scholarly journals Video: High speed Schlieren photography on match rockets

2020 ◽  
Author(s):  
Angel Lozano ◽  
Yun Liu
Keyword(s):  
High Speed ◽  
Schlieren Photography

A study of the collapse of arrays of cavities

1988 ◽  
Vol 190 ◽  
pp. 409-425 ◽  
Author(s):  
J. P. Dear ◽  
J. E. Field
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
High Speed Photography ◽  
Cavitation Damage ◽  
Major Mechanism ◽  
Collapse Mechanisms ◽  
Multiple Jets ◽  
Circular Holes ◽  
Schlieren Photography ◽  
Thick Glass

This paper describes a method for examining the collapse of arrays of cavities using high-speed photography and the results show a variety of different collapse mechanisms. A two-dimensional impact geometry is used to enable processes occurring inside the cavities such as jet motion, as well as the movement of the liquid around the cavities, to be observed. The cavity arrangements are produced by first casting water/gelatine sheets and then forming circular holes, or other desired shapes, in the gelatine layer. The gelatine layer is placed between two thick glass blocks and the array of cavities is then collapsed by a shock wave, visualized using schlieren photography and produced from an impacting projectile. A major advantage of the technique is that cavity size, shape, spacing and number can be accurately controlled. Furthermore, the shape of the shock wave and also its orientation relative to the cavities can be varied. The results are compared with proposed interaction mechanisms for the collapse of pairs of cavities, rows of cavities and clusters of cavities. Shocks of kbar (0.1 GPa) strength produced jets of c. 400 m s−1 velocity in millimetre-sized cavities. In closely-spaced cavities multiple jets were observed. With cavity clusters, the collapse proceeded step by step with pressure waves from one collapsed row then collapsing the next row of cavities. With some geometries this leads to pressure amplification. Jet production by the shock collapse of cavities is suggested as a major mechanism for cavitation damage.

On the Synchronization of Candle Oscillators

2021 ◽  
pp. 335-349
Author(s):  
Yavor Yordanov ◽  
Keyword(s):  
Collective Behavior ◽  
High Speed ◽  
Gas Flows ◽  
Hot Gas ◽  
Schlieren Photography

In this study we will investigate an interesting collective behavior of candles. It has been observed that when several candles burn close to each other they form a common flame that exhibits oscillations in size and brightness. If two such oscillators burn together, they interact and the oscillations of the resultant system depend on the distance between them. The aim of this investigation, inspired by Problem 5 of the International Young Physicists Tournament in 2021, is to theoretically explain the phenomenon through overlapping of hot gas flows and radiation, as well as to check our understanding and measure additional parameters experimentally using advanced techniques, such as high speed schlieren photography.

Experiment on Thin Structure Behavior of Explosion Flame Flow Field

2010 ◽  
Vol 44-47 ◽  
pp. 2793-2797
Author(s):  
Xian Feng Chen ◽  
Y. Zhang ◽  
M. Chen ◽  
Shao Feng Ren ◽  
Xiao L. Song
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Flame Structure ◽  
Propagation Mechanism ◽  
Flame Acceleration ◽  
Turbulent Transition ◽  
Schlieren Photography ◽  
Optical Measure ◽  
Air Explosion ◽  
And Control

To prevent and control fire and explosion disasters, the premixed methane-air explosion was performed under restricted condition. In the experiment, the high speed schlieren photography system was used to record the flame characteristics and propagation mechanism. At the same time the ion current probe was used to reveal the inner flame structure characteristics. Based on the images of High Speed Schlieren Photography, the flame acceleration and flame structure were discussed in detail. In addition, the flow field characteristic of explosion flame was disclosed clearly. The microscopic evolving process of laminar-turbulent transition was accomplished in the period of flame structure change. As an alternative observation and detect technique, the high speed schlieren photograph system was used to capture flame front microstructure dynamic process precisely. Based on burning chemical and explosive dynamics, the optical measure method can record flame dynamic behavior visually, which further helps to disclose flame microstructure characteristic and the inner dynamic mechanism.

Growth of Flame Front Turbulence

1986 ◽  
Vol 108 (4) ◽  
pp. 877-881 ◽  
Author(s):  
T. Tsuruda ◽  
M. Harayama ◽  
T. Hirano
Keyword(s):  
Experimental Study ◽  
Combustion Chamber ◽  
Flame Front ◽  
Pressure Wave ◽  
High Speed ◽  
Wall Turbulence ◽  
Pressure Waves ◽  
Fuel Type ◽  
Fuel Concentration ◽  
Schlieren Photography

An experimental study was performed on the growth of flame front turbulence by stimulating a laminar propagating flame with weak pressure waves, which were generated by sudden breaking of the membrane separating a small chamber from the combustion chamber. The flame front behavior was explored by using high-speed schlieren photography. About one millisecond after the first weak pressure wave passed the flame front, a very fine disturbance appeared at the central part of the flame front, where no effect of the wall turbulence could appear. Then, the area and strength of the disturbance were observed to increase rapidly. The effects of the pressure wave intensity, fuel concentration, and fuel type on the growth of this type of flame front turbulence were examined in detail.

3D Printing of Spark-Ignited Flame Kernels, Experimentally Captured by 3D-Computer Tomography and Multi-Directional Schlieren Photography

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Yojiro Ishino ◽  
Naoki Hayashi ◽  
Yuta Ishiko ◽  
Kimihiro Nagase ◽  
Kazuma Kakimoto ◽  
...  
Keyword(s):  
Computer Tomography ◽  
High Speed ◽  
Turbulent Flame ◽  
3D Ct ◽  
Ct Reconstruction ◽  
Flame Kernel ◽  
Custom Made ◽  
3D Printed ◽  
Schlieren Photography ◽  
Bottom Left

Non-scanning 3D-CT(Computer Tomography) technique employing a multi-directional quantitative schlieren photographic system with flash light source, has been performed to obtain instantaneous density distributions of spark-ignited laminar / turbulent flame kernels. For simultaneous schlieren photography, the custom-made 20-directional schlieren camera was constructed and used. The concept of the multi-directional shclieren system is shown in top-right figure. Each quantitative schlieren optical system, indicated in top-left figure, is characterized by a rectangular-shaped right source with uniform luminosity. Middle-left picture gives the appearance of the multi-directional schlieren camera. The flame kernels are made by spark ignition for a fuel-rich propane-air premixed gas (flow velocity :1.0 m/s, equivalence ratio :1.4 ). Spark electrodes of 0.4 mm diameter with 1.0 mm gap are used. First, development of laminar flame kernel is indicated in high-speed images of middle-right figure. 3D printed model of the CT reconstruction result (left in bottom-left photograph) shows the spherical shape of flame kernel with a pair of deep wrinkles. The wrinkle is considered to be caused by spark electrodes. Next turbulent flame kernel behind turbulence promoting grid is selected (turbulence intensity 0.26 m/s). The high-speed images of bottom-right figures show corrugated flame shape. 3D model of CT result (right in bottom-left photo.) expresses the instantaneous 3D turbulent flame kernel shapes. These 3D solid models based on 3D-CT reconstructed data of 2 ms, are 3D-printed as 2 times large size for threshold density level of 0.7 kg/m3.

Numerical modelling of turbulent flow in a combustion tunnel

1982 ◽  
Vol 304 (1484) ◽  
pp. 303-325 ◽  
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
High Speed ◽  
Large Scale ◽  
Numerical Technique ◽  
Vortex Method ◽  
Reacting Flow ◽  
Exothermic Process ◽  
Schlieren Photography ◽  
Large Scale Flow

A numerical technique is presented for the analysis of turbulent flow associated with combustion. The technique uses Chorin’s random vortex method (r.v.m .), an algorithm capable of tracing the action of elementary turbulent eddies and their cumulative effects without imposing any restriction upon their motion. In the past, the r.v.m . has been used with success to treat non-reacting turbulent flows, revealing in particular the mechanics of large-scale flow patterns, the so-called coherent structures. Introduced here is a flame propagation algorithm , also developed by Chorin, in conjunction with volume sources modelling the mechanical effects of the exothermic process of combustion. As an illustration of its use, the technique is applied to flow in a combustion tunnel w here the flame is stabilized by a back-facing step. Solutions for both non-reacting and reacting flow fields are obtained. Although these solutions are restricted by a set of far-reaching idealizations, they nonetheless mimic quite satisfactorily the essential features of turbulent combustion in a lean propane—air mixture that were observed in the laboratory by means of high speed schlieren photography.

3D Printing of Instantaneous Turbulent Flame Shapes, Experimentally Captured by 3D-Computer Tomography and Multi-Directional Schlieren Photography

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yojiro Ishino ◽  
Naoki Hayashi ◽  
Yuta Ishiko ◽  
Ili Fatimah Bt Abd Razak ◽  
Yu Saiki ◽  
...  
Keyword(s):  
Computer Tomography ◽  
High Speed ◽  
Turbulent Flame ◽  
Flame Structure ◽  
Turbulent Flames ◽  
Density Level ◽  
Exit Velocity ◽  
Solid Models ◽  
Custom Made ◽  
Schlieren Photography

Non-scanning 3D-CT(Computer Tomography) technique employing a multi-directional quantitative schlieren photographic system(top-left picture) with flash light source, has been performed to obtain instantaneous density distributions of high-speed turbulent flames(for reference, the target flame of 8 m/s exit velocity is indicated in the right-top picture). For simultaneous schlieren photography, the custom-made 20-directional schlieren camera was constructed and used. The target turbulent flame is high-speed flames, anchored on the burner of a nozzle exit of 4.2 mm diameter. The image set of 20 directional schlieren images are processed by MLEM CT-algorithm to obtain the 3D reconstruction of instantaneous density distribution. The solid models(bottom picture) of threshold density level of 0.7 kg/m3 are 3D-printed as 4 times large size for detail observations. The average exit velocity of the propane-air mixture of equivalence ratio of 1.1 is set to be 10, 8, 6 and 4 m/s (models from left to right in the bottom picture). The solid models show the complicated shape of the high speed turbulent flames. The flame structure of higher speed flame has fine scale corrugations. This corresponds to the “corrugated flamelets regime” of the Borghi & Peters diagram well.

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