Convection patterns in a liquid metal under an imposed horizontal magnetic field.

Physical review. E, Statistical, nonlinear, and soft matter physics · 2013 · Unclear · Insufficient evidence

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Study snapshot

PublicationPhysical review. E, Statistical, nonlinear, and soft matter physics · 2013

Study typeengineering

Reported directionUnclear

Evidence ratingInsufficient

Abstract

We performed laboratory experiments of Rayleigh-Bénard convection with liquid gallium under various intensities of a uniform imposed horizontal magnetic field. An ultrasonic velocity profiling method was used to visualize the spatiotemporal structure of the flows with simultaneous monitoring of the temperature fluctuations in the liquid gallium layer. The explored Rayleigh numbers Ra range from the critical value for onset of convection to 10(5); the Chandrasekhar number Q covers values up to 1100. A regime diagram of the convection patterns was established in relation to the Ra and Q values for a square vessel with aspect ratio 5. We identified five flow regimes: (I) a fluctuating large-scale pattern without rolls, (II) weakly constrained rolls with fluctuations, (III) a continuous oscillation of rolls, (IV) repeated roll number transitions with random reversals of the flow direction, and (V) steady two-dimensional (2D) rolls. These flow regimes are classified by the Ra/Q values, the ratio of the buoyancy to the Lorentz force. Power spectra from the temperature time series indicate that regimes I and II have the features of developed turbulence, while the other regimes do not. The region of steady 2D rolls (Busse balloon) extends to high Ra values in the present setting by a horizontal magnetic field and regime V is located inside the Busse balloon. Concerning the instabilities of the steady 2D rolls, regime III is the traveling wave convection developed from the oscillatory instability. Regime IV can be regarded as a state of phase turbulence, which is induced by intermittent occurrences of the skewed-varicose instability.

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Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeengineering

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Laboratory Rayleigh-Bénard convection experiments in liquid gallium under varying intensities of a uniform imposed horizontal magnetic field mapped five flow regimes across Ra (from onset to 10^5) and Q (up to 1100). Regimes I–II showed features of developed turbulence in temperature power spectra, while regimes III–V did not; a region of steady 2D rolls extended to high Ra under the horizontal magnetic field, with additional regimes interpreted as traveling-wave convection and phase turbulence linked to specific instabilities.

Outcomes measured

Rayleigh-Bénard convection patterns in liquid gallium under a uniform imposed horizontal magnetic field
Flow regime classification as a function of Rayleigh number (Ra) and Chandrasekhar number (Q)
Temperature fluctuation power spectra / turbulence features
Instabilities of steady 2D rolls (oscillatory instability, skewed-varicose instability)

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "imposed horizontal magnetic field (laboratory)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Rayleigh-Bénard convection patterns in liquid gallium under a uniform imposed horizontal magnetic field",
    "Flow regime classification as a function of Rayleigh number (Ra) and Chandrasekhar number (Q)",
    "Temperature fluctuation power spectra / turbulence features",
    "Instabilities of steady 2D rolls (oscillatory instability, skewed-varicose instability)"
  ],
  "main_findings": "Laboratory Rayleigh-Bénard convection experiments in liquid gallium under varying intensities of a uniform imposed horizontal magnetic field mapped five flow regimes across Ra (from onset to 10^5) and Q (up to 1100). Regimes I–II showed features of developed turbulence in temperature power spectra, while regimes III–V did not; a region of steady 2D rolls extended to high Ra under the horizontal magnetic field, with additional regimes interpreted as traveling-wave convection and phase turbulence linked to specific instabilities.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "Rayleigh-Bénard convection",
    "liquid gallium",
    "horizontal magnetic field",
    "Chandrasekhar number",
    "Rayleigh number",
    "flow regimes",
    "ultrasonic velocity profiling",
    "temperature fluctuations",
    "turbulence",
    "Busse balloon",
    "oscillatory instability",
    "skewed-varicose instability"
  ],
  "suggested_hubs": []
}

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Identifiers and source

DOI: 10.1103/physreve.88.063020
PubMed: 24483570

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