scholarly journals An experimental study of water-entry cavitating flows of an end-closed cylindrical shell based on the high-speed imaging technology

2016 ◽  
Vol 65 (1) ◽  
pp. 014704
Author(s):  
Lu Zhong-Lei ◽  
Wei Ying-Jie ◽  
Wang Cong ◽  
Sun Zhao
Keyword(s):  
Experimental Study ◽  
Cylindrical Shell ◽  
High Speed ◽  
Water Entry ◽  
Cavitating Flows ◽  
High Speed Imaging ◽  
Imaging Technology ◽  
Closed Cylindrical Shell

Experimental study of fibre breakup and shot formation in melt blowing nozzle designs

2020 ◽  
pp. 152808372094927 ◽  
Author(s):  
Ignacio Formoso ◽  
Alejandro Rivas ◽  
Gerardo Beltrame ◽  
Gorka S Larraona ◽  
Juan Carlos Ramos ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Flux Ratio ◽  
Adhesive Bond ◽  
Operating Conditions ◽  
Nozzle Geometry ◽  
Dimensionless Temperature ◽  
Melt Blowing ◽  
High Speed Imaging ◽  
Adhesive Bonds

The high demand for quality in the manufacture of absorbent hygiene products requires the adhesive bonds between layers to be as uniform as possible. An experimental study was conducted on two industrial multihole melt blowing nozzle designs used for hot-melt adhesive applications for hygiene products, in order to study two defects that influence the quality of the adhesive bond: fibre breakup, resulting in contamination, and the presence of shots, undesirable lumps that end up in the finished product. To this end, the fibre dynamics were captured at the nozzle exit region by using high-speed imaging. From the results it was observed that die drool is the main source of shot formation, while fibre breakup occurs as a result of applying a sufficiently large force in the direction perpendicular to the fibre. In addition, three dimensionless parameters were defined, the first two being the air-polymer flux ratio and the dimensionless temperature ratio, both of which represent the operating conditions, and the remaining one being the force ratio, which represents the nozzle geometry. The effect of these parameters on fibre breakup and shot formation was studied and the results indicate that both the operating conditions and the nozzle geometry were responsible for the onset of the fibre breakup and for the formation of shots. More precisely, both defects turned out to be dominated by the air-polymer flux ratio and the air tilt angle. The results that emerge from this study are useful for the enhancement of industrial melt blowing nozzles.

Design of Air-Lock Valve of the Mesh Roller-Type Unginned Cotton and Film Remnant Separator

2013 ◽  
Vol 278-280 ◽  
pp. 121-127
Author(s):  
Hong Lei An ◽  
Ruo Yu Zhang ◽  
Za Kan ◽  
Xiao Liang Li ◽  
Ying Lan Jiang
Keyword(s):  
Friction Coefficient ◽  
Flow Condition ◽  
High Speed ◽  
High Speed Imaging ◽  
Imaging Technology ◽  
Validation Test

Air-lock valve is an important part of the mesh roller-type unginned cotton and film remnant separator. To improve the structure of the air-lock valve, the cotton flow condition in the separator was analyzed by using high speed imaging technology firstly. Then friction coefficient between unginned cotton and mesh roller was tested by experiment. Meanwhile, some parameters of the air-lock valve were obtained by analyzing different phenomenons that are blockings in the air-lock valve during running of the separator. Finally, the validation test was done, the results indicate that the improved air-lock valve is more reasonable than before, and the blocking can be avoided successfully.

scholarly journals Unsteady forces on spheres during free-surface water entry

2012 ◽  
Vol 704 ◽  
pp. 173-210 ◽  
Author(s):  
Tadd T. Truscott ◽  
Brenden P. Epps ◽  
Alexandra H. Techet
Keyword(s):  
Free Surface ◽  
Surface Water ◽  
High Speed ◽  
Accurate Determination ◽  
Water Entry ◽  
High Speed Imaging ◽  
Air Cavity ◽  
Unsteady Forces ◽  
Unsteady Force ◽  
Low Mass

AbstractWe present a study of the forces during free-surface water entry of spheres of varying masses, diameters, and surface treatments. Previous studies have shown that the formation of a subsurface air cavity by a falling sphere is conditional upon impact speed and surface treatment. This study focuses on the forces experienced by the sphere in both cavity-forming and non-cavity-forming cases. Unsteady force estimates require accurate determination of the deceleration for both high and low mass ratios, especially as inertial and hydrodynamic effects approach equality. Using high-speed imaging, high-speed particle image velocimetry, and numerical simulation, we examine the nature of the forces in each case. The effect of mass ratio is shown, where a lighter sphere undergoes larger decelerations and more dramatic trajectory changes. In the non-cavity-forming cases, the forces are modulated by the growth and shedding of a strong, ring-like vortex structure. In the cavity-forming cases, little vorticity is shed by the sphere, and the forces are modulated by the unsteady pressure required for the opening and closing of the air cavity. A data-driven boundary-element-type method is developed to accurately describe the unsteady forces using cavity shape data from experiments.

The water entry of a sphere in a jet

2019 ◽  
Vol 863 ◽  
pp. 956-968 ◽  
Author(s):  
Nathan B. Speirs ◽  
Jesse Belden ◽  
Zhao Pan ◽  
Sean Holekamp ◽  
George Badlissi ◽  
...  
Keyword(s):  
Structural Damage ◽  
High Speed ◽  
Early Time ◽  
Water Entry ◽  
Rigid Sphere ◽  
High Speed Imaging ◽  
Near Surface ◽  
Image Velocimetry ◽  
Surface Particle ◽  
Force Reduction

The forces on an object impacting the water are extreme in the early moments of water entry and can cause structural damage to biological and man-made bodies alike. These early-time forces arise largely from added mass, peaking when the submergence is much less than one body length. We experimentally investigate a means of reducing impact forces on a rigid sphere by placing the sphere inside a jet of water so that the jet strikes the quiescent water surface prior to entry of the sphere into the pool. The water jet accelerates the pool liquid and forms a cavity into which a sphere falls. Through on-board accelerometer measurements and high-speed imaging, we quantify the force reduction compared to the case of a sphere entering a quiescent pool. Finally, we find the emergence of a critical jet volume required to maximize force reduction; the critical volume is rationalized using scaling arguments informed by near-surface particle image velocimetry (PIV) data.

Experimental study on oblique water entry of projectiles

2016 ◽  
Vol 30 (28) ◽  
pp. 1650348 ◽  
Author(s):  
Chenggong Zhao ◽  
Cong Wang ◽  
Yingjie Wei ◽  
Xiaoshi Zhang ◽  
Tiezhi Sun
Keyword(s):  
Experimental Study ◽  
Impact Velocity ◽  
High Speed ◽  
Transition Point ◽  
Water Entry ◽  
High Speed Photography ◽  
Initial Water ◽  
Before And After ◽  
Velocity Attenuation ◽  
Cavity Evolution

An experimental study of oblique water entry of projectiles with different noses has been conducted using high-speed photography technology. The images of the initial water entry impact, cavity evolution, and the closure and shedding of vortices of cavity are presented in the paper. The results reveal that for high-speed oblique water entry (the initial impact velocity [Formula: see text][Formula: see text]50 m/s), the cavity attached to the projectile is symmetrical and free from the influence of gravity. The shedding of the water–vapor–air mixture in the tail of the cavity produces vortices which disappear in the rear of the projectile trajectory. Particular attention is given to the velocity attenuation of the projectile after water entry. The results show that there is a transition point at the time corresponding to the surface seal of the cavity during the velocity attenuation after oblique water entry, and the rates of velocity attenuation are different before and after this transition point. Additionally, the chronophotography of the cavity evolution shows that the time when the surface seal of the cavity occurs decreases with the increase of the initial impact velocity of the projectile.

Experimental study on the cavity dynamics in high-speed oblique water-entry

2018 ◽  
Vol 50 (4) ◽  
pp. 045511 ◽  
Author(s):  
Chen Chen ◽  
Qingpeng Ma ◽  
Yingjie Wei ◽  
Cong Wang
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Water Entry

scholarly journals Water entry of deformable spheres

2017 ◽  
Vol 824 ◽  
pp. 912-930 ◽  
Author(s):  
Randy C. Hurd ◽  
Jesse Belden ◽  
Michael A. Jandron ◽  
D. Tate Fanning ◽  
Allan F. Bower ◽  
...  
Keyword(s):  
Material Properties ◽  
High Speed ◽  
Large Scale ◽  
Hydrodynamic Pressure ◽  
Oscillation Period ◽  
Water Entry ◽  
Effective Diameter ◽  
High Speed Imaging ◽  
Rigid Spheres ◽  
Velocity Change

When a rigid body collides with a liquid surface with sufficient velocity, it creates a splash curtain above the surface and entrains air behind the sphere, creating a cavity below the surface. While cavity dynamics has been studied for over a century, this work focuses on the water entry characteristics of deformable elastomeric spheres, which has not been studied. Upon free surface impact, an elastomeric sphere deforms significantly, giving rise to large-scale material oscillations within the sphere resulting in unique nested cavities. We study these phenomena experimentally with high-speed imaging and image processing techniques. The water entry behaviour of deformable spheres differs from rigid spheres because of the pronounced deformation caused at impact as well as the subsequent material vibration. Our results show that this deformation and vibration can be predicted from material properties and impact conditions. Additionally, by accounting for the sphere deformation in an effective diameter term, we recover previously reported characteristics for time to cavity pinch off and hydrodynamic force coefficients for rigid spheres. Our results also show that velocity change over the first oscillation period scales with the dimensionless ratio of material shear modulus to impact hydrodynamic pressure. Therefore, we are able to describe the water entry characteristics of deformable spheres in terms of material properties and impact conditions.

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