scholarly journals Numerical Study on the Characteristics of Pressure Fluctuations in an Axial-Flow Water Pump

2014 ◽  
Vol 6 ◽  
pp. 565061 ◽  
Author(s):  
Zhi-Jun Shuai ◽  
Wan-You Li ◽  
Xiang-Yuan Zhang ◽  
Chen-Xing Jiang ◽  
Feng-Chen Li
Keyword(s):  
Numerical Simulations ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Axial Flow ◽  
Rotation Frequency ◽  
Dominant Frequency ◽  
Water Pump ◽  
Flow Induced Vibration ◽  
Impeller Blade

Flow induced vibration due to the dynamics of rotor-stator interaction in an axial-flow pump is one of the most damaging vibration sources to the pump components, attached pipelines, and equipment. Three-dimensional unsteady numerical simulations were conducted on the complex turbulent flow field in an axial-flow water pump, in order to investigate the flow induced vibration problem. The shear stress transport (SST) k-ω model was employed in the numerical simulations. The fast Fourier transform technique was adopted to process the obtained fluctuating pressure signals. The characteristics of pressure fluctuations acting on the impeller were then investigated. The spectra of pressure fluctuations were predicted. The dominant frequencies at the locations of impeller inlet, impeller outlet, and impeller blade surface are all 198 Hz (4 times of the rotation frequency 49.5 Hz), which indicates that the dominant frequency is in good agreement with the blade passing frequency (BPF). The first BPF dominates the frequency spectrum for all monitoring locations inside the pump.

Unsteady Numerical and Experimental Study of Cavitation in Axial Pump

2014 ◽  
Vol 4 (1) ◽  
pp. 55-68
Author(s):  
Mohamed Adel ◽  
Nabil H. Mostafa
Keyword(s):  
Numerical Simulation ◽  
Void Growth ◽  
High Speed ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Two Phase ◽  
Impeller Blade ◽  
Axial Pump

This paper presents an experimental and three-dimensional numerical study of unsteady, turbulent, void growth and cavitation simulation inside the passage of the axial flow pump. In this study a 3D Navier-Stokes code was used (CFDRC, 2008) to model the two-phase flow field around a four blades axial pump. The governing equations are discretized on a structured grid using an upwind difference scheme. The numerical simulation used the standard K-e turbulence model to account for the turbulence effect. The numerical simulation of void growth and cavitation in an axial pump was studied under unsteady calculating. Pressure distribution and vapor volume fraction were completed versus time at different condition. The computational code has been validated by comparing the predicated numerical results with the experiment. The predicted of cavitation growth and distribution on the impeller blade also agreed with that visualized of high speed camera.

Fluid-Structure Interaction Modeling of a Subsea Jumper Pipe

2014 ◽  
Author(s):  
Mohammad A. Elyyan ◽  
Yeong-Yan Perng ◽  
Mai Doan
Keyword(s):  
Multiphase Flow ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Fluid Structure Interaction ◽  
Flow Experience ◽  
Flow Induced Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Start Up ◽  
Interaction Modeling

Flow-induced vibration (FIV) is one of the main reasons for subsea piping failure, where subsea pipes, which typically carry multiphase flow, experience large fluctuating forces. These fluctuating forces can induce severe vibrations leading to premature piping failure. This paper presents a transient numerical study of a typical subsea M-shape jumper pipe that is carrying a gas-liquid multiphase flow subject to a slug frequency of 4.4 Hz, starting from rest to include the start-up effect as part of the study. 3-D numerical simulations were used to capture the fluid-structure interaction (FSI) and estimate pipe deformations due to fluctuating hydrodynamic forces. In this paper, two FSI approaches were used to compute the pipe deformations, two-way coupled and one-way decoupled. Analysis of the results showed that decoupled (one-way) FSI approach overestimated the peak pipe deformation by about 100%, and showed faster decay of fluctuations than coupled (two-way) FSI analysis. The assessment of resonant risk due to FIV is also discussed.

scholarly journals Numerical study of jets produced by conical wire arrays on the Magpie pulsed power generator

2010 ◽  
Vol 6 (S274) ◽  
pp. 429-432
Author(s):  
Matteo Bocchi ◽  
Jerry P. Chittenden ◽  
Andrea Ciardi ◽  
Francisco Suzuki-Vidal ◽  
Gareth N. Hall ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Pulsed Power ◽  
Astrophysical Jets ◽  
Power Generator ◽  
Wire Arrays ◽  
Pulsed Power Generator

AbstractWith the aim to model jets produced by conical wire arrays on the MAGPIE generator, and to strengthen the link between laboratory and astrophysical jets, we performed three-dimensional magneto-hydro-dynamic numerical simulations using the code GORGON and successfully reproduced the experiments. We found that a minimum resolution of ~100 μm is required to retrieve the unstable character of the jet. Moreover, arrays with less wires produce more unstable jets with stronger magnetic fields around them.

Numerical Studies on Effect of Stepped Tip Clearance Height on the Performance of Single Stage Transonic Axial Flow Compressor

2013 ◽  
Author(s):  
Pritam Batabyal ◽  
Dilipkumar B. Alone ◽  
S. K. Maharana
Keyword(s):  
Numerical Study ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Flow ◽  
Single Stage ◽  
Tip Clearance ◽  
Baseline Model ◽  
Axial Flow Compressor ◽  
Design Speed ◽  
Flow Compressor

This paper presents a numerical case study of various stepped tip clearances and their effect on the performance of a single stage transonic axial flow compressor, using commercially available software ANSYS FLUENT 14.0. A steady state, implicit, three dimensional, pressure based flow solver with SST k-Ω turbulence model has been selected for the numerical study. The stepped tip clearances have been compared with the baseline model of zero tip clearance at 70% and 100 % design speed. It has been observed that the compressor peak stage efficiency and maximum stage pressure ratio decreases as the tip clearances in the rear part are increased. The stall margin also increases with increase in tip clearance compared to the baseline model. An ‘optimum’ value of stepped tip clearance has been obtained giving peak stage compressor performance. The CFD results have been validated with the earlier published experimental data on the same compressor at 70% design speed.

Numerical Study of the Amplitude and the Convection Speed of Periodic Large-Scale Vortices in a Square Array of Cylinders Subjected to Axial Flow

2018 ◽  
Author(s):  
Laurent De Moerloose ◽  
Jeroen De Ridder ◽  
Jan Vierendeels ◽  
Joris Degroote
Keyword(s):  
Large Scale ◽  
Flow Instability ◽  
Numerical Study ◽  
Temporal Frequency ◽  
Pressure Fluctuations ◽  
Computational Cost ◽  
Axial Flow ◽  
Diameter Ratio ◽  
Convection Speed ◽  
Square Array

A square array of cylinders subjected to axial flow is commonly encountered in nuclear reactors and other heat exchangers. Large-scale vortices have been observed in the gaps between the cylinders, both experimentally and numerically. These periodic flow instabilities occur in tightly-spaced cylinder arrays and originate from the velocity difference between the gap and the subchannel regions. The pressure fluctuations caused by the coherent vortex structures are possibly a source of fretting and fatigue in the aforementioned applications. In order to quantify and comprehend this phenomenon, Large-Eddy Simulations are performed on an incompressible, Newtonian fluid flowing adiabatically through a numerical domain containing a single rigid cylinder with periodic boundary conditions, representative for a cylinder in an infinite square array. Subsequently, the temporal frequency spectrum of the wall pressure profile is calculated. The spatial autocorrelation function of this Fourier spectrum, the so-called Cross Spectral Density function, contains information regarding the amplitude and convection speed of the pressure fluctuations. It is shown that the flow instability is strongest for a pitch-over-diameter ratio of 1.03. Also, the simulations indicate that the convection speed is monotonously increasing with the pitch-over-diameter ratio. An updated model for this convection speed is proposed. Finally, it is shown that the single-cylinder approximation has its limitations, but provides valuable information with minimal computational cost.

Effect of Struts Downstream of Low Pressure Turbine on Tone Noise Generation

2020 ◽  
Author(s):  
Ravil Nigmatullin ◽  
Larisa Terenteva
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Maximum Amplitude ◽  
Low Pressure ◽  
Mode Analysis ◽  
Low Pressure Turbine ◽  
Noise Characteristics ◽  
The Impact

Abstract In the present work a numerical study of tone noise generated by the last stage of the Low Pressure Turbine (LPT) of an aircraft engine designed for a medium-haul civilian aircraft has been conducted. The impact of struts on the tone noise characteristics is estimated. The method for turbine noise calculation is based on numerical integration of the three-dimensional unsteady Reynolds averaged Navier-Stokes equations using an in-house code for multi-stage simulations. To obtain the tonal characteristics of the generated noise, the pressure pulsation field is processed using the methods of radial mode analysis. The calculated pressure fluctuations contain all possible components of the frequency-modal spectrum, which allows us to determine profile of the generated tone noise and find propagating modes with maximum amplitude. The calculations showed that the presence of struts leads to a scattering effect, which manifests as an increase in the number of generated circumferential modes. These circumferential modes propagate both downstream and upstream and increase the total level of tone noise. The amplitudes of circumferential modes related to two different types of the interaction, rotor-stator and rotor-struts, are compared.

A Numerical Study on the Structure of Tip Clearance Flow in a Highly Forward-Swept Axial-Flow Fan

2002 ◽  
Author(s):  
Gong Hee Lee ◽  
Je Hyun Baek
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Streamwise Velocity ◽  
Tip Clearance ◽  
Wake Flow ◽  
Axial Flow Fan ◽  
Step Method ◽  
Fractional Step Method ◽  
Tip Clearance Flow

A three-dimensional Navier-Stokes analysis was performed to investigate the tip clearance flows in a highly forward-swept axial flow fan operating at design condition. The numerical solution was based on a fractional step method, and two-layer k-ε model was used to obtain the eddy viscosity. The tip leakage vortex decayed very quickly inside the blade passage and, thus, no distinct leakage vortex appeared behind trailing edge. The main reason was the severe decrease of the streamwise velocity of the vortex. Also the interaction of the vortex with the casing boundary layer and the through-flow were other possibilities of the fast decay of the vortex. Comparison between the numerical results and LDV measurements data indicated that the complex viscous flow patterns inside the tip region as well as the wake flow could be properly predicted, but more refinement in numerical aspects are needed.

Scaling the Performance of Micro-Fans

2003 ◽  
Author(s):  
R. Grimes ◽  
E. Walsh ◽  
S. Kunz ◽  
M. Davies ◽  
D. Quin
Keyword(s):  
Numerical Simulations ◽  
Radial Flow ◽  
Three Dimensional ◽  
Axial Flow ◽  
Scaling Analysis ◽  
Electronic Systems ◽  
Two Dimensional ◽  
Local Loss ◽  
Micro Scale ◽  
Fan Performance

Pumping of liquids and gases in micro fluidic systems has been the focus of much attention in recent times. Miniaturisation of traditional rotating pumps such as axial and radial flow designs, has been limited by the fabrication techniques employed. As a result of these limitations, the geometry of the majority of rotating micro pumps has been two-dimensional. This paper addresses issues of scaling in micro axial flow fans. The anticipated primary application will be in cooling compact electronic systems, but the results are applicable to a much wider range of pumping applications. Using novel fabrication techniques a series of geometrically similar three dimensional fans were fabricated, ranging in size from the macro to the micro scale. Experimental techniques are described which will be used for the characterisation of these fans. A scaling analysis is used to show how reduced fan scale causes increased local loss as fan dimensions are reduced to the micro scale. Numerical simulations of flow in the channels between the fan blades were performed to investigate the validity of the scaling theory, the results of which give confidence in the scaling analysis. The fundamental finding of this work is that a reduction in scale is accompanied by a reduction in efficiency and thus fan performance.

Rotating Stall in a Single-Stage Axial Flow Compressor

1996 ◽  
Vol 118 (2) ◽  
pp. 189-196 ◽  
Author(s):  
C. A. Poensgen ◽  
H. E. Gallus
Keyword(s):  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Axial Flow ◽  
Transition Process ◽  
Measured Data ◽  
Rotating Stall ◽  
Single Stage ◽  
Axial Flow Compressor ◽  
Flow Compressor ◽  
Modal Route

This paper describes the results on an experimental investigation of rotating stall flow inside a single-stage axial flow compressor. Tests were carried out in two steps. First, measurements were taken to investigate the transition process into rotating stall. The compressor starts into rotating stall via the “modal route” with a single rotating stall cell. Further throttling yields to a two-cell shape followed by a significant outlet pressure drop. Both transition processes are discussed in detail. Results from the Moore–Greitzer theory are compared with measured data. In a second step, measurements were taken to determine the three-dimensional unsteady structure of a fully developed rotating-stall cell. Based on unsteady total pressure and three-dimensional hot-wire data, the structure of a rotating stall cell could be resolved in detail upstream and downstream of the rotor. A typical part-span stall was found. By inserting the measured data into the Euler equations, convective and unsteady effects on the pressure fluctuations can be isolated. A dependence between the radial flow inside the stall cell and the unsteady flow accelerations was found.

Numerical study of acoustic radiation due to a supersonic turbulent boundary layer

2014 ◽  
Vol 746 ◽  
pp. 165-192 ◽  
Author(s):  
Lian Duan ◽  
Meelan M. Choudhari ◽  
Minwei Wu
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Numerical Simulations ◽  
Surface Pressure ◽  
Free Stream ◽  
Acoustic Radiation ◽  
Numerical Study ◽  
Near Field ◽  
Pressure Fluctuations ◽  
Spatial Coherence

AbstractDirect numerical simulations are used to examine the pressure fluctuations generated by fully developed turbulence in a Mach 2.5 turbulent boundary layer, with an emphasis on the acoustic fluctuations radiated into the free stream. Single- and multi-point statistics of computed surface pressure fluctuations show good agreement with measurements and numerical simulations at similar flow conditions. Consistent with spark shadowgraphs obtained in free flight, the quasi-homogeneous acoustic near field in the free-stream region consists of randomly spaced wavepackets with a finite spatial coherence. The free-stream pressure fluctuations exhibit important differences from the surface pressure fluctuations in amplitude, frequency content and convection speeds. Such information can be applied towards improved modelling of boundary layer receptivity in conventional supersonic facilities and, hence, enable a better utilization of transition data acquired in such wind tunnels. The predicted acoustic characteristics are compared with the limited available measurements. Finally, the numerical database is used to understand the acoustic source mechanisms, with the finding that the supersonically convecting eddies that can directly radiate to the free stream are confined to the buffer zone within the boundary layer.

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