Application of the Rainbow Schlieren Method in Free Underexpanded Jets

2013 ◽  
Vol 313-314 ◽  
pp. 750-753
Author(s):  
Wen Tang Wu ◽  
Yan Ji Hong ◽  
Ji Fei Ye ◽  
Guan Lei Jiang
Keyword(s):  
Experimental Investigation ◽  
Pressure Ratio ◽  
Schlieren Method ◽  
Schlieren Technique ◽  
Underexpanded Jets ◽  
Schlieren System ◽  
Operation Method ◽  
Nozzle Pressure ◽  
Jet Structure ◽  
Rainbow Schlieren

An experimental investigation into free underexpanded jets is described. In this paper the experiment took the axis-symmetry unexpended jets as the object, used the typical "Z" schlieren system and replaced the edge with rainbow filter.The rainbow schlieren method is used to obtain measurements in underexpanded jets with nozzle pressure ratios ranging from 2.97 to 19.80. Obtaining the result of that the influence of pressure ratio on jet structure. This paper provides an operation method in the concrete and some useful reference for the rainbow schlieren technique.

scholarly journals Rainbow schlieren measurements in underexpanded jets from square supersonic micro nozzles

2018 ◽  
Vol 180 ◽  
pp. 02058
Author(s):  
Hiroaki Maeda ◽  
Hikaru Fukuda ◽  
Shinichiro Nakao ◽  
Yoshiaki Miyazato ◽  
Yojiro Ishino
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Vortex Sheet ◽  
Quantitative Agreement ◽  
Dimensional Structure ◽  
Operating Pressure ◽  
Underexpanded Jets ◽  
Free Jet ◽  
Rainbow Schlieren Deflectometry ◽  
Rainbow Schlieren

The slightly underexpanded free jet issued from a supersonic micro nozzle with a design Mach number of 1.5 and a square shape of 1 mm × 1 mm at the nozzle exit has been experimentally investigated using the rainbow schlieren deflectometry combined with the computed tomography where the nozzle operating pressure ratio is held constant at 4.0. Density fields in the free jet obtained from the rainbow schlieren deflectometry are the vortex sheet theory proposed by Tam. It is shown that there is good quantitative agreement between experiment and theory. It is shown that the rainbow schlieren deflectometry is a useful tool for studying the three-dimensional structure of shock containing free jets from micro-scale supersonic nozzles.

scholarly journals Experimental Research on Wall Pressure Distribution in C-D Nozzle at Mach number 1.1 for Area Ratio 3.24

2019 ◽  
Vol 8 (2S3) ◽  
pp. 971-975 ◽  
Keyword(s):  
Experimental Investigation ◽  
Mach Number ◽  
Flow Field ◽  
Pressure Distribution ◽  
Pressure Ratio ◽  
Area Ratio ◽  
Wall Pressure ◽  
Circulation Zone ◽  
Nozzle Pressure Ratio ◽  
Nozzle Pressure

In this experimental investigation the work reported is about the influence of control on the flow field in the suddenly expanded duct at low supersonic Mach number. A Convergent-divergent (CD) nozzle was designed and fabricated out of brass material assembled with the suddenly expanded duct which was also made of brass material. At the re-circulation zone, the flow field was controlled by using the micro jets of 1 mm diameter as an orifice and the control was arranged at an interval of 90 degrees at 6.5 mm from the central axis of the main jet. The measured wall pressure distribution was presented for Mach number 1.1 for the duct diameter of 18 mm leading to the area ratio 3.24. The L/D ratio of the duct was varied from 1 to 10, and the nozzle pressure ratio (NPR) considered for the experiments was from 3, 5, 7, 9 and 11. The present results have demonstrated that the micro jets do not influence the flow field in the duct adversely and the flow field remained identical in the presence of control or absence of control

scholarly journals Investigation of efficacy of low length-to-diameter ratio and nozzle pressure ratio on base pressure in an abruptly expanded flow

2018 ◽  
Vol 172 ◽  
pp. 01004
Author(s):  
Fharrukh Ahmed ◽  
S. A. Khan
Keyword(s):  
Pressure Ratio ◽  
Flow Regulation ◽  
Base Pressure ◽  
Regulation Mechanism ◽  
Nozzle Pressure Ratio ◽  
Control Efficacy ◽  
Remarkable Change ◽  
Cross Sectional ◽  
Circular Duct ◽  
Nozzle Pressure

This study has been carried out to assess the efficacy of the flow regulations in the form of tiny jets to regulate the pressure in the base region of an abruptly expanded duct. Four tiny jets of 1mm diameter placed at 90° intervals at 6.5 mm distance from the main jet in the wake region of the base were employed as flow management mechanism. The experiments were conducted at the inertia level of M = 2.5 & 3.0. The jets from the nozzles were expanded abruptly into a circular duct with four cross-sectional areas of 2.56, 3.24, 4.84 and 6.25. The L/D ratio of the enlarged duct considered was from 10 to 1 and experiments were conducted for Nozzle Pressure Ratio (NPR) from 3 to 11. Since the jets Mach numbers are high and the highest NPR tested was 11 which imply that the flow remains over expanded, even though, with increase in the NPR, the level of over expansion will decrease. It is well known that for over expanded nozzles an oblique shock will be formed at the nozzle lip, which in turn will result in the increase of the base pressure once it passes through the shock wave. From the results it is observed that for the NPRs 3 and 5 there is no appreciable gain in the base pressure, and hence, control employed as tiny jets are not effective, however, at NPR 7, 9, and 11 there is remarkable change in the base pressure values. This clearly indicates that NPR plays a significant role to decide on the magnitude of the base pressure and the control efficacy of the flow regulation mechanism as the tiny jets. It is found that the present method of flow regulation mechanism can be used as effective regulator of the base flows in an abruptly expanded duct. The control does not alter the nature of the flow in the enlarge duct.

Optimum structure of a laval nozzle for an abrasive air jet based on nozzle pressure ratio

2020 ◽  
Vol 364 ◽  
pp. 343-362 ◽  
Author(s):  
Yong Liu ◽  
Juan Zhang ◽  
Jianping Wei ◽  
Xiaotian Liu
Keyword(s):  
Laval Nozzle ◽  
Pressure Ratio ◽  
Optimum Structure ◽  
Nozzle Pressure Ratio ◽  
Air Jet ◽  
Nozzle Pressure

scholarly journals MECHANISMS OF GENERATION AND SOURCES OF NOISE IN SUPERSONIC JETS

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 144-150
Author(s):  
Vladislav Emelyanov ◽  
Aleksey Tsvetkov ◽  
Konstantin Volkov
Keyword(s):  
Pressure Ratio ◽  
Supersonic Jet ◽  
Numerical Data ◽  
Jet Flows ◽  
Noise Generation ◽  
Noise Sources ◽  
Cavity Depth ◽  
Flow Parameters ◽  
Nozzle Pressure ◽  
Physical Pattern

Interest in the development of models and methods focused on the mechanisms of noise generation in jet flows is due to strict noise requirements produced by various industrial devices, as well as the possibilities of using sound in engineering and technological processes. The tools of physical and computational modeling of gas dynamics and aero-acoustics problems are considered, and noise sources and mechanisms of noise generation in supersonic jet flows are discussed. The physical pattern of the flow in free supersonic under-expanded jets is discussed on the basis of experimental and numerical data, as well as the flow structure arising from the interaction of a supersonic under-expanded jet with a cylindrical cavity. The influence of the nozzle pressure ratio and cavity depth on the sound pressure level, amplitude and frequency characteristics of the flow parameters is studied.

Behavior of Underexpanded Jet Impinging on Sphere

2007 ◽  
Author(s):  
Masaki Endo ◽  
Yoko Sakakibara ◽  
Junjiro Iwamoto
Keyword(s):  
Flow Field ◽  
High Frequency ◽  
Laser Cutting ◽  
Separation Bubble ◽  
Jet Impingement ◽  
Screech Tone ◽  
Underexpanded Jet ◽  
Underexpanded Jets ◽  
Shock Region ◽  
Jet Structure

An underexpanded jet is utilized in industries as well as aviation field, e.g. to cool a body by the jet impingement, to remove molten metal in laser cutting, etc. One of the biggest problems is noise radiating from the jet which has high frequency, or screech tone. It is pointed out that the noise is closely related to the structure of the jet. In this paper, the underexpanded jets on a plate and hemispheres of different radii are visualized using the shadowgraph and Schlieren methods so as to analyze the jet structure, especially the flow field above the object, or the shock region. As a result, the radius of the hemisphere is found to have an effect not on the shape greatly, but on the location of the plate shock, and furthermore on the formation of separation bubble on the surface.

Flow Characterization of Supersonic Jets Issuing From Double-Beveled Nozzles

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Jie Wu ◽  
H. D. Lim ◽  
Xiaofeng Wei ◽  
T. H. New ◽  
Y. D. Cui
Keyword(s):  
Supersonic Jets ◽  
Navier Stokes ◽  
Shock Cell ◽  
Potential Core ◽  
Schlieren System ◽  
Flow Characterization ◽  
Mixing Behavior ◽  
Nozzle Pressure ◽  
Significant Mass

Supersonic jets at design Mach number of 1.45 issuing from circular 30 deg and 60 deg double-beveled nozzles have been investigated experimentally and numerically in the present study, with a view to potentially improve mixing behavior. Reynolds-averaged Navier–Stokes (RANS) simulations of the double-beveled nozzles and a benchmark nonbeveled nozzle were performed at nozzle-pressure-ratios (NPR) between 2.8 and 5.0, and the results are observed to agree well with Schlieren visualizations obtained from a modified Z-type Schlieren system. Double-beveled nozzles are observed to produce shorter potential core lengths, modifications to the first shock cell lengths that are sensitive toward the NPR and jet half-widths that are typically wider and narrower along the trough-to-trough (TT) and peak-to-peak (PP) planes, respectively. Lastly, using double-beveled nozzles leads to significant mass flux ratios at NPR of 5.0, with a larger bevel-angle demonstrating higher entrainment levels.

Numerical Simulation of Supersonic Jet Control by Tabs with Slanted Perforation

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
G. Ezhilmaran ◽  
Suresh Chandra Khandai ◽  
Yogesh Kumar Sinha ◽  
S. Thanigaiarasu
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Near Field ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Pressure Gradients ◽  
Nozzle Pressure Ratio ◽  
Nozzle Pressure ◽  
Jet Control ◽  
Different Diameters

Abstract This paper presents the numerical simulation of Mach 1.5 supersonic jet with perforated tabs. The jet with straight perforation tab was compared with jets having slanted perforated tabs of different diameters. The perforation angles were kept as 0° and 10° with respect to the axis of the nozzle. The blockage areas of the tabs were 4.9 %, 4.9 % and 2.4 % for straight perforation, 10° slanted perforation ( {{{\Phi }}_{\ }} = 1.3 mm) and 10° slanted perforation ( {{{\Phi }}_{\ }} = 1.65 mm) respectively. The 3-D numerical simulations were carried out using the software. The mixing enhancements caused by these tabs were studied in the presence of adverse and favourable pressure gradients, corresponding to nozzle pressure ratio (NPR) of 3, 3.7 and 5. For Mach number 1.5 jet, NPR 3 corresponds to 18.92 % adverse pressure gradients and NPR 5 corresponds to 35.13 % favourable pressure gradients. The centerline Mach number of the jet with slanted perforations is found to decay at a faster rate than uncontrolled nozzle and jet with straight perforation tab. Mach number plots were obtained at both near-field and far field downstream locations. There is 25 % and 65 % reduction in jet core length were observed for the 0° and 10° perforated tabs respectively in comparison to uncontrolled jet.

scholarly journals Effects of Nozzle Pressure Ratio and Nozzle-to-Plate Distance to Flowfield Characteristics of an Under-Expanded Jet Impinging on a Flat Surface

Aerospace ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 4 ◽  
Author(s):  
Duy Thien Nguyen ◽  
Blake Maher ◽  
Yassin Hassan
Keyword(s):  
Vector Fields ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Impinging Jets ◽  
Central Plane ◽  
Mean Velocity ◽  
Image Velocimetry ◽  
Nozzle Pressure ◽  
Pod Analysis ◽  
Impingement Surface

The current work experimentally investigates the flowfield characteristics of an under-expanded turbulent jet impinging on a solid surface for various nozzle-to-plate distances 2.46 D j , 1.64 D j , and 0.82 D j ( D j is the jet hydraulic diameter), and nozzle pressure ratios (NPRs) ranging from 2 to 2.77 . Planar particle image velocimetry (PIV) measurements were performed in the central plane of the test nozzle and near the impingement surface. From the obtained PIV velocity vector fields, flow characteristics of under-expanded impinging jets, such as mean velocity, root-mean-square fluctuating velocity, and Reynolds stress profiles, were computed. Comparisons of statistical profiles obtained from PIV velocity measurements were performed to study the effects of the impingement surface, nozzle-to-plate distances, and NPRs to the flow patterns. Finally, proper orthogonal decomposition (POD) analysis was applied to the velocity snapshots to reveal the statistically dominant flow structures in the impinging jet regions.

Tab Aspect Ratio Effect on Supersonic Jet Mixing

2015 ◽  
Vol 32 (3) ◽  
Author(s):  
Mrinal Kaushik ◽  
E. Rathakrishnan
Keyword(s):  
Aspect Ratio ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Small Scale ◽  
Jet Mixing ◽  
Core Length ◽  
Nozzle Pressure ◽  
The Waves ◽  
Length Reduction ◽  
Better Than

AbstractThe efficacy of introducing mixing promoting small-scale vortices by two rectangular tabs, of aspect ratio 1.0, 1.5 and 2.0, placed at diametrically opposite locations at the exit of a Mach 1.73 convergent–divergent circular nozzle has been experimentally investigated, for NPRs from 4 to 8, covering overexpanded, correctly expanded and underexpanded states of the jet. The area blockage due to the each tab was 2.5% of the nozzle exit area. Keeping the blockage constant, the aspect ratio (defined as the ratio of length to width of the tab) was varied. A maximum core length reduction of 84.6% was caused by the tabs of aspect ratio 1.0, at underexpanded conditions corresponding to NPR (nozzle pressure ratio) 6. At this NPR, tabs of aspect ratio 1.5 and 2.0 caused core length reduction of 76.9% and 61.5%, respectively. The mixing promoting efficiency of aspect ratio 1.0 is found to be better than 1.5 and 2.0, at all NPRs of the present study, except NPR 5. The shadowgraph pictures of the uncontrolled and controlled jets clearly demonstrate the effectiveness of the tabs in weakening the waves in the jet core.

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