Characteristics of Sheet Formed by Collision of Two Elliptical Jets at Short Impact Distance

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Fei Zhao ◽  
Li-jun Yang ◽  
Chao-jie Mo ◽  
Xue-de Li
Keyword(s):  
Axial Ratio ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Force Balance ◽  
Liquid Jets ◽  
Balance Equations ◽  
Oblique Collision ◽  
Circular Jets ◽  
Good Agreement ◽  
Impact Distance

The research on characteristics of impinging jet has a long history and focuses mainly on the circular jets, whereas the impingement of noncircular jets, such as elliptical jets, receives much less attention. This paper investigated liquid sheet resulting from the oblique collision of two elliptical jets at short impact distance. The elliptical liquid jets contract and collide obliquely at impact point, forming a sheet in the form of a leaf bounded by a thicker rim. An improved theoretical model, taking jet contraction into account, for two elliptical impinging jets is established. The sheet features are obtained by combining the conservation equations between the liquid jet and sheet with the force balance equations of the sheet rim. The calculated sheet shapes are compared with the experiments, and the results show good agreement. The experimental results also indicate that the liquid sheet formed by elliptical jets tends to be larger and more unstable than that formed by circular jets. Based on the model, the effects of axial ratio and impact distance on the sheet characteristics, such as sheet shape and thickness, are also studied.

Study on some Aspects of Breakup Characteristics of Power-Law Fluid with Impinging Jets Based on Mechanics Properties

2012 ◽  
Vol 625 ◽  
pp. 57-60
Author(s):  
En Dong Wang ◽  
Yan Yin ◽  
Qing Du
Keyword(s):  
Power Law ◽  
High Speed ◽  
Wave Length ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
Power Law Fluid ◽  
Round Jets ◽  
Breakup Length ◽  
Jet Velocity

Shear-thinning power-law fluid is a kind of non-Newtonian fluid in which the viscosity is a function of shear rate. Impinging jets system is used to study the breakup characteristics of power-law liquid sheets formed by two symmetrical round jets in this study. High quality images are obtained from the experiment with a high speed camera and breakup length is extracted from the images. Closed-rim sheet, web-like sheet and ligaments sheet are observed with the increase of jet velocity. A series of images show that the wave length on the surface of sheets tends to decline as the jet velocity increases. At a low We number, the breakup length increases with an increasing We number. However, it first increases and then decreases when the liquid sheet breaks up at a high We number. The liquid jets with larger diameter collide to each other and lead to a liquid sheet with a smaller breakup length.

Detailed Numerical Simulation of Two Impinging Jets With Moderate Injection Velocities

2019 ◽  
Author(s):  
Yue Ling ◽  
Weixiao Shang ◽  
Jun Chen
Keyword(s):  
Thickness Distribution ◽  
Sheet Thickness ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
Rocket Engines ◽  
Flow Solver ◽  
Plane Normal ◽  
Jet Injectors ◽  
Propellant Rocket

Abstract Impinging-jet injectors are commonly used in liquid propellant rocket engines. Two cylindrical liquid jets impinge at a certain angle and form a liquid sheet in the plane normal to the jets. When the Reynolds and Weber numbers are large, the liquid sheet becomes unstable and disintegrates into liquid ligaments and droplets. In the present study, we focus on cases with moderate injection velocities so that the liquid sheet remains unbroken. Detailed numerical simulations are performed using the adaptive multiphase flow solver, Basilisk. The volume-of-fluid method is used to resolve the gas-liquid interface. Grid-refinement studies are conducted to verify the formation of the liquid sheet is accurately captured in simulation. The numerical results are compared to the recent experimental measurement of the sheet thickness distribution by partial coherent interferometry and a good agreement is achieved.

Thickness Variation of a Liquid Sheet Formed by Two Impinging Jets Using Holographic Interferometry

1998 ◽  
Vol 120 (3) ◽  
pp. 482-487 ◽  
Author(s):  
Y.-B. Shen ◽  
D. Poulikakos
Keyword(s):  
Holographic Interferometry ◽  
Thickness Distribution ◽  
Azimuthal Angle ◽  
Radial Distance ◽  
Sheet Thickness ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
Thickness Variation ◽  
Proportionality Constant

In the work presented in this paper a real time holographic interferometry technique is developed to measure instantaneously and nonintrusively the thickness distribution of a liquid sheet formed by the impingement of two liquid jets. The experimental results are compared with earlier largely unverified analytical predictions. It is shown that the assumption that the sheet thickness is inversely proportional to the radial distance from the impingement point is in principle good. The dependence of the theoretically obtained proportionality constant on the azimuthal angle, however, while exhibiting the same trend it also shows some quantitative differences. Reasons are given in the context of the work. In addition, a weak effect of the jet velocity on the proportionality constant is found to exist. In the theories no such effect was modeled. Finally, comparisons between theoretical and experimental isothickness contours show differences. Overall, there appears to be a justification for improved theoretical studies including effects such as that of gravitation.

HOLOGRAPHY EXPERIMENTS IN THE BREAKUP REGION OF A LIQUID SHEET FORMED BY TWO IMPINGING JETS

1995 ◽  
Vol 5 (4-5) ◽  
pp. 387-402 ◽  
Author(s):  
B. S. Kang ◽  
Y. B. Shen ◽  
D. Poulikakos
Keyword(s):  
Impinging Jets ◽  
Liquid Sheet

Thermal Performance Analysis of a Rectangular Longitudinal Finned Solar Air Heater With Semicircular Absorber Plate

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Satyender Singh ◽  
Prashant Dhiman
Keyword(s):  
Thermal Performance ◽  
Numerical Solutions ◽  
Solar Air Heater ◽  
Duct Flow ◽  
Balance Equations ◽  
Absorber Plate ◽  
Ansys Fluent ◽  
Air Heater ◽  
Glass Cover ◽  
Good Agreement

Thermal performance of a single-pass single-glass cover solar air heater consisting of semicircular absorber plate finned with rectangular longitudinal fins is investigated. The analysis is carried out for different hydraulic diameters, which were obtained by varying the diameter of the duct from 0.3–0.5 m. One to five numbers of fins are considered. Reynolds number ranges from 1600–4300. Analytical solutions for energy balance equations of different elements and duct flow of the solar air heater are presented; results are compared with finite-volume methodology based numerical solutions obtained from ansys fluent commercial software, and a fairly good agreement is achieved. Moreover, analysis is extended to check the effect of double-glass cover and the recycle of the exiting air. Results revealed that the use of double-glass cover and recycle operation improves the thermal performance of solar air heater.

scholarly journals Atomization patterns produced by the oblique collision of two Newtonian liquid jets

2010 ◽  
Vol 22 (4) ◽  
pp. 042101 ◽  
Author(s):  
Stephen D. Hoath ◽  
Graham D. Martin ◽  
Ian M. Hutchings
Keyword(s):  
Newtonian Liquid ◽  
Liquid Jets ◽  
Oblique Collision

Dynamics of Liquid Sheet Breakup in Splash Plate Atomization

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
G. Thunivumani ◽  
Hrishikesh Gadgil
Keyword(s):  
Solid Surface ◽  
Weber Number ◽  
Jet Impingement ◽  
Liquid Sheet ◽  
Force Balance ◽  
Impingement Angle ◽  
Wide Range ◽  
Perforated Sheet ◽  
Sheet Breakup ◽  
Regime Map

An experimental study was conducted to investigate the breakup of a liquid sheet produced by oblique impingement of a liquid jet on a plane solid surface. Experiments are carried out over a wide range of jet Weber number (80–6300) and various jet impingement angles (30 deg, 45 deg, and 60 deg) are employed to study the sheet dynamics. The breakup of a liquid sheet takes place in three modes, closed rim, open rim, and perforated sheet, depending upon the Weber number. The transitions across the modes are also influenced by the impingement angle with the transition Weber number reducing with increase in impingement angle. A modified regime map is proposed to illustrate the role of impingement angle in breakup transitions. A theoretical model based on force balance at the sheet edge is developed to predict the sheet parameters by taking the shear interaction between the sheet and the solid surface into account. The sheet shape predicted by the model fairly matches with the experimentally measured sheet shape. The breakup length and width of the sheet are measured and comparisons with the model predictions show good agreement in closed rim mode of breakup.

Cavitation Inception Behind a Jet-Propelled Body

2007 ◽  
Author(s):  
William Hambleton ◽  
Eduard Amromin ◽  
Roger E. A. Arndt ◽  
Svetlana Kovinskaya
Keyword(s):  
Velocity Ratio ◽  
The Body ◽  
Force Balance ◽  
Water Tunnel ◽  
Minimum Diameter ◽  
Cavitation Inception ◽  
Initial Comparison ◽  
Jet Velocity ◽  
Good Agreement

Cavitation inception behind an axissymmetric body driven by a waterjet has been studied experimentally and numerically. Water tunnel tests have been performed with the body mounted on a force balance. The transom of the body contained a nozzle located along the centerline. Tests were carried out for various water tunnel speeds such that jet velocity ratio, VJ/U, could be varied in the range 0 to 2. Distinctly different cavitation patterns were observed at zero jet velocity (when cavitation appeared in spiral vortices in such flows) and at a various jet velocity ratios (when cavitation appeared between counter-rotating vortices around the jet in such flows). Cavitation inception/disappearance has been determined visually. The body drag was also measured. An analytical method for determination of cavitation inception index has been developed on the basis of a viscous-inviscid interaction concept, with employment of special semiempirical approximations for vortices and consideration of surface tension. These approximations have been preliminarily validated for nozzle jet cavitation (for nozzle discharge in co-flow). It was assumed that visualization allows detection of cavities (bubbles) of 0.4mm-0.5mm diameter or larger. The cavitation inception index is defined as the cavitation index for cavities of such minimum diameter when these cavities are located between counter-rotating vortices. The initial comparison of predicted and measured values of the cavitation inception index shows good agreement.

Consistent Theoretical Model of Mean Diameter and Size Distribution by Liquid Sheet Atomization

2012 ◽  
Author(s):  
Chihiro Inoue ◽  
Toshinori Watanabe ◽  
Takehiro Himeno ◽  
Seiji Uzawa ◽  
Mitsuo Koshi
Keyword(s):  
Theoretical Model ◽  
Kinetic Energy ◽  
Droplet Diameter ◽  
Velocity Profiles ◽  
Liquid Sheet ◽  
Estimation Methods ◽  
Liquid Jets ◽  
Injection Velocity ◽  
Size Distributions ◽  
Mean Diameter

A consistent theoretical model is proposed and validated for calculating droplet diameters and size distributions. The model is derived based on the energy conservation law including the surface free energy and the Laplace pressure. Under several hypotheses, the law derives an equation indicating that atomization results from kinetic energy loss. Thus, once the amount of loss is determined, the droplet diameter is able to be calculated without the use of experimental parameters. When the effects of ambient gas are negligible, injection velocity profiles of liquid jets are the essential cause of the reduction of kinetic energy. The minimum Sauter mean diameter produced by liquid sheet atomization is inversely proportional to the injection Weber number when the injection velocity profiles are laminar or turbulent. A non-dimensional distribution function is also derived from the mean diameter model and Nukiyama-Tanasawa’s function. The new estimation methods are favorably validated by comparing with corresponding mean diameters and the size distributions, which are experimentally measured under atmospheric pressure.

Design and Experimental Study of a Bioinspired Wall-Climbing Robot With Multi-Locomotion Modes

2018 ◽  
Author(s):  
Linsen Xu ◽  
Jinfu Liu ◽  
Jiajun Xu ◽  
Xuan Wu ◽  
Shengyao Fan
Keyword(s):  
Virtual Prototyping ◽  
Transition Process ◽  
Adhesive Force ◽  
Force Balance ◽  
Switching System ◽  
Climbing Robot ◽  
Dynamics Model ◽  
Balance Equations ◽  
Vacuum Generator ◽  
Overturning Moment

In this article, a novel wall-climbing locomotion mechanism, which can adapt multiple wall surfaces is developed to imitate the special animals, such as geckoes or flies. The spiny and adhesive belts are adopted in this robot to implement climbing on different kinds of wall surfaces instead of the vacuum generator for moving quietly and quickly. The switching mechanism is brought out to realize the belts switching between different surfaces, and a tail made up of two torsional springs and a supporting part is designed to overcome the robot’s overturning moment. So the mechanical system of the robot consists of four parts: the power and drive system, the moving mechanisms (spiny and adhesive), the switching system and the tail. Then the virtual prototyping of the robot with multi-locomotion modes is brought out, and the different gaits on the rough surface, the smooth surface and the transition process are analyzed. During the spine gait using the spine belts, the adhesive force should overcome the robot gravity and drive it, so the drive torque can obtained by building the force balance equations of the robot, which include the supporting forces of the spine belts and the tail. During the adhesive gait using the adhesive rubber belts, the force balance equations should include the supporting forces of the adhesive belts and the tail. And during the transition gait, the force balance equations include all of the above forces. So the mechanical model of the robot can be built according to the above analysis. Finally, the experimental prototype of the wall-climbing robot is manufactured and the wall-climbing experiments are carried out to testify its functions. The experiments show that the robot can adapt to different wall surfaces, and the torque parameters obtained based on the dynamics model can ensure the robot to locomote stably.

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