scholarly journals Numerical study of drop shape effects in binary drop film interactions for different density ratios

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Jonas Steigerwald ◽  
Anne Geppert ◽  
Bernhard Weigand
Keyword(s):  
Numerical Study ◽  
Drop Shape ◽  
Shape Effects ◽  
Density Ratios

scholarly journals Hydrodynamics Around a Deep-Draft Semi-Submersible With Various Corner Shapes

2018 ◽  
Author(s):  
Yibo Liang ◽  
Longbin Tao
Keyword(s):  
Numerical Model ◽  
Experimental Test ◽  
Numerical Study ◽  
Water Channel ◽  
Hydrodynamic Characteristics ◽  
Shape Design ◽  
Circulating Water ◽  
Fluid Physics ◽  
Shape Effects ◽  
Geometric Study

A numerical study on flow over a stationary deep-draft semi-submersible (DDS) with various corner shapes was carried out to investigate the corner shape effects on the overall hydrodynamics. Three models based on a typical DDS design with different corner shapes were numerically investigated under 45° incidence. The present numerical model has been validated by an experimental test carried out in a circulating water channel. It is demonstrated that, as the corner shape design changed, the hydrodynamic characteristics alter drastically. In addition, the flow patterns were examined to reveal some insights of the fluid physics due to the changing of different corner shape designs. The detailed numerical results from the geometric study will provide a good guidance for future practical designs.

Numerical study of asymmetric and axisymmetric thermal jet with entropy generation concept

2021 ◽  
Vol 15 (1) ◽  
pp. 7628-7636
Author(s):  
D. Belakhal ◽  
Kouider Rahmani ◽  
Amel Elkaroui Elkaroui ◽  
Syrine Ben Haj Ayech ◽  
Nejla Mahjoub Saïd ◽  
...  
Keyword(s):  
Entropy Generation ◽  
Numerical Study ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Variable Density ◽  
Current Investigation ◽  
Numerical Resolution ◽  
Different Temperatures ◽  
Density Ratios ◽  
The Impact

In the current investigation, numerical study of a thermal jet of asymmetric (rectangular and elliptical) and axisymmetric (circular) geometry was investigated with variable density to verify the impact of the ratio of density and geometry on the generation of entropy. The central jet was brought to different temperatures (194, 293 and 2110 K) to obtain density ratios (0.66, 1 and 7.2) identical to a mixture jet ((Air-CO2), (Air-Air) and (Air-He)), respectively. Solving the three-dimensional numerical resolution of the Navier Stocks for turbulent flow permanent enclosed on the turbulence model K-εstandard was made. The results acquired are compared with that carried out in previous experimental studies, where it was concluded that, the axisymmetric (circular) geometry increases the entropy generation.

Suppression of Instabilities in Low-Density Jets via Density-Profile Control

2012 ◽  
Author(s):  
Sukanta Bhattacharjee ◽  
Sumanta Acharya
Keyword(s):  
Density Profile ◽  
Thermal Plasma ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Low Density ◽  
Instability Mode ◽  
Global Instability ◽  
Density Profiles ◽  
Profile Control ◽  
Density Ratios

A numerical study is conducted to understand the global instability of very low-density jets (as encountered in thermal plasmas). The simulations have been carried out for different density ratios, S = ρj /ρ∞, ranging from 0.5 to 0.01, and different Reynolds numbers. The results show that the global instability mode exists in the range of density ratios investigated. A strategy for reducing the instability by altering the density profile of the surrounding gas stream is explored. Specifically, a ramp density profile or a step shape with an outward offset was studied, and it was observed that there was a reduction in the instability amplitude with the modified density profiles. Such a lowering in the instability fluctuations can be beneficial in stabilizing the thermal plasma behavior.

scholarly journals Hydrodynamics Around a Deep-Draft Semi-Submersible With Biomimetic Tubercle Corner Design

2019 ◽  
Author(s):  
Yibo Liang ◽  
Weichao Shi ◽  
Longbin Tao
Keyword(s):  
Shear Layer ◽  
Numerical Study ◽  
Three Dimensional ◽  
Leading Edge ◽  
Hydrodynamic Performance ◽  
Shape Design ◽  
Fluid Physics ◽  
Motion Responses ◽  
Shape Effects ◽  
Spanwise Flow

Abstract Leading-edge tubercles have been investigating widely on the performance of foils in the last decade. In this study, the biomimetic tubercle design has been applied to the corner shape on a deep-draft semi-submersible. A numerical study on flow over a deep-draft semi-submersible (DDS) with a biomimetic tubercle corner shape was carried out to investigate the corner shape effects on the overall hydrodynamics and motion responses. The hydrodynamic performance of the biomimetic tubercle corner is compared with a traditional round corner design platform. It is demonstrated that, as the corner shape design changed, the motion responses alter drastically. In addition, the flow patterns were examined to reveal some insights into fluid physics due to the biomimetic tubercle corner design. The comprehensive numerical results showed that the three-dimensional effect, which causes spanwise flow, can be reduced by a continuous spanwise (column-wise) variation of the shear-layer separation points.

A Preliminary Numerical Study on the Effect of High Freestream Turbulence on Anti-Vortex Film Cooling Design at High Blowing Ratio

2010 ◽  
Author(s):  
Benson K. Hunley ◽  
Andrew C. Nix ◽  
James D. Heidmann
Keyword(s):  
Heat Flux ◽  
Film Cooling ◽  
Numerical Study ◽  
Length Scale ◽  
Freestream Turbulence ◽  
Blowing Ratio ◽  
Net Heat Flux ◽  
Cooling Design ◽  
Adiabatic Effectiveness ◽  
Density Ratios

Researchers at NASA Glenn Research Center have developed and investigated a novel film cooling design, the anti-vortex hole (AVH), which has been shown to cancel or counter the vorticity generated by conventional holes and increase film effectiveness at high blowing ratios and low turbulence levels. This paper presents preliminary CFD results on the film effectiveness and net heat flux reduction at high blowing ratio and elevated freestream turbulence levels for the adjacent AVH. Baseline cases at low turbulence levels of 5% intensity and length scale of Λx/dm = 1 with a nominal blowing ratio of 2 and a density ratios of 1 and 2 were compared to previous results reported by Heidmann [1]. Higher freestream turbulence cases were investigated with a turbulence intensity and length scale of 10% and Λx/dm = 1 and 3, respectively. Results showed that higher freestream turbulence improves adiabatic effectiveness for the AVH design.

scholarly journals Three-dimensional multimode Rayleigh–Taylor and Richtmyer–Meshkov instabilities at all density ratios

2003 ◽  
Vol 21 (3) ◽  
pp. 327-334 ◽  
Author(s):  
D. KARTOON ◽  
D. ORON ◽  
L. ARAZI ◽  
D. SHVARTS
Keyword(s):  
Theoretical Model ◽  
Statistical Model ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Three Dimensional ◽  
3D Simulations ◽  
Analysis Scheme ◽  
Wide Range ◽  
Density Ratios ◽  
Good Agreement

The three-dimensional (3D) turbulent mixing zone (TMZ) evolution under Rayleigh–Taylor and Richtmyer–Meshkov conditions was studied using two approaches. First, an extensive numerical study was made, investigating the growth of a random 3D perturbation in a wide range of density ratios. Following that, a new 3D statistical model was developed, similar to the previously developed two-dimensional (2D) statistical model, assuming binary interactions between bubbles that are growing at a 3D asymptotic velocity. Confirmation of the theoretical model was gained by detailed comparison of the bubble size distribution to the numerical simulations, enabled by a new analysis scheme that was applied to the 3D simulations. In addition, the results for the growth rate of the 3D bubble front obtained from the theoretical model show very good agreement with both the experimental and the 3D simulation results. A simple 3D drag–buoyancy model is also presented and compared with the results of the simulations and the experiments with good agreement. Its extension to the spike-front evolution, made by assuming the spikes' motion is governed by the single-mode evolution determined by the dominant bubbles, is in good agreement with the experiments and the 3D simulations. The good agreement between the 3D theoretical models, the 3D numerical simulations, and the experimental results, together with the clear differences between the 2D and the 3D results, suggest that the discrepancies between the experiments and the previously developed models are due to geometrical effects.

Numerical Simulation of Hydrodynamics of a Heavy Liquid Drop Covered by Vapor Film in a Water Pool

2002 ◽  
Author(s):  
W. M. Ma ◽  
Z. L. Yang ◽  
A. Giri ◽  
B. R. Sehgal
Keyword(s):  
Level Set ◽  
Liquid Drop ◽  
Numerical Study ◽  
Immiscible Fluids ◽  
Navier Stokes ◽  
Vapor Film ◽  
Water Pool ◽  
Reactor Accident ◽  
Density Ratios ◽  
Level Set Approach

A numerical study on the hydrodynamics of a droplet covered by vapor film in water pool is carried out. Two level set functions are used as to implicitly capture the interfaces among three immiscible fluids (melt-drop, vapor and coolant). This approach leaves only one set of conservation equations for the three phases. A high-order Navier-Stokes solver, called Cubic-Interpolated Pseudo-Particle (CIP) algorithm, is employed in combination with level set approach, which allows large density ratios (up to 1000), surface tension and jump in viscosity. By this calculation, the hydrodynamic behavior of a melt droplet falling into a volatile coolant is simulated, which is of great significance to reveal the mechanismof steam explosion during a hypothetical severe reactor accident.

scholarly journals A Numerical Study of Anti-Vortex Film Cooling Designs at High Blowing Ratio

2008 ◽  
Author(s):  
James D. Heidmann
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Experimental Studies ◽  
Navier Stokes ◽  
Round Hole ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Lift Off ◽  
Density Ratios ◽  
Film Cooling Holes

A concept for mitigating the adverse effects of jet vorticity and lift-off at high blowing ratios for turbine film cooling flows has been developed and studied at NASA Glenn Research Center. This “anti-vortex” film cooling concept proposes the addition of two branched holes from each primary hole in order to produce a vorticity counter to the detrimental kidney vortices from the main jet. These vortices typically entrain hot freestream gas and are associated with jet separation from the turbine blade surface. The anti-vortex design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The anti-vortex film cooling hole concept has been modeled computationally for a single row of 30 degree angled holes on a flat surface using the 3D Navier-Stokes solver Glenn-HT. A modification of the anti-vortex concept whereby the branched holes exit adjacent to the main hole has been studied computationally for blowing ratios of 1.0 and 2.0 and at density ratios of 1.0 and 2.0. This modified concept was selected because it has shown the most promise in recent experimental studies. The computational results show that the modified design improves the film cooling effectiveness relative to the round hole baseline and previous anti-vortex cases, in confirmation of the experimental studies.

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