scholarly journals NUMERICAL INVESTIGATION OF TURBULENT BUBBLY FLOW UNDER BREAKING WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 66
Author(s):  
James T Kirby ◽  
Gangfeng Ma ◽  
Morteza Derakhti ◽  
Fengyan Shi
Keyword(s):  
Surf Zone ◽  
Bubbly Flow ◽  
Temporal Distribution ◽  
Breaking Waves ◽  
Air Bubbles ◽  
Computational Framework ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Air Water Interface ◽  
Entrained Air

We establish a framework for describing the spatial and temporal distribution of entrained air bubbles under breaking surface waves. The computational framework is based on a large eddy simulation (LES) in 3-D together with a VOF treatment of the air-water interface. An Eulerian multiphase approach is used in order to track the entrained bubbles as a number density distribution. Examples of numerical results for breaking periodic surf zone waves are illustrated.

A Large Eddy Simulation of the Bubbly Flow in Vertical Tube

2012 ◽  
Author(s):  
Peng Zhang ◽  
Xu Hong
Keyword(s):  
Large Eddy Simulation ◽  
Eddy Viscosity ◽  
Bubbly Flow ◽  
Turbulence Models ◽  
Vertical Tube ◽  
Simulation Approach ◽  
Bubble Distribution ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Two Fluid

This paper simulates the dispersed bubbly flow in a vertical tube with two different turbulence models based on Eulerian two-fluid frameworks. Both the RANS (Reynolds Averaged N-S equation) approach and LES (Large Eddy Simulation) approach can get results agreed with experiment well. The “wall peak” bubble distribution is captured. Compare with RANS with SST (Shear Stress Transport) turbulence model, the LES with WALE (Wall-Adapted Local Eddy-viscosity) sub-grid model can give transient and detail information of the flow field, and it shows better agreement.

scholarly journals Measurement of Convective Entrainment Using Lagrangian Particles

2013 ◽  
Vol 70 (1) ◽  
pp. 266-277 ◽  
Author(s):  
Kyongmin Yeo ◽  
David M. Romps
Keyword(s):  
Direct Measurement ◽  
Cloud Base ◽  
Entrainment Rate ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Environmental Air ◽  
Cumulus Congestus ◽  
Entrained Air ◽  
Eulerian Methods ◽  
Good Agreement

Abstract Lagrangian particle tracking is used in a large-eddy simulation to study an individual cumulus congestus. This allows for the direct measurement of the convective entrainment rate and of the residence times of entrained parcels within the cloud. The entrainment rate obtained by Lagrangian direct measurement is found to be higher than that obtained using the recently introduced method of Eulerian direct measurement. This discrepancy is explained by the fast recirculation of air in and out of cloudy updrafts, which Eulerian direct measurement is unable to resolve. By filtering these fast recirculations, the Lagrangian calculation produces a result in very good agreement with the Eulerian calculation. The Lagrangian method can also quantify some aspects of entrainment that cannot be probed with Eulerian methods. For instance, it is found that more than half of the air that is entrained by the cloud during its lifetime is air that was previously detrained by the cloud. Nevertheless, the cloud is highly diluted by entrained air: for cloudy air above 2 km, its mean height of origin is well above the cloud base. This paints a picture of a cloud that rapidly entrains both environmental air and its own detritus.

scholarly journals Analysis of Air Bubbles in the Surf Zone Breaking Waves by Imaging Technique

2009 ◽  
Vol 65 (1) ◽  
pp. 96-100
Author(s):  
Yusuke MATSUO ◽  
Nobuhito MORI ◽  
Takaaki SHIGEMATSU ◽  
Shohachi KAKUNO
Keyword(s):  
Surf Zone ◽  
Imaging Technique ◽  
Breaking Waves ◽  
Air Bubbles

scholarly journals Numerical Study on Tsunami Hazard Mitigation Using a Submerged Breakwater

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Taemin Ha ◽  
Jeseon Yoo ◽  
Sejong Han ◽  
Yong-Sik Cho
Keyword(s):  
Wave Reflection ◽  
Surf Zone ◽  
Numerical Study ◽  
Tsunami Hazard ◽  
Coastal Communities ◽  
Coastal Structures ◽  
Accurate Analysis ◽  
Submerged Breakwater ◽  
Eddy Simulation ◽  
Large Eddy

Most coastal structures have been built in surf zones to protect coastal areas. In general, the transformation of waves in the surf zone is quite complicated and numerous hazards to coastal communities may be associated with such phenomena. Therefore, the behavior of waves in the surf zone should be carefully analyzed and predicted. Furthermore, an accurate analysis of deformed waves around coastal structures is directly related to the construction of economically sound and safe coastal structures because wave height plays an important role in determining the weight and shape of a levee body or armoring material. In this study, a numerical model using a large eddy simulation is employed to predict the runup heights of nonlinear waves that passed a submerged structure in the surf zone. Reduced runup heights are also predicted, and their characteristics in terms of wave reflection, transmission, and dissipation coefficients are investigated.

Large eddy simulation of breaking waves

2001 ◽  
Vol 42 (1) ◽  
pp. 53-86 ◽  
Author(s):  
Erik Damgaard Christensen ◽  
Rolf Deigaard
Keyword(s):  
Large Eddy Simulation ◽  
Breaking Waves ◽  
Eddy Simulation ◽  
Large Eddy

Three-Dimensional Large Eddy Simulation of Breaking Waves

1999 ◽  
Vol 41 (3-4) ◽  
pp. 281-301 ◽  
Author(s):  
Yasunori Watanabe ◽  
Hiroshi Saeki
Keyword(s):  
Large Eddy Simulation ◽  
Three Dimensional ◽  
Breaking Waves ◽  
Eddy Simulation ◽  
Large Eddy

Experimental Study of Turbulence and Entrained Air Characteristics in a Plunging Breaking Solitary Wave

2020 ◽  
Vol 03 (01n02) ◽  
pp. 2050001
Author(s):  
Lian Tang ◽  
Yun-Ta Wu ◽  
Onyx. W. H. Wai ◽  
Pengzhi Lin
Keyword(s):  
Solitary Wave ◽  
Void Fraction ◽  
High Speed ◽  
Surf Zone ◽  
Phase Speed ◽  
Breaking Waves ◽  
High Speed Camera ◽  
Ensemble Averaging ◽  
The Mean ◽  
Entrained Air

The entrained air and turbulence characteristics under a breaking solitary wave on a 1:20 sloping beach are investigated through laboratory measurement. Free surface elevation is obtained from wave gauge measurements. Wave breaking process is captured in detail by a high-speed camera. The bubble image velocimetry (BIV) is used to measure the velocity and the fiber optic reflectometer (FOR) is used to capture instantaneous void fraction in the aerated region. The mean void fraction and velocities in the aerated region are obtained by ensemble averaging over 22 repetitions. Results show that the maximum mean void fraction is 0.6 in the collapsing cavity region and is 0.35 in the splash up region. The time series of the mean void fraction has good synchronization with the instantaneous images taken by high-speed camera. The maximum horizontal velocity occurs in the splash up region and reaches 1.17C shortly after the plunging jet hits the water surface, with C being the phase speed of the primary wave. The turbulence intensities over the entire aerated region are presented and discussed. The measured data can be used for the calibration and verification of the numerical model for aerated flows simulation under breaking waves in the surf zone.

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