An Improved Lifting Line Model for the Design of Marine Propellers

2006 ◽  
Vol 43 (02) ◽  
pp. 100-113
Author(s):  
Fahri Celik ◽  
Mesut Guner
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Cfd Analysis ◽  
Vortex System ◽  
Marine Propellers ◽  
Propeller Design ◽  
Trailing Vortices ◽  
Realistic Representation ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method ◽  
Lifting Line

This paper describes a procedure for the design of marine propellers where more realistic representation of the slipstream shape by the trailing vortex system is taken into account. The slipstream shape behind the propeller is allowed to deform and to align with the direction of local velocity, which is obtained by the sum of the inflow velocity and induced velocities due to the trailing vortices. In classical lifting line approaches, that deformation is neglected. Applications for an autonomous underwater vehicle (AUV) and a fishing vessel are carried out to demonstrate propeller design and the effect of the slipstream contraction. Furthermore, a computational fluid dynamics (CFD) analysis based on the finite volume method and experimental validation of the method are carried out for the propellers. CFD analysis and experimental results are compared with the results obtained from present method.

Analysis of Hydrodynamic Characteristics in the Process of Autonomous Underwater Vehicle Docking

2015 ◽  
Author(s):  
Xiaoxu Du ◽  
Huan Wang
Keyword(s):  
Drag Coefficient ◽  
Autonomous Underwater Vehicle ◽  
Simple Algorithm ◽  
Underwater Vehicle ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Successful Operation ◽  
Underwater Docking ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

The successful operation of an Autonomous Underwater Vehicle (AUV) requires the capability to return to a dock. A number of underwater docking technologies have been proposed and tested in the past. The docking allows the AUV to recharge its batteries, download data and upload new instructions, which is helpful to improve the working time and efficiency. During the underwater docking process, unsteady hydrodynamic interference occurs between the docking device and an AUV. To ensure a successful docking, it is very important that the underwater docking hydrodynamics of AUV is understood. In this paper, numerical simulations based on the computational fluid dynamics (CFD) solutions were carried out for a 1.85m long AUV with maximum 0.2 m in diameter during the docking process. The two-dimensional AUV model without fin and rudder was used in the simulation. The mathematical model based on the Reynolds-averaged Navier-Stokes (RANS) equations was established. The finite volume method (FVM) and the dynamic structured mesh technique were used. SIMPLE algorithm and the k-ε turbulence model in the Descartes coordinates were also adopted. The hydrodynamics characteristics of different docking states were analyzed, such as the different docking velocity, the docking device including baffle or not. The drag coefficients of AUV in the process of docking were computed for various docking conditions, i.e., the AUV moving into the docking in the speed of 1m/s, 2m/s, 5m/s. The results indicate that the drag coefficient increases slowly in the process of AUV getting close to the docking device. When the AUV moves into the docking device, the drag coefficient increases rapidly. Then the drag coefficient decreases rapidly. The drag coefficient decreases with the increase of velocity when AUV enters the docking device. It was also found that the drag coefficient can be effectively reduced by dislodging the baffle of docking device.

Development of a Lifting-Line-Based Method for Preliminary Propeller Design

2018 ◽  
Author(s):  
Jose Rodolfo Chreim ◽  
Marcos de Mattos Pimenta ◽  
Joao Lucas Dozzi Dantas ◽  
Gustavo R. S. Assi ◽  
Eduardo Tadashi Katsuno
Keyword(s):  
Convergence Rates ◽  
Control Points ◽  
Numerical Implementation ◽  
Marine Propellers ◽  
Propeller Design ◽  
Line Theory ◽  
Thrust And Torque ◽  
Lifting Line ◽  
Lifting Line Theory

A novel formulation for marine propellers based on adaptations from wing lifting-line theory is presented; the method is capable of simulating propellers with skewed and raked blades. It also incorporates the influence of viscosity on thrust and torque from hydrofoil data through a nonlinear scheme that changes the location of the control points iteratively. Several convergence studies are conducted to verify the different aspects of the numerical implementation and the results indicate satisfactory convergence rates for Kaplan, KCA, and B-Troost propellers. It is expected that the method accurately describes thrust, torque, and efficiency under the moderately loaded propeller assumption.

scholarly journals Effects of mesh loop modes on performance of unstructured finite volume GPU simulations

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Yue Weng ◽  
Xi Zhang ◽  
Xiaohu Guo ◽  
Xianwei Zhang ◽  
Yutong Lu ◽  
...  
Keyword(s):  
Finite Volume ◽  
Data Access ◽  
Data Locality ◽  
Data Dependence ◽  
Speed Up ◽  
Computational Fluid Dynamics Cfd ◽  
Overall Performance ◽  
Volume Method ◽  
Cell Data ◽  
Unstructured Finite Volume Method

AbstractIn unstructured finite volume method, loop on different mesh components such as cells, faces, nodes, etc is used widely for the traversal of data. Mesh loop results in direct or indirect data access that affects data locality significantly. By loop on mesh, many threads accessing the same data lead to data dependence. Both data locality and data dependence play an important part in the performance of GPU simulations. For optimizing a GPU-accelerated unstructured finite volume Computational Fluid Dynamics (CFD) program, the performance of hot spots under different loops on cells, faces, and nodes is evaluated on Nvidia Tesla V100 and K80. Numerical tests under different mesh scales show that the effects of mesh loop modes are different on data locality and data dependence. Specifically, face loop makes the best data locality, so long as access to face data exists in kernels. Cell loop brings the smallest overheads due to non-coalescing data access, when both cell and node data are used in computing without face data. Cell loop owns the best performance in the condition that only indirect access of cell data exists in kernels. Atomic operations reduced the performance of kernels largely in K80, which is not obvious on V100. With the suitable mesh loop mode in all kernels, the overall performance of GPU simulations can be increased by 15%-20%. Finally, the program on a single GPU V100 can achieve maximum 21.7 and average 14.1 speed up compared with 28 MPI tasks on two Intel CPUs Xeon Gold 6132.

Analysis of an Airfoil Using a Transition and Turbulence Model

2016 ◽  
Vol 819 ◽  
pp. 356-360
Author(s):  
Mazharul Islam ◽  
Jiří Fürst ◽  
David Wood ◽  
Farid Nasir Ani
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Turbulence Model ◽  
Original Version ◽  
Transitional Region ◽  
Cfd Analysis ◽  
Computational Fluid Dynamics Cfd

In order to evaluate the performance of airfoils with computational fluid dynamics (CFD) tools, modelling of transitional region in the boundary layer is very critical. Currently, there are several classes of transition-based turbulence model which are based on different methods. Among these, the k-kL- ω, which is a three equation turbulence model, is one of the prominent ones which is based on the concept of laminar kinetic energy. This model is phenomenological and has several advantageous features. Over the years, different researchers have attempted to modify the original version which was proposed by Walter and Cokljat in 2008 to enrich the modelling capability. In this article, a modified form of k-kL-ω transitional turbulence model has been used with the help of OpenFOAM for an investigative CFD analysis of a NACA 4-digit airfoil at range of angles of attack.

DETERMINATION OF DRAG AND LIFT RELATED COEFFICIENTS OF AN AUV USING COMPUTATIONAL AND EXPERIMENTAL FLUID DYNAMICS METHODS

2021 ◽  
Vol 162 (A2) ◽  
Author(s):  
E Javanmard ◽  
Sh Mansoorzadeh ◽  
A Pishevar ◽  
J A Mehr
Keyword(s):  
Fluid Dynamics ◽  
Autonomous Underwater Vehicle ◽  
Experimental Tests ◽  
Hydrodynamic Coefficients ◽  
Experimental Fluid Dynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Drag And Lift ◽  
Control Surfaces ◽  
Experimental Fluid

Determination of hydrodynamic coefficients is a vital part of predicting the dynamic behavior of an Autonomous Underwater Vehicle (AUV). The aim of the present study was to determine the drag and lift related hydrodynamic coefficients of a research AUV, using Computational and Experimental Fluid Dynamics methods. Experimental tests were carried out at AUV speed of 1.5 m s-1 for two general cases: I. AUV without control surfaces (Hull) at various angles of attack in order to calculate Hull related hydrodynamic coefficients and II. AUV with control surfaces at zero angle of attack but in different stern angles to calculate hydrodynamic coefficients related to control surfaces. All the experiments carried out in a towing tank were also simulated by a commercial computational fluid dynamics (CFD) code. The hydrodynamic coefficients obtained from the numerical simulations were in close agreement with those obtained from the experiments.

scholarly journals OPTIMIZING THE VELOCITY OF RING SHAPE PARAMETER FOR DESIGNING THE NOZZLES USING CFD

2021 ◽  
pp. 1-10
Author(s):  
Obai Younis ◽  
Reem Ahmed ◽  
Ali Mohammed Hamdan ◽  
Dania Ahmed
Keyword(s):  
Shape Parameter ◽  
Maximum Velocity ◽  
Simulation Software ◽  
Governing Equations ◽  
Ansys Fluent ◽  
Ring Shape ◽  
Ring Location ◽  
Computational Fluid Dynamics Cfd ◽  
Triangular Elements ◽  
Volume Method

This study aims to optimize the velocity of ring shape parameter for designing the nozzles using computational fluid dynamics (CFD) and investigated the flow in nozzles using ANSYS, Inc. simulation software. The model geometries were defined using ANSYS FLUENT-Design Modeler platform. All nozzles were designed on unstructured triangular elements comprising of 1200000 mesh nodes. The differential governing equations were applied in ANSYS FLUENT based on a finite volume method. The distance and dimensions of ring location significantly influence the velocity of water during flow where the maximum velocity at double rings reduces the surface area at distance of 7mm and 15mm and 2x2 mm dimensions. Considering 8, 10, and 12 bar liner proportions, there was an increase in the velocity at maximum points in ring shapes.

scholarly journals An investigation of unsteady 3D effects on trailing edge flaps

2016 ◽  
Author(s):  
Eva Jost ◽  
Annette Fischer ◽  
Galih Bangga ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Trailing Edge ◽  
Trailing Vortices ◽  
Trailing Edge Flaps ◽  
Negative Effect ◽  
3D Effects ◽  
Computational Fluid Dynamics Cfd ◽  
Trailing Edge Flap ◽  
The Impact ◽  
2D Airfoil ◽  
High Influence

Abstract. The present study investigates the impact of unsteady and viscous 3D aerodynamic effects on a wind turbine blade with trailing edge flap by means of Computational Fluid Dynamics (CFD). Harmonic oscillations are simulated on the DTU 10 MW rotor with a morphing flap of 10 % chord extent ranging from 70 % to 80 % blade radius. The deflection frequency is varied in the range between 1 p and 6 p. To quantify 3D effects, rotor simulations are compared to 2D airfoil computations and the 2D theory by Theodorsen. A significant influence of trailing and shed vortex structures has been found which leads to an amplitude reduction and hysteresis of the lift response in the flap section with regard to the deflection signal. For the 3D rotor results greater amplitude reductions and a less pronounced hysteresis is observed compared to the 2D airfoil case. Blade sections neighboring the flap experience however an opposing impact and hence partly compensate the negative effect of trailing vortices in the flap section in respect to integral loads. The comparison to steady flap deflections at the 3D rotor revealed the high influence of dynamic inflow effects.

Sign in / Sign up

Export Citation Format

Share Document