Large‐Eddy Simulation of Unsteady Flow in a Mixed‐Flow Pump

Kato, Chisachi; Mukai, Hiroshi; Manabe, Akira

doi:10.1155/s1023621x03000320

Cited by 43 publications

(22 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Unfortunately, although DNS gives the most precise results, the computational time is prohibitive for practical applications. The prevailing route to simulate time dependent flows is the LES method (Nobuhiro et al, 2003;Kato et al, 2003;Ji et al, 2013) proposed by Smagorinski (1963). Typically, LES resolves all the dynamically important scales of motion and a significant portion of the inertial scales.…”

Section: Introductionmentioning

confidence: 99%

Partially-Averaged Navier-Stokes Model for Predicting Cavitating Flow in Centrifugal Pump

Liu

Wang

et al. 2014

Engineering Applications of Computational Fluid Mechanics

View full text Add to dashboard Cite

Cavitation is a common phenomenon in pump industries, which leads to severe problems, like vibration and noise. It may degrade the pump performance and even damage the solid surface. So it is significant to give a precise prediction of the pump cavitation performance. The original k-ε model is widely used in the past years. However, it is reported that high viscosity of the original k-ε model dampens cavitation instabilities and hence makes it difficult to capture the detachment of the bubbles. Aiming at improving the predictive capability, the partiallyaveraged Navier-Stokes (PANS) is employed in this paper to predict the pump cavitation performance. Experiments on a centrifulgal pump with twisted blades are carried out to validate the simulations. The results show that, compared with the original k-ε model, the PANS model with lower f k value gives a more accurate prediction and can reduce the eddy viscosity in the cavity region, leading to capturing the unsteady bubble shedding phenomenon. The experimental visualizations are performed and the evolution of the cavitation inception and development are obtained exactly at the impeller inlet. Comparisons with the transient numerical simulations are made, which demonstrates the PANS model can successfully capture the cavitation detachment. Finally, the blade load pressure, the pressure distribution in impeller and the pressure fluctuations are analyzed. Good agreement is noticed between simulations and experiment. So it can be concluded that the PANS model can effectively reduce eddy viscosity in cavitating flow in centrifugal pumps and improve the numerical simulation prediction of pump cavitation performance.

show abstract

Section: Introductionmentioning

confidence: 99%

Partially-Averaged Navier-Stokes Model for Predicting Cavitating Flow in Centrifugal Pump

Liu

Wang

et al. 2014

Engineering Applications of Computational Fluid Mechanics

View full text Add to dashboard Cite

show abstract

“…The discrepancy between CFD and experimental results may be attributed to the grid resolution around the blade surface, and the current mesh resolution may be insufficient to resolve the turbulent boundary layer developing on the blade surface. Furthermore, effects of the leakage flow through the clearance are not considered in the present numerical simulation [15]. However, it can be found that the tendency of CFD results has a good agreement with the test results.…”

Section: Validation Of the Numerical Methodsmentioning

confidence: 95%

“…By neglecting the incompressible effect of the fluid, LES governing equations [15] to [17] can be described in the following form.…”

Section: Governing Equationsmentioning

confidence: 99%

“…One portion flows out of the casing discharge nozzle, whereas the other portion circulates around the casing once more prior to exiting. Kato et al [15] and [16] described internal flows of a high-specific-speed mixed-flow pump at low flow rates using large-eddy simulation (LES), and it showed that the head-flow curve exhibited weak Flow Unsteadiness and Pressure Pulsations in a Nuclear Reactor Coolant Pump instability characteristics. Posa et al [17] reported the LES method used in a mixed-flow pump, where a structured cylindrical coordinate solver with optimal conservation properties was utilized in conjunction with an immersed-boundary method.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Flow Unsteadiness and Pressure Pulsations in a Nuclear Reactor Coolant Pump

Ni¹,

Yang²,

Gao³

et al. 2016

SV-JME

View full text Add to dashboard Cite

A nuclear reactor coolant pump (RCP) [1], the device in the reactor core and the steam generator that transfers the heat energy [2], is the "heart" of a nuclear reactor driving the circulation flow of the coolant in the main loop [3]. The nuclear reactor coolant pump is the only rotating part of the nuclear island, so it belongs in a nuclear safety grade one facility. Moreover, it is also the main energy-consuming equipment in the nuclear power plants, which must be guaranteed to operate continuously over a long term and without trouble. An investigation on the internal flow in the mixed-flow nuclear reactor coolant pump is one of the key problems for the development of reactor coolant pumps in large pressurized water reactors. Some investigations have been conducted to study the design of the mixed-flow pump [4] and [5] and flows instabilities [6] and [7]. However, most of them only focus on the unsteady pressure pulsation in impeller [8] and [9] or the performance of the nuclear reactor coolant pump [10] and [11]. The unsteady flow structure of a mixed-flow nuclear reactor coolant pump, especially in certain specific regions, is very important to the safety analysis of a nuclear reactor, as it could generate serious flow-induced vibration, threatening the pump integrity [8]. Therefore, a comprehensive analysis and prediction of pressure pulsation caused by intense rotor-stator interaction are essential for the design of the mixed-flow nuclear reactor coolant pump [12] and [13]. At present, in order to improve the efficiency and stable operation of the nuclear reactor coolant pump, the complicated internal unsteady flow structures should be thoroughly illustrated.The nuclear reactor coolant pump has a special structure equipped with a spherical casing, which determines a typical and complex flow pattern within the pump. Knierim et al.[14] designed a new type of reactor coolant pump for a 1400 MW nuclear power plant. The impeller and diffuser were gradually optimized based on the computational fluid dynamics (CFD). The volute casing is a spherical shape with a discharge nozzle facing the impeller, and the flow structures in the region around the discharge nozzle are uniform. The region of the discharge nozzle itself is characterized by the fact that the flow below the outlet port is divided into two parts. One portion flows out of the casing discharge nozzle, whereas the other portion circulates around the casing once more prior to exiting. Kato et al.[15] and [16] described internal flows of a high-specific-speed mixed-flow pump at low flow rates using large-eddy simulation (LES), and it showed that the head-flow curve exhibited weak • Flow separations and backflows easily occur at the diffuser channels near the discharge nozzle region.• At the left region of the casing, the discharge nozzle is affected significantly by an intense rotor-stator interaction effect.• In the right and middle of the casing nozzle, unsteady flow structures are more complicated.• An unsteady vortex-shedding effect would motivate evid...

show abstract

“…[1] study the flow characteristics of the unsteady and unstable flow using LES subgrid turbulence model. Abroad Kato [2] study the unsteady flow characteristics of mixed flow pump under off-designed condition based on LES sub-grid turbulence model. Miorini, et.al.…”

Section: Introductionmentioning

confidence: 99%

The Numerical Simulation of Unsteady Flow in a Mixed flow Pump Guide Vane

Wang

2013

International Journal of Fluid Machinery and Systems

View full text Add to dashboard Cite

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluid's rotation is the same to impeller in the guide vane adhere.

show abstract

Large‐Eddy Simulation of Unsteady Flow in a Mixed‐Flow Pump

Cited by 43 publications

References 6 publications

Partially-Averaged Navier-Stokes Model for Predicting Cavitating Flow in Centrifugal Pump

Partially-Averaged Navier-Stokes Model for Predicting Cavitating Flow in Centrifugal Pump

Flow Unsteadiness and Pressure Pulsations in a Nuclear Reactor Coolant Pump

The Numerical Simulation of Unsteady Flow in a Mixed flow Pump Guide Vane

Contact Info

Product

Resources

About