Cavitating and Structured Jets for Mechanical Bits to Increase Drilling Rate—Part II: Experimental Results

Johnson, V. E.; Chahine, Georges L.; Lindenmuth, William T.; Conn, A. F.; Frederick, G.S.; Giacchino, G. J.

doi:10.1115/1.3231054

Cited by 22 publications

(14 citation statements)

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“…This conclusion should not be generalized to any form of forced jets, particularly not to cases of strong excitation. In another study, involving enhancement of cavitation using specially designed, 'self excited' nozzles, Johnson et al (1982) show that sufficiently strong excitation can increase the inception indices (presumably of macroscopic cavitationsince they can see the cavities). Another unresolved issue is the little effect acoustic excitation has on the hydrodynamic spectra of the trigger transducer (figure 9b).…”

Section: Efsect Of Acoustic Excitationmentioning

confidence: 98%

Pressure fluctuations and their effect on cavitation inception within water jets

Ran

Katz

1994

J. Fluid Mech.

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Instantaneous and phase averaged pressure distributions in the near field of a jet, and their effects on the conditions for the onset of cavitation are studied in detail. The measurements are performed by using microscopic bubbles as pressure sensors, and holography as a means of detecting them. Experiments are performed at Red exceeding 4 × 105, with and without acoustic excitation. The results show that the highest negative pressure peaks (–0.97) and the resulting cavitation inception occur because of vortex pairing. Prior to pairing the negative peaks are between –0.8 and –0.9. Weak acoustic excitation changes the entire flow structure and the spatial distributions of bubbles, but has little effect on the onset of cavitation. Downstream of the potential core the highest pressure peaks (∼ –0.6) are considerably smaller, in agreement with the occurrence of cavitation there. It is also shown that although the r.m.s. values of pressure fluctuations do not vary with the jet speed, the probability distribution changes significantly, causing a reduction in the inception index with increasing velocity. The probability of cavitation inception is estimated from the distributions of bubbles and pressure peaks. It is shown that the actual, non-uniform bubble distribution increases the probability of inception owning to migration of the bubbles to the low pressure regions.

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Section: Efsect Of Acoustic Excitationmentioning

confidence: 98%

Pressure fluctuations and their effect on cavitation inception within water jets

Ran

Katz

1994

J. Fluid Mech.

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“…Trends with velocity, on the other hand, are conflicting. In some studies the cavitation inception index increases with velocity (Johnson et al 1982); in others it decreases (Kobayashi 1967;Ran & Katz 1994) and in certain studies both trends occur (Pauchet et al 1992) depending on the Reynolds number. Thus, the trend of σ i with diameter is not simply a Reynolds number effect.…”

Section: Some Observed Trends In the Onset Of Cavitationmentioning

confidence: 99%

“…Typically, a turbulent shear layer contains primary (spanwise) and secondary vortices (Konrad 1976;Breidenthal 1981;Jimenez 1983;Bernal 1981;Jimenez, Cogollos & Bernal 1985;Bernal & Roshko 1986;Lasheras, Cho & Maxworthy 1986) and numerous studies (Kermeen & Parkin 1957;Ooi & Acosta 1983;Johnson et al 1982;Katz 1984;Katz & O'Hern 1986;O'Hern 1990;Ran & Katz 1991, 1994Belahadji, Franc & Michel 1995;Pauchet, Retailleau & Woillez 1992 and others mentioned in a detailed review by Arndt 1981) have focused on the relationship between these structures and cavitation. In small jets and small separated regions (Ooi & Acosta 1983;Johnson et al 1982;Ran & Katz 1994) cavitation inception occurs in the core of primary vortex structures that develop as the shear layer rolls up. However, as the size and the characteristic Reynolds number of the separated region increase, especially in plane shear flows, cavitation occurs with increasing frequency in the secondary, axial vortices (Katz & O'Hern 1986;O'Hern 1990;Belahadji et al 1995).…”

Section: Introductionmentioning

confidence: 99%

The flow structure in the near field of jets and its effect on cavitation inception

1999

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Cavitation experiments performed in the near field of a 50 mm diameter (D) jet at ReD = 5 × 105, showed inception in the form of inclined ‘cylindrical’ bubbles at axial distances (x/D) less than 0.55, with indices of 2.5. On tripping the boundary layer, cavitation inception occurred at x/D ≈ 2, as distorted ‘spherical’ bubbles with inception indices of 1.7. To investigate these substantial differences, the near field of the jet was measured using PIV. Data on the primary flow, the strength distribution of the ‘streamwise’ vortices and the velocity profiles within the initial boundary layers were obtained. The untripped case showed a direct transition to three-dimensional flow in the near field (x/D < 0.7) even before rolling up to distinct vortex rings. Strong ‘streamwise’ vortices with strengths up to 25% of the jet velocity times the characteristic wavelength were seen. Cavitation inception occurred in the core of these vortices. In contrast, in the tripped jet the vortex sheet rolled up to the familiar Kelvin–Helmholtz vortex rings with weak secondary vortices. Using the measured nuclei distribution, strengths and straining of the ‘streamwise’ structures, the rates of cavitation events were estimated. The estimated results match very well the measured cavitation rates. Also, the Reynolds stresses in the near field of the jet show similar trends and magnitudes to those of Browand & Latigo (1979) and Bell & Mehta (1990) for a plane shear layer.

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“…The cavitation is further applied to a nozzle design, wherein the speed and volume of the water jet can be modified. The application of this device is pervasive, and its key factor is the water flow outside the nozzle’s water hole outlet 13, 14, 33 . Miyamoto et al 20 performed a study on using micro-bubbles with an average diameter of 70 micrometers to remove oil residues on surfaces, which had higher cleaning action than normal bubbles; if combined with detergent with micro-bubbles, this can make absorption of detergent around bubbles more effective, and, therefore, the cleaning effect is more significant.…”

Section: Literature Reviewmentioning

confidence: 99%

Study on oral hygiene by nanobubbles from high-density nozzle

Lin

2020

Journal of Applied Biomaterials & Functional Materials

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An experiment was performed on oral bacteria removal using the design variables, which included the three-segment rotor speed of the testing device and three types of stainless steel meshes (with different layers). The overall hygienic results showed an effect of up to 95% bacteria removal, and some combinations had 100% hygienic effect. The study proposed that the use of nanobubble generated by a high-density stainless-steel mesh-manufactured nozzle removes dental bacteria. In addition, the device could also be used for auxiliary oral hygiene to decrease the frequency of future medical visits due to periodontal diseases or to enable the device to assist patients with severe periodontal disease more conveniently for oral hygiene.

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Cavitating and Structured Jets for Mechanical Bits to Increase Drilling Rate—Part II: Experimental Results

Abstract: Analyses of self-excited, resonating jets have been corroborated by laboratory experiments. These structured jets achieved cavitation at greater ambient pressures and showed enhanced erosivity in comparison to the nonstructured jets from conventional drill bit nozzles.

Cited by 22 publications

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Pressure fluctuations and their effect on cavitation inception within water jets

Pressure fluctuations and their effect on cavitation inception within water jets

The flow structure in the near field of jets and its effect on cavitation inception

Study on oral hygiene by nanobubbles from high-density nozzle

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