scholarly journals Water Hammer Simulation Method in Pressurized Pipeline with a Moving Isolation Device

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1794
Author(s):  
Kang Zhang ◽  
Wei Zeng ◽  
Angus R. Simpson ◽  
Shimin Zhang ◽  
Chao Wang
Keyword(s):  
Cfd Simulation ◽  
Simulation Method ◽  
Water Hammer ◽  
Time Step ◽  
Mutual Independence ◽  
Space Step ◽  
Complex Boundary ◽  
Large Water ◽  
Isolation Device ◽  
Subsea Pipelines

Smart isolation devices (SIDs) are commonly used in pressurized subsea pipelines that need to be maintained or repaired. The sudden stoppage of the SID may cause large water hammer pressures, which may threaten both the pipeline and the SID. This paper proposes a simulation method by using a coupled dynamic mesh technique to simulate water hammer pressures in the pipeline. Unlike other water hammer simulations, this method is the first to be used in the simulation in pipelines with a moving object. The implicit method is applied to model the moving SID since it has the mutual independence between the space step and the time step. The movement of the SID is achieved by updating the size of the computational meshes close to the SID at each time step. To improve the efficiency of the simulation and the ability of handling complex boundary conditions, the pipe sections far away from the SID can also be simulated by using the explicit Method of Characteristics (MOC). Verifications were conducted using the simulated results from the Computational Fluid Dynamics (CFD) numerical simulation. Two scenarios have been studied and the comparisons between the simulated results by using the dynamic meshes in 1D methods and those by the CFD simulation show a high correlation, thus validating the new method proposed in this paper.

Research on CFD Simulation of the Cement Slurry Mixer

2012 ◽  
Vol 621 ◽  
pp. 196-199
Author(s):  
Shui Ping LI ◽  
Ya Li Yuan ◽  
Lu Gang Shi
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Cfd Simulation ◽  
Structural Parameters ◽  
Internal Flow ◽  
Simulation Method ◽  
Cement Slurry ◽  
Fluid Machinery ◽  
Computational Fluid Dynamics Cfd ◽  
Machinery Design

Numerical simulation method of the internal flow field of fluid machinery has become an important technology in the study of fluid machinery design. In order to obtain a high-performance cement slurry mixer, computational fluid dynamics (CFD) techniques are used to simulate the flow field in the mixer, and the simulation results are studied. According to the analysis results, the structural parameters of the mixer are modified. The results show the mixer under the revised parameters meet the design requirements well. So CFD analysis method can shorten design period and provide valuable theoretical guidance for the design of fluid machinery.

Clustered Cell Parallelization for GPU Computing of Silicon Anisotropic Etching Simulation

2013 ◽  
Author(s):  
Jianhua Li ◽  
Jingyuan Chen ◽  
Yan Wang ◽  
Jianhua Huang
Keyword(s):  
Graphics Processing Units ◽  
Gpu Computing ◽  
Cell Model ◽  
Application Programming Interface ◽  
Simulation Method ◽  
Anisotropic Etching ◽  
Time Step ◽  
Ca Model ◽  
Application Programming ◽  
Graphics Processing

The parallelization of silicon anisotropic etching simulation with the cellular automata (CA) model on graphics processing units (GPUs) is challenging, because the numbers of computational tasks in etching simulation dynamically change and the existing parallel CA mechanisms do not fit in GPU computation well. In this paper, an improved CA model, called clustered cell model, is proposed for GPU-based etching simulation. The model consists of clustered cells, each of which manages a scalable number of atoms. In this model, only the etching and update of states for the atoms on the etching surface and their unexposed neighbors are performed at each CA time step, whereas the clustered cells are reclassified in a longer time step. With this model, a crystal cell parallelization method is given, where clustered cells are allocated to threads on GPUs in the simulation. With the optimizations from the spatial and temporal aspects as well as a proper granularity, this method provides a faster process simulation. The proposed simulation method is implemented with the Compute Unified Device Architecture (CUDA) application programming interface. Several computational experiments are taken to analyze the efficiency of the method.

scholarly journals CFD Simulation and Experimental Study on Coupled Motion Response of Ship with Tank in Beam Waves

2022 ◽  
Vol 10 (1) ◽  
pp. 113
Author(s):  
Tao He ◽  
Dakui Feng ◽  
Liwei Liu ◽  
Xianzhou Wang ◽  
Hua Jiang
Keyword(s):  
Working Conditions ◽  
Large Scale ◽  
Cfd Simulation ◽  
Stokes Equations ◽  
Body Motion ◽  
Time Step ◽  
Coupled Motion ◽  
Motion Response ◽  
Time Step Size ◽  
Tank Sloshing

Tank sloshing is widely present in many engineering fields, especially in the field of marine. Due to the trend of large-scale liquid cargo ships, it is of great significance to study the coupled motion response of ships with tanks in beam waves. In this study, the CFD (Computational Fluid Dynamics) method and experiments are used to study the response of a ship with/without a tank in beam waves. All the computations are performed by an in-house CFD solver, which is used to solve RANS (Reynold Average Navier-Stokes) equations coupled with six degrees-of-freedom solid-body motion equations. The Level Set Method is used to solve the free surface. Verification work on the grid number and time step size has been conducted. The simulation results agree with the experimental results well, which shows that the numerical method is accurate enough. In this paper, several different working conditions are set up, and the effects of the liquid height in the tank, the size of the tank and the wavelength ratio of the incident wave on the ship’s motion are studied. The results show the effect of tank sloshing on the ship’s motion in different working conditions.

scholarly journals Comparison of Two Single Stage Low-Pressure Rotary Lobe Expander Geometries in Terms of Operation

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4512
Author(s):  
Michalina Kurkus-Gruszecka ◽  
Piotr Krawczyk
Keyword(s):  
Cfd Simulation ◽  
Mechanical Energy ◽  
Electric Energy ◽  
Low Pressure ◽  
Single Stage ◽  
Small Scale ◽  
Operational Parameters ◽  
Data Simulation ◽  
Time Step ◽  
Geometry Model

In the article the computational fluid dynamics (CFD) simulation and calculated operational parameters of the single stage low-pressure rotary lobe expander compared with the values obtained from a different geometry simulation are presented. Low-pressure rotary lobe expanders are rotary engines that use a compressed gas to produce mechanical energy, which in turn can be converted into another form, i.e., electric energy. Currently, expanders are used in narrow areas, but have a large potential in the energy production from gases of low thermodynamic parameters. The first geometry model was designed on the basis of an industrial device and validated with the empirical data. Simulation of the second geometry was made based on a validated model in order to estimate the operational parameters of the device. The CFD model included the transient simulation of compressible fluid in the geometry changing over time and the rotors motion around two rotation axes. The numerical model was implemented in ANSYS CFX software. After obtaining simulation results in the form of parameters monitors for each time step, a number of calculations were performed using a written code analysing the CFD program output files. The article presents the calculation results and the geometries comparison in terms of work efficiency. The research indicated that the construction of the device on a small scale could cause a significant decrease in the aforementioned parameter, caused by medium leaks in the expander clearances.

Meshing Method for Transient Computation With Complex Geometry in CFD

2002 ◽  
Author(s):  
J. L. Kueny ◽  
B. Dore´ ◽  
G. Coppens
Keyword(s):  
Complex Geometry ◽  
Mesh Adaptation ◽  
Moving Mesh ◽  
Computational Time ◽  
Tangential Displacement ◽  
Time Step ◽  
Local Observation ◽  
Complex Boundary ◽  
Accuracy Of Results ◽  
Main Ideas

The description of mesh evolution during a transient computation with moving walls and mesh adaptation has to respect many rules. Using a good mesh for each computational time step is important for accuracy of results. The complexity of geometry can make this objective more complex. A method has been developed to obtain a good moving mesh description with complex boundary geometry. It is based on a local observation of boundary movement and can be resumed by two main ideas: • Add cells where the volume of solution domain increases. • Slide the mesh where the boundary has a tangential displacement.

Simulation of Cantilever Column under the Isolation Device Considering Additional Moment

2012 ◽  
Vol 195-196 ◽  
pp. 684-687
Author(s):  
Hua Ying Zhang ◽  
Hui Li ◽  
Xin Zhang ◽  
Rui Song Pan
Keyword(s):  
Bending Moment ◽  
Simulation Method ◽  
Second Order ◽  
Order Moment ◽  
Isolation System ◽  
Vertical Bearing ◽  
Isolation Device ◽  
Column Comparison

To accurately simulate the second-order bending moment caused by the superstructure shift in the isolation system is difficult. A simulation method of considering the second-order moment is put forward in this paper, and which is used to obtain the push-over curve of the cantilever column. Comparison of the push-over curves that with or without considering the additional moment is shown in this paper. The comparison presents evidence reduction, and embodies the decrease of stiffness. This simulation method can effectively balance the affection of the upper structure shift to the vertical bearing member under the isolator.

Toward Unified Hybrid Simulation Techniques for Spiking Neural Networks

2014 ◽  
Vol 26 (6) ◽  
pp. 1055-1079 ◽  
Author(s):  
Michiel D'Haene ◽  
Michiel Hermans ◽  
Benjamin Schrauwen
Keyword(s):  
Neural Network ◽  
Hybrid Approach ◽  
Simulation Method ◽  
Time Step ◽  
Simulation Techniques ◽  
Simulation Engine ◽  
Weak Points ◽  
The Common ◽  
Network Simulators ◽  
The Ideal

In the field of neural network simulation techniques, the common conception is that spiking neural network simulators can be divided in two categories: time-step-based and event-driven methods. In this letter, we look at state-of-the art simulation techniques in both categories and show that a clear distinction between both methods is increasingly difficult to define. In an attempt to improve the weak points of each simulation method, ideas of the alternative method are, sometimes unknowingly, incorporated in the simulation engine. Clearly the ideal simulation method is a mix of both methods. We formulate the key properties of such an efficient and generally applicable hybrid approach.

A Time-Parallel CFD Approach for Unsteady Combustor Flow Analysis and Design Optimization

2012 ◽  
Author(s):  
Moresh J. Wankhede ◽  
Neil W. Bressloff ◽  
Andy J. Keane
Keyword(s):  
Flow Field ◽  
Domain Decomposition ◽  
Design Optimization ◽  
Cfd Simulation ◽  
Simulation Method ◽  
Spatial Domain ◽  
Parallel Simulation ◽  
Analysis And Design ◽  
Temporal Domain ◽  
Parallel Cfd

Computational fluid dynamics (CFD) simulations to predict and visualize the reacting flow dynamics inside a combustor require fine resolution over the spatial and temporal domain, making them computationally very expensive. The traditional time-serial approach for setting up a parallel combustor CFD simulation is to divide the spatial domain between computing nodes and treat the temporal domain sequentially. However, it is well known that spatial domain decomposition techniques are not very efficient especially when the spatial dimension (or mesh count) of the problem is small and a large number of nodes are used, as the communication costs due to data parallelism becomes significant per iteration. Hence, temporal domain decomposition has some attraction for unsteady simulations, particularly on relatively coarse spatial meshes. The purpose of this study is two-fold: (i), to develop a time-parallel CFD simulation method and apply it to solve the transient reactive flow-field in a combustor using an unsteady Reynolds-averaged Navier Stokes (URANS) formulation in the commercial CFD code FLUENT™ and (ii) to investigate its benefits relative to a time-serial approach and its potential use for combustor design optimization. The results show that the time-parallel simulation method correctly captures the unsteady combustor flow evolution but, with the applied time-parallel formulation, a clear speed-up advantage, in terms of wall-clock time, is not obtained relative to the time-serial approach. However, it is clear that the time-parallel simulation method provides multiple stages of transient combustor flow-field solution data whilst converging towards a final converged state. The availability of this resulting data could be used to seed multiple levels of fidelity within the framework of a multi-fidelity co-Kriging based design optimization strategy. Also, only a single simulation would need to be setup from which multiple fidelities are available.

Numerical Simulation of Real-Gas Flow in a Supersonic Turbine Nozzle Ring

2002 ◽  
Vol 124 (2) ◽  
pp. 395-403 ◽  
Author(s):  
J. Hoffren ◽  
T. Talonpoika ◽  
J. Larjola ◽  
T. Siikonen
Keyword(s):  
Power Plants ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Low Cost ◽  
Design Procedure ◽  
Rankine Cycle ◽  
Simulation Method ◽  
Ideal Gas ◽  
Working Fluid ◽  
Real Gas

In small Rankine cycle power plants, it is advantageous to use organic media as the working fluid. A low-cost single-stage turbine design together with the high molecular weight of the fluid leads to high Mach numbers in the turbine. Turbine efficiency can be improved significantly by using an iterative design procedure based on an accurate CFD simulation of the flow. For this purpose, an existing Navier-Stokes solver is tailored for real gas, because the expansion of an organic fluid cannot be described with ideal gas equations. The proposed simulation method is applied for the calculation of supersonic flow in a turbine stator. The main contribution of the paper is to demonstrate how a typical ideal-gas CFD code can be adapted for real gases in a very general, fast, and robust manner.

scholarly journals Saul’yev and Group Explicit Methods

2019 ◽  
pp. 19
Author(s):  
Ole Østerby
Keyword(s):  
Error Estimation ◽  
Parabolic Equations ◽  
Parallel Computers ◽  
Global Error ◽  
Explicit Methods ◽  
Step Size ◽  
Time Step ◽  
Space Step ◽  
Linear Problems ◽  
Global Error Estimation

The Saul’yev methods for parabolic equations are implicit in form, but can be solved explicitly and are therefore interesting in connection with non-linear problems. Abdullah’s Group Explicit methods are parallel in nature and therefore interesting when using parallel computers. The  main objective of this paper is to study the accuracy of these methods. Using global error estimation we show that for all these methods the time step must be bounded by the square of the space step size to ensure a global error which can be estimated. As a curiosity we show that the two original Saul’yev methods in fact solve two different differential equations.  

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