Water Flow Visualization in a Converging-Diverging Glass Nozzle

2016 ◽  
Author(s):  
Aaron Schmidt ◽  
B. Terry Beck ◽  
Mohammad H. Hosni
Keyword(s):  
Flow Visualization ◽  
Flow Velocity ◽  
High Speed ◽  
Digital Camera ◽  
High Speed Camera ◽  
Nozzle Throat ◽  
Glass Spheres ◽  
Seed Particles ◽  
Flow Through ◽  
Nozzle Inlet

Water flow through a converging-diverging glass nozzle experiences a pressure drop and its velocity increases as it flows through the converging section. For an inviscid fluid, the pressure minimum occurs at the nozzle throat, where the cross-sectional area is minimum. If the minimum pressure is below the water vapor pressure, cavitation may occur. Viscous fluid flow through a converging-diverging nozzle experiences more complex flow patterns. Additionally, fluid through the nozzle may be driven into the metastable region and subsequently cavitate at a lower pressure than the vapor pressure. The dynamic conditions that trigger cavitation in a converging-diverging nozzle are not well understood; moreover, direct measurements involving invasive probe insertion in the region of cavitation onset can induce cavitation. The study of a glass converging-diverging nozzle allowed for noninvasive flow visualization and quantitative observational measurements to be made. A high-speed digital camera was used to capture qualitative and quantitative information on the flow pattern inside the nozzle. The transient time period during cavitation onset was visualized at 35,000 frames per second. Video from the high-speed digital camera revealed that the cavitation front began approximately one nozzle throat diameter downstream from the nozzle throat. Small glass sphere seed particles and injected bubbles were used to trace flow through the nozzle and measure flow velocity at different locations in the nozzle. Small injected bubbles were tracked using the high-speed camera to measure the flow velocity in the nozzle inlet and converging sections. Glass spheres of 10 μm and 120 μm diameter were introduced to the flow to visualize the flow inside the nozzle and track flow velocity. The 120 μm glass spheres were visible using the high-speed camera and were tracked to measure flow velocity in the converging and throat regions of the nozzle. The 120 μm spheres were large enough to provide nucleation sites for cavitation and were seen to trigger cavitation near the nozzle throat. The cavitation induced by the glass spheres occurred upstream of the cavitation front previously observed in the absence of the spheres at identical nozzle inlet and outlet pressures. This shift in the cavitation front suggested the presence of metastable flow through the nozzle throat in the absence of seed particles. The 120 μm spheres also revealed that the flow had separated from the nozzle wall downstream of the nozzle throat. Tracking bubbles produced by the cavitation front also permitted flow visualization of the regions of separated flow, which first separated from the wall upstream of the cavitation front. Flow visualization of cavitation in the converging-diverging glass nozzle obtained by the high-speed digital camera provided valuable information regarding the conditions that lead to cavitation. High-speed imaging revealed the dynamic fluid behaviors during the onset of cavitation. Bubble and seed particle tracking provided velocity information at several locations throughout the nozzle. Visualization of the entire region of cavitation allowed for the measurement of the cavitation region length, which varied depending upon the nozzle outlet pressure.

Numerical Simulation of Evaporating Two-Phase Flow in a High-Aspect-Ratio Microchannel with Bends

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Junsik Lee ◽  
Junsub Kim ◽  
Hyungsoo Lim ◽  
Je Sung Bang ◽  
Jeong Min Seo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flow Visualization ◽  
Film Cooling ◽  
High Speed ◽  
National Research Council ◽  
Air Cooling ◽  
Hole Size ◽  
High Efficient ◽  
Flow Through ◽  
Effusion Hole

Effusion cooling is one of the attractive methods for next generation high-efficient gas turbine which has a very hot gas temperature above 1,600oC. For higher effectiveness of the air cooling, the air-cooled flow through effusion-holes does not penetrate into the mainstream flow but still remains within freestream boundary layer. So the air-cooled surface temperature maintains at relatively lower than film cooling. Effusion cooling is generally known as operating in small effusion-hole size which is less than 0.2 mm. This study is intended to examine optimum effusion-hole size of the microscale effusion cooling through flow visualization. The air flow through effusion-holes is visualized using an oil atomizer, a DSPP laser-sheet illumination, and a high-speed CCD imaging. The visualized results show flow patterns and characteristics with different blowing ratio, BR = ρcUc / ρ∞U∞, (BR = 0.17 and 0.53) and effusion-hole size (D = 0.2 mm, 0.5 mm and 1.0 mm). The flow visualization condition is fixed at the mainstream Reynolds number of 10,000 and hole-to-hole spacing of 4 (S/D = 4). For larger effusion-hole of 1.0 mm [(a) and (b)], the effusion flow can penetrate into boundary layer which exhibits a film cooling. However the effusion flow is observed to be remained within boundary layer which shows an effusion cooling for smaller effusion-hole of 0.2 mm [(e) and (f)]. In case of (c) and (d), a series of vortical structure is also observed to be within the boundary layer along the effusion flat plate. Note that the effusion-hole size of 0.5 mm can be a candidate for making effusion cooling possible. [This work was supported by National Research Council of Science and Technology (NST) grant funded by the Ministry of Science, ICT and Future Planning, Korea (Grant No. KIMM-NK203B).]

Experimental Study of Liquid-Liquid Flow Through Upward Vertical to Horizontal Transition

2017 ◽  
Author(s):  
Ricardo A. Mazza ◽  
Fábio K. Suguimoto
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
High Speed ◽  
Phase Flow ◽  
High Speed Camera ◽  
Bend Radius ◽  
Two Phase ◽  
Pressure Transducers ◽  
Flow Through ◽  
Bend Flow

This work consists of an experimental analysis of the liquid-liquid two-phase flow of water-kerosene through a vertical bend. The duct has diameter of 0.026 m, the bend radius is 0.125 m and the superficial velocities of the water and kerosene ranged from 0.1 to 1.0 m/s. The pressures drops were measured by differential pressure transducers SMAR LD301, the holdups were determined by the method of trapping fluid using quick-closing valves and the flow patterns was determined using a high-speed camera. The bend pressure gradient is increased with the superficial velocities of both phases. The bend coefficient has no correlation with the mixture Reynolds number, such as in single-flows. The modified Reynolds number proposed by [1] described accurately the bend flow pattern.

Peculiar flow patterns of RBCs suspended in viscous fluids and perfused through a narrow tube (25 μm)

2009 ◽  
Vol 297 (2) ◽  
pp. H583-H589 ◽  
Author(s):  
Hiromi Sakai ◽  
Atsushi Sato ◽  
Naoto Okuda ◽  
Shinji Takeoka ◽  
Nobuji Maeda ◽  
...  
Keyword(s):  
High Speed ◽  
Tube Wall ◽  
Digital Camera ◽  
Major Axis ◽  
Flow Patterns ◽  
Narrow Tube ◽  
Flow Through ◽  
Newtonian Viscous Fluid ◽  
First Time ◽  
Near Wall

Red blood cells (RBCs) generally deform to adopt a parachute-like, torpedo-like, or other configuration to align and flow through a capillary that is narrower than their major axis. As described herein, even in a narrow tube (25 μm) with diameter much larger than that of a capillary, flowing RBCs at 1 mm/s align axially and deform to a paraboloid shape in a viscous Newtonian fluid (505 kDa dextran medium) with viscosity of 23.4–57.1 mPa·s. A high-speed digital camera image showed that the silhouette of the tip of RBCs fits a parabola, unlike the shape of RBCs in capillaries, because of the longer distance of the RBC-free layer between the tube wall and the RBC surface (∼8.8 μm). However, when RBCs are suspended in a “non-Newtonian” viscous fluid (liposome-40 kDa dextran medium) with a shear-thinning profile, they migrate toward the tube wall to avoid the axial lining, as “near-wall-excess,” which is usually observed for platelets. This migration results from the presence of flocculated liposomes at the tube center. In contrast, such near-wall excess was not observed when RBCs were suspended in a nearly Newtonian liposome-albumin medium. Such unusual flow patterns of RBCs would be explainable by the principle; a larger particle tends to flow near the centerline, and a small one tends to go to the wall to flow with least resistance. However, we visualized for the first time the complete axial aligning and near-wall excess of RBCs in the noncapillary size tube in some extreme conditions.

scholarly journals Flow visualization of bubbly jet flow by using high-speed camera system

2004 ◽  
Vol 24 (Supplement1) ◽  
pp. 123-124
Author(s):  
Masaaki ISHIKAWA ◽  
Koji OKAMOTO ◽  
Haruki MADARAME
Keyword(s):  
Flow Visualization ◽  
High Speed ◽  
Jet Flow ◽  
High Speed Camera ◽  
Camera System ◽  
Bubbly Jet

Flow through axial-flow-turbomachinery blading

2018 ◽  
Author(s):  
Marcel Escudier
Keyword(s):  
Flow Velocity ◽  
Compressible Flow ◽  
Dimensional Analysis ◽  
Incompressible Flow ◽  
Compressible Fluid ◽  
Axial Flow ◽  
Linear Cascade ◽  
Dimensional Parameters ◽  
Flow Through

This chapter is concerned primarily with the flow of a compressible fluid through stationary and moving blading, for the most part using the analysis introduced in Chapter 11. The principles of dimensional analysis are applied to determine the appropriate non-dimensional parameters to characterise the performance of a turbomachine. The analysis of incompressible flow through a linear cascade of aerofoil-like blades is followed by the analysis of compressible flow. Velocity triangles for flow relative to blades, and Euler’s turbomachinery equation, are introduced to analyse flow through a rotor. The concepts introduced are applied to the analysis of an axial-turbomachine stage comprising a stator and a rotor, which applies to either a compressor or a turbine.

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