Comparison of Experimental Towing Test and CFD Analysis of a Bare Hull Model on the Surface

2021 ◽  
Vol 163 (A3) ◽  
Author(s):  
Thu Han Tun ◽  
Ye Thet Htun ◽  
Aung Khaing Min
Keyword(s):  
Model Test ◽  
Surface Resistance ◽  
Surface Condition ◽  
Wave Formation ◽  
Complex Nature ◽  
Cfd Analysis ◽  
Cfd Simulations ◽  
Hull Form ◽  
Model Experiments ◽  
Key Aspects

In designing submarines, hull form selection, resistance, and powering are key aspects. The bare hull form of a submarine can be considered according to five parameters. Surface resistance is important should it be necessary to operate at relatively high Froude Numbers. Due to the complex nature of the flow around the hull, model experiments are still the most reliable approach to determining surface resistance. CFD simulations enable surface condition analysis using FINEMarine. The towing mechanism must be taken into account and so this was designed to fix the pitch motion and measure the hydrodynamic forces. This paper outlines the towing method, comparing the model test and the CFD results, as well as providing a comparison of wave formation from the towing test and the CFD results. The results show that resistance increased significantly above a model speed of 1.4 m/s. Furthermore, above this speed, as the resistance of the model rose, the downforce gradually decreased.

scholarly journals THE EXPERIMENTAL METHOD AND CFD STUDY OF THE BARE HULL FORM OF UNDERWATER VEHICLE AT NEAR SURFACE CONDITION

2021 ◽  
Vol 11 (1) ◽  
pp. 24-33
Author(s):  
Thu Han Tun ◽  
Ye Thet Htun
Keyword(s):  
High Speed ◽  
Surface Condition ◽  
Underwater Vehicle ◽  
Hull Form ◽  
Near Surface ◽  
Towing Tank ◽  
Model Experiments ◽  
Friction Component ◽  
High Froude Number ◽  
Towing Tank Test

Hull form selection, resistance and powering are important in designing underwater vehicle. An underwater vehicle bare hull form is based on the five parameters due to the interaction between the propeller and the hull. When they are running on the surface condition, there will be problems likely as surface vessel, but the main hull of the underwater vehicle is below the waterline with low freeboard. The underwater vehicles are operating with high speed at a high Froude Number. Therefore, the wave making component becomes important in surface resistance. The wave making resistance of the underwater vehicle model at surface condition is analyzed by using CFD tools. Friction component of resistance is calculated by using ITTC’57 correlation line. The flow around the ship’s hull is complicated, so that model experiments are still the most reliable data source on ship resistance determination. The bare hull form of underwater vehicle resistance is based on the model experiments and CFD results. The towing mechanism arrangement should be considered at model. Therefore, towing mechanism is designed for model testing. This paper discusses the towing method and result between model test and CFD. This paper also makes comparison of wave formation Towing tank test and CFD at various speeds. The model was tested with bare hull form of underwater vehicle in the Ship Model Towing Tank at Marine Hydrodynamics Centre, Myanmar Maritime University. CFD analysis is also carried out and the results are compared for surface condition. The three software packages XFLOW, XMESH and XPAN are used for CFD simulations. The comparison of results shows that the coefficient differences are less staggered based on the speed.

Guidelines for CFD Simulations of Spar VIM

2013 ◽  
Author(s):  
Charles Lefevre ◽  
Yiannis Constantinides ◽  
Jang Whan Kim ◽  
Mike Henneke ◽  
Robert Gordon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Test Data ◽  
Model Test ◽  
Model Tests ◽  
Full Scale ◽  
Mooring System ◽  
Time Step ◽  
Cfd Simulations ◽  
Scaled Model ◽  
Sway Motion

Vortex-Induced Motion (VIM), which occurs as a consequence of exposure to strong current such as Loop Current eddies in the Gulf of Mexico, is one of the critical factors in the design of the mooring and riser systems for deepwater offshore structures such as Spars and multi-column Deep Draft Floaters (DDFs). The VIM response can have a significant impact on the fatigue life of mooring and riser components. In particular, Steel Catenary Risers (SCRs) suspended from the floater can be sensitive to VIM-induced fatigue at their mudline touchdown points. Industry currently relies on scaled model testing to determine VIM for design. However, scaled model tests are limited in their ability to represent VIM for the full scale structure since they are generally not able to represent the full scale Reynolds number and also cannot fully represent waves effects, nonlinear mooring system behavior or sheared and unsteady currents. The use of Computational Fluid Dynamics (CFD) to simulate VIM can more realistically represent the full scale Reynolds number, waves effects, mooring system, and ocean currents than scaled physical model tests. This paper describes a set of VIM CFD simulations for a Spar hard tank with appurtenances and their comparison against a high quality scaled model test. The test data showed considerable sensitivity to heading angle relative to the incident flow as well as to reduced velocity. The simulated VIM-induced sway motion was compared against the model test data for different reduced velocities (Vm) and Spar headings. Agreement between CFD and model test VIM-induced sway motion was within 9% over the full range of Vm and headings. Use of the Improved Delayed Detached Eddy Simulation (IDDES, Shur et al 2008) turbulence model gives the best agreement with the model test measurements. Guidelines are provided for meshing and time step/solver setting selection.

CFD-Analysis of Coverplate Receiver Flow

1996 ◽  
Author(s):  
Oliver Popp ◽  
Horst Zimmermann ◽  
J. Kutz
Keyword(s):  
Turbine Rotor ◽  
Geometrical Parameters ◽  
Receiver Design ◽  
Cfd Analysis ◽  
Efficiency Improvement ◽  
System Efficiency ◽  
Cfd Simulations ◽  
Air Supply ◽  
Cooling Air ◽  
Contour Design

The flow field in a preswirled cooling air supply to a turbine rotor has been investigated by means of CFD-simulations. Coefficients for system efficiency are derived. The influences of various geometrical parameters for different configurations have been correlated with the help of appropriate coefficients. For some of the most important geometrical parameters of the coverplate receiver design recommendations have been found. For the preswirl nozzles the potential of efficiency improvement by contour design is highlighted.

scholarly journals CFD analysis of the fluid motion in the isolation rooms

2021 ◽  
Vol 850 (1) ◽  
pp. 012025
Author(s):  
P Tamil Selvan ◽  
K Abhiram ◽  
Ch Anu Raghava ◽  
V Naveen Sai
Keyword(s):  
World Health Organization ◽  
Atmospheric Pressure ◽  
Pressure Difference ◽  
Fluid Motion ◽  
Particle Diameter ◽  
World Health ◽  
Cfd Analysis ◽  
Cfd Simulations ◽  
The World ◽  
Health Organization

Abstract COVID-19 is declared as a pandemic by WHO (world health organization) which has led to many deaths all over the world. This study deals with the fluid motion in the isolation rooms with 12 or more ACH (air changes per hour) and maintaining a minimum pressure difference of 2.5 Pascal that can help in reducing the transmission of the virus from affected people. ANSI/ASHRAE guidelines are considered for the analysis. These Isolation rooms help in eradicating the spread of the contaminated particles to the surroundings by creating a pressure less than the atmospheric pressure in in the room. CFD simulations are carried to study the fluid motion of the particles emitted by the patient inside the room. The Analysis is carried out with various human cough velocities of different particle diameters and we observed from the results that the time taken by the particles to reach the exhaust increases with increase in particle diameter, and the flow inside the room increases with increase in human cough velocity.

Extrapolation of Propulsion Tests for Ships with Appendages and Complex Propulsors

2001 ◽  
Vol 38 (03) ◽  
pp. 145-157
Author(s):  
Jan Holtrop
Keyword(s):  
Scale Effect ◽  
Model Test ◽  
Test Results ◽  
Extrapolation Methods ◽  
Passive Components ◽  
Model Experiments

Prediction of ship powering is traditionally based on the results of model experiments. This paper covers the extrapolation of model test results for ships that may have a multitude of appendages and one or more complex propulsors. The major differences from conventional extrapolation methods are the application of the scale effect corrections to the model propulsion test, the treatment of the appendages and acknowledging the effects of the propeller load on the propulsion parameters. The last feature is considered essential to successfully handle complex propulsors with both rotating and passive components.

CFD Analysis on Similarity Criteria of Hydrodynamic Characteristics for Gravity-Installed Anchors

2019 ◽  
Author(s):  
Jiancai Gao ◽  
Haixiao Liu
Keyword(s):  
Model Testing ◽  
Model Tests ◽  
Similarity Criteria ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Cfd Analysis ◽  
Cfd Simulations ◽  
Tests Of Gravity ◽  
Free Falling ◽  
Reduced Scale

Abstract For reduced-scale model tests of gravity-installed anchors (GIAs), it is of great significance to extrapolate the testing results to prototype. This highlights the necessity of investigation of similarity criteria. The present work aims to find the similarity criteria of three prioritized hydrodynamic characteristics including VT, HP, and Cd for GIAs during installation in water through CFD simulations. In the present study, free falling processes of different reduced-scale T98 anchor models and prototype anchor is simulated, from which VT, HP, and Cd are extracted and analyzed to get the fitting curves for these three characteristics over reduced-scale λ. Based on these curves, hydrodynamic characteristics for prototype and other reduced-scale model can be extrapolated from model testing results. And, the researching procedure in this paper sets an example and reference to study about similarity criteria for other hydrodynamic characteristics.

Numerical Simulation and Experimental Validation on the Surf-Riding and Broaching of a Fishing Vessel

2016 ◽  
Author(s):  
Liwei Yu ◽  
Ning Ma ◽  
Sheming Fan ◽  
Peiyuan Feng ◽  
Xiechong Gu
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Model Test ◽  
Periodic Motion ◽  
Following Seas ◽  
Weakly Nonlinear ◽  
Model Experiments ◽  
Time Histories ◽  
Wave Heights ◽  
Surf Riding

Model experiments and numerical simulations on the surf-riding and broaching in following seas of a 42.5m long purse seiner are conducted. Firstly, the free running model experiments with various ship speeds and wave heights are performed in the towing tank to reproduce the phenomena of surf-riding and broaching. Then, the 6-DOF weakly nonlinear unified model is applied to simulate the motions of the purse seiner with the same cases as the model experiments. Through the comparison between results of model test and numerical simulation, the occurrence conditions of periodic motion, surf-riding and broaching are roughly determined. Finally, it is found that although it is difficult for the numerical simulations to get the same time histories as model tests, the modes of motion (periodic motion, surf-riding or broaching) obtained from the numerical simulations agree well qualitatively and quantitatively in part with the model test results.

Sign in / Sign up

Export Citation Format

Share Document