scholarly journals Numerical study of topographically-induced local severe winds in stably stratified fluid

1999 ◽  
Vol 2 ◽  
pp. 583-592 ◽  
Author(s):  
Takanori UCHIDA ◽  
Yuji OHYA
Keyword(s):  
Numerical Study ◽  
Stratified Fluid

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.

On the three-dimensional internal waves excited by topography in the flow of a stratified fluid

1994 ◽  
Vol 263 ◽  
pp. 293-318 ◽  
Author(s):  
Hideshi Hanazaki
Keyword(s):  
Internal Waves ◽  
Numerical Study ◽  
Mach Reflection ◽  
Three Dimensional ◽  
Stratified Fluid ◽  
Linear Wave ◽  
Kp Equation ◽  
Subcritical Flow ◽  
Boussinesq Fluid ◽  
Upstream Waves

A numerical study of the three-dimensional internal waves excited by topography in the flow of a stratified fluid is described. In the resonant flow of a nearly two-layer fluid, it is found that the time-development of the nonlinearly excited waves agrees qualitatively with the solution of the forced KP equation or the forced extended KP equation. In this case, the upstream-advancing solitary waves become asymptotically straight crested because of abnormal reflection at the sidewall similar to Mach reflection. The same phenomenon also occurs in the subcritical flow of a nearly two-layer fluid. However, in the subcritical flow of a linearly stratified Boussinesq fluid, the two-dimensionalization of the upstream waves can be interpreted as the separation of the lateral modes due to the differences in the group velocity of the linear wave, although this does not mean in general that the generation of upstream waves is describable by the linearized equation.

Numerical study of the vorticity generation behind a sphere descending in a density-stratified fluid

2020 ◽  
Vol 2020 (0) ◽  
pp. OS03-15
Author(s):  
Manta TOMITA ◽  
Tatsuya YASUDA ◽  
Shinya OKINO ◽  
Hideshi HANAZAKI
Keyword(s):  
Numerical Study ◽  
Stratified Fluid ◽  
Vorticity Generation

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 Three-dimensional stability of a horizontally sheared flow in a stably stratified fluid

2007 ◽  
Vol 570 ◽  
pp. 297-305 ◽  
Author(s):  
AXEL DELONCLE ◽  
JEAN-MARC CHOMAZ ◽  
PAUL BILLANT
Keyword(s):  
Froude Number ◽  
Dimensional Stability ◽  
Numerical Study ◽  
Three Dimensional ◽  
Stratified Fluid ◽  
Two Dimensional ◽  
Horizontal Shear ◽  
Homogeneous Fluid ◽  
Sheared Flow ◽  
Vertical Scales

This paper investigates the three-dimensional stability of a horizontal flow sheared horizontally, the hyperbolic tangent velocity profile, in a stably stratified fluid. In an homogeneous fluid, the Squire theorem states that the most unstable perturbation is two-dimensional. When the flow is stably stratified, this theorem does not apply and we have performed a numerical study to investigate the three-dimensional stability characteristics of the flow. When the Froude number, Fh, is varied from ∞ to 0.05, the most unstable mode remains two-dimensional. However, the range of unstable vertical wavenumbers widens proportionally to the inverse of the Froude number for Fh ≪ 1. This means that the stronger the stratification, the smaller the vertical scales that can be destabilized. This loss of selectivity of the two-dimensional mode in horizontal shear flows stratified vertically may explain the layering observed numerically and experimentally.

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