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Stable explicit stepwise marching scheme in ill-posed time-reversed 2D Burgers' Equation

Published

Author(s)

Alfred S. Carasso

Abstract

This paper constructs an unconditionally stable explicit difference scheme, marching backward in time, that can solve an important, but limited, class of time-reversed 2D Burgers' initial value problems. Stability is achieved by applying a compensating smoothing operator at each time step to quench the instability. This leads to a distortion away from the true solution. However, in many interesting cases, the cumulative error is sufficiently small to allow for useful results. Effective smoothing operators based on $(-\Δ)^p$, with real $p > 2$, can be efficiently synthesized using FFT algorithms, and this may be feasible even in non-rectangular regions. Similar stabilizing techniques were successfully applied in other ill-posed evolution equations. The analysis of numerical stabilty is restricted to a related linear problem. Extensive numerical experiments indicate such linear stability results remain valid when the explicit scheme is applied to a significant class of time-reversed nonlinear 2D Burgers' initial value problems. As illustrative examples, the paper uses fictitiously blurred $256 \times 256$ pixel images, obtained by using sharp images as initial values in well-posed, forward 2D Burgers equations. Such images are associated with highly irregular underlying intensity data that can seriously challenge ill-posed reconstruction procedures. Deblurring these images proceeds by applying the stabilized explicit scheme on the corresponding time-reversed 2D Burgers' equation. Successful recovery from severely distorted data is shown to be possible, even at high Reynolds numbers.
Citation
Inverse Problems in Science and Engineering
Volume
27

Keywords

2D viscous Burgers' equation backward in time, High Reynolds numbers, Stabilized explicit marching difference scheme, Numerical experiments.

Citation

Carasso, A. (2018), Stable explicit stepwise marching scheme in ill-posed time-reversed 2D Burgers' Equation, Inverse Problems in Science and Engineering, [online], https://doi.org/10.1080/17415977.2018.1523905. (Accessed July 18, 2024)

Issues

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Created August 31, 2018, Updated September 25, 2020