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Acta Aeronautica et Astronautica Sinica ›› 2025, Vol. 46 ›› Issue (17): 131713.doi: 10.7527/S100-6893.2025.31713

• Fluid Mechanics and Flight Mechanics • Previous Articles     Next Articles

Fast calculation method of Poisson equation source term for BOS measuring density field

Jian ZHANG1, Zhengyu ZHANG2(), Yang YANG2, Fengxue QIAN2, Xiaoxia LI1, Caigang WANG1, Jiajie LUO1   

  1. 1.School of Information Engineering,Southwest University of Science and Technology,Mianyang 621010,China
    2.High Speed Areodynamics Institute,China Aerodynamics Research and Development Center,Mianyang 621000,China
  • Received:2024-12-25 Revised:2025-01-13 Accepted:2025-02-10 Online:2025-02-27 Published:2025-02-27
  • Contact: Zhengyu ZHANG E-mail:zhang_zy@189.cn
  • Supported by:
    National Natural Science Foundation of China(11872069)

Abstract:

Background-Oriented Schlieren (BOS) is a vital non-intrusive method for measuring fluid density field. The finite difference method is employed to solve the Poisson equation for calculating the projected density field. However, existing approaches for computing the source term of the Poisson equation (which mainly includes the first-order partial derivatives of the light deflection angle at the grid nodes) are time-consuming and poor precision at discontinuities with abrupt changes. To address this issue, a fast calculation method of Poisson equation source term for BOS measuring density field is proposed. A Hash function between the point coordinates and the light deflection angle field data is presented to rapidly locate the BOS measurement points, their deflection angles in a local area centered around a given point, and the interpolation-based derivative formula for this local area are constructed. A region division method is proposed for areas with abrupt changes in light deflection angle, where first-order partial derivatives are computed separately using Hash tables and local interpolation. Simulation results show a 56.66% reduction in residuals and a 75.8% decrease in peak error near abrupt changes. For a cavity wind tunnel model, the method yields a finer density field and achieves a 411.85 speedup over existing Poisson source term methods. Two supersonic wind tunnel tests, on a 7° cone-cylinder and a sonic boom model, validate the method, with weak head shock waves closely matching theory and a maximum density ratio error of only 3.9%. The method proposed in this paper therefore improves the rapid and accuracy of the density field measurement, and can capture weak shock waves, offering substantial application value.

Key words: density field reconstruction, light deflection angle, background-oriented schlieren, Poisson equation, Hash function

CLC Number: