scholarly journals Effect of Specimen Placement on Model Rock Blasting

2021 ◽  
Author(s):  
Zong-Xian Zhang ◽  
Li Yuan Chi ◽  
Qingbin Zhang
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Rock Specimen ◽  
Base Material ◽  
Scale Model ◽  
Small Scale ◽  
High Speed Photography ◽  
Rock Blasting ◽  
Ground Material ◽  
Very High

AbstractSmall-scale model blasting plays an important role in understanding mechanism of rock fragmentation by blasting and improving blast technology in rock and mining engineering. Because a specimen (or model) often needs to be placed on either a ground or another material in model blasting, an additional interface appears between the specimen and the ground (or material), compared with an engineering blast that does not have such an interface. In this paper, four model blasts with high-speed photography were presented. The results showed that: (1) as the impedance of a rock specimen was smaller than that of the ground material, the specimen was thrown up and a certain amount of kinetic energy was brought with such a bounce. Thus, this placement should be avoided in model blasts. (2) As a rock specimen was placed on three blocks of the same type of rock as the specimen the specimen was not bounced up during blasting. Correspondingly, no kinetic energy was induced by specimen bounce. Therefore, this placement is recommended for model blasting. If very high specific charge must be used in model blasting, the above-recommended method will not work well due to possible breakage of the base material during blasting. In this case, the rock specimen can be placed on a material with smaller impedance than that of the rock specimen so that specimen bounce can be reduced. Accordingly, such a possible specimen bounce should be estimated by stress wave analysis.

scholarly journals Fracture Initiation, Gas Ejection, and Strain Waves Measured on Specimen Surfaces in Model Rock Blasting

2020 ◽  
Author(s):  
Zong-Xian Zhang ◽  
Li Yuan Chi ◽  
Yang Qiao ◽  
De-Feng Hou
Keyword(s):  
High Speed ◽  
Fracture Initiation ◽  
Dynamic Strain ◽  
High Speed Photography ◽  
Surface Cracks ◽  
Rock Blasting ◽  
Measured Velocity ◽  
Strain Waves ◽  
Gas Penetration ◽  
Radial Cracks

AbstractCrack velocity, gas ejection, and stress waves play an important role in determining delay time, designing a blast and understanding the mechanism of rock fragmentation by blasting. In this paper, the emerging times of the earliest cracks and gas ejection on the lateral surfaces of cylindrical granite specimens with a diameter of 240 mm and a length of 300 mm were determined by high-speed photography, and the strain waves measured by an instrument of dynamic strain measurement during model blasting. The results showed that: (1) the measured velocity of gas penetration into the radial cracks was in a range of 196–279 m/s; (2) the measured velocity of a radial crack extending from the blasthole to the specimen surface varied from 489 to 652 m/s; (3) the length of strain waves measured was about 2800 µs, which is approximately 1000 times greater than the detonation time. At about 2850 µs after detonation was initiated, gases were still ejected from the surface cracks, and the specimens still stood at their initial places, although surface cracks had opened widely.

Flow Visualization Study of Jet and Bucket Interactions in Traditional and Hooped Pelton Runner

2019 ◽  
Author(s):  
Gaurangkumar Chaudhari ◽  
Salim Channiwala ◽  
Samip Shah ◽  
Digvijay Kulshreshtha
Keyword(s):  
Flow Visualization ◽  
Flow Pattern ◽  
High Speed ◽  
Early Stage ◽  
Small Scale ◽  
High Speed Photography ◽  
Pelton Turbine ◽  
Single Jet ◽  
Absolute Frame ◽  
First Time

Abstract This paper aims to study the flow pattern in and around a bucket of a Traditional and a Hooped Pelton runner at single injector operation and illustrates different stages of jet interaction. High speed photography is used to study the flow pattern, keeping the camera in different positions relative to the jet and to the bucket. It is concluded from the results that the flow visualization study, provides exceptional observations with an absolute frame of reference to mark the bucket duty period of a single-jet Pelton runner. The small scale models display erosion damages at the bucket lips, this indicated that the high pressure occur in the early stage of interaction. This fact is substantiated by the present flow visualization studies for the first time. The uncertainty of the free surface outflow within the Pelton turbine bucket establishes good documentation. The results are helpful to know the interaction between the jet and bucket of Pelton turbine.

Experimental Study on Cavitation Motion of Underwater Vehicle With Protrusions

2020 ◽  
Author(s):  
Zhaoyu Qu ◽  
Ning Gan ◽  
Yingyu Chen ◽  
Nana Yang
Keyword(s):  
High Speed ◽  
Underwater Vehicle ◽  
Test Method ◽  
Scale Model ◽  
Small Scale ◽  
Reduced Pressure ◽  
Local Flow ◽  
Bubble Generation ◽  
Scale Characteristics ◽  
Motion Characteristics

Abstract For underwater vehicles with protrusions (external structure), the geometric shape of the protrusions is bound to affect the local flow field of the vehicles during the moving process of the vehicles, thus affecting the generation, development and collapse of cavitation around the vehicles. The cavitation may break, fall off and collapse randomly, and other local movements may affect the motion attitude of the underwater vehicle. It is an effective method to study fluid dynamics to simulate prototype cases with small scale models. In this paper, we mainly use the small scale model test method to explore the cavitation motion characteristics of the vehicle in water with protrusions. Through the establishment of a set of vehicle motion test equipment under reduced pressure, a series of experiments were conducted on this basis to explore the motion characteristics of vehicle cavitation under different bump shapes. In this study, two high-speed cameras were used to simultaneously record cavitation generation, development, collapse and other characteristics, to analyze the bubble generation mechanism and scale characteristics caused by the bulge, and then to study the influence of cavitation induced by the bulge on the motion attitude of the vehicle.

scholarly journals Rates of Dissipation of Turbulent Kinetic Energy in a High Reynolds Number Tidal Channel

2016 ◽  
Vol 33 (4) ◽  
pp. 817-837 ◽  
Author(s):  
Justine M. McMillan ◽  
Alex E. Hay ◽  
Rolf G. Lueck ◽  
Fabian Wolk
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
High Speed ◽  
Flow Speed ◽  
Small Scale ◽  
Tidal Channel ◽  
Dissipation Rates ◽  
Channel Separation ◽  
Shear Probe

AbstractThe ability to estimate the rate of dissipation (ε) of turbulent kinetic energy at middepth in a high-speed tidal channel using broadband acoustic Doppler current profilers (ADCPs) is assessed by making comparisons to direct measurements of ε obtained using shear probes mounted on a streamlined underwater buoy. The investigation was carried out in Grand Passage, Nova Scotia, Canada, where the depth-averaged flow speed reached 2 m s−1 and the Reynolds number was 8 × 107. The speed bin–averaged dissipation rates estimated from the ADCP data agree with the shear probe data to within a factor of 2. Both the ADCP and the shear probe measurements indicate a linear dependence of ε on the cube of the flow speed during flood and much lower dissipation rates during ebb. The ebb–flood asymmetry and the small-scale intermittency in ε are also apparent in the lognormal distributions of the shear probe data. Possible sources of bias and error in the ε estimates are investigated, and the most likely causes of the discrepancy between the ADCP and shear probe estimates are the cross-channel separation of the instruments and the high degree of spatial variability that exists in the channel.

Sympathetic detonation and initiation by impact

1958 ◽  
Vol 246 (1245) ◽  
pp. 274-281 ◽  
Keyword(s):  
Kinetic Energy ◽  
Detonation Wave ◽  
High Speed ◽  
Incident Shock ◽  
Shock Pressure ◽  
The Body ◽  
Detonation Pressure ◽  
Air Gaps ◽  
Solid Explosives ◽  
Very High

High-speed photographic techniques have been used to investigate the sympathetic detonation of solid explosives by shocks propagated across air gaps and solid barriers. It has been observed that initiation takes place within the body of the receptor stick, rather than at the surface, if the shock pressure is appreciably less than the detonation pressure. The depth in the receptor at which initiation occurs depends systematically upon the pressure of the incident shock ; the lower the pressure the deeper the point of initiation. Detonation always occurs at the shock front, but, under the conditions of the experiments completed thus far, does not propagate backward into the preshocked explosive. The propagation velocity of the detonation wave in the receptor is, at least initially, greater than that observed under ordinary conditions. Studies of initiation by impact have shown many points of similarity. Initiation takes place within the body of the target explosive block, at a point ahead of the striking projectile, except at very high velocities of impact. The depth in the explosive and the distance ahead of the projectile at which initiation occurs depend mainly upon the velocity of the projectile and upon the shape of its front. In agreement with previous work, it has been shown that the kinetic energy of the impacting projectile is not a basic parameter in determining the probability of initiation or the conditions under which it occurs.

Microprocessor Field Impactometer Calibration: Do We Measure Drops’ Momentum or Their Kinetic Energy?

2008 ◽  
Vol 25 (5) ◽  
pp. 742-753 ◽  
Author(s):  
Paweł Licznar ◽  
Janusz Łomotowski ◽  
Sławomir Błoński ◽  
Grzegorz J. Ciach
Keyword(s):  
Kinetic Energy ◽  
Physical Quantity ◽  
Calibration Curve ◽  
High Speed ◽  
Low Cost ◽  
Field Measurements ◽  
Rain Gauge ◽  
High Speed Photography ◽  
Sensor Output ◽  
Impact Position

Abstract This study presents the construction and calibration of a low-cost piezoelectric microprocessor impactometer designed for the field measurements of the rainfall kinetic energy (KE) flux. Its precise calibration was performed in laboratory conditions using waterdrops of different sizes and fall velocities. High-speed photography was applied to measure the velocity of each waterdrop. Although the impactometer constructed for this study is not able to measure the momentum of waterdrops, its accuracy for measuring their KE is excellent. It was found that the processing of the piezoelectric signal might determine which physical quantity is measured by different impactometers. It was also found that the distance between the waterdrop impact position and the impactometer center has a significant effect on the sensor output. A scheme to account for this effect is developed in this study, and the calibration curve for field applications of the impactometer is derived. In addition, an example comparison of the concurrent field measurements of KE flux using the impactometer and rainfall rates using a weighing rain gauge is given.

scholarly journals Ultimate lateral pressures exerted on buried pipelines by the initiation of submarine landslides

Landslides ◽  
2021 ◽  
Author(s):  
Weiyuan Zhang ◽  
Amin Askarinejad
Keyword(s):  
High Speed ◽  
Imaging System ◽  
Hybrid Approach ◽  
Scale Model ◽  
Small Scale ◽  
Shear Strain Rate ◽  
Submarine Landslides ◽  
Fluid Inertia ◽  
Buried Pipelines ◽  
Slope Instabilities

AbstractSubmarine slope instabilities are considered one of the major threats for offshore buried pipelines. This paper presents a novel method to evaluate the ultimate pressure acting on a buried pipeline during the liquefaction of an inclined seabed. Small-scale model tests with pipes buried at three different embedment ratios have been conducted at an enhanced centrifugal acceleration condition. A high-speed, high-resolution imaging system was developed to quantify the soil displacement field of the soil body and to visualize the development of the liquefied zone. The measured lateral pressures were compared with the hybrid approach proposed for the landslide–pipeline interaction in clay-rich material by Randolph and White (2012) and Sahdi et al. (2014). The hybrid approach is proved to be able to predict later pressures induced by the movement of (partially) liquefied sand on buried pipelines. It is found that the fluid inertia (fluid dynamics) component plays an important role when the non-Newtonian Reynolds number >~2 or the shear strain rate > 4.5 × 10−2 sec−1.

Aerodynamic and Vibration Analysis of the Morphing Wings of a Hypersonic Vehicle

2020 ◽  
Author(s):  
Mohammad Khairul Habib Pulok ◽  
Uttam K. Chakravarty
Keyword(s):  
Vibration Analysis ◽  
High Speed ◽  
Thermal Loading ◽  
Hypersonic Vehicle ◽  
Vibration Characteristics ◽  
Scale Model ◽  
Small Scale ◽  
Hypersonic Vehicles ◽  
Morphing Wings ◽  
Wing Morphing

Abstract Hypersonic vehicles are receiving great attention in recent years due to their high speed and long-range capabilities. The shock waves come into consideration as a propagating disturbance for any aircraft when it exceeds the speed of sound. Complex environment and flight requirements of the hypersonic vehicles are leading the researchers to focus on several design considerations. Adaptive shape deformation is one of the prospective areas among them which has an impact on thermal loading, global and local load factors, vehicle acceleration, total energy dissipation, and fuel consumption. The wings play a key role in the aerodynamic performances of a flying machine; therefore, the overall performance of the hypersonic vehicle can be improved by applying morphing technologies on the wing. Morphing can help with reducing wave drag, increasing lift-to-drag ratio as well as enhancing flight endurance, and extending the range for a hypersonic vehicle. In this study, the telescopic wing morphing profile is considered for the aerodynamics and vibration analysis. The experimental validations of the aerodynamics and vibration characteristics are conducted by a wind-tunnel experiment and a vibration-testing arrangement, respectively, using a small-scale model of the wing. The computational analysis of the aerodynamics and vibration characteristics of the morphing wings are conducted and compared. Thus, a comprehensive study including the comparison between morphing modes can establish a standard to choose the appropriate morphing technique for the hypersonic vehicles.

Observation of crack propagation in saline ice and freshwater ice with fluid inclusion

2003 ◽  
Vol 81 (1-2) ◽  
pp. 159-166
Author(s):  
M Arakawa ◽  
V F Petrenko
Keyword(s):  
Crack Propagation ◽  
Electrical Resistance ◽  
Crack Velocity ◽  
High Speed ◽  
High Speed Photography ◽  
Low Density ◽  
Conductive Liquid ◽  
Freshwater Ice ◽  
Maximum Crack ◽  
Very High

A key process of crack propagation in saline ice is the interaction between the crack and fluid inclusions. We observed their interaction in freshwater ice using very high-speed photography (VHSP) and found that the low-density fluids (air and inert liquid, Fluorinert, 1.78 g/cm3) could not impede the crack effectively, interrupting the propagation for less than 10 µs. The high-density liquid mercury, (13.8 g/cm3) impeded the crack more effectively, stalling the development of the crack for more than 20 µs. The crack velocity in saline ice was measured using two different methods: electrical resistance method (ERM) and VHSP. These two methods returned very different mean velocities, 15 m/s for the ERM and 250 m/s for the VHSP. We found that in ice with conductive liquid inclusions, the ERM measured the time it took to break liquid bridges stretched across a crack rather than the crack velocity. Results from the VHSP show that the maximum crack velocity in saline ice was 500 m/s, which is one-half of that found in freshwater ice. From our results using freshwater ice with inclusions, we conclude that liquid inclusions in saline ice may play a role in this retardation. PACS No.: 62.20Mk

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