scholarly journals An experimental and numerical study of the vortices generated by hydrofoils

2009 ◽  
Vol 16 (3) ◽  
pp. 11-17 ◽  
Author(s):  
J. Szantyr ◽  
R. Biernacki ◽  
P. Flaszyński ◽  
P. Dymarski ◽  
M. Kraskowski
Keyword(s):  
Velocity Field ◽  
Cross Sections ◽  
Numerical Study ◽  
Turbulence Models ◽  
Marine Propeller ◽  
Flow Conditions ◽  
Tip Vortices ◽  
Cavitation Tunnel ◽  
Computer Codes ◽  
Propeller Blades

An experimental and numerical study of the vortices generated by hydrofoils The article presents the results of the research project concerning the process of formation of the tip vortices shed from hydrofoils of different geometry in different flow conditions. Three hydrofoils resembling the contemporary marine propeller blades have been selected for the study. The experimental part of the project consisted of the LDA measurements of the velocity field in three cross-sections of the vortex generated by the hydrofoils in the cavitation tunnel. The numerical part of the project consisted of calculations of the corresponding velocity field by means of three computer codes and several selected turbulence models. The comparative analysis of the experimental and numerical results, leading to the assessment of the accuracy of the numerical methods, is included.

PIV Measurements of Propeller Flow Field in a Large Cavitation Tunnel

2011 ◽  
Author(s):  
Takayuki Mori ◽  
Risa Kimoto ◽  
Kenji Naganuma
Keyword(s):  
Flow Field ◽  
Velocity Profiles ◽  
Marine Propeller ◽  
Measured Velocity ◽  
Piv Measurements ◽  
Tip Vortices ◽  
Systems Research ◽  
Tracer Particles ◽  
Cavitation Tunnel ◽  
Blade Tip

Flow field around a marine propeller was measured by means of PIV technique in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense, Japan. Test section of the tunnel is 2m(W) × 2m(H) × 10m(L) and it contains 2000m3 of water. 2-dimensional PIV (2-D PIV) and stereo PIV (SPIV) measurements were made for a five-bladed highly skewed marine propeller. In the case of 2-D PIV measurements, high spatial resolution measurements were possible by seeding relatively small amount of tracer particles. Phase-averaged flow fields showed details on evolution of tip vortices. In the case of SPIV measurements, much larger amounts of tracer particles were required, and it was difficult to perform high resolution measurements. Phase averaged velocity profiles from SPIV measurements showed good agreement with 2-D PIV-measured results. PIV-measured results were compared with results of LDV measurements. Although PIV-measured velocity profiles showed fairly good agreements with LDV-measured results, some discrepancies were found at the blade tip region.

scholarly journals Ring thruster — a preliminary optimisation study

2009 ◽  
Vol 16 (1) ◽  
pp. 43-46 ◽  
Author(s):  
Leszek Matuszewski
Keyword(s):  
Computer Code ◽  
Hydrodynamic Characteristics ◽  
Significant Feature ◽  
Design Procedures ◽  
Cavitation Tunnel ◽  
New Type ◽  
Computer Codes ◽  
The Subject ◽  
Propeller Blades ◽  
Design Calculations

Ring thruster — a preliminary optimisation study The ring thruster is a new type of propeller, for which there is no experimental data to verify analytical design calculations. A significant feature of the ring thruster is the absence of a shaft. Propeller blades are mounted to the ring rotating inside the housing, which has the shape of a nozzle. For this reason the ring thruster is closest, with respect to both the construction and principle of operation, to the Kort nozzle propeller. The absence of a shaft and no gap between the blades and the nozzle make it impossible to fully relay on results obtained from Kort nozzle propeller examination. What is more, the already existing computer codes developed for designing Kort nozzle propellers cannot be directly used for designing ring thrusters either. That is why for this purpose a new code determining hydrodynamic characteristics based on the theory of the vortex lifting surface will be used. When using the above method, some differences between calculated and experimentally recorded results are expected to be observed. To a significant extent, the level of the torque taken by the thruster will be affected by drag of the rotating ring to which the blades are fixed. Examining a propeller equipped with a rotating ring has revealed that the expected torque increment may reach as much as a few per cent, at the comparable level of axial force (thrust). At the present stage of ring propeller investigations there is no data available on how to shape the ring propeller blades. Possible comparison calculations, done using the existing computer code, will allow, the most, the shape of the blades to be determined for preliminary tests in the cavitation tunnel and on a self-propelled model. And only the results obtained in these tests will provide opportunities for verification of preliminary design calculations. It should be stressed, however, that developing design procedures for this type of propellers will require additional optimisation calculations, with further experimental verification. And this should be the subject of separate investigations.

Numerical Study of Turbulent Flow Through Rib-Roughened Channels With Mist Injection

2014 ◽  
Author(s):  
Fifi N. M. Elwekeel ◽  
Qun Zheng ◽  
Antar M. M. Abdala
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Cross Sections ◽  
Numerical Study ◽  
Turbulence Models ◽  
Uniform Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Sst Turbulence Model ◽  
Volume Method

This study investigated heat transfer characteristics on various shaped ribs on the lower channel wall using steam and steam/mist as cooling fluid. The lower wall is subjected to a uniform heat flux condition while others walls are insulated. Calculations are carried out for ribs with square ribs (case A), triangular ribs (case B), trapezoidal ribs (case C) and (case D) cross sections over a range of Reynolds numbers (14000–35000), constant mist mass fraction (6%) and fixed rib height and pitch. To investigate turbulence model effects, computations based on a finite volume method, are carried out by utilizing three turbulence models: the standard k-ω, Omega Reynolds Stress (ωRS) and Shear Stress Transport (SST) turbulence models. The predicted results from using several turbulence models reveal that the SST turbulence model provide better agreement with available measurements than others. It is found that the heat transfer coefficients are enhanced in ribbed channels with injection of a small amount of mist. The steam/mist provides the higher heat transfer enhancement over steam when trapezoidal shaped ribs (38°, case C).

scholarly journals Numerical prediction of steady and unsteady tip vortex cavitation on hydrofoils

2012 ◽  
Vol 19 (3) ◽  
pp. 3-15 ◽  
Author(s):  
Paweł Flaszyński ◽  
Jan A. Szantyr ◽  
Krzysztof Tesch
Keyword(s):  
Cross Sections ◽  
Transverse Velocity ◽  
Numerical Prediction ◽  
Tip Vortex ◽  
Grid Structure ◽  
Flow Conditions ◽  
Tip Vortex Cavitation ◽  
Numerical Predictions ◽  
Cavitation Tunnel ◽  
Discrete Grid

ABSTRACT The article presents the numerical method for prediction of tip vortex cavitation generated on hydrofoils. This method has been developed in the course of numerical and experimental research described in earlier publications. The objective of the research was to design the optimum discrete grid structure for this specific computational task and to select the best turbulence model for such an application The article includes a short description of the method and a computational example demonstrating its performance. In this example the results of numerical prediction of the cavitating tip vortex obtained from two commercial CFD codes are compared with experimental photographs taken in the cavitation tunnel in the corresponding flow conditions. Altogether nine different flow conditions are tested and analyzed, but only selected results are included. The accuracy of the numerical predictions is discussed and the reasons for minor existing discrepancies are identified. The unsteady tip vortex calculations are also presented, showing the fluctuations of the transverse velocity components predicted for three cross-sections of the cavitating vortex kernel.

Finite difference code for velocity and surface traction of a Fluid between Two Eccentric Spheres

2015 ◽  
Vol 11 (1) ◽  
pp. 2960-2971
Author(s):  
M.Abdel Wahab
Keyword(s):  
Velocity Field ◽  
Angular Velocity ◽  
Finite Difference ◽  
Numerical Study ◽  
Outer Sphere ◽  
Equation Of Motion ◽  
Annular Region ◽  
Surface Traction ◽  
Angular Velocities ◽  
Axis Passing

The Numerical study of the flow of a fluid in the annular region between two eccentric sphere susing PHP Code isinvestigated. This flow is created by considering the inner sphere to rotate with angular velocity 1  and the outer sphererotate with angular velocity 2  about the axis passing through their centers, the z-axis, using the three dimensionalBispherical coordinates (, ,) .The velocity field of fluid is determined by solving equation of motion using PHP Codeat different cases of angular velocities of inner and outer sphere. Also Finite difference code is used to calculate surfacetractions at outer sphere.

Numerical study of the flow of a mixture of reacting gases in an inhomogeneous catalyst layer

2003 ◽  
Vol 3 ◽  
pp. 246-254
Author(s):  
C.I. Mikhaylenko ◽  
S.F. Urmancheev
Keyword(s):  
Velocity Field ◽  
Chemical Reactions ◽  
Porous Layer ◽  
Computational Experiment ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Catalyst Layer ◽  
Granular Catalyst ◽  
Fluid Velocity Field

The behavior of a liquid flowing through a fixed bulk porous layer of a granular catalyst is considered. The effects of the nonuniformity of the fluid velocity field, which arise when the surface of the layer is curved, and the effect of the resulting inhomogeneity on the speed and nature of the course of chemical reactions are investigated by the methods of a computational experiment.

scholarly journals Aluminium alloy cross-sections under uniaxial bending and compression: A numerical study

2021 ◽  
Vol 1058 (1) ◽  
pp. 012011
Author(s):  
Evangelia Georgantzia ◽  
Michaela Gkantou ◽  
George S. Kamaris ◽  
Kunal Kansara ◽  
Khalid Hashim
Keyword(s):  
Aluminium Alloy ◽  
Cross Sections ◽  
Numerical Study

A numerical study on combined baffles quick-separation device

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ehsan Dehdarinejad ◽  
Morteza Bayareh ◽  
Mahmud Ashrafizaadeh
Keyword(s):  
Turbulent Flows ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Turbulence Models ◽  
Complete Separation ◽  
Solid Particles ◽  
Flow Rates ◽  
Separation Device ◽  
Coupling Technique ◽  
Laminar And Turbulent Flows

Abstract The transfer of particles in laminar and turbulent flows has many applications in combustion systems, biological, environmental, nanotechnology. In the present study, a Combined Baffles Quick-Separation Device (CBQSD) is simulated numerically using the Eulerian-Lagrangian method and different turbulence models of RNG k-ε, k-ω, and RSM for 1–140 μm particles. A two-way coupling technique is employed to solve the particles’ flow. The effect of inlet flow velocity, the diameter of the splitter plane, and solid particles’ flow rate on the separation efficiency of the device is examined. The results demonstrate that the RSM turbulence model provides more appropriate results compared to RNG k-ε and k-ω models. Four thousand two hundred particles with the size distribution of 1–140 µm enter the device and 3820 particles are trapped and 380 particles leave the device. The efficiency for particles with a diameter greater than 28 µm is 100%. The complete separation of 22–28 μm particles occurs for flow rates of 10–23.5 g/s, respectively. The results reveal that the separation efficiency increases by increasing the inlet velocity, the device diameter, and the diameter of the particles.

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