Numerical Study of Circular Hydraulic Jump Using Volume-of-Fluid Method

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Mohammad Passandideh-Fard ◽  
Ali Reza Teymourtash ◽  
Mohammad Khavari
Keyword(s):  
Ethylene Glycol ◽  
Parametric Study ◽  
Hydraulic Jump ◽  
Numerical Study ◽  
Volumetric Flow Rate ◽  
Volume Of Fluid ◽  
Vof Method ◽  
Sudden Increase ◽  
Different Types ◽  
Microgravity Conditions

When a vertical liquid jet impacts on a solid and horizontal surface, the liquid starts spreading radially on the surface, until a sudden increase in the fluid height occurs and a circular hydraulic jump (CHJ), easily seen in the kitchen sink, is formed. In this study, the formation of CHJ is numerically simulated by solving the flow governing equations, continuity and momentum equations, along with an equation to track the free surface advection using the volume-of-fluid (VOF) method and Youngs’ algorithm. The numerical model is found to be capable of simulating the jump formation and its different types. Extensive comparisons are performed between the model results and those of the available experiments and modified Watson’s theory. The model is shown to accurately predict the jump location and its behavior. Also a parametric study for the effects of different parameters including volumetric flow rate, downstream height, viscosity and gravity on the jump radius, and its characteristics is carried out. Compared with previous works on CHJ available in the literature, employing the VOF method considering the surface tension effects and performing a full parametric study and a complete comparison with experiments and theory are new in this paper. The simulations are performed for two different liquids, water and ethylene glycol, where it is found that the jump is more stable and its location is less sensitive to the downstream height for the more viscous liquid (ethylene glycol). When the downstream height is increased, the radius of the circular hydraulic jump reduces up to a certain limit after which there would be no stable jump. If the gravity is decreased, the radius of the jump and the length of the transition zone will both increase. The radius of the jump in microgravity conditions is less sensitive to the downstream height than it is in normal gravity.

scholarly journals Effect of the coefficient of restitution and friction in the granular Leidenfrost effect in the absence of gravity. A numerical study

2021 ◽  
Vol 249 ◽  
pp. 14016
Author(s):  
Daniel Schiochet Nasato ◽  
Heiko Briesen
Keyword(s):  
Coefficient Of Friction ◽  
Parametric Study ◽  
Granular Media ◽  
Numerical Study ◽  
Packing Fraction ◽  
Coefficient Of Restitution ◽  
Granular System ◽  
The Coefficient Of Friction ◽  
Leidenfrost Effect ◽  
Microgravity Conditions

In this study the granular Leidenfrost effect in the absence of gravity is investigated numerically by means of the discrete element method. Apart from identifying the phenomena, a parametric study to quantify the influence of the coefficient of restitution and friction in the packing fraction of the granular media is carried on numerically. Surprisingly, both the coefficient of restitution and the coefficient of friction exhibit an influence of the same magnitude in the packing fraction of the granular system, which has not been reported in experiments and simulation of granular Leidenfrost regime under gravity or microgravity conditions.

A Numerical Study on Flow Characteristics of 2D Vertical Liquid Jet Striking a Horizontal Surface

2010 ◽  
Author(s):  
M. Kimiaghalam ◽  
M. Passandideh-Fard
Keyword(s):  
Reynolds Number ◽  
Hydraulic Jump ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Newtonian Liquid ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Moderate Reynolds Number ◽  
Different Types ◽  
Newtonian Liquids

We studied numerically impingement of vertical liquid jets of moderate Reynolds number for both Newtonian and non-Newtonian liquids to clarify the structure formation of circular hydraulic jump and the phenomenon of jet buckling. First, we have studied the hydraulic jump characteristics and governing parameters for a laminar water jet. Moreover, different types of hydraulic jump have been investigated by varying the height of a circular wall around the bed in flow downstream. The results show that a circular hydraulic jump has two kinds of steady states which can be reached by changing wall height. Next, we studied the impingement of a non-Newtonian liquid jet on a solid surface. In this case, we observe that instead of having a significant hydraulic jump, jet buckling phenomenon happens. The results were used in order to achieve a better understanding of the jet buckling phenomenon and the conditions in which this phenomenon happens.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

A Non-Cooperative Game Analysis of Competition between Content Providers in the Internet Market

2019 ◽  
Vol 15 (1) ◽  
pp. 88-104 ◽  
Author(s):  
M'hamed Outanoute ◽  
Hamid Garmani ◽  
Mohamed Baslam ◽  
Rachid El Ayachi ◽  
Belaid Bouikhalene
Keyword(s):  
Quality Of Service ◽  
Detailed Analysis ◽  
Cooperative Game ◽  
Price Of Anarchy ◽  
Numerical Study ◽  
Pure Nash Equilibrium ◽  
Game Analysis ◽  
Different Types ◽  
Internet Market

In internet market, content providers (CPs) continue to play a primordial role in the process of accessing different types of data. Competition in this area is fierce; customers are looking for providers that offer them good content (credibility of content and quality of service) with a reasonable price. In this work, the authors analyze this competition between CPs and the economic influence of their strategies on the market. The authors formulate their problem as a non-cooperative game among multiple CPs for the same market. Through a detailed analysis, the researchers prove uniqueness of a pure Nash Equilibrium (NE). Furthermore, a fully distributed algorithm to converge on the NE point is presented. In order to quantify how efficient the NE point is, a detailed analysis of the Price of Anarchy (PoA) is adopted to ensure the performance of the system at equilibrium. Finally, an extensive numerical study is provided to describe the interactions between CPs and to point out the importance of quality of service (QoS) and credibility of content in the market.

scholarly journals Parametric Analysis of Rotational Effects in Seismic Design of Tall Structures

2021 ◽  
Vol 11 (2) ◽  
pp. 597
Author(s):  
Milan Sokol ◽  
Rudolf Ároch ◽  
Katarína Lamperová ◽  
Martin Marton ◽  
Justo García-Sanz-Calcedo
Keyword(s):  
Seismic Design ◽  
Parametric Study ◽  
Tall Buildings ◽  
Soil Parameters ◽  
Eurocode 8 ◽  
Tall Structures ◽  
Rotational Components ◽  
Different Types ◽  
Depth Study

This paper uses a parametric study to evaluate the significance of the rotational components of Earth’s motion in a seismic design. The parametric study is based on the procedures included in Eurocode 8, Part 6. Although the answer to the question of when the effects of rotational components are important is quite a complex one and requires a more in-depth study, our aim was to try to assess this question in a relatively quick manner and with acceptable accuracy. The first part of the paper is devoted to derivation of a simple formula that can be used for expressing the importance of rotational components in comparison with the classic seismic design without their usage. The quasi-static analysis, assuming inertial forces, is used. A crucial role plays the shape of the fundamental mode of the vibration. Due to simplicity reasons, well-known expression for estimation of the first eigenmode as an exponential function with different power coefficients that vary for different types of buildings is used. The possibility of changing the soil parameters is subsequently included into the formula for estimation of the fundamental frequency of tall buildings. In the next part, the overall seismic analyses of complex FEM models of 3D buildings and chimneys are performed. The results from those analyses are then compared with those from simplified calculations. The importance of the soil characteristics for determination of whether it is necessary to take into account the rotational effects is further discussed.

Bejan’s Constructal Theory Analysis of Gas-Liquid Cooled Finned Modules

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Giulio Lorenzini ◽  
Simone Moretti
Keyword(s):  
Thermal Behavior ◽  
Heat Exchangers ◽  
High Performance ◽  
Numerical Study ◽  
Constructal Theory ◽  
Electronic Components ◽  
Theory Analysis ◽  
Pressure Losses ◽  
Different Types ◽  
Overall Performance

High performance heat exchangers represent nowadays the key of success to go on with the trend of miniaturizing electronic components as requested by the industry. This numerical study, based on Bejan’s Constructal theory, analyzes the thermal behavior of heat removing fin modules, comparing their performances when operating with different types of fluids. In particular, the simulations involve air and water (as representative of gases and liquids), to understand the actual benefits of employing a less heat conductive fluid involving smaller pressure losses or vice versa. The analysis parameters typical of a Constructal description (such as conductance or Overall Performance Coefficient) show that significantly improved performances may be achieved when using water, even if an unavoidable increase in pressure losses affects the liquid-refrigerated case. Considering the overall performance: if the parameter called Relevance tends to 0, air prevails; if it tends to 1, water prevails; if its value is about 0.5, water prevails in most of the case studies.

A Parametric Numerical Study of Radiative Transfer in Thermotropic Materials

2013 ◽  
Author(s):  
Adam C. Gladen ◽  
Susan C. Mantell ◽  
Jane H. Davidson
Keyword(s):  
Particle Size ◽  
Radiative Transfer ◽  
Optical Thickness ◽  
Parametric Study ◽  
Volume Fraction ◽  
Numerical Study ◽  
Anisotropic Scattering ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Size Parameter

A thermotropic material is modeled as an absorbing, thin slab containing anisotropic scattering, monodisperse, spherical particles. Monte Carlo ray tracing is used to solve the governing equation of radiative transfer. Predicted results are validated by comparison to the measured normal-hemispherical reflectance and transmittance of samples with various volume fraction and relative index of refraction. A parametric study elucidates the effects of particle size parameter, scattering albedo, and optical thickness on the normal-hemispherical transmittance, reflectance, and absorptance. The results are interpreted for a thermotropic material used for overheat protection of a polymer solar absorber. For the preferred particle size parameter of 2, the optical thickness should be less than 0.3 to ensure high transmittance in the clear state. To significantly reduce the transmittance and increase the reflectance in the translucent state, the optical thickness should be greater than 2.5 and the scattering albedo should be greater than 0.995. For optical thickness greater than 5, the reflectance is asymptotic and any further reduction in transmittance is through increased absorptance. A case study is used to illustrate how the parametric study can be used to guide the design of thermotropic materials. Low molecular weighted polyethylene in poly(methyl methacrylate) is identified as a potential thermotropic material. For this material and a particle radius of 200 nm, it is determined that the volume fraction and thickness should equal 10% and 1 mm, respectively.

Advanced understanding of local wetting behaviour in gas-liquid-solid packed beds using CFD with a volume of fluid (VOF) method

2017 ◽  
Vol 170 ◽  
pp. 378-392 ◽  
Author(s):  
Wei Du ◽  
Jianzhou Zhang ◽  
Panpan Lu ◽  
Jian Xu ◽  
Weisheng Wei ◽  
...  
Keyword(s):  
Volume Of Fluid ◽  
Vof Method ◽  
Packed Beds

scholarly journals Mixing Characteristics Of Gas-Liquid Flow In A Static Mixer: A Numerical Study

2020 ◽  
Vol 12 (2) ◽  
Author(s):  
Ryan Anugrah Putra
Keyword(s):  
Liquid Velocity ◽  
Numerical Study ◽  
Axial Distance ◽  
Sudden Increase ◽  
Static Mixer ◽  
Mixing Condition ◽  
Mixing Characteristics ◽  
Euler Model ◽  
Gas Liquid Flow ◽  
Liquid Flows

Mixing characteristics of gas-liquid co-current upward flow inside a vertical pipe equipped with a helical static mixer element were numerically investigated. The results from computational fluid dynamics (CFD) simulations with Euler-Euler model of three different length to diameter ratio (L/D) of the static mixer elements were compared. All simulated static mixers provide a better mixing condition in the comparison with the one without a static element. The sudden increase of rotational strength indicated by the liquid velocity curl was observed once the gas-liquid flows enter the static-mixer element zone. The smallest L/D static mixer provides the highest liquid velocity curl in the smallest axial distance providing the most effective mixing process among the tested elements. The best mixing characteristics shown by radial gas distribution was achieved with the static mixer with a smallest L/D.

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