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A letter for objective Liutex

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Abstract

Vortex structures, detected by the existing popular vortex identification methods, of the same case are generally different if the results are measured by different observers, who are moving with different coordinate systems. These coordinate systems can be inertial or non-inertial. Galilean invariance can solve the moving observer problems in different inertial coordinate systems. A variable is invariant under Galilean transformation is called Galilean invariant. Galilean invariant vortex identification methods can provide invariant vortex structures based on different inertial observers. However, for some situations, the observers are non-inertial, e.g., the observer is sitting on an aircraft which is accelerating or rotating. In such a situation, it requires to use an objective method. Objectivity represents a property that one variable is not observer-dependent (the observer’s motion can be either inertial or non-inertial). A strategy based on a zero-vorticity (measured in inertial frame) reference point is proposed in this letter to find the objective vortex structure. Liutex is chosen as the vortex indicator and two numerical examples are used to test the proposed strategy. The results show that the strategy is effective.

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Acknowledgement

The authors acknowledge the financial support from UTA Mathematics Department and are grateful to Texas Advanced Computation Center (TACC) for providing computing resources.

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Authors and Affiliations

  1. Department of Mathematics, University of Texas at Arlington, Arlington, Texas, 76019, USA

    Yifei Yu & Chaoqun Liu

  2. School of Mathematical Science, Soochow University, Suzhou, 215006, China

    Yi-qian Wang

Authors
  1. Yifei Yu
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  2. Yi-qian Wang
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  3. Chaoqun Liu
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Corresponding author

Correspondence to Chaoqun Liu.

Additional information

Biography: Yifei Yu (1996–), Male, Ph. D. Candidate

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Yu, Y., Wang, Yq. & Liu, C. A letter for objective Liutex. J Hydrodyn 34, 965–969 (2022). https://doi.org/10.1007/s42241-022-0064-x

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  • DOI: https://doi.org/10.1007/s42241-022-0064-x

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