Low-speed preconditioning for strongly coupled integration of Reynolds-averaged Navier–Stokes equations and two-equation turbulence models

Campobasso, M. Sergio; Yan, M.; Bonfiglioli, Aldo; Gigante, Fabio; Ferrari, Lorenzo; Balduzzi, Francesco; Bianchini, Alessandro

doi:10.1016/j.ast.2018.03.015

Cited by 27 publications

(13 citation statements)

References 35 publications

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“…In the shear stress transport (SST) model, the k- turbulence model is combined with the Wilcox two-equation k- turbulence model through a blending function (Menter et al 1994). The model k- is used near the wall, and the k- model is used in the well-developed flow field away from the wall (Anup et al 2014;Campobasso et al 2018). Thus, the SST model fully combines the high precision of the k- model in separated flow simulations and the low sensitivity of the k- model to initial turbulence parameters, making it one of the most widely used turbulence models at present.…”

Section: Numerical Computationmentioning

confidence: 99%

Effect of Guide Vane Pitch Circle Diameter on Pressure Fluctuation in Vaneless Zone of Francis Turbine

2020

JAFM

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In a Francis turbine, the guide vanes are arranged in the direction of flow behind the stay vanes. And as it is generally believed that the outlet angle of water after it flows through the spiral case and stay vanes is fixed, the flow and flow circulation are altered by changing the opening of the guide vanes so as to change the output of the turbine. The rotor-stator interaction effect induced by the interaction between the guide vanes and the runner of the Francis turbine was one of the main causes of the pressure fluctuation. The effect of guide vanes placement on pressure fluctuation in vaneless zone of Francis turbine was studied. In this study, the commercial software ANSYS CFX16.0 was used for the three-dimensional numerical simulation of the whole flow passage of a Francis turbine model in a power station. The turbulence model used in the calculation was the shear stress transport (SST) model. The independence between the total number of computational meshes and the timestep was verified to ensure the reliability of the calculation results. Five schemes with different diameters of the guide vanes distribution circle were proposed including D0/D1 (guide vane pitch circle diameter /diameter of runner inlet) equaling to 1.119, 1.128, 1.138, 1.144, and 1.15. The steady calculation results showed that, when the turbine was operating under the design condition, D0/D1 increased from 1.119 to 1.15, and the turbine efficiency and output showed a monotonically increasing trend, with the efficiency increased by 0.17 percentage point and output increased by 3.91kw. Twenty monitoring points were set up in the vaneless zone between the guide vanes and the runner to collect pressure fluctuation signals in the vaneless zone. By analyzing the characteristics of unsteady pressure fluctuations in the vaneless zone under design conditions of the five schemes, the optimal position of the guide vanes was determined. The numerical results showed that the pressure fluctuation amplitude at monitoring points in the same axial direction increased gradually from the top cover to the bottom ring. When the unit operated under the design conditions, by increasing the guide vane pitch circle diameter, the rotor-stator interaction between the guide vanes and the runner domain was weakened, and the pressure fluctuation amplitude in the vaneless zone between the guide vanes and the runner was reduced, thereby the stability of unit operation was improved.

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Section: Numerical Computationmentioning

confidence: 99%

Effect of Guide Vane Pitch Circle Diameter on Pressure Fluctuation in Vaneless Zone of Francis Turbine

2020

JAFM

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“…In the present study, the FLUENT software was selected for the numerical simulations. The density-based compressible flow formulation of the Euler equations have proven to be very successful for the analysis of high-speed flows (Campobasso et al 2018;Cao et al 2019b). Because the medium in the throttling device is compressible high-speed fluid, the density-based solver in FLUENT was adopted in this paper.…”

Section: Mathematical Modelmentioning

confidence: 99%

Flow Characteristics of Wet Natural Gas in Different Throttling Devices

Cao¹,

Chu²,

Song³

et al. 2019

Frontiers in Heat and Mass Transfer

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Wet natural gas widely exists in the natural gas industry, and the selection of throttling devices plays an important role in wet natural gas transportation. In order to study the flow field characteristics of different throttling devices in wet natural gas pipelines, a set of Laval nozzles, orifice plates, and plate valves have been designed. The standard k-ε model was selected for numerical simulation. By changing inlet pressure, inlet temperature or volume fraction of water-liquid, the pressure field and temperature fields of different throttling devices were obtained, and the influence of the presence of a shockwave on the flow fields of the throttling devices was analyzed. Different throttling devices have significantly different operating characteristics. Therefore, appropriate throttling devices should be selected in different conditions in order to control the pressure of wet natural gas transportation and reduce gas hydrate formation. The present simulation results show that under identical conditions, the throat pressure and temperature of the Laval nozzle are the lowest, the throat pressure of the orifice plate is the highest, and the throat temperature of the plate valve is the highest.

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“…The term ∂Φ c f /∂U δU is the numerical dissipation, whose construction requires diagonalizing the Jacobian ∂Φ c f /∂U . Since, unlike in the case of the compressible RANS and SST equations [4], the Jacobians of the RANS and SST equations are decoupled in the incompressible case, only the Jacobian of the RANS equations is considered below, namely:…”

Section: Space Discretizationmentioning

confidence: 99%

Harmonic Balance Navier–Stokes Analysis of Tidal Stream Turbine Wave Loads

Cavazzini

Campobasso

Marconcini

et al. 2019

Recent Advances in CFD for Wind and Tidal Offshore Turbines

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ARCTIC, a novel incompressible Reynolds-averaged Navier-Stokes finite volume code for the hydrodynamic analysis of open rotor unsteady loads is presented. One of its unique features is a harmonic balance solver enabling high-fidelity analyses of turbine periodic hydrodynamic loads with runtimes reduced by more than one order of magnitude over conventional time-domain CFD, and with negligible accuracy penalty. The strength of the new technology is demonstrated by analyzing with both harmonic balance and time-domain solvers the load fluctuations of a realistic tidal stream turbine. Such fluctuations are caused by a harmonic perturbation of the freestream velocity similar to that due to surface gravity waves.

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Low-speed preconditioning for strongly coupled integration of Reynolds-averaged Navier–Stokes equations and two-equation turbulence models

Cited by 27 publications

References 35 publications

Effect of Guide Vane Pitch Circle Diameter on Pressure Fluctuation in Vaneless Zone of Francis Turbine

Effect of Guide Vane Pitch Circle Diameter on Pressure Fluctuation in Vaneless Zone of Francis Turbine

Flow Characteristics of Wet Natural Gas in Different Throttling Devices

Harmonic Balance Navier–Stokes Analysis of Tidal Stream Turbine Wave Loads

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