Numerical study on the interaction between the internal and surface waves by a 2D hydrofoil moving in two-layer stratified fluid

2020 ◽  
pp. 147509022097416
Author(s):  
Kwan-Woo Kim ◽  
Ju-Han Lee ◽  
Kwang-Jun Paik ◽  
Weoncheol Koo ◽  
Young-Gyu Kim
Keyword(s):  
Internal Wave ◽  
Water Temperature ◽  
Mixture Model ◽  
Numerical Study ◽  
Stratified Flow ◽  
Stratified Fluid ◽  
Flow Volume ◽  
Cfd Model ◽  
Vof Model ◽  
Submergence Depth

The water temperature in the ocean varies according to its depth and generates a thermocline layer. An internal wave can be excited by an object moving near the thermocline layer because the density changes owing to the water temperature. The internal wave propagates and interacts with the surface wave. This study aims to investigate the internal wave propagation in a two-layer stratified flow, generated by 2D hydrofoil (NACA0012) using a RANS based CFD model. Eulerian multiphase methods were used for the modeling of the two-layer stratified flow; Volume of Fluid (VOF) model and mixture model. A two-layer stratified fluid consisting of air(ρair)-water1(ρw1)-water2(ρw2) is considered instead of the thermocline layer to simplify the numerical simulations. The generation and propagation of the internal wave were investigated, with different configurations of the speed and submergence depth of the hydrofoil. The result suggested that the VOF model shows better agreement with the experimental data compared to the mixture model.

scholarly journals Numerical Study for Experiment on Wave Pattern of Internal Wave and Surface Wave in Stratified Fluid

2019 ◽  
Vol 33 (3) ◽  
pp. 236-244
Author(s):  
Ju-Han Lee ◽  
Kwan-Woo Kim ◽  
Kwang-Jun Paik ◽  
Won-Cheol Koo ◽  
Yeong-Gyu Kim
Keyword(s):  
Surface Wave ◽  
Internal Wave ◽  
Numerical Study ◽  
Wave Pattern ◽  
Stratified Fluid

Numerical study of internal wave–wave interactions in a stratified fluid

2000 ◽  
Vol 415 ◽  
pp. 65-87 ◽  
Author(s):  
A. JAVAM ◽  
J. IMBERGER ◽  
S. W. ARMFIELD
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Numerical Study ◽  
Experimental Studies ◽  
Interaction Mechanism ◽  
Stratified Fluid ◽  
Interaction Region ◽  
Staggered Grid ◽  
Open Boundary ◽  
Wave Interactions

A finite volume method is used to study the generation, propagation and interaction of internal waves in a linearly stratified fluid. The internal waves were generated using single and multiple momentum sources. The full unsteady equations of motion were solved using a SIMPLE scheme on a non-staggered grid. An open boundary, based on the Sommerfield radiation condition, allowed waves to propagate through the computational boundaries with minimum reflection and distortion. For the case of a single momentum source, the effects of viscosity and nonlinearity on the generation and propagation of internal waves were investigated.Internal wave–wave interactions between two wave rays were studied using two momentum sources. The rays generated travelled out from the sources and intersected in interaction regions where nonlinear interactions caused the waves to break. When two rays had identical properties but opposite horizontal phase velocities (symmetric interaction), the interactions were not described by a triad interaction mechanism. Instead, energy was transferred to smaller wavelengths and, a few periods later, to standing evanescent modes in multiples of the primary frequency (greater than the ambient buoyancy frequencies) in the interaction region. The accumulation of the energy caused by these trapped modes within the interaction region resulted in the overturning of the density field. When the two rays had different properties (apart from the multiples of the forcing frequencies) the divisions of the forcing frequencies as well as the combination of the different frequencies were observed within the interaction region.The model was validated by comparing the results with those from experimental studies. Further, the energy balance was conserved and the dissipation of energy was shown to be related to the degree of nonlinear interaction.

Numerical Study of Turbulence Nanofluid Flow to Distinguish Multiphase Flow Models for In-House Programming

2016 ◽  
Author(s):  
Anchasa Pramuanjaroenkij ◽  
Amarin Tongkratoke ◽  
Sadık Kakaç
Keyword(s):  
Mixture Model ◽  
Heat Exchangers ◽  
High Performance ◽  
Numerical Study ◽  
Experimental Studies ◽  
Working Fluid ◽  
Eulerian Model ◽  
Time Consumption ◽  
Vof Model ◽  
Multiphase Models

Fluid flow with particles are found in many engineering applications such as flows inside lab-on-a-chips and heat exchangers. In heat exchangers, nanofluids or base fluids mixed with nanoparticles are applied to be used as the working fluid instead of the traditional base fluids which have low thermal-physical properties. The nanoparticle diameters are in the range from 1 to 100 nanometers are mixed with the traditional base fluids before they are applied inside the heat exchangers and the nanofluids have been proved continually that they enhance heat transfer rates of the heat exchangers. Turbulent and laminar nanofluid flows have shown different enhancements in different conditions. This work focused on comparing different turbulent nanofluid simulations which used the computational fluid dynamics, CFD, with different multiphase models. The Realizable k-ε turbulence model coupled with three multiphase models; Volume of Fluid (VOF) model, Mixture model and Eulerian model, were considered and compared. The heat exchanger geometry in the work was rectangular as in the electrical device application and the nanofluid was a mixture between Al2O3 and water. All simulated results, then, were compared with experimental results. The comparisons showed that numerical results did not deviate from each other but their delivered-time consumptions and complications were different. If one develops his own code, Eulerian model was the most complicated while Mixture model and Eulerian model consumed longer performing times. Although the Eulerian model delivered-time consumption was long but it provided the best results, so the Eulerian model should be chosen when time consumption and errors play important roles. From this ordinary study, the first significant step of in-house program developments has started. The time consumption still indicated that the high performance computers should be selected, and properties obtained from the experimental studies should be imported to the simulation to increase the result accuracy.

Numerical Study of Pitch Angle on H-Type Vertical Axis Wind Turbine

2012 ◽  
Vol 499 ◽  
pp. 259-264
Author(s):  
Qi Yao ◽  
Ying Xue Yao ◽  
Liang Zhou ◽  
S.Y. Zheng
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Numerical Study ◽  
Vertical Axis ◽  
Azimuth Angle ◽  
Power Coefficient ◽  
Cfd Model ◽  
Vertical Axis Wind Turbine ◽  
Sliding Mesh ◽  
Mesh Technique

This paper presents a simulation study of an H-type vertical axis wind turbine. Two dimensional CFD model using sliding mesh technique was generated to help understand aerodynamics performance of this wind turbine. The effect of the pith angle on H-type vertical axis wind turbine was studied based on the computational model. As a result, this wind turbine could get the maximum power coefficient when pitch angle adjusted to a suited angle, furthermore, the effects of pitch angle and azimuth angle on single blade were investigated. The results will provide theoretical supports on study of variable pitch of wind turbine.

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