scholarly journals Numerical Study on Wave-Ice Interaction in the Marginal Ice Zone

2020 ◽  
Vol 9 (1) ◽  
pp. 4
Author(s):  
Tiecheng Wu ◽  
Wanzhen Luo ◽  
Dapeng Jiang ◽  
Rui Deng ◽  
Shuo Huang
Keyword(s):  
Sea Ice ◽  
Numerical Study ◽  
Test Results ◽  
Towing Tank ◽  
Marginal Ice Zone ◽  
Computational Fluid Dynamics Cfd ◽  
Numerical Research ◽  
Ice Floes ◽  
Cfd Method ◽  
Six Degree Of Freedom

The effect of waves on ice sheet is critical in the marginal ice zone (MIZ). Waves break large sea ice into small pieces and cause them to collide with each other. Simultaneously, the interaction between sea ice and waves attenuates these waves. In this study, a numerical research is conducted based on a computational fluid dynamics (CFD) method to investigate the response of single ice floe to wave action. The obtained results demonstrate that the sea ice has a violent six degree of freedom (6DoF) motion in waves. Ice floes with different sizes, thicknesses, and shapes exhibit different 6DoF motions under the action of waves. The heave and surge response amplitude operator (RAO) of the sea ice are related to wavelength. Furthermore, the overwash phenomenon can be observed in the simulation. The obtained results are compared with the model test in the towing tank based on artificial ice, and they agree well with test results.

An anti-crystallization design of selective catalytic reduction nozzle holder

2021 ◽  
pp. 095440702097084
Author(s):  
Dewen Liu ◽  
Kai Lu ◽  
Shusen Liu ◽  
Yan Wu ◽  
Shuzhan Bai
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Injection System ◽  
Test Results ◽  
Verification Methods ◽  
Crystallization Risk ◽  
Protective Cover ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Good Agreement

From the aspect of reducing the risk of crystallization on nozzle surface, a new design of nozzle protective cover was to solve the problem in selective catalytic reduction (SCR) urea injection system. The simulation calculation and experimental verification methods were used to compare different schemes. The results show that reducing the height of nozzle holder can reduce the vortex currents near nozzle surface and effectively reduce the risk of crystallization on the nozzle surface. It is proposed to install a protective cover in the nozzle holder under the scheme of reducing the height of nozzle holder, which can further eliminate the vortex. Simulation and test results demonstrate good agreement under the rated running condition. The scheme of adding a protective cover in the nozzle holder shows the least crystallization risk by computational fluid dynamics (CFD) method. The crystallization cycle test shows that, after the height of nozzle holder is reduced, the risk of crystallization on the nozzle surface is reduced correspondingly. The addition of a protective cover in the nozzle holder solves the problem of crystallization on the nozzle surface, which provides a new method for anti-crystallization design.

scholarly journals Numerical study of flow characteristics on wing airfoil eppler 562 with whitcomb winglet variations

2018 ◽  
Vol 204 ◽  
pp. 04009
Author(s):  
S.P Setyo Hariyadi ◽  
Sutardi ◽  
Wawan Aries Widodo ◽  
Muhammad Anis Mustaghfirin ◽  
Arifandi Rachmadiyan
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Fuel Efficiency ◽  
Flow Characteristics ◽  
Lower Surface ◽  
Computational Fluid Dynamics Cfd ◽  
Fluid Flow Characteristics ◽  
Conducting Research ◽  
Cfd Method ◽  
Wing Airfoil

Winglet is a tool used to improve the efficiency of aircraft and UAV performance by preventing fluid flow jump from lower surface to upper surface at wingtip. The addition of this winglet resulted in improved lift and reduction of drag force from the aircraft wing or UAV. From Whitcomb's research, it was found that the use of winglet on a full size airplane can increase fuel efficiency by 7%. The research led to the idea of conducting research on fluid flow characteristics on the UAV wing with the Eppler 562 airfoil combined with the whitcomb winglet. This numerical study was conducted using the Computational Fluid Dynamics (CFD) method based on the advantages of using this simulation that can review the fluid flow in macroscopic way. This study is provide accurate fluid flow visualization results and can improve the performance of the wings when compared with wings without winglet (plain wing). Wing with the Eppler 562 airfoil combined with the whitcomb winglet results reduction in rotating motion that makes velocity components as opposed to lift.

Experimental and Numerical Study on the Flow Reduction in the Moonpool of Floating Offshore Structure

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Seon Oh Yoo ◽  
Hyun Joe Kim ◽  
Dong Yeon Lee ◽  
Booki Kim ◽  
Seung Ho Yang
Keyword(s):  
Numerical Study ◽  
Internal Flow ◽  
Navier Stokes ◽  
Test Results ◽  
Internal Flows ◽  
Offshore Structure ◽  
Flow Reduction ◽  
Gap Flow ◽  
Sloshing Mode ◽  
Computational Fluid Dynamics Cfd

Recently, drillship moonpools are getting longer and wider for the higher operability. With this trend, violent internal flows are getting more concerned in terms of the safety and operability, which have been reported during the operations even in mild seas. Also, it is well known that the internal flow gives higher resistance during the transit of drillship. In this study, to see the effect of larger damping devices, a series of experimental and numerical study was carried out for the four moonpool designs; the ordinary plain moonpool, the moonpool with a recess deck, the moonpool with an isolated recess deck (island deck), and moonpool with a combination of island deck, splash plates, and wave absorber. From the model tests, it was found that the internal flow of the moonpool was significantly reduced by the application of the wave absorber. In case of the moonpool with the island deck, the sloshing mode oscillations was not observed due to the gap flow between the inner wall of the moonpool and the recess. For the in-depth understanding of the flow behaviors and characteristics, the internal flow of the moonpool has been investigated using Reynolds-averaged Navier–Stokes based computational fluid dynamics (CFD) code. The various moonpool designs were simulated to identify the effect of each device for the internal flow reduction of the moonpool. The CFD analysis results with regular waves, the water surface responses inside moonpool such as the flow pattern and resonance frequency, were compared with model test results and showed reasonably good agreements.

scholarly journals Brief communication: Pancake ice floe size distribution during the winter expansion of the Antarctic marginal ice zone

2018 ◽  
Author(s):  
Alberto Alberello ◽  
Miguel Onorato ◽  
Luke Bennetts ◽  
Marcello Vichi ◽  
Clare Eayrs ◽  
...  
Keyword(s):  
Sea Ice ◽  
Size Distribution ◽  
Marginal Ice Zone ◽  
Ice Floes ◽  
The Antarctic

Abstract. The size distribution of pancake ice floes is calculated from images acquired during a voyage to the Antarctic marginal ice zone in the winter expansion season. Results show that 50 % of the sea ice area is made up by floes with diameters 2.3–4 m. The floe size distribution shows two distinct slopes on either side of the 2.3–4 m range. It is conjectured that growth of pancakes from frazil forms the distribution of small floes (D  4 m).

scholarly journals Trim Influence on Kriso Container Ship (KCS): An Experimental and Numerical Study

2017 ◽  
Author(s):  
Emil Shivachev ◽  
Mahdi Khorasanchi ◽  
Alexander H. Day
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Study ◽  
Computational Cost ◽  
Breaking Waves ◽  
Computational Techniques ◽  
Container Ship ◽  
Towing Tank ◽  
Operational Life ◽  
Computational Fluid Dynamics Cfd

There has been a lot of interest in trim optimisation to reduce fuel consumption and emissions of ships. Many existing ships are designed for a single operational condition with the aim of producing low resistance at their design speed and draft with an even keel. Given that a ship will often sail outside this condition over its operational life and moreover some vessels such as LNG carriers return in ballast condition in one leg, the effect of trim on ships resistance will be significant. Ship trim optimization analysis has traditionally been done through towing tank testing. Computational techniques have become increasingly popular for design and optimization applications in all engineering disciplines. Computational Fluid Dynamics (CFD), is the fastest developing area in marine fluid dynamics as an alternative to model tests. High fidelity CFD methods are capable of modelling breaking waves which is especially crucial for trim optimisation studies where the bulbous bow partially emerges or the transom stern partially immerses. This paper presents a trim optimization study on the Kriso Container Ship (KCS) using computational fluid dynamics (CFD) in conjunction with towing tank tests. A series of resistance tests for various trim angles and speeds were conducted at 1:75 scale at design draft. CFD computations were carried out for the same conditions with the hull both fixed and free to sink and trim. Dynamic sinkage and trim add to the computational cost and thus slow the optimisation process. The results obtained from CFD simulations were in good agreement with the experiments. After validating the applicability of the computational model, the same mesh, boundary conditions and solution techniques were used to obtain resistance values for different trim conditions at different Froude numbers. Both the fixed and free trim/sinkage models could predict the trend of resistance with variation of trim angles; however the fixed model failed to measure the absolute values as accurately as the free model. It was concluded that a fixed CFD model, although computationally faster and cheaper, can find the optimum trim angle but cannot predict the amount of savings with very high accuracy. Results concerning the performance of the vessel at different speeds and trim angles were analysed and optimum trim is suggested.

A numerical analysis on different-generation prototypes of ventricular assist device

2019 ◽  
Vol 10 (05) ◽  
pp. 1950029
Author(s):  
Ali Tavakoli Golpaygani ◽  
Kamran Hassani ◽  
Alireza Karimi ◽  
Amin Nokhbe Zaeim
Keyword(s):  
Ventricular Assist Device ◽  
Numerical Study ◽  
Heart Diseases ◽  
Shear Stresses ◽  
Assist Device ◽  
Ventricular Assist ◽  
Curved Blade ◽  
Concurrent Study ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

The ventricular assist device (VAD) assists the patients with heart diseases for limited and prolonged periods. This device synchronizes with normal heart activities to help foster its performance. Consequently, its sensitive design requires high accuracy. The pumps are the essential part of every VAD which should operate in wide ranges of flow and pressure. As there are various types of VAD under different designs, it is neither practical nor plausible to experimentally/clinically investigate their performances. Therefore, in the concurrent study, a numerical study was carried out on four different generation prototypes of VAD pumps for reaching an optimum design. Using computational fluid dynamics (CFD) method, the software derived, showed and streamlined the flow field shear stress both inside the VAD and its blades. Furthermore, the vortices and flow rate-pressure curves were observed. The results showed that the curved blade pumps operate better compared to that of the straight blade types, concerning the provision of enough pressure and less damage to the red blood cells. The results have implications not only for comparing different types of VAD designs but also for understanding the resulted shear stresses and pressures as a result of the blade’s structure.

scholarly journals Effect of water resistance on predictions of ship ice resistance using towing tests in ice basin

2021 ◽  
Vol 4 (398) ◽  
pp. 43-52
Author(s):  
Kirill Sazonov ◽  
◽  
Grigory Kanevsky ◽  
Mikhail Lobachev ◽  
◽  
...  
Keyword(s):  
Test Data ◽  
Model Test ◽  
Hydrodynamic Interaction ◽  
Water Resistance ◽  
Test Results ◽  
Improved Method ◽  
Towing Tank ◽  
Ice Floes ◽  
Ice Resistance

Object and purpose of research. The object under study is a method to determine ice resistance using towing tests of ship models. The purpose of the work is to develop a method that takes into account the water resistance effect on predictions of full-scale ship ice resistance. Materials and methods. The materials for development are model test data and earlier methods for determination of ice resistance on models, as well as recommendations of the International Towing Tank Conference (ITTC). Main results. The method is suggested to take into account the water resistance in analyzing the towing test data obtained in the ice basin, as well as the method for extrapolating the ice resistance due to hydrodynamic interaction of ice floes with underwater hull, including the scale effect. Conclusions. The methods that take into account the water resistance effect on predictions of ship ice resistance based on towing test data obtained in ice basins are reviewed and analyzed. An improved method to include the water resistance effect in a more correct way is suggested. For better comparison of test results in ice basin it is required to introduce a common method of including the water resistance effect using the method suggested in this work.

scholarly journals Experimental and Numerical Study of Orifice Coefficient of Cargo Tank Design of LNG Vessels

2020 ◽  
Vol 10 (19) ◽  
pp. 6667
Author(s):  
Se-Yun Hwang ◽  
Kwang-Sik Kim ◽  
Ho-Sang Jang ◽  
Jang-Hyun Lee
Keyword(s):  
Numerical Study ◽  
Operating Pressure ◽  
Cfd Analysis ◽  
Storage Tanks ◽  
Insulation System ◽  
Design Factor ◽  
International Regulations ◽  
Computational Fluid Dynamics Cfd ◽  
Tank Design ◽  
Cfd Method

Liquid cargo storage tanks of liquefied natural gas (LNG) carriers are designed by strict standards to maintain the cryogenic state (−163 °C). For most LNG cargo storage tanks, it is mandatory to install a system that can safely store leaked fluid for 15 days in the case of leakage of liquid cargo due to crack of the insulation system. To ensure safety, it is necessary to predict the amount of LNG spilling from the cracks in the insulation panels. Although international regulations are provided, they rely on a conservative and consistent coefficient. In this study, experimental and numerical methods were applied to examine the design factor used to predict the flow rate in the tank design process. To check the amount of leakage that occurs under pressure conditions of LNG tanks, an experiment was conducted using crack specimens and pressure containers filled with water. In order to simulate the leakage of LNG, the amount of leakage was predicted using the Computational Fluid Dynamics (CFD) method. The distribution of leakage quantity was investigated according to the shape of the crack through the pressure vessel experiment and the analysis. Through CFD analysis, the leakage rate of LNG was calculated for each operating pressure condition through the crack. Finally, the results of this study examined the need to identify and reconsider the coefficients due to international guidelines and other factors in calculating orifice coefficients applied to the design of LNG tanks.

Numerical Study on Pressure Difference of Valve Core in Vertical Pilot-Control Globe Valve

2017 ◽  
Author(s):  
Zhi-xin Gao ◽  
Fu-qiang Chen ◽  
Jin-yuan Qian ◽  
Zhi-jiang Jin
Keyword(s):  
Pressure Difference ◽  
Numerical Study ◽  
Orifice Diameter ◽  
Inlet Velocity ◽  
Before And After ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Globe Valve ◽  
Opening And Closing ◽  
Core Displacement

Vertical pilot-control globe valve (VPCGV) is a novel globe valve that costs little driving energy and responds quickly. In VPCGV, the opening and closing forces are related to the pressure difference before and after the valve core. In this paper, parameters that have influences on pressure difference such as orifice diameter, valve core displacement, and inlet velocity are thoroughly investigated by computational fluid dynamics (CFD) method. It is found that pressure difference increases with the raising of inlet velocity and the diminishing of valve core displacement, and middle-sized orifice diameter is the best in VPCGV. Furthermore, the correlation between pressure difference and inlet velocity is obtained, which can be beneficial for the selection of VPCGV under certain conditions.

Numerical Study of a Flap Rudder Based on Turbulence Model LES

2011 ◽  
Vol 88-89 ◽  
pp. 240-243 ◽  
Author(s):  
Shu Guang Wu ◽  
Hean Liu
Keyword(s):  
Fluid Dynamics ◽  
Turbulence Model ◽  
Numerical Study ◽  
Boundary Layer Separation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fluctuation Range ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Two Sides

The flap rudder flow field at Re 1.4×106 is calculated using computational fluid dynamics (CFD) method. Large eddy simulation (LES) turbulence model is adopted. The results shows that boundary layer separation phenomenon appears in flap after the gap, and as angle of flap (AOF) is increased, the separation tends to asymmetry, the pressure fluctuation range is becomes higher. There is no eddy in gap when AOF is 0°, but as AOF increases, the eddy in gap appears because of the pressure difference between two sides of the rudder.

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