Closure to “Discussion of ‘Shock Wave and Flow Velocity Measurements in a High Speed Fan Rotor Using the Laser Velocimeter’” (1977, ASME J. Eng. Power, 99, p. 188)

1977 ◽  
Vol 99 (2) ◽  
pp. 188-188
Author(s):  
D. C. Wisler
Keyword(s):  
Shock Wave ◽  
Flow Velocity ◽  
High Speed ◽  
Velocity Measurements

Shock Wave and Flow Velocity Measurements in a High Speed Fan Rotor Using the Laser Velocimeter

1977 ◽  
Vol 99 (2) ◽  
pp. 181-187 ◽  
Author(s):  
D. C. Wisler
Keyword(s):  
Shock Wave ◽  
Flow Velocity ◽  
High Speed ◽  
Fluid Dynamic ◽  
Equations Of Motion ◽  
Seed Particle ◽  
Gas Velocity ◽  
Velocity Measurements ◽  
Rotating Blade ◽  
Finite Difference Solution

The laser velocimeter, an instrument capable of making nondisturbing gas velocity measurements, was used to determine shock wave locations and to make gas velocity measurements within the rotating blade row of a 550-m/s (1800-ft/s)-tip speed fan rotor. The velocimeter measures the transit time of a seed particle across interference fringes produced at the intersection of a split and crossed laser beam. The rotor flowfields were obtained at several radial immersions for operating-line and near-stall throttle settings. The results show the change in shock pattern and flow velocity as the compressor is throttled toward stall. Analytical predictions of the flowfield were also obtained using both the method of characteristics and a time-dependent, finite-difference solution of the fluid dynamic equations of motion. The analytical results and the flowfield measurements are considered to be in good agreement.

An Experimental Study of Spark Anemometry for In-Cylinder Velocity Measurements

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
D. P. Gardiner ◽  
G. Wang ◽  
M. F. Bardon ◽  
M. LaViolette ◽  
W. D. Allan
Keyword(s):  
Experimental Study ◽  
Flow Velocity ◽  
High Speed ◽  
Spark Ignition Engine ◽  
Constant Current ◽  
Velocity Measurements ◽  
Lower Velocity ◽  
Freestream Velocity ◽  
Channel Shape ◽  
Spark Channel

It has been demonstrated by previous researchers that an approximate value of the bulk flow velocity through the spark plug gap of a running spark ignition engine may be deduced from the voltage and current wave forms of the spark. The technique has become known as spark anemometry and offers a robust means of velocity sensing for engine combustion chambers and other high temperature environments. This paper describes an experimental study aimed at improving performance of spark anemometry as an engine research tool. Bench tests were conducted using flow provided by a calibrated nozzle apparatus discharging to atmospheric pressure. While earlier studies had relied upon assumptions about the shape of the stretching spark channel to relate the spark voltage to the flow velocity, the actual spark channel shape was documented using high-speed video in the present study. A programmable ignition system was used to generate well-controlled constant current discharges. The spark anemometry apparatus was then tested in a light duty automotive engine. Results from the image analysis of the spark channel shape undertaken in the present study have shown that the spark kernel moves at a velocity of less than that of the freestream gas velocity. A lower velocity threshold exists below, which there is no response from the spark. It is possible to obtain a consistent, nearly linear relationship between the first derivative of the sustaining voltage of a constant current spark and the freestream velocity if the velocity falls within certain limits. The engine tests revealed a great deal of cycle-to-cycle variation in the in-cylinder velocity measurements. Instances where the spark restrikes occur during the cycle must also be recognized in order to avoid false velocity indications.

High-speed two-frame shadowgraphy for velocity measurements of laser-induced plasma and shock-wave evolution

2011 ◽  
Vol 36 (15) ◽  
pp. 2782 ◽  
Author(s):  
Peter Gregorčič ◽  
Janez Možina
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Velocity Measurements ◽  
Wave Evolution ◽  
Laser Induced Plasma

Towards Simultaneous Density and Flow Velocity Measurements of High-speed Flows Using Filtered Rayleigh Scattering

2022 ◽  
Author(s):  
David Feng ◽  
Tom P. Jenkins ◽  
Yue Wu ◽  
Jacob George
Keyword(s):  
Flow Velocity ◽  
High Speed ◽  
Rayleigh Scattering ◽  
Velocity Measurements ◽  
High Speed Flows

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.

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