Numerical and Experimental Investigation on the Flow Induced Oscillations of a Single-Blade Pump Impeller

2005 ◽  
Vol 128 (4) ◽  
pp. 783-793 ◽  
Author(s):  
F.-K. Benra
Keyword(s):  
Stokes Equations ◽  
Sewage Water ◽  
Hydrodynamic Forces ◽  
Time Dependent ◽  
Outer Side ◽  
Water Pump ◽  
Pump Rotor ◽  
Wide Range ◽  
Dependent Flow ◽  
Blade Pump

This contribution is addressed to the periodically unsteady flow forces of a single-blade sewage water pump, which affect the impeller and produce radial deflections of the pump shaft. The hydrodynamic excitation forces were calculated from the time dependent flow field, which was computed by numerical simulation of the three-dimensional, viscous, time-dependent flow in the pump. A commercial computer code was used to determine the time accurate Reynolds averaged Navier-Stokes equations. The transient radial flow forces at all time steps for a complete impeller revolution affect the rotor of the single-blade pump and stimulate it to strong oscillations. To determine the influence of the vibration stimulation forces on the dynamic behavior of the pump rotor, an investigation of the rotor’s structural dynamics was accomplished. A dynamic time analysis for the pump rotor provided the dynamic answer from the structural model of the rotor under the influence of the flow forces. The hydrodynamic forces, which were calculated before, were defined as external forces and applied as the load on the rotor. The resulting impeller deflections were calculated by a transient analysis of the pump rotor system using the commercial finite element method software PROMECHANICA. To verify the results obtained by standard numerical methods, the radial deflections of the impeller of a commercial sewage water pump, which has been investigated numerical in advance, were measured for the horizontal and for the vertical coordinate direction by proximity sensors. The measured data were compared to the computed amounts for a wide range of pump operation. The results show a good agreement for a strong part of an impeller revolution for all investigated operating points. The simultaneous measurement of vibration accelerations at the outer side of the pump casing showed the effects of the time-dependent flow, which produce hydrodynamic forces acting at the impeller of the pump and stimulating it to strong oscillations.

Comparison of Experimental and Numerical Obtained Velocity Fields in a Single-Blade Centrifugal Pump

2006 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen ◽  
Marcel Zwingenberg
Keyword(s):  
Numerical Simulations ◽  
Centrifugal Pump ◽  
Transient Flow ◽  
Stokes Equations ◽  
Reverse Flow ◽  
Strong Dependence ◽  
Time Dependent ◽  
Wide Range ◽  
Operating Points ◽  
Blade Pump

The development of a pressure and a suction surface of a single-blade pump impeller leads to a strong asymmetric pressure distribution at the perimeter of the rotor outlet. The interaction of the impeller flow with the pump casing produces a flow field which is periodic with the impeller turning. In a numerical approach the transient flow in a complete single-blade centrifugal pump has been calculated by solving the 3-dimensional time dependent Reynolds averaged Navier-Stokes equations (URANS) with a commercial CFD code for a wide range of pump operation. A strong dependence from the impeller position has been recognized for all flow parameters. Especially at off-design conditions the flow in the impeller and in the casing showed stall and reverse flow at particular impeller positions. Experiments have been used to validate the numerical investigations of the time dependent flow in the single-blade pump. The submersible pump, completely made of transparent plastic, has been investigated in detail by the Particle Image Velocimetry. The phase averaged 2D-velocity field inside the pump was measured for the same operating points which were investigated by numerical methods in advance. Measurement planes near the hub and the shroud disc and also at mid-span of the blade were chosen to expose the 3D-character of the flow inside the pump. The measured velocities were compared to the results from numerical simulations in detail. The good agreement between measurements and calculations, which was obtained for all investigated operating points, certifies the numerical simulations a high accuracy.

A numerical investigation of fluid flows induced by the oscillations of thin plates and evaluation of the associated hydrodynamic forces

2019 ◽  
Vol 874 ◽  
pp. 1057-1095 ◽  
Author(s):  
Artem N. Nuriev ◽  
Airat M. Kamalutdinov ◽  
Andrey G. Egorov
Keyword(s):  
Stokes Equations ◽  
Experimental Studies ◽  
Flow Regimes ◽  
Hydrodynamic Forces ◽  
Thin Plates ◽  
Oscillatory Process ◽  
Dimensionless Frequency ◽  
Two Dimensional ◽  
Wide Range ◽  
Hydrodynamic Influence

The paper is devoted to the problem of harmonic oscillations of thin plates in a viscous incompressible fluid. The two-dimensional flows caused by the plate oscillations and their hydrodynamic influence on the plates are studied. The fluid motion is described by the non-stationary Navier–Stokes equations, which are solved numerically on the basis of the finite volume method. The simulation is carried out for plates with different thicknesses and shapes of edges in a wide range of control parameters of the oscillatory process: dimensionless frequency and amplitude of oscillations. For the first time in the framework of one model all two-dimensional flow regimes, which were found earlier in experimental studies, are described. Two new flow regimes emerging along the stability boundaries of symmetric flow regimes are localized. The map of flow regimes in the frequency–amplitude plane is constructed. The analysis of the hydrodynamic influence of flows on the plates allow us to establish new effects associated with the influence of the shape of the plates on the drag and inertia forces. Due to these effects, the values of hydrodynamic forces can differ by 90 % at the same parameters of the oscillation. The lower and upper estimates of hydrodynamic forces obtained in the work have a good agreement with the experimental data presented in the literature.

Onset of cellular convection in a salinity gradient due to a lateral temperature gradient

1974 ◽  
Vol 63 (3) ◽  
pp. 563-576 ◽  
Author(s):  
C. F. Chen
Keyword(s):  
Salinity Gradient ◽  
Critical Rayleigh Number ◽  
Time Dependent ◽  
Field Equations ◽  
Stable States ◽  
Critical Wavelength ◽  
Wide Range ◽  
Random Disturbances ◽  
Dependent Flow ◽  
The Stability

We consider the two-dimensional problem of a linearly stratified salt solution contained between two infinite vertical plates. The fluid and the plates are initially at the same temperature. At t = 0, one of the plates is given a step increase in temperature, while the other is maintained at the initial temperature. A time-dependent basic flow is thus generated. The stability of such a time-dependent flow is analysed using an initial value problem approach to the linear stability equations. The method consists of initially distributing small random disturbances of given vertical wavelength throughout the fluid. The disturbances may be in the vorticity, temperature or salinity. The linearized field equations are integrated numerically. The growth or decay of the kinetic energy of the perturbation delineates unstable and stable states. Results have been obtained for a wide range of gap widths. The critical wavelength and the critical Rayleigh number compare favourably with those obtained previously in both physical and numerical experiments.

Theoretical and Experimental Investigation on the Flow Induced Vibrations of a Centrifugal Pump

2004 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Transient Flow ◽  
Stokes Equations ◽  
Computer Code ◽  
Numerical Approach ◽  
Experimental Investigations ◽  
Pump Operation ◽  
Pump Rotor ◽  
Wide Range

The transport of fluids which include a lot of impurities is often done by special single-stage pumps. In order to avoid clogging of the pumps, the impellers have only one blade. This minimum blade number brings strong disadvantages during the pump operation. The rotation of the impeller in the pump casing produces a strongly uneven pressure field along the perimeter of the casing. The resulting periodically unsteady flow forces affect the impeller and produce radial deflections of the pump shaft which can be recognized as vibrations at the bearing blocks or at the pump casing. These vibrations will also be transferred to the pump casing and attached pipes. In a numerical approach the hydrodynamic excitation forces of a single-blade pump were calculated from the time dependent flow field. The flow field is known from the numerical simulation of the three-dimensional, viscous, unsteady flow in the pump by using a commercial computer code determining the Reynolds averaged Navier-Stokes equations (URANS). The periodically unsteady flow forces were computed for a complete impeller revolution. This forces affect the rotor of the pump and stimulate it to oscillations. The computed forces were defined as external forces and applied as the load on the rotor for a structural analysis. The resulting oscillations of the rotor were calculated by a transient analysis of the rotors structure using a commercial FEM-Method. To verify the calculated results, experimental investigations have been performed. The deflections of the pump rotor were measured with proximity sensors in a wide range of pump operation. Measurements of the vibration accelerations at the pump casing showed the visible effects of the transient flow. To minimize the vibration amplitudes the energizing forces have been reduced by attaching a compensation mass at the impeller. This procedure can be used as “operational balancing” of the pump rotor for a certain point of operation.

Periodically Unsteady Flow in a Single-Blade Centrifugal Pump: Numerical and Experimental Results

2005 ◽  
Author(s):  
F.-K. Benra ◽  
H. J. Dohmen ◽  
M. Sommer
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Sewage Water ◽  
Numerical Results ◽  
Experimental Results ◽  
Time Dependent ◽  
Pump Operation ◽  
Wide Range ◽  
Operating Points

The composition of sewage water with partially large portions of fibers and solids requires a special pump design, in order to avoid operational disturbances by clogging. In most applications for sewage water transport, single-stage pumps with single-blade impellers are used. With this special impeller geometry largest flow channels can be realized. So fibers and solids up to an appropriate size can be transported by the pump. This minimum impeller blade number however brings disadvantages for pump operation. The development of a pressure and a suction surface of the blade gives an asymmetric pressure distribution at the perimeter of the rotor outlet and a periodically unsteady flow field arises. In a numerical approach the time accurate flow in a single-blade centrifugal pump has been calculated by solving the 3-dimensional time dependent Reynolds averaged Navier-Stokes equations (URANS) in a wide range of pump operation. The investigation of the flow included all details between suction flange and pressure flange of the pump. The numerical results show a strong dependence from impeller position for all flow parameters. For the investigated operating points strong vortices have been obtained at particular impeller positions. Experimental results have been used to verify the numerical results of time dependent flow in the single-blade pump. The computed flow field has been compared to results which were obtained from optical measurements of flow velocities by Particle Image Velocimetry at different impeller positions. A very good qualitative agreement between measurements and calculations has been obtained for all investigated operating points.

Experimental Investigation of Flow Induced Rotor Oscillations in a Centrifugal Sewage Water Pump

Volume 3 ◽  
2004 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen ◽  
Oliver Schneider
Keyword(s):  
Experimental Investigation ◽  
Static Pressure ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Sewage Water ◽  
Water Pump ◽  
Flow Rates ◽  
Pump Rotor ◽  
Pump Shaft ◽  
Impeller Geometry

Most of the pumps for sewage transport have a special impeller geometry in order to avoid operational disturbances by clogging. The almost exclusively used single stage machines particularly are equipped with single-blade impellers. With this impeller geometry a strongly uneven pressure field along the perimeter of the pump casing can be expected. The resulting periodically unsteady flow forces affect the impeller and produce strong radial deflections of the pump shaft. In this contribution the experimental investigation of the dynamic behavior of the pump rotor as a consequence of the transient hydrodynamic forces is described. To verify the calculated rotor oscillations measurements were performed at several rotating speeds and at different volume flow rates. The pump which before has been investigated numerical was equipped with several sensors. The deflections of the pump rotor were measured with two proximity sensors. The measurement of the vibration accelerations at the pump casing showed the effects of the transient hydrodynamic stimulation forces. Measurements of the static pressure in the casing allowed a correlation between the rotor oscillations and the pressure fluctuations produced by the single-blade impeller.

Numerical Simulations of Three-Dimensional Flows in a Cubic Cavity With an Oscillating Lid

1993 ◽  
Vol 115 (4) ◽  
pp. 680-686 ◽  
Author(s):  
Reima Iwatsu ◽  
Jae Min Hyun ◽  
Kunio Kuwahara
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Time Dependent ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Navier Stokes Equations ◽  
Sinusoidal Oscillations ◽  
Dependent Flow

Numerical studies are made of three-dimensional flow of a viscous fluid in a cubical container. The flow is driven by the top sliding wall, which executes sinusoidal oscillations. Numerical solutions are acquired by solving the time-dependent, three-dimensional incompressible Navier-Stokes equations by employing very fine meshes. Results are presented for wide ranges of two principal physical parameters, i.e., the Reynolds number, Re ≤ 2000 and the frequency parameter of the lid oscillation, ω′ ≤ 10.0. Comprehensive details of the flow structure are analyzed. Attention is focused on the three-dimensionality of the flow field. Extensive numerical flow visualizations have been performed. These yield sequential plots of the main flows as well as the secondary flow patterns. It is found that the previous two-dimensional computational results are adequate in describing the main flow characteristics in the bulk of interior when ω′ is reasonably high. For the cases of high-Re flows, however, the three-dimensional motions exhibit additional complexities especially when ω′ is low. It is asserted that, thanks to the recent development of the supercomputers, calculation of three-dimensional, time-dependent flow problems appears to be feasible at least over limited ranges of Re.

Evaluation of Various Approximate Solutions for Fluid Inertia Effects on the Dynamic Performance of a Stepped Thrust Bearing

1985 ◽  
Vol 107 (1) ◽  
pp. 39-45 ◽  
Author(s):  
Y. Haruyama ◽  
T. Kazamaki ◽  
A. Mori ◽  
H. Mori
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Stokes Equations ◽  
Dynamic Performance ◽  
Approximate Solutions ◽  
Time Dependent ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Dependent Term ◽  
Wide Range

Based on the Navier-Stokes equations in which the pressure is assumed to be constant across the film thickness, various approximate solutions and the exact one for the dynamic performance of an infinitely wide, stepped thrust bearing in a laminar flow regime are presented under the assumption of a small harmonic vibration. From comparison of the approximate solutions with the exact one, it is concluded that some kind of averaging approach in which the time dependent term is treated exactly while the convective inertia terms are averaged out across the film thickness gives close approximations in a wide range of designing conditions, and that the other kind of averaging approach in which all the inertia terms including the time dependent term are averaged out across the film thickness gives fairly good approximations.

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