Natural nuclei population dynamics in cavitation tunnels

Khoo, MT; Venning, James A.; Pearce, BW; Takahashi, Koji; Mori, Takayuki; Brandner, PA

doi:10.1007/s00348-019-2843-x

Cited by 24 publications

(23 citation statements)

References 25 publications

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“…Hydrodynamic measurements typically report lower populations, partly because optical techniques may also detect non-cavitating particles and also due to the quality of the water itself. However, the power-law trends observed across all measurements are generally comparable (Khoo et al, 2020) with a phenomenological model proposed by Franklin (1992) which describes the relationship between nuclei size and concentration as a power law with an index of −4. While this indicates a universal characteristic of water, Khoo et al (2020) noted temporal variations in the nuclei population which naturally occurs in a cavitation tunnel, also known as the natural nuclei population, which may be described as a nuclei deplete population.…”

Section: Suction Sidesupporting

confidence: 87%

“…However, the power-law trends observed across all measurements are generally comparable (Khoo et al, 2020) with a phenomenological model proposed by Franklin (1992) which describes the relationship between nuclei size and concentration as a power law with an index of −4. While this indicates a universal characteristic of water, Khoo et al (2020) noted temporal variations in the nuclei population which naturally occurs in a cavitation tunnel, also known as the natural nuclei population, which may be described as a nuclei deplete population. This is in contrast to those populations found in cavitating wakes or flows deliberately injected with microbubbles, whose nuclei concentrations are several orders of magnitude higher, as discussed by Brandner (2018) and Khoo et al (2020).…”

Section: Suction Sidesupporting

confidence: 87%

“…While this indicates a universal characteristic of water, Khoo et al (2020) noted temporal variations in the nuclei population which naturally occurs in a cavitation tunnel, also known as the natural nuclei population, which may be described as a nuclei deplete population. This is in contrast to those populations found in cavitating wakes or flows deliberately injected with microbubbles, whose nuclei concentrations are several orders of magnitude higher, as discussed by Brandner (2018) and Khoo et al (2020). Temporal variations in natural nuclei populations in cavitation tunnels highlight the importance of understanding nuclei population dynamics and of monitoring.…”

Section: Suction Sidementioning

confidence: 97%

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Statistical aspects of tip vortex cavitation inception and desinence in a nuclei deplete flow

et al. 2020

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Tip vortex cavitation (TVC) inception and desinence behaviour of a NACA 0012 cross-section, elliptical hydrofoil is investigated from a statistical perspective in a cavitation tunnel. Measurements were made for incidences from 4 • to 16 • and Reynolds numbers from 1.0×10 6 to 2.1×10 6 . The statistics of TVC inception were quantified by taking repeated measurements of the time until the appearance of a tip vortex cavity for a range of fixed incidences. In other experiments, the angle of attack was continuously increased until inception then decreased until desinence for a range of fixed cavitation numbers. The data were primarily acquired via an automated process using a laser and photodiode to detect the presence of a cavity. Measurements show that TVC inception in a nuclei deplete flow is a probabilistic process for which a large dataset is required for accurate characterisation. The probability of ingesting and activating a nucleus increases with time at a given test condition due to the increased volume of water exposed to low pressures. TVC desinence exhibits far less statistical variation than inception and is largely independent of the natural nuclei population. It does, however, exhibit hysteresis which is dependent on the topology of the cavitating flow. For the desinence of unattached cavitation, there is a small hysteresis between the inception and desinence indices. However, desinence is delayed for attached cavitation.

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Section: Suction Sidesupporting

confidence: 87%

Section: Suction Sidesupporting

confidence: 87%

Section: Suction Sidementioning

confidence: 97%

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Statistical aspects of tip vortex cavitation inception and desinence in a nuclei deplete flow

et al. 2020

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“…Various seeding conditions were investigated where the freestream flow ranged from being deplete of active nuclei through to that with an abundance of microbubble nuclei. For the deplete case no nuclei are injected such that only the natural population is present in the tunnel water which do not provide active nuclei in the freestream for this flow condition [18,10,9]. For the nucleated cases, poly-disperse microbubbles are injected upstream of the honeycomb, as shown in figure 1.…”

Section: Methodsmentioning

confidence: 99%

Control of Cloud Cavitation through Microbubbles

Venning¹,

Pearce²,

Brandner³

2020

Australasian Fluid Mechanics Conference (AFMC)

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The dynamics of cloud cavitation about a 3D hydrofoil are investigated experimentally in a cavitation tunnel with deplete, sparse and abundant freestream nuclei populations. The rectangular-planform, NACA 0015 hydrofoil was tested at a Reynolds number of 1.4 × 10 6 , an incidence of 6 • and a cavitation number of 0.55. High-speed photography of cavitation shedding phenomena was acquired simultaneously with unsteady force measurement to enable identification of cavity shedding modes corresponding with force spectral peaks. Nuclei populations were varied through the injection of polydisperse microbubbles. Both the deplete and abundant cases were characterised by large-scale cloud cavitation. For a sparsely seeded flow, however, coherent fluctuations are significantly reduced due to random nuclei activation and cavity breakup resulting in minimum relative unsteady lift.

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“…Nuclei populations can vary within and between environmental and laboratory waters [14]. They are known to influence TVC behaviour, with earlier onset of cavitation measured in flows with higher concentrations of larger nuclei, also known as 'weak' water [1,10,13].…”

Section: Introductionmentioning

confidence: 99%

Nucleation Effects on Tip Vortex Cavitation Inception Location

Khoo¹,

Venning²,

Pearce³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

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Nuclei, or microbubble, populations are inextricably linked to tip vortex cavitation (TVC) inception and dynamics. In order to gain a better quantitative understanding of this relationship, high-speed video measurements were taken in a cavitation tunnel of TVC inception locations about an elliptical hydrofoil in flows with mono-and polydisperse injected nuclei populations.Sample sizes of O(1000) were acquired. For both populations, inception occurred between 0.02 chord lengths upstream of the hydrofoil tip and about 2.1 chord lengths downstream along the cavity trajectory. However, inception location distribution varied significantly with nuclei population. This is explained by the higher concentrations of weaker nuclei in the monodisperse case, which increases the distance along the vortex within which nuclei are susceptible to cavitation. These results provide the foundation for studies on TVC dynamics and acoustics.

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Natural nuclei population dynamics in cavitation tunnels

Cited by 24 publications

References 25 publications

Statistical aspects of tip vortex cavitation inception and desinence in a nuclei deplete flow

Statistical aspects of tip vortex cavitation inception and desinence in a nuclei deplete flow

Control of Cloud Cavitation through Microbubbles

Nucleation Effects on Tip Vortex Cavitation Inception Location

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