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 of Flow Characteristics Around Confined Cylinder using OpenFOAM

2018 ◽  
Vol 7 (4.35) ◽  
pp. 617
Author(s):  
P. Mathupriya ◽  
L. Chan ◽  
H. Hasini ◽  
A. Ooi
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Numerical Study ◽  
Vortex Formation ◽  
Plane Channel ◽  
Flow Characteristics ◽  
Strong Interactions ◽  
Two Dimensional ◽  
Computational Fluid Dynamics Cfd ◽  
Shedding Frequency

The numerical study of the flow over a two-dimensional cylinder which is symmetrically confined in a plane channel is presented to study the characteristics of vortex shedding. The numerical model has been established using direct numerical simulation (DNS) based on the open source computational fluid dynamics (CFD) code named OpenFOAM. In the present study, the flow fields have been computed at blockage ratio, β of 0.5 and at Reynolds number, Re of 200 and 300. Two-dimensional simulations investigated on the effects of Reynolds number based on the vortex formation and shedding frequency. It was observed that the presence of two distinct shedding frequencies appear at higher Reynolds number due to the confinement effects where there is strong interactions between boundary layer, shear layer and the wake of the cylinder. The range of simulations conducted here has shown to produce results consistent with that available in the open literature. Therefore, OpenFOAM is found to be able to accurately capture the complex physics of the flow.

Numerical Study of Inlet and Geometry Effects on Discharge Coefficients for Liquid Jet Emanating From a Plain-Orifice Atomizer

2002 ◽  
Vol 18 (3) ◽  
pp. 153-161 ◽  
Author(s):  
Chun-Lang Yeh
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Discharge Coefficient ◽  
Numerical Study ◽  
Surface Force ◽  
Diameter Ratio ◽  
The Body ◽  
Liquid Jet ◽  
Discharge Coefficients ◽  
Geometry Effects

AbstractA computational model for flow in a plain-orifice atomizer is established to examine the inlet and geometry effects on discharge coefficients. The volume of fluid (VOF) method with finite volume formulation was employed to capture the liquid/gas interface. A continuum Surface Force (CSF) model was adopted to model the surface tension. The body-fitted coordinate system was used to facilitate the configuration of the atomizer. The influences of the inlet chamfer angle, the orifice length/diameter ratio, the Reynolds number, and the inlet turbulence intensity are analyzed. It is found that the optimum discharge coefficient occurs at a chamfer angle of about 50°. The discharge coefficient at first increases with the increase in the orifice length/diameter ratio and then it decreases. The discharge coefficient increases with the increase in the Reynolds number up to Re = 40000, after which it remains sensibly constant. The influence of the inlet turbulence intensity on discharge coefficient is not significant, especially for a longer orifice.

Numerical Analysis of Sub-Millimeter-Scale Microturbomachinery Aerothermodynamics

2008 ◽  
Author(s):  
Philippe B. Martel ◽  
Luc G. Fre´chette
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Microelectromechanical Systems ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Viscous Effects ◽  
Analysis And Design ◽  
Moderate Reynolds Number ◽  
Throat Width ◽  
Solid Foundation

This paper presents a complete numerical study of the aerothermodynamics of subsonic moderate Reynolds number microturbomachinery using 2D computational fluid dynamics (CFD) on 24 cascade geometries and covering over 2000 conditions. Profile and mixing losses, as well as deviation and heat transfer correlations are developed for use in mean-line analysis and design. Both losses and thermal transfer tend to increase with decreasing Reynolds number, Mach number, and throat width. Deviation follows large scale turbomachinery behavior but tends to increase with viscous effects. A slender cascade geometry using a modified profile is suggested, potentially increasing isentropic efficiency by as much as 15%. This work defines a solid foundation for the design of microturbines used in power microelectromechanical systems (MEMS), such as gas and steam microturbines with sub-millimeter-scale blade chords operating at moderate Reynolds numbers (100 < Rec < 2000).

Numerical Study of Airfoil Tonal Noise Reduction using Segmented Elastic Panel Configuration

2021 ◽  
Vol 263 (4) ◽  
pp. 2916-2929
Author(s):  
Arif Muhammad Irsalan ◽  
Garret C. Y. Lam ◽  
Randolph C. K. Leung
Keyword(s):  
Reynolds Number ◽  
Noise Reduction ◽  
Numerical Study ◽  
Separation Bubble ◽  
Low Reynolds Number ◽  
Flow Characteristics ◽  
Tonal Noise ◽  
Airfoil Surface ◽  
Passive Method ◽  
Low Reynolds

In this paper, a novel passive method for airfoil tonal noise reduction is proposed using a configuration of two segmented elastic panels mounted on the airfoil. Numerical investigation using perturbation evolution method is carried out at a low Reynolds number based on airfoil chord of 5x10 and an angle of attack of 5. The passive method of employing a single panel has shown promising tonal noise reduction capabilities where the resonating panel located just ahead of the sharp growth of boundary layer instability within the airfoil separation bubble provided the strongest reduction of instabilities and noise reduction up to 3 dB has been achieved. The idea is extended in the present study by employing a two-panel configuration based on the localized flow characteristics over the airfoil surface. Five different panel configurations are designed and their effectiveness in terms of tonal noise reduction is evaluated and compared with baseline configuration. The azimuth and spectral analyses indicate the different extent of noise reduction for each configuration and even noise amplification in one of them. A significant noise reduction up to 8 dB is observed for the optimum configuration indicating the effectiveness of this novel method for devices operating at low Reynolds number.

Impingement Heat Transfer of Free-Surface Liquid Jets

2002 ◽  
Author(s):  
Albert Y. Tong
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Stagnation Region ◽  
Navier Stokes Equations ◽  
Impingement Heat Transfer

The problem of convective heat transfer of a circular liquid jet impinging onto a substrate is studied numerically. The objective of the study is to understand the hydrodynamics and heat transfer of the impingement process. The Navier-Stokes equations are solved using a finite-volume formulation. The free surface of the jet is tracked by the volume-of-fluid method. The energy equation is modeled by using an enthalpy-based formulation. Detailed flow fields as well as free surface contours and pressure distributions on the substrate have been obtained. Local Nusselt number variations along the solid surface have also been calculated. The effects of several key parameters on the hydrodynamics and heat transfer of an impinging liquid jet have been examined. It has been found that the jet-inlet velocity profile and jet elevation have a significant effect on the hydrodynamics and heat transfer, particularly in the stagnation region, of an impinging jet. The numerical results have been compared with experimental data obtained from the literature. The close agreement supports the validity of the numerical study.

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.

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