Numerical Simulation of VLEC Hydrodynamic Response Coupled with Tank Sloshing

2015 ◽  
Author(s):  
Zhou Qinghua ◽  
Li Xiaoling ◽  
Yang Qi ◽  
B. Qin
Keyword(s):  
Three Dimensional ◽  
Ship Motion ◽  
Movement Behavior ◽  
Structural Safety ◽  
Navier Stokes ◽  
Linear Potential ◽  
Fluid Sloshing ◽  
Response Amplitude Operators ◽  
Cfd Method ◽  
Tank Sloshing

The coupling effects of tank sloshing on the ship motion and wave-induced loads of a very large ethane carrier (VLEC) with 83000m3 loading capacity and four membrane tanks are systematically investigated. The ship motion equation coupled with tank sloshing is calculated in the frequency domain based on three dimensional linear potential flow theory. The added mass, damping coefficient and restoring stiffness correction due to tank sloshing are considered. The response amplitude operators (RAO) of ship motion and sectional loads with and without considering tank sloshing are obtained. Taking ship motion dynamic response as excitation input condition, the three dimensional fluid sloshing movement behavior and sloshing-induced impact pressure are simulated by the computational fluid dynamics (CFD) method. The Renormalized Group (RNG) k-ε turbulence model is selected and used with the Reynolds-Averaged Navier-Stokes (RANS) equation; the volume of fluid method is adopted to predict the free surface elevation. The results provide valuable references for the overall design and structural safety assessment of VLEC.

Numerical Study on Ship Motion Fully Coupled with LNG Tank Sloshing in CFD Method

2019 ◽  
Vol 16 (06) ◽  
pp. 1840022 ◽  
Author(s):  
Yuan Zhuang ◽  
Decheng Wan
Keyword(s):  
Incident Wave ◽  
Numerical Study ◽  
Three Dimensional ◽  
Ship Motion ◽  
Wave Flow ◽  
Motion Responses ◽  
Lng Tank ◽  
Cfd Method ◽  
Tank Sloshing ◽  
Fully Coupled

In this paper, numerical simulations of ship motion coupled with LNG tank sloshing in waves are considered. The fully coupled problems are performed by our in-house RANS/DES solver, naoe-FOAM-SJTU. The internal tank sloshing and external wave flow are solved simultaneously. The considered model is a three-dimensional simplified LNG FPSO with two prismatic tanks. The ship motion responses are carried out in beam waves to compare with existing experimental data to validate this solver. The coupling effects between ship motion and sloshing tanks are observed. The anti-rolling characteristics are found, and this kind of characteristic is obvious in low-filling conditions. Different incident wave amplitudes and frequencies are considered. When the incident wave frequency is close to ship motion natural frequency, the ship motion response is strong and an overturning behavior in sloshing tanks is observed. Meanwhile, impact pressures on bulkhead are also discussed. The pressure signal explains the phenomenon in tanks we discussed before.

Multiple Ship Motion Simulation Code Correlation with Model Test Results

2017 ◽  
Author(s):  
James A. Coller ◽  
Andrew Silver ◽  
Okey Nwogu ◽  
Benjamin S.H. Connell
Keyword(s):  
Real Time ◽  
Model Test ◽  
Three Dimensional ◽  
Angle Measurement ◽  
Ship Motion ◽  
Ship Motions ◽  
Simulation Code ◽  
Forecasting System ◽  
Scale Experiment ◽  
Response Amplitude Operators

The US Nav has developed a real-time multi-ship ship motion forecasting system which combines forecast wave conditions with ship motion simulations to produce a prediction of the relative motions between two ships operating in a skin-to-skin configuration. The system utilizes two different simulation methods for predicting ship motions: MotionSim and Reduced Order Model (ROM) based on AEGIR. MotionSim is a fast three-dimensional panel method that is used to estimate the Response Amplitude Operators (RAOs) necessary for multi-ship motion predictions. The ROM works to maximize the accuracy of high fidelity ship motion prediction methods while maintaining the computational speed required for real-time forecasting. A model scale experiment was performed in 2015 on two Navy ships conventionally moored together. The predicted relative ship motions from MotionSim and ROM were compared to the model data using three different metrics: RMS (root mean square) ratio, correlation coefficient, and average angle measurement (AAM).This paper provides an overview of the two methods for predicting the multi-ship motions, a description of the model test, challenges faced during testing, and a discussion on the methodology of the evaluation and the results of each code correlation.

scholarly journals Airflow inside the nasal cavity: visualization using computational fluid dynamics

2010 ◽  
Vol 4 (4) ◽  
pp. 657-661 ◽  
Author(s):  
Mohammed Zubair ◽  
Vizy Nazira Riazuddin ◽  
Mohammed Zulkifly Abdullah ◽  
Rushdan Ismail ◽  
Ibrahim Lutfi Shuaib ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Nasal Cavity ◽  
Three Dimensional ◽  
Clinical Importance ◽  
Navier Stokes ◽  
Tomographic Images ◽  
Computed Tomographic ◽  
Continuity Equations ◽  
Cfd Method

Abstract Background: It is of clinical importance to examine the nasal cavity pre-operatively on surgical treatments. However, there is no simple and easy way to measure airflow in the nasal cavity. Objectives: Visualize the flow features inside the nasal cavity using computational fluid dynamics (CFD) method, and study the effect of different breathing rates on nasal function. Method: A three-dimensional nasal cavity model was reconstructed based on computed tomographic images of a healthy Malaysian adult nose. Navier-Stokes and continuity equations for steady airflow were solved numerically to examine the inspiratory nasal flow. Results: The flow resistance obtained varied from 0.026 to 0.124 Pa.s/mL at flow-rate from 7.5 L/min to 40 L/min. Flow rates by breathing had significant influence on airflow velocity and wall shear-stress in the vestibule and nasal valve region. Conclusion: Airflow simulations based on CFD is most useful for better understanding of flow phenomenon inside the nasal cavity.

Database of Sail Shapes vs. Sail Performance and Validation of Numerical Calculation for Upwind Condition

2007 ◽  
Author(s):  
Yutaka Masuyama ◽  
Yusuke Tahara ◽  
Toichi Fukasawa ◽  
Naotoshi Maeda
Keyword(s):  
Numerical Method ◽  
Vortex Lattice ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Numerical Calculations ◽  
Navier Stokes ◽  
Coupling Scheme ◽  
Aerodynamic Coefficients ◽  
Lattice Method ◽  
Cfd Method

Database of full-scale three-dimensional sail shapes are presented with the aerodynamic coefficients for the upwind condition of IMS type sails. Three-dimensional shape data are used for the input of numerical calculations and the results are compared with the measured sail performance. The sail shapes and performance are measured using a sail dynamometer boat Fujin. The Fujin is a 34-foot LOA boat, in which load cells and charge coupled devices (CCD) cameras are installed to measure the sail forces and shapes simultaneously. The sailing conditions of the boat, such as boat speed, heel angle, wind speed, wind angle, and so on, are also measured. The tested sail configurations are as follows: mainsail with 130% jib, mainsail with 75% jib and mainsail alone. Sail shapes are measured at several height positions. The measured shape parameters are chord length, maximum draft, maximum draft position, entry angle at the luff and exit angle at the leech. From these parameters three-dimensional coordinates of the sails are calculated by interpolation. These three-dimensional coordinates are tabulated with the aerodynamic coefficients. Numerical calculations are performed using the measured sail shapes. The calculation methods are of two types; Reynolds-averaged Navier-Stokes (RANS)-based CFD and vortex lattice methods (VLM). A multi-block RANS-based CFD method was developed by one of the authors and is capable of predicting viscous flows and aerodynamic forces for complicated sail configuration for upwind as well as downwind conditions. Important features of the numerical method are summarized as follows: a Finite- Analytic scheme to discretize transport equations, a PISO type velocity-pressure coupling scheme, multi-block domain decomposition capability, and several choices of turbulence models depending on flows of interest. An automatic grid generation scheme is also included. Another calculation method, the vortex lattice method is also adopted. In this case, step-by-step calculations are conducted to attain the steady state of the sail in steady wind. Wake vortices are generated step-by-step, which flow in the direction of the local velocity vector. These calculated sail forces are compared with the measured one, and the validity of the numerical method is studied. The sail shape database and comparison with numerical calculations will provide a good benchmark for the sail performance analysis of the upwind condition of IMS type sails.

A Study of Anti-Rolling Tank on Floating Vessel

2016 ◽  
Author(s):  
Kyung Sung Kim ◽  
Byung Hyuk Lee ◽  
Moo-Hyun Kim ◽  
Jong-Chun Park ◽  
Han Suk Choi
Keyword(s):  
Volterra Series ◽  
Three Dimensional ◽  
Ship Motion ◽  
Simulation Program ◽  
Linear Potential ◽  
Hydrodynamic Coefficients ◽  
Acceleration Data ◽  
Moving Particle ◽  
Vessel Motion ◽  
External Forces

Active anti-rolling tank (ART) is sophisticated equipment on a floating vessel to reduce roll motion for the slender ship-shape vessel. Three-dimensional panel based diffraction and radiation linear potential program employed to obtain hydrodynamic coefficients of floating vessel. For the ship motion, a BEM (Boundary Element Method)-based ship motion program was used and inner sloshing effects were conducted by a particle-based CFD (Computational Fluid Dynamics) program which is the Moving Particle Semi-implicit (MPS). By using panel program, the hydrodynamic coefficients were obtained in frequency domain, and then were converted into time domain ship motion simulation program. In this procedure, time memory effect was considered by Volterra series expansion. The ship motion program and sloshing program was coupled dynamically; inner tank received displacement, velocity and acceleration data from ship motion program and use them for inner tank motion, while the ship motion program was waiting external forces due to sloshing impact loads and inertia forces/moments from sloshing simulation program. Thus, two programs run simultaneously and allowed real time coupling effects of inner sloshing on vessel motion. By comparing response amplitude operator (RAO) of the vessel without anti-rolling tank, it was shown both values have good agreement. And then comparing between vessels with and without anti-rolling tank, it is shown that the effects of ART changed and shift RAOs. Furthermore, by changing the location of ART, location effects of ART were also investigated.

On the Hydrodynamic Interaction Between Ship and Free-Surface Motions on Vessels With Moonpools

2019 ◽  
Author(s):  
Senthuran Ravinthrakumar ◽  
Trygve Kristiansen ◽  
Babak Ommani
Keyword(s):  
Free Surface ◽  
Flow Separation ◽  
Coupling Effect ◽  
Three Dimensional ◽  
Dimensional Case ◽  
Navier Stokes ◽  
Linear Potential ◽  
Two Dimensional ◽  
Sloshing Mode ◽  
Vessel Motion

Abstract Coupling between moonpool resonance and vessel motion is investigated in two-dimensional and quasi three-dimensional settings, where the models are studied in forced heave and in freely floating conditions. The two-dimensional setups are with a recess, while the quasi three-dimensional setups are without recess. One configuration with recess is presented for the two-dimensional case, while three different moonpool sizes (without recess) are tested for the quasi three-dimensional setup. A large number of forcing periods, and three wave steepnesses are tested. Boundary Element Method (BEM) and Viscous BEM (VBEM) time-domain codes based on linear potential flow theory, and a Navier–Stokes solver with linear free-surface and body-boundary conditions, are implemented to investigate resonant motion of the free-surface and the model. Damping due to flow separation from the sharp corners of the moonpool inlets is shown to matter for both vessel motions and moonpool response around the piston mode. In general, the CFD simulations compare well with the experimental results. BEM over-predicts the response significantly at resonance. VBEM provides improved results compared to the BEM, but still over-predicts the response. In the two-dimensional study there are significant coupling effects between heave, pitch and moonpool responses. In the quasi three-dimensional tests, the coupling effect is reduced significantly as the moonpool dimensions relative to the displaced volume of the ship is reduced. The first sloshing mode is investigated in the two-dimensional case. The studies show that damping due to flow separation is dominant. The vessel motions are unaffected by the moonpool response around the first sloshing mode.

scholarly journals Feasible Concept of an Air-Driven Fan with a Tip Turbine for a High-Bypass Propulsion System

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3350 ◽  
Author(s):  
Guoping Huang ◽  
Xin Xiang ◽  
Chen Xia ◽  
Weiyu Lu ◽  
Lei Li
Keyword(s):  
Fluid Dynamics ◽  
Carbon Dioxide Emissions ◽  
Three Dimensional ◽  
Propulsion System ◽  
Navier Stokes ◽  
Three Dimensional Flow ◽  
Low Pressure Turbine ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Bypass Ratio

The reduction in specific fuel consumption (SFC) is crucial for small/mid-size cost-controllable aircraft, which is very conducive to reducing cost and carbon dioxide emissions. To decrease the SFC, increasing the bypass ratio (BPR) is an important way. Conventional high-BPR engines have several limitations, especially the conflicting spool-speed requirements of a fan and a low-pressure turbine. This research proposes an air-driven fan with a tip turbine (ADFTT) as a potential device for a high-bypass propulsion system. Moreover, a possible application of this ADFTT is introduced. Thermodynamic analysis results show that an ADFTT can improve thrust from a prototype turbofan. As a demonstration, we selected a typical small-thrust turbofan as the prototype and applied the ADFTT concept to improve this model. Three-dimensional flow fields were numerically simulated through a Reynolds averaged Navier-Stokes (RANS)-based computational fluid dynamics (CFD) method. The performance of this ADFTT has the possibility of amplifying the BPR more than four times and increasing the thrust by approximately 84% in comparison with the prototype turbofan.

scholarly journals ICCM2015: A Comparison of RANS and LES Computational Methods in Analyzing Ventilation Flow Through a Room Fitted with a Two-Sided Windcatcher

2017 ◽  
Vol 14 (03) ◽  
pp. 1750021 ◽  
Author(s):  
A. Niktash ◽  
B. P. Huynh
Keyword(s):  
Natural Ventilation ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Interior Space ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Cfd Method ◽  
Good Agreement

A windcatcher is a structure for providing natural ventilation using wind power; it is usually fitted on the roof of a building to exhaust the inside stale air to the outside and supplies the outside fresh air into the building interior space working by pressure difference between outside and inside of the building. In this paper, the behavior of free wind flow through a three-dimensional room fitted with a centered position two-canal bottom shape windcatcher model is investigated numerically, using a commercial computational fluid dynamics (CFD) software package and LES (Large Eddy Simulation) CFD method. The results have been compared with the obtained results for the same model but using RANS (Reynolds Averaged Navier–Stokes) CFD method. The model with its surrounded space has been considered in both method. It is found that the achieved results for the model from LES method are in good agreement with RANS method’s results for the same model.

A Low-Order Model for Predicting Turbocharger Turbine Unsteady Performance

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Teng Cao ◽  
Liping Xu
Keyword(s):  
Power Output ◽  
Three Dimensional ◽  
Pulsating Flow ◽  
Navier Stokes ◽  
Order Model ◽  
Wave Dynamics ◽  
Predicting Performance ◽  
Set Up ◽  
Cfd Method ◽  
Low Order

In this paper, a low-order model for predicting performance of radial turbocharger turbines is presented. The model combines an unsteady quasi-three-dimensional (Q3D) computational fluid dynamics (CFD) method with multiple one-dimensional (1D) meanline impeller solvers. The new model preserves the critical volute geometry features, which is crucial for the accurate prediction of the wave dynamics and retains effects of the rotor inlet circumferential nonuniformity. It also still maintains the desirable properties of being easy to set-up and fast to run. The model has been validated against a experimentally validated full 3D unsteady Reynolds-averaged Navier–Stokes (URANS) solver. The loss model in the meanline model is calibrated by the full 3D RANS solver under the steady flow states. The unsteady turbine performance under different inlet pulsating flow conditions predicted by the model was compared with the results of the full 3D URANS solver. Good agreement between the two was obtained with a speed-up ratio of about 4 orders of magnitude (∼104) for the low-order model. The low-order model was then used to investigate the effect of different pulse wave amplitudes and frequencies on the turbine cycle averaged performance. For the cases tested, it was found that compared with quasi-steady performance, the unsteady effect of the pulsating flow has a relatively small impact on the cycle-averaged turbine power output and the cycle-averaged mass flow capacity, while it has a large influence on the cycle-averaged ideal power output and cycle-averaged efficiency. This is related to the wave dynamics inside the volute, and the detailed mechanisms responsible are discussed in this paper.

Effect of Blade Numbers on Pressure Drop of Axial Cyclone Separators by CFD

2011 ◽  
Vol 55-57 ◽  
pp. 343-347 ◽  
Author(s):  
Yi Gang Luan ◽  
Hai Ou Sun
Keyword(s):  
Pressure Drop ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Three Dimensional Model ◽  
Navier Stokes Equations ◽  
Pressure Drops ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Resistance Performance

In this article, computational fluid dynamics(CFD) method is used to predict the effect of blade numbers on the pressure drop of axial cyclone separators. A three-dimensional model is built to acquire the resistance of axial cyclone separators with different blade numbers. The flow field inside cyclone separators is calculated using 3D Reynolds-averaged Navier-Stokes equations. And turbulence model is used to simulate the Reynold stress. Also pressure drop of cyclone separators with different blade numbers is expressed as a function of different inlet velocities. At the same inlet velocity with increasing the blade numbers, pressure drops of cyclones reduce greatly. And changing the blade number of cyclone separator is an effective method to improve its resistance performance.

Sign in / Sign up

Export Citation Format

Share Document