respectively, 4.6% and 3% larger than the nominal one.

Large eddy simulation of propeller wake instabilities

The wake of a five-bladed marine propeller at design operating condition is studied using large eddy simulation (LES). The mean loads and phase-averaged flow field show good agreement with experiments. Phase-averaged and azimuthal-averaged flow fields are analysed in detail to examine the mechanisms of wake instability. The propeller wake consisting of tip and hub vortices undergoes streamtube contraction, which is followed by the onset of instabilities as evident from the oscillations of the tip vortices. Simulation results reveal a mutual-induction mechanism of instability where, instead of the tip vortices interacting among themselves, they interact with the smaller vortices generated by the roll-up of the blade trailing edge wake in the near wake. It is argued that although the mutual-inductance mode is the dominant mode of instability in propellers, the actual mechanism depends on the propeller geometry and the operating conditions. The axial evolution of the propeller wake from near to far field is discussed. Once the propeller wake becomes unstable, the coherent vortical structures break up and evolve into the far wake, composed of a fluid mass swirling around an oscillating hub vortex. The hub vortex remains coherent over the length of the computational domain.

Experimental investigation of pressure pulses and radiated noise for two alternative designs of the propeller of a high-speed craft

The present paper is focused on an experimental investigation of pressure pulses and radiated noise for two alternative designs of a propeller of a high-speed craft.The propellers have been designed in the context of a research project starting from two different rake distributions (forward rake to increase thrust and efficiency, backward rake to reduce cavitation), using different techniques (traditional lifting line / lifting surface and optimization algorithm coupled with a panel code), leading thus to rather different geometries. Propellers have been tested through cavitation tunnel experiments. The activity represents an interesting case study for this kind of measurement in presence of rather large cavitation extensions. The effects of cavitation on different components of pressure pulses and noise are investigated for the different rake distributions adopted. Results clearly shows the effects of this geometrical characteristic on cavitation and pressure pulses pointing out that, in some cases, propeller hydrodynamic performances may determine pressure pulses intensity more than cavitation extensions. A simplified numerical approach, adopting stationary RANS calculations, for the evaluation of the effects of propeller geometry, has been proposed. Results show a good correlation with measurements allowing to have an insight into the phenomenon and confirming the effect of the rake.

Development of surrogate models for the prediction of the flow around an aircraft propeller

ABSTRACTIn the present work, the derivation of two surrogate models (SMs) for modelling the flow around a propeller for small aircrafts is presented. Both methodologies use derived functions based on computations with the detailed propeller geometry. The computations were performed using k–ω shear stress transport for modelling turbulence. In the SMs, the modelling of the propeller was performed in a computational domain of disk-like geometry, where source terms were introduced in the momentum equations. In the first SM, the source terms were polynomial functions of swirl and thrust, mainly related to the propeller radius. In the second SM, regression analysis was used to correlate the source terms with the velocity distribution through the propeller. The proposed SMs achieved faster convergence, in relation to the detail model, by providing also results closer to the available operational data. The regression-based model was the most accurate and required less computational time for convergence.

고고도 장기체공 태양광 무인기 EAV-3의 프로펠러 설계 및 성능해석

고고도 장기체공 태양광 무인기 EAV-3의 프로펠러를 설계하고 전산해석을 수행하였다. 실험설계법(Design of Experiment, DOE)을 사용하여 설계변수들의 실험점들을 획득하고 목적함수와 구속함수들에 대한 크리깅 근사모델을 생성하였다. 요구조건 및 제약조건들과 함께 반응면을 평가하여 프로펠러 형상을 설계하였으며, 근사모델 기반의 최적설계를 수행하여 설계의 타당성을 검증하였다. 상용 CFD 코드를 이용하여 해석을 수행하고 그 결과를 설계코드 및 시험결과와 비교하였다. 설계점 고도에서 해석 결과가 설계코드의 예측과 잘 일치하였다. 또한 시험장치와 지지대 기둥에 의한 폐쇄효과가 풍동시험 결과에 포함되어 있으며, 이를 포함한 해석 결과가 시험 결과와 잘 일치함을 확인하였다. Design and performance analysis of propeller for solar-powered HALE UAV, EAV-3 are conducted. Experiment points of design variables are obtained by using Design of Experiment(DOE) and Kriging meta-model is generated for objective and constraints function. The geometry of propeller is designed by evaluating the response surface with requirement and restrictions. The validity of the design is verified by meta-model based optimization. Computational analyses are carried out by using commercial CFD code and the results are compared with those from a design code and wind tunnel test. The results showed good agreement with predictions of the design code at the design altitude. Also, it is confirmed that the blockage effect due to the measurement device and support strut is included in the test data and the results including this effect compare well with the test data.

Systematic probabilistic design methodology for simultaneously optimizing the ship hull–propeller system

The proposed design methodology represents a new approach to optimize the propeller–hull system simultaneously. In this paper, two objective functions are considered, the first objective function is Lifetime Fuel Consumption (LFC) and the other one is cost function including thrust, torque, open water and skew efficiencies. The variables of the propeller geometries (Z, EAR, P/D and D) and ship hull parameters (L/B, B/T, T and CB) are considered to be optimized with cavitation, blades stress of propeller. The well-known evolutionary algorithm based on NSGA-II is employed to optimize a multi-objective problem, where the main propeller and hull dimensions are considered as design variables. The results are presented for a series 60 ship with B-series propeller. The results showed that the proposed method is an appropriate and effective approach for simultaneously propeller–hull system design and is able to minimize both of the objective functions significantly.

Design and analysis of a new generation of CLT propellers

In this work, the design and the analysis of the performance of an improved tip loaded propeller geometry are proposed. Based on the experimental data and on the numerical results collected at SISTEMAR and at the University of Genoa in the case of Contracted and Tip Loaded (CLT) propellers, a new tip loaded propeller geometry is devised in order to mitigate some of the downsides of the CLT geometries increasingly adopted to improve full-scale propeller efficiency. The modified tip loaded propeller, i.e. a mix between a tip rake and a Contracted and Tip Loaded propeller, is designed via an optimization strategy using a Boundary Elements Method (BEM), a custom parametric description of the unconventional blade geometry and an optimization algorithm (of genetic type) within the modeFRONTIER environment. The reliability of the design process and of the improvements achievable with the modified tip loaded propeller are extensively verified with dedicated RANSE calculations. At first, the accuracy of the BEM, adopted for the design by optimization, is verified in terms of predicted propeller performance in order to assess its applicability for the analysis of modified tip geometries and check its confidence with respect to the allowable modifications of the blade shape. As a second step, viscous calculations are adopted to confirm the improvements of the newly designed geometries, in terms of both cavitation and predicted velocity field downstream the propeller, as a result of a better adaptation of the end plate geometry to the incoming flow. Finally, a set of unsteady calculations, by using the unsteady BEM, is carried out to verify the amplitude of the induced pressure pulses and, by comparing these numerical results with the available measurements and calculations in the case of a reference CLT propeller, to confirm the effectiveness of the modified propeller tip shape.

Measurement of noise and its correlation to performance and geometry of small aircraft propellers

A set of small model and UAV propellers is measured both in terms of aerodynamic performance and acoustic noise under static conditions. Apart from obvious correlation of noise to tip speed and propeller diameter the influence of blade pitch, blade pitch distribution, efficiency and shape of the blade is sought. Using the measured performance data a computational model for calculation of aerodynamic noise of propellers will be validated. The range of selected propellers include both propellers designed for nearly static conditions and propellers that are running at highly offdesign conditions, which allows to investigate i.e. the effect of blade stall on both noise level and performance results.

Fast Magnetic Micropropellers with Random Shapes.

Studying propulsion mechanisms in low Reynolds number fluid has implications for many fields, ranging from the biology of motile microorganisms and the physics of active matter to micromixing in catalysis and micro- and nanorobotics. The propulsion of magnetic micropropellers can be characterized by a dimensionless speed, which solely depends on the propeller geometry for a given axis of rotation. However, this dependence has so far been only investigated for helical propeller shapes, which were assumed to be optimal. In order to explore a larger variety of shapes, we experimentally studied the propulsion properties of randomly shaped magnetic micropropellers. Surprisingly, we found that their dimensionless speeds are high on average, comparable to previously reported nanofabricated helical micropropellers. The highest dimensionless speed we observed is higher than that of any previously reported propeller moving in a low Reynolds number fluid, proving that physical random shape generation can be a viable optimization strategy.

Optimum Design of Compound Helicopters that Use Higher Harmonic Control

The optimal design of a compound helicopter comprised of counterrotating coaxial rotors, a propeller, and optionally a fixed wing is investigated. The blade geometry, azimuthal blade pitch inputs, optimal shaft angle (rotor angle of attack), and division of propulsive and lifting forces among the components that minimize the total power for a given flight condition are determined. The optimal design problem is cast as a variational statement that minimizes the sum of induced and viscous power losses for a prescribed lift, propulsive force, and vehicle trim condition. The rotor, propeller, and wing geometry and control inputs are related to the far-field circulation through a lifting-line model that accounts for experimentally or computationally determined nonlinear lift and drag polars. The variational statement is discretized using a vortex lattice wake, and the resulting nonlinear constrained optimization problem is solved via Newton iteration. Results show that varying the prescribed propulsive force of the system affects the optimal shaft angle and rotor design, that higher harmonic control reduces the total vehicle power loss (inefficiency) in high-speed flight by as much as 15%, and that imposing a maximum allowable lateral lift offset can greatly increase the power loss of the coaxial rotors.

Slag Prediction in Submerged Rocket Nozzle Through Two-Phase CFD Simulations

A computational procedure has been established to predict the slag in a practical solid rocket motor with submerged nozzle. Both single-phase and two-phase flow analyses have been performed in the rocket motor port. Three-dimensional Navier-Stokes equations along with SST turbulence model have been solved for gas-phase calculations. The effect of ejected alumina particles from the propellant geometry on the flow field has been simulated through Lagrangian tracking method. The computational methodology is firstly validated by comparing against other numerical results of rocket motors available in the literature before applying the same to predict the slag accumulation of a submerged rocket motor for strategic applications. Burn-back geometries at different instants have been simulated and parametric studies were performed to find out the effect of Al 2 O 3 particle size. It was observed that the slag capture rate increases uniformly with A1 2 O 3 particle size. The predicted slag accumulation data match closely with the ground test data for the range of conditions simulated in the present work. Defence Science Journal, Vol. 65, No. 2, March 2015, pp.99-106, DOI:http://dx.doi.org/10.14429/dsj.65.7147 Normal 0 false false false EN-US X-NONE X-NONE

Application of computational fluid dynamics for the optimization of homogenization processes in wine tanks

Mixing processes for modern wine-making occur repeatedly during fermentation (e.g. yeast addition, wine fermen- tation additives), as well as after fermentation (e.g. blending, dosage, sulfur additions). In large fermentation vessels or when mixing fluids of different viscosities, an inadequate mixing process can lead to considerable costs and problems (inhomogeneous product, development of layers in the tank, waste of energy, clogging of filters). Considering advancements in computational fluid dynamics (CFD) in the last few years and the computational power of computers nowadays, most large-scale wineries would be able to conduct mixing simulations using their own tank and agitator configurations in order to evaluate their efficiency and the necessary power input based on mathematical modeling. Regardless, most companies still rely on estimations and empirical values which are neither validated nor optimized. The free open-source CFD software OpenFOAM (v.2.3.1) is used to simulate flows in wine tanks. Different agitator types, different propeller geometries and rotational speeds can be modeled and compared amongst each other in the process. Moreover, fluid properties of different wine additives can be modeled. During opti- cal post-processing using the open-source software ParaView (v.4.3) the progression of homogenization can be visualized and poorly mixed regions in the tank are revealed.

Validation of New Formulations for Propeller Analysis

This paper reports the development of a new propeller design and analysis tool. JBLADE uses an improved version of blade element momentum that embeds a new model for the three-dimensional flow equilibrium. In addition, a new method for the prediction of the airfoil drag coefficient at a 90 deg angle of attack for a better poststall modeling is also presented. The software is developed as an open-source tool for the simulation of propellers and has the capability to estimate the performance of a given propeller geometry in design and offdesign operating conditions. The software allows the introduction of the blade geometry as an arbitrary number of sections. To validate the code, the propellers from NACA Technical Report 530 by Gray (“Wind-Tunnel Tests of Two Hamilton Standard Propellers Embodying Clark Y and NACA 16-Series Blade Sections,” 1941) and NACA Technical Report 594 by Theodorsen et al. (“Characteristics of Six Propellers Including the High-Speed Range,” 1937) were simulated and the results were checked against the experimental data and against those of other available codes. Although current development work is focused in the design of airship propellers, the long-term goal of the JBLADE development is to provide a user-friendly, accurate, and validated open-source code that can be used to design and optimize propellers for distinct applications.

Hydrocomp Design and Prediction of Hydrodynamic Performance of Propeller

With the continuous development of large-scale, high-speed ship, considering economy and security of the ship, propeller design and performance research are of importance. In this paper, the best propeller is obtained by using the propeller design software HydroComp PropExpert and HydroComp PropCAD. Propeller geometry model is generated by Solidworks. Applying computational fluid dynamics method (CFD), we can take numerical simulation for the flow around the propeller. Finally, with the help of the software ANSYS, hydrodynamic performance of the design propeller can be forecasted. The results from the calculation and analysis can provide some reference for engineering practical problems and theoretical study.

Fixed-pitch Marine Propeller Geometry Design

Fixed-pitch Marine Propeller Geometry Design

Structural Design and Multi-Objective Evaluation of Composite Bladed Propeller

This paper describes the work to design a composite bladed marine propeller. The hydrodynamic load and the nonlinear structural responses are predicted by the coupled FEM/CFD method. A pre-twist strategy is used to determine a new geometry of the composite bladed propeller for improving the hydrodynamic performance. Different material schemes and symmetric stacking sequences are considered as the design parameters. An evaluation method of multi-objective function is presented for optimizing the strength, deflection and mass at design conditions. Numerical results are obtained and the optimal design scheme of the composite bladed propeller is obtained.

Analysis of a marine propeller operating in oblique flow. Part 2: Very high incidence angles

The analysis of a propeller operating in off-design conditions is one of the most attractive and challenging topics in naval hydrodynamics, because of its close connections with different aspects of ship design and performances. For these reasons, wake dynamics and propeller loads are analyzed in the present paper by means of a numerical code based on the solution of the Reynolds averaged Navier–Stokes equations, whose capability to capture propeller hydrodynamics in these extreme conditions are also investigated. The test case considered is the CNR-INSEAN E779A propeller model, for which a detailed experimental database exists for axial flow conditions; propeller geometry and computational domain are discretized by means of an overlapping grid approach.A wide range of incidence angles (10–50°) at two different loading conditions are considered, in order to analyze the propeller performance during severe off-design conditions, similar to those experienced during very complicated maneuvering scenarios. Details of average and instantaneous loads are reported, for both the complete propeller and for a single blade.The present paper is an extension of the analysis of propeller performance in oblique flow, recently proposed in [1]; here, the focus is on propeller performance at very high angle of incidence. The k-∊ and a DES turbulence models have been exploited also, in order to provide a reliable verification of the numerical results in the absence of experimental data in these extreme operating conditions.

Effect of material on hydro-elastic behaviour of marine propeller by using BEM-FEM hybrid software

ABSTRACT This paper studies the effect of material on the hydro-elastic behaviour. The geometry of flexible propeller changes due to hydrodynamic and inertial forces acting on the propeller. By using prepared software (called HYDRO-BEM and ELASTIC-FEM) the hydro-elastic features of the propeller made of various materials are analyzed. In the software the hybrid boundary element and finite element methods are used. First, the load acting on the propeller is determined by using the BEM and deformed propeller geometry is then obtained by the FEM. In the next step, the load on the deformed propeller is determined by the BEM and a new shape is obtained. The iterative procedure is repeated till the blade deflection and hydrodynamic characteristics (thrust, torque and efficiency) of the propeller become converged. Four different materials are examined. It is concluded that the hydro-elastic behaviour of the composite propeller is strongly affected by its flexibility due to light material.