Study of unsteady cavitating flow around Clark-Y hydrofoil using nonlinear PANS model with near-wall correction

2021 ◽  
Author(s):  
Benqing Liu ◽  
Wei Yang ◽  
Sien Li ◽  
Jie Chen ◽  
Biao Huang ◽  
...  
Keyword(s):  
Turbulent Transport ◽  
Cavitating Flow ◽  
Navier Stokes ◽  
Cloud Cavitation ◽  
Production Term ◽  
Dissipation Term ◽  
Lift And Drag ◽  
Lift And Drag Coefficient ◽  
Drag Ratio ◽  
Near Wall

In this paper, we describe the use of a new nonlinear partially-averaged Navier–Stokes (PANS) model with near-wall correction for simulating the cavitating flow around a Clark-Y hydrofoil. For comparison, the standard [Formula: see text]–[Formula: see text] PANS model is also used. The results demonstrate that compared to [Formula: see text]–[Formula: see text] PANS and experiment, the new PANS model shows better performance for cavitation flow, including time-averaged velocity, root mean square (rms) velocity and cavity shedding processing. Through the calculation of the lift and drag coefficient at [Formula: see text] and [Formula: see text], it can be concluded that the cavitation will decrease the lift and increase the drag of the hydrofoil, resulting in a decrease of the lift-to-drag ratio. From the analysis of different terms in both the turbulent kinetic energy (TKE) and dissipation rate transport equations of the cloud cavitation, it is found that the production term and the dissipation term are dominant in the turbulent transport, and they are mainly distributed in the vapor–liquid interface and the trailing edge of the hydrofoil.

Modeling of unsteady structure of sheet/cloud cavitation around a two-dimensional stationary hydrofoil

2015 ◽  
Vol 231 (3) ◽  
pp. 455-469 ◽  
Author(s):  
Feng Hong ◽  
Jianping Yuan ◽  
Banglun Zhou ◽  
Zhong Li
Keyword(s):  
Volume Fraction ◽  
Cavitating Flow ◽  
Wake Flow ◽  
Two Dimensional ◽  
Cavitating Flows ◽  
Cavitation Model ◽  
Ansys Fluent ◽  
Cloud Cavitation ◽  
Lift And Drag ◽  
Multi Phase

Compared to non-cavitating flow, cavitating flow is much complex owing to the numerical difficulties caused by cavity generation and collapse. In the present work, cavitating flow around a two-dimensional Clark-Y hydrofoil is studied numerically with particular emphasis on understanding the cavitation structures and the shedding dynamics. A cavitation model, coupled with the mixture multi-phase approach, and the modified shear stress transport k-ω turbulence model has been developed and implemented in this study to calculate the pressure, velocity, and vapor volume fraction of the hydrofoil. The cavitation model has been implemented in ANSYS FLUENT platform. The hydrofoil has a fixed angle of attack of α = 8° with a Reynolds number of Re = 7.5 × 105. Simulations have been carried out for various cavitation numbers ranging from non-cavitating flows to the cloud cavitation regime. In particular, we compared the lift and drag coefficients, the cavitation dynamics, and the time-averaged velocity with available experimental data. The comparisons between the numerical and experimental results show that the present numerical method is capable to predict the formation, breakup, shedding, and collapse of the sheet/cloud cavity. The periodical formation, shedding, and collapse of sheet/cloud cavity lead to substantial increase in turbulent velocity fluctuations in the cavitation regimes around the hydrofoil and in the wake flow.

Modeling of a One-Equation LES for Plant Canopy Flows

2011 ◽  
Author(s):  
Hisashi Hiraoka
Keyword(s):  
Kinetic Energy ◽  
Energy Equation ◽  
Navier Stokes ◽  
Plant Canopy ◽  
Production Term ◽  
Eddy Simulation ◽  
Dissipation Term ◽  
Wake Production ◽  
Canopy Flows ◽  
Basic Equations

A one-equation-type subgrid-scale (SGS) model was proposed in order to enable the large eddy simulation (LES) of plant canopy flows. The SGS kinetic energy equation was derived from the equations of continuity and Navier-Stokes. This equation was closed by modeling the unknown terms according to the physical meaning of each term in the equation. The wake production term in the SGS kinetic equation could be derived analytically. However, the wake dissipation term did not appear when the SGS kinetic energy equation was derived from the basic equations.

scholarly journals Shape Optimization of an Airfoil in Ground Effect for Application to WIG Craft

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Yilei He ◽  
Qiulin Qu ◽  
Ramesh K. Agarwal
Keyword(s):  
Genetic Algorithm ◽  
Flow Field ◽  
Lift Coefficient ◽  
Ground Effect ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Multiobjective Genetic Algorithm ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

This paper employs a multiobjective genetic algorithm (MOGA) to optimize the shape of a widely used wing in ground (WIG) aircraft airfoil NACA 4412 to improve its lift and drag characteristics, in particular to achieve two objectives, that is, to increase its lift and its lift to drag ratio. The commercial software ANSYS FLUENT is employed to calculate the flow field on an adaptive structured mesh generated by ANSYS ICEM software using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a one equation Spalart-Allmaras (SA) turbulence model. The results show significant improvement in both the lift coefficient and lift to drag ratio of the optimized airfoil compared to the original NACA 4412 airfoil. It is demonstrated that the performance of a wing in ground (WIG) aircraft can be improved by using the optimized airfoil.

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

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.

A nonlinear partially-averaged Navier–Stokes model with near-wall correction for separated turbulent flow

2021 ◽  
pp. 2150262
Author(s):  
Benqing Liu ◽  
Wei Yang ◽  
Sien Li ◽  
Xianbei Huang
Keyword(s):  
Turbulent Flow ◽  
Wall Friction ◽  
Navier Stokes ◽  
Wall Region ◽  
Good Resolution ◽  
Production Term ◽  
New Model ◽  
Standard Formula ◽  
Turbulent Statistics ◽  
Near Wall

A nonlinear Partially-Averaged Navier–Stokes model with near-wall correction is developed for separated turbulent flow simulations. The periodic hills flow is simulated to validate the new model and the results are compared with the standard [Formula: see text] model, MPANS model, MSST PNAS model, standard [Formula: see text] PANS model, and experimental/LES results. It is found that the new model shows better performance in the prediction of both mean velocity and turbulent statistics compared to the other models. From the prediction of the near-wall friction coefficient of periodic hills flow, the new model shows good resolution in the near-wall region by considering the near-wall damping function to turbulent viscosity, gradient production term, and turbulence scale correction term for the near-wall region. From the analysis of anisotropy-invariant and sub-filtered stress (SFS), it can be found that the nonlinear term is necessary for prediction accuracy improvement in turbulent flow simulation with strong separation.

Numerical investigation of dynamics of unsteady sheet/cloud cavitating flow using a compressible fluid model

2015 ◽  
Vol 29 (03) ◽  
pp. 1450269 ◽  
Author(s):  
Guang-Hao Chen ◽  
Guo-Yu Wang ◽  
Biao Huang ◽  
Chang-Li Hu ◽  
Zhi-Ying Wang ◽  
...  
Keyword(s):  
Numerical Model ◽  
Shock Waves ◽  
Compressible Fluid ◽  
Fluid Model ◽  
Cavitating Flow ◽  
Cloud Cavitation ◽  
Correction Model ◽  
Compressibility Effect ◽  
Cavity Collapse ◽  
Lift And Drag

In this paper, a compressible fluid model is proposed to investigate dynamics of the turbulent cavitating flow over a Clark-Y hydrofoil. The numerical simulation is based on the homogeneous mixture approach coupled with filter-based density correction model (FBDCM) turbulence model and Zwart cavitation model. Considering the compressibility effect, the equation of state of each phase is introduced into the numerical model. The results show that the predicted results agree well with experimental data concerning the time-averaged lift/drag coefficient and shedding frequency. The quasi-periodic evolution of sheet/cloud cavitation and the resulting lift and drag are discussed in detail. Especially, the present compressible-mixture numerical model is capable of simulating the shock waves in the final stage of cavity collapse. It is found that the shock waves may cause the transient significant increase and decrease in lift and drag if the cavity collapses near the foil surface.

scholarly journals A Parametric Study of Trailing Edge Flap Implementation on Three Different Airfoils Through an Artificial Neuronal Network

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 828
Author(s):  
Igor Rodriguez-Eguia ◽  
Iñigo Errasti ◽  
Unai Fernandez-Gamiz ◽  
Jesús María Blanco ◽  
Ekaitz Zulueta ◽  
...  
Keyword(s):  
Aerodynamic Coefficients ◽  
Trailing Edge ◽  
High Lift ◽  
Trailing Edge Flaps ◽  
Artificial Neural Network Ann ◽  
Lift And Drag ◽  
Artificial Neuronal Network ◽  
Naca 0012 ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Trailing edge flaps (TEFs) are high-lift devices that generate changes in the lift and drag coefficients of an airfoil. A large number of 2D simulations are performed in this study, in order to measure these changes in aerodynamic coefficients and to analyze them for a given Reynolds number. Three different airfoils, namely NACA 0012, NACA 64(3)-618, and S810, are studied in relation to three combinations of the following parameters: angle of attack, flap angle (deflection), and flaplength. Results are in concordance with the aerodynamic results expected when studying a TEF on an airfoil, showing the effect exerted by the three parameters on both aerodynamic coefficients lift and drag. Depending on whether the airfoil flap is deployed on either the pressure zone or the suction zone, the lift-to-drag ratio, CL/CD, will increase or decrease, respectively. Besides, the use of a larger flap length will increase the higher values and decrease the lower values of the CL/CD ratio. In addition, an artificial neural network (ANN) based prediction model for aerodynamic forces was built through the results obtained from the research.

scholarly journals Comparative Study of Different Turbulence Models for Cavitational Flows around NACA0012 Hydrofoil

2021 ◽  
Vol 9 (7) ◽  
pp. 742
Author(s):  
Minsheng Zhao ◽  
Decheng Wan ◽  
Yangyang Gao
Keyword(s):  
Angle Of Attack ◽  
Large Angle ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Specific Information ◽  
Cloud Cavitation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Shedding Frequency ◽  
Reynolds Average

The present work focuses on the comparison of the numerical simulation of sheet/cloud cavitation with the Reynolds Average Navier-Stokes and Large Eddy Simulation(RANS and LES) methods around NACA0012 hydrofoil in water flow. Three kinds of turbulence models—SST k-ω, modified SST k-ω, and Smagorinsky’s model—were used in this paper. The unstable sheet cavity and periodic shedding of the sheet/cloud cavitation were predicted, and the simulation results, namelycavitation shape, shedding frequency, and the lift and the drag coefficients of those three turbulence models, were analyzed and compared with each other. The numerical results above were basically in accordance with experimental ones. It was found that the modified SST k-ω and Smagorinsky turbulence models performed better in the aspects of cavitation shape, shedding frequency, and capturing the unsteady cavitation vortex cluster in the developing and shedding period of the cavitation at the cavitation number σ = 0.8. At a small angle of attack, the modified SST k-ω model was more accurate and practical than the other two models. However, at a large angle of attack, the Smagorinsky model of the LES method was able to give specific information in the cavitation flow field, which RANS method could not give. Further study showed that the vortex structure of the wing is the main cause of cavitation shedding.

Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier

2009 ◽  
Vol 367 (1899) ◽  
pp. 2885-2903 ◽  
Author(s):  
Michael Leschziner ◽  
Ning Li ◽  
Fabrizio Tessicini
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Major Elements ◽  
Wall Layer ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Models ◽  
High Reynolds ◽  
Near Wall

This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

scholarly journals Numerical simulation and experimental validation of cavitating flow in a multi-hole diesel fuel injector

2021 ◽  
pp. 146808742199863
Author(s):  
Aishvarya Kumar ◽  
Ali Ghobadian ◽  
Jamshid Nouri
Keyword(s):  
Computational Cost ◽  
Cavitating Flow ◽  
Field Analysis ◽  
Navier Stokes ◽  
Fuel Injector ◽  
Fluid Behavior ◽  
Flow Field Analysis ◽  
Charged Couple Device ◽  
Biodiesel Fuels ◽  
High Level

This study assesses the predictive capability of the ZGB (Zwart-Gerber-Belamri) cavitation model with the RANS (Reynolds Averaged Navier-Stokes), the realizable k-epsilon turbulence model, and compressibility of gas/liquid models for cavitation simulation in a multi-hole fuel injector at different cavitation numbers (CN) for diesel and biodiesel fuels. The prediction results were assessed quantitatively by comparison of predicted velocity profiles with those of measured LDV (Laser Doppler Velocimetry) data. Subsequently, predictions were assessed qualitatively by visual comparison of the predicted void fraction with experimental CCD (Charged Couple Device) recorded images. Both comparisons showed that the model could predict fluid behavior in such a condition with a high level of confidence. Additionally, flow field analysis of numerical results showed the formation of vortices in the injector sac volume. The analysis showed two main types of vortex structures formed. The first kind appeared connecting two adjacent holes and is known as “hole-to-hole” connecting vortices. The second type structure appeared as double “counter-rotating” vortices emerging from the needle wall and entering the injector hole facing it. The use of RANS proved to save significant computational cost and time in predicting the cavitating flow with good accuracy.

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