Computational Analysis of Marine-Propeller Performance Using Transition-Sensitive Turbulence Modeling

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Xiao Wang ◽  
Keith Walters
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
High Load ◽  
Boundary Layer Transition ◽  
Tip Vortex ◽  
Marine Propeller ◽  
Cfd Simulations ◽  
Propeller Performance ◽  
Thrust And Torque ◽  
Load Conditions

Almost all computational fluid dynamics (CFD) simulations of flow around marine propellers use turbulence models that are only well suited for fully turbulent flows, which in some cases may lead to accuracy degradation in the prediction of propeller performance characteristics. The discrepancy between computed thrust and torque and corresponding experimental data increases with increasing propeller load. This is due in part to the fact that a large laminar flow region is found to exist and turbulence transition takes place on propeller blades of model scale and/or under high-load conditions. In these cases, it may be necessary to consider boundary-layer transition to obtain accurate results from CFD simulations. The objective of this work is to perform simulations of a marine propeller using a transition-sensitive turbulence model to better resolve the propeller flow characteristics. Fully turbulent flow simulations are also performed for comparison purposes at various propeller load conditions. Computational results are analyzed and compared with water-tunnel and open-water experimental data. It is found that the applied transition-sensitive turbulence model is better able to resolve blade-surface stresses, flow separations, and tip-vortex originations, and, consequently, improve the prediction accuracy in propeller performance, especially under high-load conditions. Furthermore, solutions obtained using the transition-sensitive turbulence model show tip-vortex flows of higher strength, whereas results by the standard k-ω SST turbulence model indicate excessive dissipation of the vortex core.

CFD Validation for a Marine Propeller Using an Unstructured Mesh Based RANS Method

2003 ◽  
Author(s):  
Shin Hyung Rhee ◽  
Shitalkumar Joshi
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Tip Vortex ◽  
Computational Results ◽  
Marine Propeller ◽  
Experimental Conditions ◽  
Cfd Validation ◽  
Local Flow ◽  
Thrust And Torque

Results of computational fluid dynamics validation for flow around a marine propeller are presented. Computations were performed for various advance ratios following experimental conditions. The objectives of the study are to propose and verify a hybrid mesh generation strategy, and to validate computational results against experimental data with advanced computational fluid dynamics tools. Computational results for both global and local flow quantities are discussed and compared with experimental data. The predicted thrust and torque are in good agreement with the measured values. The pressure distribution and pathlines on and around the blade surface well reproduce the physics of highly skewed marine propeller flow with tip vortex. The circumferentially averaged velocity components compare well with the measured values, while the velocity and turbulence quantities in the highly concentrated tip vortex region are under-predicted. The overall results suggest that the present approach is practicable for actual propeller design procedures.

scholarly journals Assessment of CFD turbulence models for free surface flow simulation and 1-D modelling for water level calculations over a broad-crested weir floodway

Water SA ◽  
2019 ◽  
Vol 45 (3 July) ◽  
Author(s):  
Ahmed M Helmi
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Water Level ◽  
Dimensional Analysis ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Cfd Simulations ◽  
One Dimensional ◽  
The Mean ◽  
The One

Floodways, where a road embankment is permitted to be overtopped by flood water, are usually designed as broad-crested weirs. Determination of the water level above the floodway is crucial and related to road safety. Hydraulic performance of floodways can be assessed numerically using 1-D modelling or 3-D simulation using computational fluid dynamics (CFD) packages. Turbulence modelling is one of the key elements in CFD simulations. A wide variety of turbulence models are utilized in CFD packages; in order to identify the most relevant turbulence model for the case in question, 96 3-D CFD simulations were conducted using Flow-3D package, for 24 broad-crested weir configurations selected based on experimental data from a previous study. Four turbulence models (one-equation, k-ε, RNG k-ε, and k-ω) ere examined for each configuration. The volume of fluid (VOF) algorithm was adopted for free water surface determination. In addition, 24 1-D simulations using HEC-RAS-1-D were conducted for comparison with CFD results and experimental data. Validation of the simulated water free surface profiles versus the experimental measurements was carried out by the evaluation of the mean absolute error, the mean relative error percentage, and the root mean square error. It was concluded that the minimum error in simulating the full upstream to downstream free surface profile is achieved by using one-equation turbulence model with mixing length equal to 7% of the smallest domain dimension. Nevertheless, for the broad-crested weir upstream section, no significant difference in accuracy was found between all turbulence models and the one-dimensional analysis results, due to the low turbulence intensity at this part. For engineering design purposes, in which the water level is the main concern at the location of the flood way, the one-dimensional analysis has sufficient accuracy to determine the water level.

Computational Fluid Dynamics Modeling of Mixed Convection Flows in Building Enclosures

2013 ◽  
Author(s):  
Alexander Kayne ◽  
Ramesh Agarwal
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Mixed Convection ◽  
Turbulence Model ◽  
Numerical Algorithm ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Flow And Heat Transfer

In recent years Computational Fluid Dynamics (CFD) simulations are increasingly used to model the air circulation and temperature environment inside the rooms of residential and office buildings to gain insight into the relative energy consumptions of various HVAC systems for cooling/heating for climate control and thermal comfort. This requires accurate simulation of turbulent flow and heat transfer for various types of ventilation systems using the Reynolds-Averaged Navier-Stokes (RANS) equations of fluid dynamics. Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS) of Navier-Stokes equations is computationally intensive and expensive for simulations of this kind. As a result, vast majority of CFD simulations employ RANS equations in conjunction with a turbulence model. In order to assess the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for accurate simulations, it is critical to validate the calculations against the experimental data. For this purpose, we use three well known benchmark validation cases, one for natural convection in 2D closed vertical cavity, second for forced convection in a 2D rectangular cavity and the third for mixed convection in a 2D square cavity. The simulations are performed on a number of meshes of different density using a number of turbulence models. It is found that k-epsilon two-equation turbulence model with a second-order algorithm on a reasonable mesh gives the best results. This information is then used to determine the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for flows in 3D enclosures with different ventilation systems. In particular two cases are considered for which the experimental data is available. These cases are (1) air flow and heat transfer in a naturally ventilated room and (2) airflow and temperature distribution in an atrium. Good agreement with the experimental data and computations of other investigators is obtained.

Numerical Simulation and Vorticity Analysis of Cavitating Flow Around a Marine Propeller Behind the Hull

2019 ◽  
Author(s):  
Yun Long ◽  
Chengzao Han ◽  
Bin Ji ◽  
Xinping Long ◽  
Zhirong Zhang
Keyword(s):  
Experimental Data ◽  
Pressure Fluctuations ◽  
Relative Vorticity ◽  
Cavitating Flow ◽  
Numerical Results ◽  
Tip Vortex ◽  
Marine Propeller ◽  
Thrust Coefficient ◽  
Sheet Cavitation ◽  
Vorticity Transport

Abstract In this paper, the unsteady cavitating turbulent flow around a marine propeller behind the hull is simulated by the k-ω SST turbulence model coupled with the Zwart cavitation model. Three systematic refined structured meshes around the hull and propeller have been generated to study the predicted cavitation patterns and pressure fluctuations. Numerical results indicate that the predicted transient cavitating flow behind the hull wake, including sheet cavitation and tip vortex cavitation, shows quasi-periodic feature and agrees fairly well with the available experimental data. The deviations of pressure fluctuations between experimental data and numerical results are much small. With mesh refining, the cavitation region and the magnitudes of the calculated pressure fluctuations increase, while the differences between two adjacent sets of grids become smaller. In addition, the uncertainty of the thrust coefficient obtained by Factor of Safety method is significantly small. Further, the interaction between the cavitation and the vortex by the relative vorticity transport equation is illustrated. Results show that the magnitude of stretching term is obviously larger than the other three terms, and the dilatation term and the baroclinic term both have an important influence on the generation of vortices.

Numerical Computation of Tip Vortex Flow Generated by a Marine Propeller

1999 ◽  
Vol 121 (3) ◽  
pp. 638-645 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Laura L. Pauley
Keyword(s):  
Cross Section ◽  
Vortex Flow ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Marine Propeller ◽  
Mean Velocity ◽  
Cavitation Inception ◽  
Section Design ◽  
The Mean ◽  
Propeller Performance

The uniform flow past a rotating marine propeller was studied using incompressible Reynolds-averaged Navier-Stokes computations with the Baldwin-Barth turbulence model. Extensive comparison with the experimental data was made to validate the numerical results. The general characteristics of the propeller flow were well predicted. The current numerical method, however, produced an overly diffusive and dissipative tip vortex core. Modification of the Baldwin-Barth model to better predict the Reynolds stress measurements also improved the prediction of the mean velocity field. A modified tip geometry was also tested to show that an appropriate cross section design can delay cavitation inception in the tip vortex without reducing the propeller performance.

Unsteady Numerical Simulation of Cavitating Turbulent Flow Around a Highly Skewed Model Marine Propeller

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Bin Ji ◽  
Xianwu Luo ◽  
Xin Wang ◽  
Xiaoxing Peng ◽  
Yulin Wu ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Cavitating Flow ◽  
Tip Vortex ◽  
Wake Flow ◽  
Marine Propeller ◽  
Sheet Cavitation ◽  
Whole Process ◽  
Unsteady Numerical Simulation ◽  
Thrust And Torque

The cavitating flows around a highly skewed model marine propeller in both uniform flow and wake flow have been simulated by applying a mass transfer cavitation model based on Rayleigh–Plesset equation and k-ω shear stress transport (SST) turbulence model. From comparison of numerical results with the experiment, it is seen that the thrust and torque coefficients of the propeller are predicted satisfactory. It is also clarified from unsteady simulation of cavitating flow around the propeller in wake flow that the whole process of cavitating-flow evolution can be reasonably reproduced including sheet cavitation and tip vortex cavitation observed in the experiments. Furthermore, to study the effect of pressure fluctuation on the surrounding, pressure fluctuations induced by the cavitation as well as the propeller rotation are predicted at three reference positions above the propeller for comparison with the experimental data: The amplitudes of the dominant components corresponding to the first, second, and third blade passing frequencies were satisfactorily predicted. It is noted that the maximum difference of pressure fluctuation between the calculation and experiment reached 20%, which might be acceptable by usual engineering applications.

scholarly journals Grid Type and Turbulence Model Influence on Propeller Characteristics Prediction

2019 ◽  
Vol 7 (10) ◽  
pp. 374 ◽  
Author(s):  
Ante Sikirica ◽  
Zoran Čarija ◽  
Lado Kranjčević ◽  
Ivana Lučin
Keyword(s):  
Hydrodynamic Characteristics ◽  
Test Case ◽  
Marine Propeller ◽  
Ansys Fluent ◽  
Structured Grids ◽  
Performance Predictions ◽  
Hybrid Grids ◽  
Turbulent Models ◽  
Propeller Performance ◽  
Thrust And Torque

This paper evaluates the applicability of the hexahedral block structured grids for marine propeller performance predictions. Hydrodynamic characteristics for Potsdam Propeller Test Case (PPTC), namely thrust and torque coefficients, were determined using numerical simulations in two commercial solvers: Ansys Fluent and STAR-CCM+. Results were attained for hexahedral and tetrahedral hybrid grids equivalent in terms of cell count and quality, and compared to the experimental results. Furthermore, accuracy of Realizable k- ϵ and SST k- ω turbulent models when analyzing marine propeller performance was investigated. Finally, performance characteristics were assessed in cavitating flow conditions for a single advance ratio using Zwart–Gerber–Belamri and Schnerr and Sauer models. The resulting cavitation pattern was compared to cavity extents and shape noted during measurements. The results suggest that hexa and hybrid grids, in certain range of advance ratios, do provide similar results; however, for low and high ratios, structured grids in conjunction with Realizable k- ϵ model can achieve more accurate results.

Application of Nonlinear Turbulence Models for Marine Propulsors

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Prachakon Kaewkhiaw ◽  
Yodchai Tiaple ◽  
Pramote Dechaumphai ◽  
Varangrat Juntasaro
Keyword(s):  
Turbulence Model ◽  
Flow Characteristic ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Combined Effects ◽  
Marine Propeller ◽  
Efficient Design ◽  
Thrust And Torque ◽  
First Time

The realistic simulation of cavitation on a marine propeller is important for the efficient design of the propeller. However, the flow characteristic that occurred on the marine propeller is complicated and difficult to predict due to the combined effects of turbulence, cavitation, and multiphase phenomena. There is still currently no turbulence model that can predict these combined effects satisfactory. The nonlinear turbulence model is therefore modified and applied to predict the cavitation on a marine propeller for the first time in this work. It is found that the nonlinear turbulence model can predict the cavitation and hence the thrust and torque coefficients much more accurately than the existing Reynolds-averaged Navier–Stokes turbulence models including the Reynolds-stress model.

scholarly journals Aeroacoustic noise reduction by application of end plates on wall-mounted finite airfoils

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
Erik Schneehagen ◽  
Thomas F. Geyer ◽  
Ennes Sarradj ◽  
Danielle J. Moreau
Keyword(s):  
Noise Reduction ◽  
Microphone Array ◽  
Boundary Layer Transition ◽  
Tip Vortex ◽  
Layer Transition ◽  
Aeroacoustic Noise ◽  
End Plate ◽  
Array Measurements ◽  
Field Noise ◽  
Naca 0012

Abstract One known method to reduce vortex shedding from the tip of a blade is the use of end plates or winglets. Although the aerodynamic impact of such end plates has been investigated in the past, no studies exist on the effect of such end plates on the far-field noise. The aeroacoustic noise reduction of three different end-plate geometries is experimentally investigated. The end plates are applied to the free end of a wall-mounted symmetric NACA 0012 airfoil and a cambered NACA 4412 airfoil with an aspect ratio of 2 and natural boundary layer transition. Microphone array measurements are taken in the aeroacoustic open-jet wind tunnel at BTU Cottbus-Senftenberg for chord-based Reynolds numbers between 75,000 and 225,000 and angles of attack from 0$$^\circ$$ ∘ to 30$$^\circ$$ ∘ . The obtained acoustic spectra show a broad frequency hump for the airfoil base configurations at higher angles of attack that is attributed to tip noise. Hot-wire measurements taken for one configuration show that the application of an end plate diffuses the vorticity at the tip. The aeroacoustic noise contribution of the tip can be reduced when the endplates are applied. This reduction is most effective for higher angles of attack, when the tip vortex is the dominant sound source. Graphic abstract

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