Effect of Development-Zone Restrictions on the Turbulent Characteristics of Impinging Jet Flow

2011 ◽  
Author(s):  
Takefumi Kawaguchi ◽  
Chandra Shekhar ◽  
Koichi Nishino
Keyword(s):  
Impinging Jet ◽  
Jet Flow ◽  
Stagnation Region ◽  
Development Zone ◽  
Potential Core ◽  
Turbulent Statistics ◽  
Piv Measurement ◽  
Turbulent Characteristics ◽  
Inner Diameter ◽  
Solid Block

This study is to examine the turbulent characteristics of an axisymmetric impinging jet flow in the stagnation region. The flow measurement is carried out using a standard PIV technique. The changes of the turbulent characteristics of the jet with various levels of the development-zone restriction are examined. The restrictions are imposed by putting an annular, concentric, solid block around the jet, and then varying its inner diameter. The PIV measurement of the flow field is carried out for each case. The height of the block is kept constant for all the cases, with the Reynolds number of 5000, which falls well within the turbulent range. The instantaneous velocity data obtained from the PIV measurement is used to calculate the turbulent statistics. The results are compared for all of the cases. In consequence, it is found that the turbulent statistics do not change much for the block’s inner diameter larger than a critical value, which is found to be three times the inlet diameter of the jet. However, if it is smaller, the turbulent statistics vary significantly, as the inner wall of the block damages the development of the potential core of the jet.

Nonlinear Stability Analysis of Thin Film Flow from a Liquid Jet Impinging on a Circular Concentric Disk

2006 ◽  
Vol 22 (2) ◽  
pp. 115-124 ◽  
Author(s):  
P.-J. Cheng ◽  
H.-Y. Lai
Keyword(s):  
Thin Film ◽  
Linear Stability ◽  
Film Flow ◽  
Multiple Scales ◽  
Impinging Jet ◽  
Jet Flow ◽  
Liquid Jet ◽  
Conditional Stability ◽  
Thin Film Flow ◽  
Potential Core

AbstractThe paper investigates the stability of thin film flow from a liquid jet impinging on a circular concentric disk using a long-wave perturbation method to solve for the generalized nonlinear kinematic equations of free film interface. To begin with a normal mode approach is employed to obtain the linear stability solution for the film flow. In the linear stability solutions only subcritical region can be resolved. In other words, no solution of supercritical region can be obtained in linear domain. Furthermore, the role that the forces of gravitation and surface tension play in the flow is nothing but to stabilize the system. To further investigate the realistic impinging jet flow stability conditions, the weak nonlinear dynamics of a film flow is studied by using the method of multiple scales. Various subcritical nonlinear behaviors expressed in terms of absolute stability, conditional stability and explosive instability can be characterized by solving the Ginzburg-Landau equation. It is found that the jet flow will become relatively unstable for an increasing Reynolds number, a relative smaller distance from the center of the impinging jet on the disk and a smaller diameter of the exit jet. It is also concluded that the flow will always stay in a subcritical instability region if the characteristic diameter of the potential core at nozzle exit is less than 0.01mm for the numerical conditions given in this paper. In such a case when the amplitude of external flow disturbance is smaller than the threshold amplitude a stable jet flow can be ensured.

scholarly journals Trubulence Characteristics in the Stagnation Region of an Axisymmetric Impinging Jet Flow.

1996 ◽  
Vol 62 (594) ◽  
pp. 474-482
Author(s):  
Koichi NISHINO ◽  
Masanori SAMADA ◽  
Keiichi KASUYA ◽  
Kahoru TORII
Keyword(s):  
Impinging Jet ◽  
Jet Flow ◽  
Stagnation Region

Turbulence statistics in the stagnation region of an axisymmetric impinging jet flow

1996 ◽  
Vol 17 (3) ◽  
pp. 193-201 ◽  
Author(s):  
Koichi Nishino ◽  
Masanori Samada ◽  
Keiichi Kasuya ◽  
Kahoru Torii
Keyword(s):  
Impinging Jet ◽  
Jet Flow ◽  
Turbulence Statistics ◽  
Stagnation Region

scholarly journals Examination of Reynolds number effect on the development of round jet flow

2021 ◽  
pp. 39-47
Author(s):  
Olanrewaju Miracle Oyewola ◽  
Adebunmi Okediji ◽  
Olusegun Olufemi Ajide ◽  
Muyiwa Samuel Adaramola
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Jet Flow ◽  
Exit Section ◽  
Ambient Fluid ◽  
Potential Core ◽  
Round Jet ◽  
Reynolds Number Effect ◽  
Downstream Distance ◽  
Low Reynolds

In this study, the Reynolds number effect on the development of round jet flow is presented. The jet is produced from a smoothly contracting round nozzle and the flow structure is controlled by varying the air blower speed in order to obtain various Reynolds numbers (Re). The flow Reynolds number considered varies between 1140 and 9117. Mean velocity measurements were taken using hot-wire probe at different axial and lateral distances (0≤x/d≤50, where x is the downstream distance and d is the nozzle diameter) for the jet flow and at for 0≤x/d≤30 in long pipe attached to the nozzle. Measurements reveal that Reynolds number dictate the potential core length such that the higher the Reynolds number, the lower the potential core which is a measure of mixing of jet and ambient fluid. It shows that further away from the jet exit section, potential core decreases as Reynolds number increases, the velocity profile has a top hat shape very close to the nozzle exit and the shape is independent of Reynolds number. It is found that potential core extends up to x/d=8 for Reynolds number of 1140 as against conventional near field 0≤x/d≤6. This may suggest effect of very low Reynolds number. However, further investigation is required to ascertain this at extremely low Reynolds numbers. It is also observed that further away from the jet exit section, the higher the downstream distance, the higher the jet half-width (R1/2). Furthermore, the flow in the pipe shows almost constant value of normalised axial centerline velocity for a longer distance and this clearly indicates that there is mass redistribution rather than entrainment of ambient fluid. Overall, the Reynolds number controls the magnitude rather than the wavelength of the oscillation

scholarly journals Experimental Investigation of Nozzle Spacing Effects on Characteristics of Round Twin Free Jets

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Andrew Laban ◽  
Seyed Sobhan Aleyasin ◽  
Mark Francis Tachie ◽  
Mike Koupriyanov
Keyword(s):  
Symmetry Plane ◽  
Shear Layers ◽  
Significant Rise ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Potential Core ◽  
Turbulent Statistics ◽  
Spacing Ratio ◽  
Stress Ratios ◽  
Nozzle Spacing

The objective of this paper is to investigate the effects of nozzle spacing on the mean velocity and higher-order turbulent statistics of free twin round jets produced from sharp contraction nozzles. The experiments were performed in an air chamber where four nozzle spacing ratios, S/d = 2.8, 4.1, 5.5, and 7.1, were investigated at a fixed Reynolds number of 10,000. A planar particle image velocimetry (PIV) system was used to conduct the velocity measurements. The results show that downstream of the potential core, a reduction in spacing ratio leads to an earlier and more intense interaction between the jets, indicated by enhanced half-velocity width spread rate in the inner shear layers and a significant rise of turbulent intensities and vorticity thickness along the symmetry plane. A reduction in spacing ratio, however, confines the ambient fluid entrainment along the inner shear layers leading to a reduced core jet velocity decay rate. The closer proximity of the jets also leads to the decrease of Reynolds stresses in the inner shear layers but not in the outer shear layers. The Reynolds stress ratios along the jet centerline reveal the highest anisotropy in the potential core region.

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