scholarly journals 3D CFD Simulation of Phase Resonance in a Pump Turbine with an Acoustic Model

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7539
Author(s):  
Yujian Fang ◽  
Ping Huang ◽  
Shibing Jin ◽  
Demin Liu ◽  
Jinfeng Zhang ◽  
...  
Keyword(s):  
Wave Reflection ◽  
Cfd Simulation ◽  
Flow Simulation ◽  
Complex Nature ◽  
Pressure Waves ◽  
Acoustic Model ◽  
Pump Turbine ◽  
Sound Speeds ◽  
Spiral Casing ◽  
Phase Resonance

In order to understand the complex nature of the system dynamic phenomena, such as the strong vibration and noise caused by blade passage in the pump turbine, a state-of-the-art three-dimensional (3D) compressible transient simulation would be desirable to study the problem in depth. This study investigated the phase resonance (PR) that occurred during a full-load operation in the turbine mode of a pump turbine on a prototype scale. As a first step, the wave reflection at the boundaries, and the influence of the timestep and sound speeds on the behavior of traveling pressure waves inside a spiral casing, were studied. It was found that nonreflective boundary conditions and an appropriately small timestep are critical to capturing the wave reflection and superposition process inside a spiral casing; a certain kind of direct PR risk was detected in its system design. The detected direct PR differed from the well-known PR with two features: firstly, it was almost independent of the sound speeds, and secondly, the pressure distribution over the spiral circumference varied among the amplitudes. The latter feature was caused by pressure waves at every stator channel induced by a rotor stator interaction (RSI). The 3D flow simulation with an acoustic model, which couples the RSI and PR phenomena, would predict better results for understanding the problem than the simplified one-dimensional (1D) method.

PIV Validation of Blood-heart Valve Leaflet Interaction Modelling

2007 ◽  
Vol 30 (7) ◽  
pp. 640-648 ◽  
Author(s):  
R. Kaminsky ◽  
K. Dumont ◽  
H. Weber ◽  
M. Schroll ◽  
P. Verdonck
Keyword(s):  
Shear Stress ◽  
Heart Valve ◽  
Cfd Simulation ◽  
Flow Simulation ◽  
Data Sets ◽  
Arbitrary Lagrangian Eulerian ◽  
Velocity Magnitude ◽  
Image Velocimetry ◽  
Interaction Modelling ◽  
In Series

The aim of this study was to validate the 2D computational fluid dynamics (CFD) results of a moving heart valve based on a fluid-structure interaction (FSI) algorithm with experimental measurements. Firstly, a pulsatile laminar flow through a monoleaflet valve model with a stiff leaflet was visualized by means of Particle Image Velocimetry (PIV). The inflow data sets were applied to a CFD simulation including blood-leaflet interaction. The measurement section with a fixed leaflet was enclosed into a standard mock loop in series with a Harvard Apparatus Pulsatile Blood Pump, a compliance chamber and a reservoir. Standard 2D PIV measurements were made at a frequency of 60 bpm. Average velocity magnitude results of 36 phase-locked measurements were evaluated at every 10° of the pump cycle. For the CFD flow simulation, a commercially available package from Fluent Inc. was used in combination with in-house developed FSI code based on the Arbitrary Lagrangian-Eulerian (ALE) method. Then the CFD code was applied to the leaflet to quantify the shear stress on it. Generally, the CFD results are in agreement with the PIV evaluated data in major flow regions, thereby validating the FSI simulation of a monoleaflet valve with a flexible leaflet. The applicability of the new CFD code for quantifying the shear stress on a flexible leaflet is thus demonstrated. (Int J Artif Organs 2007; 30: 640–8)

scholarly journals Distribution of Pressure Fluctuations in a Prototype Pump Turbine at Pump Mode

2014 ◽  
Vol 6 ◽  
pp. 923937 ◽  
Author(s):  
Yuekun Sun ◽  
Zhigang Zuo ◽  
Shuhong Liu ◽  
Jintao Liu ◽  
Yulin Wu
Keyword(s):  
Mass Flow ◽  
Pressure Fluctuations ◽  
Dominant Frequency ◽  
Pump Mode ◽  
Pump Turbine ◽  
Guide Vanes ◽  
Path Direction ◽  
Mass Flow Rates ◽  
Operating Points ◽  
Spiral Casing

Pressure fluctuations are very important characteristics in pump turbine's operation. Many researches have focused on the characteristics (amplitude and frequencies) of pressure fluctuations at specific locations, but little researches mentioned the distribution of pressure fluctuations in a pump turbine. In this paper, 3D numerical simulations using SSTk − ω turbulence model were carried out to predict the pressure fluctuations distribution in a prototype pump turbine at pump mode. Three operating points with different mass flow rates and different guide vanes’ openings were simulated. The numerical results show how pressure fluctuations at blade passing frequency (BPF) and its harmonics vary along the whole flow path direction, as well as along the circumferential direction. BPF is the first dominant frequency in vaneless space. Pressure fluctuation component at this frequency rapidly decays towards upstream (to draft tube) and downstream (to spiral casing). In contrast, pressure fluctuations component at 3BPF spreads to upstream and downstream with almost constant amplitude. Amplitude and frequencies of pressure fluctuations also vary along different circumferential locations in vaneless space. When the mass flow and guide vanes’ opening are different, the distribution of pressure fluctuations along the two directions is different basically.

scholarly journals Placental vascular abnormalities in the mouse alter umbilical artery wave reflections

2019 ◽  
Vol 316 (3) ◽  
pp. H664-H672 ◽  
Author(s):  
Lindsay S. Cahill ◽  
Yu-Qing Zhou ◽  
Johnathan Hoggarth ◽  
Lisa X. Yu ◽  
Anum Rahman ◽  
...  
Keyword(s):  
Antiretroviral Therapy ◽  
Reflection Coefficient ◽  
Umbilical Artery ◽  
Wave Reflection ◽  
Pressure Waves ◽  
Combination Antiretroviral Therapy ◽  
Wave Reflections ◽  
Vascular Architecture ◽  
Vascular Abnormalities ◽  
The Relationship

Current methods to detect placental vascular pathologies that monitor Doppler ultrasound changes in umbilical artery (UA) pulsatility have only moderate diagnostic utility, particularly in late gestation. In fetal mice, we recently demonstrated that reflected pressure waves propagate counter to the direction of flow in the UA and proposed the measurement of these reflections as a means to detect abnormalities in the placental circulation. In the present study, we used this approach in combination with microcomputed tomography to investigate the relationship between altered placental vascular architecture and changes in UA wave reflection metrics. Fetuses were assessed at embryonic day (E) 15.5 and E17.5 in control C57BL6/J mice and dams treated with combination antiretroviral therapy (cART), a known model of fetal growth restriction. Whereas the reflection coefficient was not different between groups at E15.5, it was 27% higher at E17.5 in cART-treated mice compared with control mice. This increase in reflection coefficient corresponded to a 36% increase in the total number of vessel segments, a measure of overall architectural complexity. Interestingly, there was no difference in UA pulsatility index between groups, suggesting that the wave reflections convey information about vascular architecture that is not captured by conventional ultrasound metrics. The wave reflection parameters were found to be associated with the morphology of the fetoplacental arterial tree, with the area ratio between the UA and first branch points correlating with the reflection coefficient. This study highlights the potential for wave reflection to aid in the noninvasive clinical assessment of placental vascular pathology. NEW & NOTEWORTHY We used a novel ultrasound methodology based on detecting pulse pressure waves that propagate along the umbilical artery to investigate the relationship between changes in wave reflection metrics and altered placental vascular architecture visualized by microcomputed tomography. Using pregnant mice treated with combination antiretroviral therapy, a model of fetal growth restriction, we demonstrated that reflections in the umbilical artery are sensitive to placental vascular abnormalities and associated with the geometry of the fetoplacental tree.

scholarly journals Distribution of the external pressure coefficients on the elliptic tower: experimental measurement compared with numerical modelling

2020 ◽  
Vol 313 ◽  
pp. 00047
Author(s):  
Michal Franek ◽  
Marek Macák ◽  
Oľga Hubová
Keyword(s):  
Cfd Simulation ◽  
Flow Simulation ◽  
External Pressure ◽  
Wind Pressure ◽  
Wind Flow ◽  
Suitable Model ◽  
Pressure Coefficients ◽  
Building Model ◽  
High Rise ◽  
Experimental Values

The wind flow around the elliptical object was investigated experimentally in the BLWT wind tunnel in Bratislava and subsequently solved by computer wind flow simulation. On a high-rise building model, the external wind pressure coefficients were evaluated for different wind directions and then compared with the numerical CFD simulation in ANSYS, where different models of turbulence and mesh types were used. The aim of the article was to evaluate and compare the obtained values and after analysing the results to choose the most suitable model of turbulence and mesh types, which showed the smallest deviations from the experimental values.

3D Quasi-Unsteady Flow Simulation in a Centrifugal Pump: Comparison With the Experimental Results

2004 ◽  
Author(s):  
Miguel Asuaje ◽  
Farid Bakir ◽  
Andres Tremante ◽  
Ricardo Noguera ◽  
Robert Rey
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Cfd Simulation ◽  
Pressure Fluctuations ◽  
Pressure Sensors ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Numerical Predictions ◽  
Radial Thrust ◽  
Unsteady Flow Simulation

A 3D-CFD simulation of the impeller and volute casing of a centrifugal pump has been performed using commercial codes CFX 5.5 and CFX-TASCflow 2.12. The pump has an specific speed of 32 (metric units) and an outside impeller diameter of 400 mm. First, a 3D-flow simulation for the isolated impeller with a structured grid is presented. A sensitivity analysis regarding grid quality and turbulence models were also performed. A 3D quasi-unsteady flow simulation of the impeller-volute assembly is presented, as well. This flow simulation was carried out for several impeller blades and volute tongue relative positions. As a result, the radial thrust on the pump shaft were calculated for different flow rates. Experimental test were carried out in order to compare theoretical pressure fluctuations with the experimental ones measured by various unsteady pressure sensors placed on the impeller shroud and volute. The qualitative and quantitative results ratify numerical predictions.

Validation of CFD and Simplified Models With Experimental Data for Multiphase Flow in Bends

2013 ◽  
Author(s):  
E. Nennie ◽  
S. P. C. Belfroid ◽  
T. S. D. O’Mahoney
Keyword(s):  
Multiphase Flow ◽  
Analytical Model ◽  
Structural Model ◽  
Structural Integrity ◽  
Cfd Simulation ◽  
Flow Simulation ◽  
Computational Time ◽  
Frequency Spectra ◽  
Pipe System ◽  
Measurement Results

In this paper details of the measurement results of the forces on the bends in a 4″ setup are compared to two models. The first model is a simple analytical model and is used to estimate the forces. In the second model, CFD is used. In the experiments only resulting forces, including upstream and downstream bends and mechanical resonance and interaction is measured. The goal of the CFD was to discriminate between flow and mechanics and to evaluate the influence of a flow disturbance as a result of a bend on the force on a downstream second bend. For the simplified analytical model the amplitudes are underestimated, but the frequency spectra look very reasonable in case of the slug flow regime. The main advantage of the simplified analytical model is that the computational time is in the order of seconds, but the accuracy is still reasonable for the use in an engineering approach of determining the structural integrity of the complete pipe system. For the CFD the shape of the force function is similar to the experiments. The CFD results indicate that the forces on the second downstream bend are also measured on the first upstream bend. The accuracy of the CFD simulation is the advantage of this model, but the computational time is very long, especially if the multiphase flow simulation is coupled to the structural model.

CFD Simulation of Two-Phase Flow in a Downhole Venturi Meter

2011 ◽  
Vol 130-134 ◽  
pp. 3644-3647
Author(s):  
Ding Feng ◽  
Si Huang ◽  
Yu Hui Guan ◽  
Wei Guo Ma
Keyword(s):  
Optimal Design ◽  
Pressure Drop ◽  
Flow Field ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Flow Simulation ◽  
Phase Flow ◽  
Feed Flow Rate ◽  
Two Phase ◽  
Oil Water

This work performs an oil-water two-phase flow simulation in a downhole Venturi meter to investigate the flow field and pressure characteristics with different flow and oil-water ratios. The relation between the pressure drop and the feed flow rate in the flowmeter is investigated for its optimal design.

Investigation of Numerical Stability of Pipe-Flow Simulation under Strong Oscillation of Inlet Velocity

2012 ◽  
Vol 591-593 ◽  
pp. 801-805
Author(s):  
Xiao Gang Yi ◽  
Chao Luo ◽  
Dong Li ◽  
Zuo Liang Zhang
Keyword(s):  
Cfd Simulation ◽  
Fuel Injection ◽  
Flow Simulation ◽  
Numerical Instability ◽  
Cavitation Model ◽  
Significant Information ◽  
Inlet Velocity ◽  
Cyclic Oscillation ◽  
Volume Method ◽  
Pipe Vibration

Pressure distribution inside a fluid-conveying pipe is significant information for reasonable pipe design or mitigation of pipe vibration caused by fluid impact. Generally, a steady solution of pressure information can be obtained based on traditional CFD simulation if the inlet velocity of pipe is time independent. Unfortunately, strong oscillation of inlet velocity often happens in real engineering operations such as fuel injection or pumping process. This paper focuses on the simulation of the transient phenomenon of fluid flow inside a pipe based on the time-dependant inlet velocity. A 2D numerical pipe with an elbow is built based on Eulerian scheme and structured mesh. It is found that numerical instability occurs and convergence becomes difficult if inlet velocity presents obvious cyclic oscillation with big amplitude. Numerical oscillation increases especially when inlet velocity decreases from a big value to zero. Traditional finite volume method and cavitation model are tried and numerical results show that the convergence can be improved evidently based on cavitation model although numerical instability can not be overcome completely.

Structure Vibration of Hydropower House Induced by Francis Turbine Basing on CFD

2008 ◽  
Author(s):  
Guangjie Peng ◽  
Liang Qin ◽  
Zhengwei Wang ◽  
Huijing Tian ◽  
Yongyao Luo
Keyword(s):  
Guide Vane ◽  
Flow Simulation ◽  
Fem Analysis ◽  
Francis Turbine ◽  
Test Results ◽  
Hydropower House ◽  
Prototype Test ◽  
Hydraulic Load ◽  
Structure Vibration ◽  
Spiral Casing

The method of CFD is adopted to carry out 3-D unsteady turbulent flow simulation through the whole flow passage of 2# Francis turbine in Wanjiazhai hydropower station. The flow fields of spiral casing, stay vane, guide vane, runner, and tail tube are obtained. The pressure fluctuation of tail tube is also acquired and compared with the prototype test results in time domain and frequency domain. It shows that the numerical results and the experimental results are well identical. On the base, the problems of load distribution in the couple boundary between flow field of turbine and structure field of house and of hydraulic load transferring to machinery foundation by shaft are investigated. Consequently it achieves dynamic analogy of hydraulic load in hydropower house FEM analysis successfully. It provides method of analyzing hydropower house vibration accurately.

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