scholarly journals Numerical Investigations of Unsteady Flow in a Centrifugal Pump with a Vaned Diffuser

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Olivier Petit ◽  
Håkan Nilsson
Keyword(s):  
Centrifugal Pump ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Centrifugal Impeller ◽  
Test Case ◽  
Vaned Diffuser ◽  
Pump Test ◽  
Steady Simulation ◽  
Turbulent Models ◽  
Cfd Analyses

Computational fluid dynamics (CFD) analyses were made to study the unsteady three-dimensional turbulence in the ERCOFTAC centrifugal pump test case. The simulations were carried out using the OpenFOAM Open Source CFD software. The test case consists of an unshrouded centrifugal impeller with seven blades and a radial vaned diffuser with 12 vanes. A large number of measurements are available in the radial gap between the impeller and the diffuse, making this case ideal for validating numerical methods. Results of steady and unsteady calculations of the flow in the pump are compared with the experimental ones, and four different turbulent models are analyzed. The steady simulation uses the frozen rotor concept, while the unsteady simulation uses a fully resolved sliding grid approach. The comparisons show that the unsteady numerical results accurately predict the unsteadiness of the flow, demonstrating the validity and applicability of that methodology for unsteady incompressible turbomachinery flow computations. The steady approach is less accurate, with an unphysical advection of the impeller wakes, but accurate enough for a crude approximation. The different turbulence models predict the flow at the same level of accuracy, with slightly different results.

Effects of Different Turbulence Models on Three-Dimensional Unsteady Cavitating Flows in the Centrifugal Pump and Performance Prediction

2019 ◽  
Vol 20 (3-4) ◽  
pp. 487-509 ◽  
Author(s):  
Ahmed Ramadhan Al-Obaidi
Keyword(s):  
Centrifugal Pump ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Experimental Results ◽  
Centrifugal Pumps ◽  
Operation Condition ◽  
Sst Model ◽  
And Performance ◽  
Turbulent Models

AbstractIn centrifugal pumps, it is important to select appropriate turbulence model for the numerical simulation in order to obtain reliable and accurate results. In this work, ten turbulence models in 3-D transient simulation for the centrifugal pump are chosen and compared. The pump performance is validated with experimental results. The numerical results reveal that the SST turbulence model was closer to the experimental results in predicting head. In addition, the pressure variation trend for the ten models is very similar which increases and then decreases from the inlet to outlet of the pump along the streamline. The SST k-ω model predicts the performance of the pump was more accurately than other turbulent models. Furthermore, the results also found that the error is the least at design operation condition 300(l/min), which is around 1.98 % for the SST model and 2.14 % and 2.38 % for the LES and transition omega model. Within 7.61 %, the errors at higher flow rate 350(l/min) for SST. The error for SST model is smaller as compared to different turbulent models. For the Realizable k-ɛ model, the errors fluctuate were more high than other models.

A Simulation of the Unsteady Interaction of a Centrifugal Impeller With its Vaned Diffuser: Flows Analysis

1994 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
High Loss ◽  
Swirl Angle ◽  
Unsteady Interaction ◽  
Unsteady Effects

The aim of this paper is to help advance our understanding of the complex, three-dimensional, unsteady flow associated with the interaction of a splattered centrifugal impeller and its vaned diffuser. A time-resolved simulation is presented of the Krain stage performed using a time-accurate, 3D, unstructured mesh, solution-adaptive Navier-Stokes solver. The predicted flowfield, compared with experiment where available, displays a complex, unsteady interaction especially in the neighbourhood of the diffuser entry zone which experiences large periodic flow unsteadiness. Downstream of the throat, although the magnitude of this unsteadiness diminishes rapidly, the flow has a highly distorted three-dimensional character. The loss levels in the diffuser are then investigated to try and determine how time-mean loss levels compare with the levels expected from “equivalent” steady flow analysis performed by using the circumferentially averaged exit flow from the impeller as inlet to the diffuser. It is concluded that little loss could be attributed directly to unsteady effects but rather that the principle cause of the rather high loss levels observed in the diffuser is the strong spanwise distortion in swirl angle at inlet which initiates a strong hub/comer stall.

scholarly journals Numerical Investigation of Boundary Layers in Wet Steam Nozzles

2016 ◽  
Author(s):  
Jörg Starzmann ◽  
Fiona R. Hughes ◽  
Alexander J. White ◽  
Marius Grübel ◽  
Damian M. Vogt
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Side Wall ◽  
Turbulence Models ◽  
Test Case ◽  
Wet Steam ◽  
Compression Waves ◽  
Wall Boundary Layer ◽  
Two Dimensional Flow

Condensing nozzle flows have been used extensively to validate wet steam models. Many test cases are available in the literature and in the past a range of numerical studies have dealt with this challenging task. It is usually assumed that the nozzles provide a one- or two-dimensional flow with a fully turbulent boundary layer. The present paper reviews these assumptions and investigates numerically the influence of boundary layers on dry and wet steam nozzle expansions. For the narrow nozzle of Moses and Stein it is shown that the pressure distribution is significantly affected by the additional blockage due to the side wall boundary layer. Comparison of laminar and turbulent flow predictions for this nozzles suggests that laminar-turbulent transition only occurs after the throat. Other examples are the Binnie nozzle and the Moore nozzles for which it is known that sudden changes in wall curvature produce expansion and compression waves that interact with the boundary layers. The differences between two- and three-dimensional calculations for these cases and the influence of laminar and turbulent boundary layers are discussed. The present results reveal that boundary layer effects can have a considerable impact on the mean nozzle flow and thus on the validation process of condensation models. In order to verify the accuracy of turbulence modelling a test case that is not widely known internationally is included within the present study. This experimental work is remarkable because it includes boundary layer data as well as the usual pressure measurements along the nozzle centreline. Predicted and measured boundary layer profiles are compared and the effect of different turbulence models is discussed. Most of the numerical results are obtained with the in-house wet steam RANS-solver, Steamblock, but for the purpose of comparison the commercial program ANSYS CFX is also used, providing a wider range of standard RANS-based turbulence models.

Using the DLR-F6 Aircraft Model for the Evaluation of the Academic CFD Code “Galatea”

2014 ◽  
Author(s):  
Georgios N. Lygidakis ◽  
Ioannis K. Nikolos
Keyword(s):  
Large Fraction ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Fluid Flows ◽  
Wind Tunnels ◽  
Navier Stokes ◽  
Test Case ◽  
Tetrahedral Elements ◽  
Computational Performance ◽  
Volume Method

Nowadays, the research in the aerospace scientific field relies strongly on CFD (Computational Fluid Dynamics) algorithms, avoiding (initially at least) a large fraction of the extremely time and money consuming experiments in wind tunnels. In this paper such a recently developed academic CFD code, named Galatea, is presented in brief and validated against a benchmark test case. The prediction of compressible fluid flows is succeeded by the relaxation of the Reynolds Averaged Navier-Stokes (RANS) equations, along with appropriate turbulence models (k-ε, k-ω and SST), employed on three-dimensional unstructured hybrid grids, composed of prismatic, pyramidical and tetrahedral elements. For the discretization of the computational field a node-centered finite-volume method is implemented, while for improved computational performance Galatea incorporates an agglomeration multigrid methodology and a suitable parallelization strategy. The proposed algorithm is evaluated against the Wing-Body (WB) and the Wing-Body-Nacelles-Pylons (WBNP) DLR-F6 aircraft configurations, demonstrating its capability for a good performance in terms of accuracy and geometric flexibility.

scholarly journals CFD Modelling of Naturally Ventilated Double Skin Façades: Comparisons among 2D and 3D Models

2021 ◽  
Vol 65 (2-4) ◽  
pp. 330-336
Author(s):  
Camilla Lops ◽  
Nicola Germano ◽  
Sabino Matera ◽  
Valerio D’Alessandro ◽  
Sergio Montelpare
Keyword(s):  
Energy Requirement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
3D Models ◽  
Computational Effort ◽  
Correct Prediction ◽  
Cfd Modelling ◽  
Double Skin ◽  
Cfd Analyses ◽  
Double Skin Facades

Nowadays, Double Skin Façades (DSFs) are popular technologies adopted for both new and existing buildings. Since their introduction, new configurations and materials started to be tested to improve the DSF energy behaviour and function. Such complex technologies, able to improve comfort conditions of occupied spaces and decrease building energy requirement, are strictly related to the design phase that should be carefully evaluated. The correct prediction of air fluxes inside the DSF cavity, in fact, is highly influenced by the adopted analysis hypothesis and settings. Moreover, the absence of multiple experimental campaigns and empirical validations in the sector represents the major concerns for scientists and researchers. Among the possible numerical approaches for studying DSFs, Computational Fluid Dynamics (CFD) analyses confirm to be the most suitable solution. The CFD modelling activity presented in this paper intends to compare various Double Façade configurations by adopting bi- and three-dimensional domains and different turbulence models. According to the obtained results, 2D simulations can predict airflows inside and around the DSF channel with good approximation and reasonable computational effort. Moreover, the velocity profiles estimated by the turbulence formulations are in good accordance, underling only a few slight variations in proximity to the DSF layers.

scholarly journals Numerical Simulation of the Sound Field of a Five-Stage Centrifugal Pump with Different Turbulence Models

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1777 ◽  
Author(s):  
Wang ◽  
Liu ◽  
Wang ◽  
Zhou ◽  
Jiang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Sound Field ◽  
Turbulence Models ◽  
Stress Transfer ◽  
External Noise ◽  
Vaned Diffuser ◽  
Noise Characteristics ◽  
Vibration Experiment ◽  
Response Method

To study the influence of the turbulence model on the sound field of pumps, the standard k-ε, Re-normalization Group (RNG) k-ε and Shear Stress Transfer (SST) k-ω models were employed to simulate flow and sound fields of a five-stage centrifugal pump with a vaned-diffuser. The vibration characteristics of the pump were simulated with the modal response method. A vibration experiment in the pump was carried out to verify the feasibility of the numerical simulation of the hydrodynamic noise in the pump. Results show that in the spectrum of internal and external noise, the peak value appears at axial passing frequency (APF) and its harmonic frequency. Compared with the standard k-ε model, the RNG k-ε and SST k-ω models show good consistence with the noise characteristics of experimental results, indicating the characteristic frequency and revealing the approximate behavior of the sound field in the pump. In general, the simulation of the sound field based on the RNG k-ε model is most appropriate for the multistage centrifugal pump with a vaned-diffuser.

Numerical Prediction of a Multistage Centrifugal Pump Performance With Stationary and Moving Mesh

2015 ◽  
Author(s):  
Alessandro Nocente ◽  
Tufan Arslan ◽  
Torbjørn K. Nielsen
Keyword(s):  
Centrifugal Pump ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Transient State ◽  
Computational Effort ◽  
Phase Flow ◽  
Two Phase ◽  
Ansys Fluent ◽  
Performance Report

The present work reviews a comparison between calculations of a steady and unsteady three dimensional (3D) flow past the diffuser channels of a centrifugal pump. The commercial software ANSYS Fluent has been used. The considered domain is one of the three stages, since each has exactly the same design. In the first part, simulations are carried out at the best efficiency point (BEP) both steady and transient state, single phase flow and four different turbulence models. Results are compared with the performance report from the manufacturer. In the second part, only the realizable k-ε turbulence model has been taken into account. The simulations have been repeated for different mass flows and the results were again compared with the data from the manufacturer. The comparison performed in the first part shows that integral quantities results are not sensibly influenced by the turbulence model. The comparison at different mass flow shows that the steady state simulations demonstrated to be a good approximation of the transient state, always containing the error within an acceptable limit. The minor computational effort needed makes it attractive to be used for further investigations which will involve two-phase flow studies on the same pump.

Aerodynamic Optimization Design of Vaned Diffusers for the 100 kW Micro Gas Turbine’s Centrifugal Compressor

2008 ◽  
Author(s):  
Guang Xi ◽  
Zhiheng Wang ◽  
Chunmei Zhang ◽  
Minjian Yuan
Keyword(s):  
Centrifugal Compressor ◽  
Surrogate Model ◽  
High Speed ◽  
Optimization Design ◽  
Performance Test ◽  
Three Dimensional ◽  
Centrifugal Impeller ◽  
Aerodynamic Optimization ◽  
Vaned Diffuser ◽  
Practical Engineering

In this paper the design optimization of vaned diffuser for the 100kW microturbine’s centrifugal compressor is carried out. The forward-loaded and the conventional airfoil diffusers are respectively redesigned based on the surrogate model and the three dimensional viscous flow analyses. The objective of the optimization is to redesign the diffuser that assures, for a given operating condition of the centrifugal impeller, the stage isentropic efficiency to be highest. Using the surrogate model the optimization process is accelerated and the 3D flow analysis’s application to the practical engineering design is efficiently realized. To validate the optimization result, the compressor stage performance test is performed on a high speed centrifugal compressor test rig with one original diffuser and its redesigned, respectively.

Influence of Rotation on Dynamic Stall

2013 ◽  
Vol 58 (3) ◽  
pp. 1-9 ◽  
Author(s):  
A. D. Gardner ◽  
K. Richter
Keyword(s):  
Three Dimensional ◽  
Time History ◽  
Turbulence Models ◽  
Dynamic Stall ◽  
Test Case ◽  
Test Cases ◽  
Pitching Moment ◽  
Pitching Motion ◽  
Rotating Blade ◽  
Wind Tunnel Data

A computational investigation of the effect of rotation on two-dimensional (2D) deep dynamic stall has been undertaken, showing that the effect of rotation is to reduce the severity of the pitching moment peak and cause earlier reattachment of the flow. A generic single blade rotor geometry was investigated, which had a pitching oscillation around the quarter-chord axis while in hover, causing angle-driven dynamic stall. The results at the midpoint of the blade have the same Mach number (0.31), Reynolds number (1.15 × 106), and pitching motion (α = 13° ± 7°) as a dynamic stall test case for which significant experimental wind tunnel data and 2D computations exist. The rotating blade is compared with 2D computations and computations using the same blade without rotation at Mach 0.31 and with the same pitching motion. All test cases involve geometries propagating into undisturbed flow with no downwash. The three-dimensional (3D) grid computed without rotation had lower lift at the reference section than for a 2D computation with the same geometric angle of attack time history, and the lift overshoot classically observed for Spalart–Allmaras turbulence models during 2D dynamic stall was significantly reduced in the 3D case. Rotation reduced the strength of the dynamic stall vortex, which reduced the accompanying pitching moment peak by 25%.

The Influence of Vaned Diffuser Outlet Diameters on Operating Performance of a Single-Stage Centrifugal Pump

2018 ◽  
Author(s):  
Xiangyuan Zhu ◽  
Fen Lai ◽  
Liping Zhu ◽  
Guojun Li
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Numerical Approach ◽  
Radial Force ◽  
Hydrodynamic Performance ◽  
Stable Operation ◽  
Vaned Diffuser

To enhance the efficiency and stable operation, the unsteady pressure fluctuations in a centrifugal pump and the radial force on an impeller are investigated for three different vaned diffuser outlet diameters. The steady-state hydrodynamic performance of the centrifugal pump with three different vaned diffuser outlet diameters was experimentally measured. Numerical simulations were used to obtain the hydrodynamic performance of the experimental centrifugal pump based on the Reynolds-averaged Navier-Stokes (RANS) and turbulence models. The numerical results of the hydrodynamic performance were in agreement with the experimental data. The accuracy of the utilized numerical approach was demonstrated. The unsteady flow characteristics of the centrifugal pump were numerically studied. With increasing diffuser vane outlet diameter, the flow field within the volute became more non-uniform, and the pressure fluctuation was more drastic. Moreover, because of the influence of the non-uniform flow field and the pressure fluctuation, the radial force on the impeller increased.

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