Investigation of Periodically Unsteady Flow in a Radial Pump by CFD Simulations and LDV Measurements

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Jianjun Feng ◽  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Unsteady Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Measurement Data ◽  
Load Condition ◽  
Navier Stokes ◽  
Complex Flow ◽  
Data Set ◽  
Vaned Diffuser ◽  
Radial Pump

The periodically unsteady flow fields in a low specific speed radial diffuser pump have been investigated both numerically and experimentally for the design condition (Qdes) and also one part-load condition (0.5Qdes). Three-dimensional, unsteady Reynolds-averaged Navier–Stokes equations are solved on high-quality structured grids with the shear stress transport turbulence model by using the CFD (computational fluid dynamics) code CFX-10. Furthermore, two-dimensional laser Doppler velocimetry (LDV) measurements are successfully conducted in the interaction region between the impeller and the vaned diffuser, in order to capture the complex flow with abundant measurement data and to validate the CFD results. The analysis of the obtained results has been focused on the behavior of the periodic velocity field and the turbulence field, as well as the associated unsteady phenomena due to the unsteady interaction. In addition, the comparison between CFD and LDV results has also been addressed. The blade orientation effects caused by the impeller rotation are quantitatively examined and detailedly compared with the turbulence effect. This work offers a good data set to develop the comprehension of the impeller-diffuser interaction and how the flow varies with relative impeller position to the diffuser in radial diffuser pumps.

A 3D Unsteady Flow Analysis in a Doubly Constricted Tube

2000 ◽  
Author(s):  
B. V. Rathish Kumar ◽  
T. Yamaguchi ◽  
H. Liu ◽  
R. Himeno
Keyword(s):  
Pressure Drop ◽  
Unsteady Flow ◽  
Stokes Equations ◽  
Vortex Formation ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
In Series ◽  
3D Unsteady Flow

Abstract Unsteady flow dynamics in a doubly constricted vessel is analyzed by using a time accurate Finite Volume solution of three dimensional incompressible Navier-Stokes equations. Computational experiments are carried out for various values of Reynolds number in order to assess the criticality of multiple mild constrictions in series and also to bring out the subtle 3D features like vortex formation. Studies reveal that pressure drop across a series of mild constrictions can get physiologically critical. Further this pressure drop is found to be sensitive to the spacing between the constrictions and also to the oscillatory nature of the inflow profile.

Calculation of Unsteady Flow in a Centrifugal Pump With Vaned Diffuser Using Staggered and Collocated Grid Methods

2009 ◽  
Author(s):  
D. de Kleine ◽  
B. P. M. van Esch ◽  
J. G. M. Kuerten ◽  
A. W. Vreman
Keyword(s):  
Unsteady Flow ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Flow Simulation ◽  
Simulation Software ◽  
Staggered Grid ◽  
Centrifugal Pumps ◽  
Vaned Diffuser ◽  
Collocated Grid ◽  
Radial Pump

For the design of turbomachines like compressors, turbines, fans, and centrifugal pumps, more and more use is made of commercially available flow simulation software. To the authors best knowledge, in all cases discretization schemes based on a collocated grid are used. However, using a collocated grid method, the incompressible Navier-Stokes equations can suffer from odd-even decoupling. The adaptations necessary to suppress odd-even decoupling in incompressible flows result in calculations which are either less accurate or more time-consuming, especially for unsteady flows. In this paper we apply an alternative method based on a staggered-grid approach. The method is ideally suited for calculating unsteady incompressible flow on highly non-uniform block-structured grids. The unsteady flow in a radial pump with a vaned diffuser is calculated in 2D and compared with results obtained with a commercially available code. The time-dependent velocity and pressure fields are validated with experimental results available in literature.

High Fidelity Simulation of Safety Relief Valve Internal Flows

2015 ◽  
Author(s):  
Yunchao Yang ◽  
Alexis Lefebvre ◽  
Ge-Cheng Zha ◽  
Qing-Feng Liu ◽  
Jun Fan ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Complex Geometry ◽  
Three Dimensional ◽  
Weno Scheme ◽  
Inlet Pressure ◽  
Navier Stokes ◽  
Implicit Time ◽  
Complex Flow ◽  
Relief Valve ◽  
Expansion Waves

This paper presents a numerical methodology and simulation for three-dimensional transonic flow in Safety Relief Valves. Simulation of safety relief valve flows is very challenging due to complex flow paths, high pressure variation, supersonic flow with shock and expansion waves, boundary layers, etc. The 3D unsteady Reynolds averaged Navier-Stokes (URANS) equations with one-equation Spalart-Allmaras turbulence model is used. A fifth order WENO scheme for the inviscid flux and a second order central differencing for the viscous terms are employed to discretize the Navier-Stokes equations. The low diffusion E-CUSP scheme used as the approximate Riemann solver suggested by Zha et al. is utilized with the WENO scheme to evaluate the inviscid fluxes. Implicit time marching method with 2nd order temporal accuracy using Gauss-Seidel line relaxation is employed to achieve a fast convergence rate. Parallel computing is implemented to save wall clock simulation time. The valve flows with air under different inlet pressures and temperatures are successfully simulated for the full geometry with all the fine leakage channels. A 3D mesh topology is generated for the complex geometry. Detailed simulations of air flow are accomplished with inlet gauge pressure 0.5MPa and 2.1MPa. The simulated air mass flow rate agrees excellently with the experimental results with an error of 0.26% for the inlet pressure of 0.5Mpa, and an error of 2.5% for the inlet pressure of 2.1MPa. The shock waves and expansion waves downstream of the orifice are very well resolved.

Experimental and Numerical Analysis of Compressor Inlet Volutes

1997 ◽  
Author(s):  
V. Michelassi ◽  
M. Giachi
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Computer Code ◽  
Navier Stokes ◽  
Complex Flow ◽  
Flow Distortion ◽  
Navier Stokes Equations ◽  
Flow Angle ◽  
Compressor Impeller ◽  
Compressor Inlet

A typical compressor inlet volute is studied by using both experimental and numerical approaches. The highly distorted and complex flow pattern is measured in two typical configurations. Measurements include velocity, flow angle, Mach number and losses. The same geometries are analyzed by using a computer code which solves the three-dimensional Navier-Stokes equations. Turbulence effects are modeled by a two-equation turbulence model. The set of measurements shows the flow distortion induced by the volute, and also highlights how this distortion can be controlled or largely reduced by small modifications to the geometry. The computational results indicate an overall good agreement with the measurements and allow reproducing the changes in the pattern induced by the changes in volute geometry. Both the measurements and computations prove the importance of the optimal design of this component which controls the uniformity of the flow approaching the compressor impeller.

scholarly journals Simulations Of Steady Flows Through Cylindrical Geometries With And Without Local Constrictions By Multiparticle Collision Dynamics

2021 ◽  
Author(s):  
Salil K. Bedkihal
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Slip Boundary Condition ◽  
Navier Stokes ◽  
Steady Flows ◽  
Particle Interactions ◽  
Collision Dynamics ◽  
Complex Flow ◽  
Multiparticle Collision Dynamics ◽  
Complex Particle

In this thesis, a recently developed particle-based method called multiparticle collision dynamics (MPC) is used to simulate steady flows through three-dimensional constricted axisymmetric cylinders. The work is motivated by complex particle interactions in blood flow such as aggregation and the need to be able to capture these effects in physiologically relevant complex flow geometries. This is the first time that MPC dynamics has been applied to simulate flows though constrictions. The particle collisions in MPC dynamics are numerically more efficient than other particle-based simulation methods. Particle interactions with the cylinder walls are modeled using bounce-back (BB) and loss in tangential, reversal of normal (LIT) boundary conditions. BB is an analog of the macroscopic no-slip boundary condition, and LIT gives slip. Finally, an averaging procedure is employed to make a connection with the solution to the Navier-Stokes equations. Interesting differences have been found in the velocity profiles obtained using MPC with BB and LIT, compared to Navier-Stokes.

scholarly journals 3D Flow Structures and Operating Characteristic of an Industrial Fluid Coupling

1995 ◽  
Author(s):  
H. Huitenga ◽  
T. Formanski ◽  
N. K. Mitra ◽  
M. Fiebig
Keyword(s):  
Turbulence Modeling ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Complex Flow ◽  
Navier Stokes Equations ◽  
Laminar And Turbulent Flow ◽  
Fluid Coupling ◽  
Complex Flow Structure ◽  
Insight Into

A liquid circulating between an input rotor and an output rotor transmits power in a fluid coupling. Insight into the flow field is required to influence the transmission behaviour. Parameter studies of model geometries of fluid couplings were presented previously. Laminar and turbulent flow fields and characteristic curves of an actual industrial fluid coupling have been computed from the numerical solution of the three-dimensional, nonsteady Navier-Stokes equations on a body fitted rotating coordinate system. Results show the complex flow structure and vortices that determine the transported angular momentum. Comparison with measured torque suggests that the turbulence modeling by standard k-ϵ model may be inadequate at large slip.

Simulation of the Piston Driven Flow Inside a Cylinder With an Eccentric Port

1998 ◽  
Vol 120 (2) ◽  
pp. 319-326 ◽  
Author(s):  
Adrin Gharakhani ◽  
Ahmed F. Ghoniem
Keyword(s):  
Unsteady Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Vortex Method ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Solid Boundary ◽  
Surface Boundary ◽  
Time Varying ◽  
Stroke Length

A grid-free Lagrangian approach is applied to simulate the high Reynolds number unsteady flow inside a three-dimensional domain with moving boundaries. For this purpose, the Navier-Stokes equations are expressed in terms of the vorticity transport formulation. The convection and stretch of vorticity are obtained using the Lagrangian vortex method, while diffusion is approximated by the random walk method. The boundary-element method is used to solve a potential flow problem formulated to impose the normal flux condition on the boundary of the domain. The no-slip condition is satisfied by a vortex tile generation mechanism at the solid boundary, which takes into account the time-varying boundary surfaces due to, e.g., a moving piston. The approach is entirely grid-free within the fluid domain, requiring only meshing of the surface boundary, and virtually free of numerical diffusion. The method is applied to study the evolution of the complex vortical structure forming inside the time-varying semi-confined geometry of a cylinder equipped with an eccentric inlet port and a harmonically driven piston. Results show that vortical structures resembling those observed experimentally in similar configurations dominate this unsteady flow. The roll-up of the incoming jet is responsible for the formation of eddies whose axes are nearly parallel to the cylinder axis. These eddies retain their coherence for most of the stroke length. Instabilities resembling conventional vortex ring azimuthal modes are found to be responsible for the breakup of these toroidal eddies near the end of the piston motion. The nondiffusive nature of the numerical approach allows the prediction of these essentially inviscid phenomena without resorting to a turbulence model or the need for extremely fine, adaptive volumetric meshes.

Computational Modelling of Flow in Idealised and Realistic Airway Bifurcations

2004 ◽  
Author(s):  
Kevin Heraty ◽  
Nathan Quinlan
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Computational Modelling ◽  
General Purpose ◽  
Complex Flow ◽  
Data Set ◽  
Surface Modelling ◽  
Idealised Model ◽  
Complex Flow Structure ◽  
Realistic Geometry

Understanding of the flow of air and particles in the lung is essential to the success of pulmonary drug delivery. The main objective of this work is to characterize the flow in a single geometrically realistic tracheobronchial bifurcation by computational methods. Much research to date (e.g. Comer et al [1]) is based on idealised geometry put forward by Weibel [2]. Another aim of this project, therefore, is to compare observed flows in realistic and idealised geometries in order to evaluate the validity of the simplified models. A computational model of a realistic geometry was generated using images obtained from the Visible Human data set (Banvard [3]), which comprises a three-dimensional anatomical picture of a human cadaver. Extracts from this data set were used with image processing and surface modelling software to generate a geometric description of a 4th generation bifurcation. The geometry of the idealised model is based on the Weibel model A. The unsteady flow of air through the bifurcation was then modelled computationally. A general purpose computational fluid dynamics package, CFX5®, was used to predict the entire three-dimensional unsteady flow field inside the bifurcation. It was assumed that the airflow was unsteady, incompressible and laminar at the location of the 4th generation airway in the lung. Computations were carried out for a Reynolds number of 510 (based on the average velocity in the parent branch of the bifurcation). The walls of the airway were assumed to be rigid. Computational results for air flow highlight the complex flow structure in the realistic geometry, and indicate major discrepancies between realistic and idealised geometry models.

Numerical Study of the Pulsating Flow at the Tongue Region of a Centrifugal Pump for Several Flow Rates

2008 ◽  
Author(s):  
Rau´l Barrio ◽  
Jorge Parrondo ◽  
Eduardo Blanco ◽  
Joaqui´n Ferna´ndez
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Numerical Predictions ◽  
Partial Load ◽  
Flow Through

A numerical study is presented on the unsteady flow at the tongue region of a single suction volute-type centrifugal pump with a specific speed of 0.46. The flow through the pump, available at laboratory, was simulated by means of a commercial CFD software that solved the Reynolds averaged Navier-Stokes equations for three-dimensional unsteady flow (3D-URANS). A sensitivity analysis of the numerical model was carried out and the numerical predictions were compared with previous experimental results of both global and unsteady variables. Once validated, the model was used to study the flow pulsations associated to the interaction between the impeller blades and the volute tongue as a function of the flow rate, from partial load to overload. The study allowed relating the passage of the impeller blades with the tangential and radial velocity pulsations at some reference positions and with the pressure pulsations at the tongue region.

scholarly journals Simulations Of Steady Flows Through Cylindrical Geometries With And Without Local Constrictions By Multiparticle Collision Dynamics

2021 ◽  
Author(s):  
Salil K. Bedkihal
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Slip Boundary Condition ◽  
Navier Stokes ◽  
Steady Flows ◽  
Particle Interactions ◽  
Collision Dynamics ◽  
Complex Flow ◽  
Multiparticle Collision Dynamics ◽  
Complex Particle

In this thesis, a recently developed particle-based method called multiparticle collision dynamics (MPC) is used to simulate steady flows through three-dimensional constricted axisymmetric cylinders. The work is motivated by complex particle interactions in blood flow such as aggregation and the need to be able to capture these effects in physiologically relevant complex flow geometries. This is the first time that MPC dynamics has been applied to simulate flows though constrictions. The particle collisions in MPC dynamics are numerically more efficient than other particle-based simulation methods. Particle interactions with the cylinder walls are modeled using bounce-back (BB) and loss in tangential, reversal of normal (LIT) boundary conditions. BB is an analog of the macroscopic no-slip boundary condition, and LIT gives slip. Finally, an averaging procedure is employed to make a connection with the solution to the Navier-Stokes equations. Interesting differences have been found in the velocity profiles obtained using MPC with BB and LIT, compared to Navier-Stokes.

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