Numerical Modeling of Unsteady Cloud Cavitation around a Clark-Y Hydrofoil Based on Modified SST Model

A density correction function was introduced into SST (shear stress transport) model in CFX by user defined subroutine. The unsteady cloud cavitation around a Clark-y hydrofoil was numerically simulated using the modified SST model, associated with Zwart cavitation model. The quasi-periodic evolution of cloud cavity and lift coefficient variation were analysed. The results compared with experimental data show that the modified SST model reduces turbulent viscosity in the rear part of cavity and the reentrant jet in cloud cavitation is predicted. The quasi-periodic evolution of cavity generation, development and collapse is captured accurately and the calculated lift coefficient curve is consistent with the experimental date. It can be concluded that the modified SST model used in this paper has a good applicability in the unsteady cloud cavitation simulation.

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Application of Modified PANS Model for Computation of Cloud Cavitation around a Clark-Y Hydrofoil

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.456.173 ◽

2013 ◽

Vol 456 ◽

pp. 173-177

Author(s):

Wei Dong Shi ◽

Guang Jian Zhang

Keyword(s):

Turbulent Viscosity ◽

Lift Coefficient ◽

Correction Function ◽

Navier Stokes ◽

Two Phase ◽

Cloud Cavitation ◽

Cavity Shedding ◽

Time Average ◽

Phase Mixture ◽

Experimental Values

A density correction function was introduced to the Partially-Averaged Navier-Stokes Model (PANS) taking into account the local compressibility of two-phase mixture. The standard k-ε model, PANS model and the modified PANS model were used to simulate the unsteady cloud cavitation around a Clark-y hydrofoil and the evolutions of cavity shape, time-averaged turbulence viscosity distribution and lift coefficient variation were investigated. The results compared with experimental data show that the PANS model and the modified PANS model strongly reduce the turbulent viscosity and predict the cloud cavity shedding behavior observed in the experiment successfully, while the cavitation area and time-average lift coefficient predicted by the modified PANS model is closer to the experimental values than the original PANS model.

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Sensitization of the SST Turbulence Model to Rotation and Curvature by Applying the Spalart-Shur Correction Term

Volume 6: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2008-50480 ◽

2008 ◽

Cited By ~ 18

Author(s):

Pavel E. Smirnov ◽

Florian R. Menter

Keyword(s):

Turbulent Flows ◽

Turbulence Model ◽

Transport Model ◽

Correction Term ◽

Computational Cost ◽

Reynolds Stresses ◽

Wide Range ◽

Sst Model ◽

Shear Stress Transport Model ◽

Sst Turbulence Model

A rotation-curvature correction suggested earlier by Spalart and Shur for the one-equation Spalart-Allmaras turbulence model is adapted to the Shear Stress Transport model. This new version of the model (SST-CC) has been extensively tested on a wide range of both wall-bounded and free shear turbulent flows with system rotation and/or streamline curvature. Predictions of the SST-CC model are compared with available experimental and DNS data, on one hand, and with the corresponding results of the original SST model and advanced Reynolds stresses transport model (RSM), on the other hand. It is found, that in terms of accuracy the proposed model significantly improves the original SST model and is quite competitive with the RSM, whereas its computational cost is significantly less than that of the RSM.

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Simulation of Biomass Combustion with Modified Flue Gas Tract

Applied Sciences ◽

10.3390/app11031278 ◽

2021 ◽

Vol 11 (3) ◽

pp. 1278

Author(s):

Nikola Čajová Kantová ◽

Sławomir Sładek ◽

Jozef Jandačka ◽

Alexander Čaja ◽

Radovan Nosek

Keyword(s):

Particulate Matter ◽

Human Health ◽

Flue Gas ◽

Transport Model ◽

Turbulent Viscosity ◽

Biomass Combustion ◽

Final Model ◽

Concept Model ◽

Viscosity Models ◽

Shear Stress Transport Model

The combustion of biomass is accompanied by the formation of particulate matter, the presence of which in the atmosphere harms human health. It is important to show the issues of reducing these pollutants and their impact on human health. This article focuses on the process of biomass combustion. The used model consists of two parts: the combustion chamber and the flue gas tract. The article shows four types of modification of the flue gas tract designed to reduce the amount of particulate matter in the atmosphere. Baffles are located in the flue gas tract, which is designed to capture the particulate matter. The final model is simulated by turbulent–viscosity models, k-ε realizable model, and then k-ω shear stress transport model. The interaction between turbulence and chemical reactions is expressed by using the Eddy Dissipation Concept model. The results then show different profiles of temperature, velocity, and particle distribution. Based on the evaluated data from two different calculations, it can be concluded that the baffles have a significant effect on the reduction of particulate matter in the atmosphere. The used baffles are able to capture mainly particles with a diameter greater than 100 µm. A significant number of particles with a diameter lower than 100 µm flows from the flue gas tract to the surrounding environment.

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Numerical Analysis of Water Suction Effect on Lift and Drag Coefficient of a Hydrofoil With Cavitation

Volume 1: Symposia, Parts A, B and C ◽

10.1115/fedsm2009-78270 ◽

2009 ◽

Author(s):

Mohammad J. Izadi

Keyword(s):

Drag Coefficient ◽

Mass Flow ◽

Static Pressure ◽

Turbulent Viscosity ◽

Lift Coefficient ◽

Vapor Bubbles ◽

Cloud Cavitation ◽

Lift And Drag ◽

Lift And Drag Coefficient ◽

Unsteady Cavitating Flow

Cavitation is the formation of the vapor bubbles within a liquid where the flow dynamics, cause the local static pressure to drop below the vapor pressure. This phenomenon can cause undesirable effects on the hydrofoils such as a decrease in the lift and an increase in the drag. In the present study, the unsteady cavitating flow over a 3-D hydrofoil is numerically simulated. The purpose of this work is to investigate the effect of the upper surface suction in the cavitation area on the lift and drag coefficients of a hydrofoil. An unsteady uniform flow of water over a 3-D NACA hydrofoil is numerically simulated. The full cavitation model along with the RNG k-ε turbulence model is implemented. A modification to the turbulent viscosity, which is necessary to simulate the cloud cavitation, is implemented. The simulation is implemented for various angles of attack and various suction velocities. Comparison between some experimental data and the numerical simulation obtained here is done in order to validate the numerical results. The results obtained here show that, as the mass flow of the water suction increases, the drag coefficient is decreased for large angles of attack, but for small angles of attack it does not change as much. As the mass flow of the water suction increases, the lift coefficient is decreased for small angles of attack and for larger angles of attack the lift coefficient is increased.

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Several Cases for the Validation of Turbulence Models Implementation

Applied Sciences ◽

10.3390/app11083377 ◽

2021 ◽

Vol 11 (8) ◽

pp. 3377

Author(s):

Michael D. Polewski ◽

Paul G. A. Cizmas

Keyword(s):

Fluid Dynamics ◽

Experimental Data ◽

Transport Model ◽

Turbulence Models ◽

Numerical Results ◽

Test Cases ◽

Turbine Cascade ◽

Near Wake ◽

Shear Stress Transport Model ◽

Standard Configuration

This paper presents several test cases that were used to validate the implementation of two turbulence models in the UNS3D code, an in-house code. The two turbulence models used were the Shear Stress Transport model and the Spalart–Allmaras model. These turbulence models were explored using the numerical results generated by three computational fluid dynamics codes: NASA’s FUN3D and CFL3D, and UNS3D. Four cases were considered: a flat plate case, an airfoil near-wake, a backward-facing step, and a turbine cascade known as the Eleventh Standard Configuration. The numerical results were compared among themselves and against experimental data.

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Roughness Corrections for the k–ω Shear Stress Transport Model: Status and Proposals

Journal of Fluids Engineering ◽

10.1115/1.4028122 ◽

2014 ◽

Vol 137 (2) ◽

Cited By ~ 22

Author(s):

B. Aupoix

Keyword(s):

Shear Stress ◽

Transport Model ◽

Wall Region ◽

Large Set ◽

Transition Regime ◽

Wall Roughness ◽

Shear Stress Transport ◽

Sst Model ◽

Shear Stress Transport Model ◽

Simplified Analysis

Various corrections were previously proposed to account for wall roughness with the k–ω and shear stress transport (SST) models. A simplified analysis, based upon the wall region analysis, is proposed to characterize the behavior of these roughness corrections. As this analysis points out some deficiencies for each correction, two new corrections are proposed for the SST model, to reproduce different behaviors, mainly in the transition regime. The correction development is based upon a previously developed strategy. A large set of boundary layer experiments is used to compare the different roughness corrections, confirm the failures of previous proposals, and validate the present ones. Moreover, it assesses the proposed simplified analysis. It also evidences the difficulty to determine the equivalent sand grain roughness for a given surface. The Colebrook based correction is recommended while the Nikuradse based one can add information about the envelope of possible behaviors in the transition regime.

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CFD Computation of Water Injection on Lift and Drag of a Hydrofoil With Cavitation

Volume 1: Symposia, Parts A, B and C ◽

10.1115/fedsm2009-78269 ◽

2009 ◽

Author(s):

Mohammad J. Izadi ◽

Pejman Hazegh Fetratjou

Keyword(s):

Numerical Simulation ◽

Drag Coefficient ◽

Turbulence Model ◽

Mass Flow ◽

Bubble Dynamics ◽

Turbulent Viscosity ◽

Lift Coefficient ◽

Water Injection ◽

Cloud Cavitation ◽

Lift And Drag

The occurrence of cavitation on hydrofoils can cause undesirable effects such as a decrease in lift, and an increase in drag. The goal of this research is to investigate the effect of water injection on the lift and drag coefficient of a hydrofoil. An unsteady uniform flow of water over a 3-D NACA hydrofoil is numerically simulated. For the numerical simulation of a cavitating flow, a bubble dynamics cavitation model is used to describe the generation and evaporation of the vapor phase. The RNG k-ε turbulence model is used as a turbulence model. A modification to the turbulent viscosity, which is necessary to simulate the cloud cavitation, is implemented. This simulation is implemented for various angles of attack and different injection velocities. Comparison between experimental data and the numerical simulation obtained here is done to validate the numerical results. The results presented show that, as the mass flow of the water injection increases, the lift coefficient decreases for all angles of attack but the rate of this decrease decreases for higher angles of attack. As the mass flow rate increases, the drag coefficient increases more for small angles of attack, and decreases for larger angles of attack, and the injection does not change the drag coefficient as much for large angles of attack. In general, water injection does not increase the lift and does not decrease the drag for all angles of attack.

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CFD of Water Injection on Lift and Drag of a 2-D Hydrofoil With Cavitation

Volume 2: Fora ◽

10.1115/fedsm2009-78173 ◽

2009 ◽

Author(s):

Mohammad J. Izadi

Keyword(s):

Numerical Simulation ◽

Drag Coefficient ◽

Turbulence Model ◽

Mass Flow ◽

Bubble Dynamics ◽

Turbulent Viscosity ◽

Lift Coefficient ◽

Water Injection ◽

Cloud Cavitation ◽

Lift And Drag

Undesirable effects such as a decrease in lift and an increase in drag can be the result of the occurrence of cavitation on hydrofoils. The goal of this research is to investigate the effect of water injection on the lift and drag coefficient of a 2-D hydrofoil. An unsteady uniform flow of water over a NACA hydrofoil (2D) is numerically simulated. For the numerical simulation of a cavitating flow, a bubble dynamics cavitation model is used to describe the generation and evaporation of the vapor phase. The RNG k-ε turbulence model is used as a turbulence model. To simulate the cloud cavitation, a modification to the turbulent viscosity which is necessary, is implemented. This simulation is done for various angles of attack and different injection velocities. Comparison between experimental data and the numerical simulation obtained here is done to validate the numerical results. The results presented here show that, as the mass flow of the water injection increases, the lift coefficient decreases for all angles of attack but the rate of this decrease decreases for higher angles of attack. As the mass flow rate increases, the drag coefficient increases more for small angles of attack and decrease for larger angles of attack.

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Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

Hydrology Research ◽

10.2166/nh.1992.0007 ◽

1992 ◽

Vol 23 (2) ◽

pp. 89-104 ◽

Cited By ~ 30

Author(s):

Ole H. Jacobsen ◽

Feike J. Leij ◽

Martinus Th. van Genuchten

Keyword(s):

Experimental Data ◽

Unsaturated Flow ◽

Transport Model ◽

Time Moment ◽

Breakthrough Curves ◽

Coarse Sand ◽

Retardation Factor ◽

Parameter Determination ◽

Model Parameters ◽

Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

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