Turbulent Flame Speed Can Increase under Curvature Smoothing

Hung V. Tran, Jack Xin, Yifeng Yu

Tran, Xin and Yu construct a smooth periodic three-dimensional shear flow V=(0,0,f(x₁,x₂)) and direction (2,2,1) whose homogenized G-equation flame speed has c(0)=0 and positive right derivative as curvature diffusivity d tends to zero. For small d the cutoff is inactive, so the physical cutoff cell speed increases.

Sources for this record

What was already known

A monotone-slowdown theorem held for two-dimensional shear flows. The three-dimensional question was open because the one-dimensional profile argument does not extend to its two-dimensional cell problem.

AI involvement AI-centered

ChatGPT 5.5 Plus suggested ansatzes and the orbit-average mechanism. Tran, Xin and Yu directed the search, made the construction rigorous and independently verified the resulting claims and proofs.

The model supplied the central orbit-average construction mechanism under a human-directed search; the authors established the rigorous theorem.

Importance Notable

Refutes monotone slowdown in the stated three-dimensional G-equation model.

Limitations

The conclusion applies to the specified homogenized model and shear-flow class, not all combustion models. The precise final ansatz coefficients are not traced to a preserved model transcript.

Technical verification Formal (human)

The named authors explicitly report independent verification of all resulting claims and proofs, including the constructed counterexample. This is source-reported completed human checking, not an independent check here.

Formal checking

Independent author verification and rigorous written proof

Checker
Hung V. Tran, Jack Xin and Yifeng Yu
Scope
Theorem 1's smooth three-dimensional shear-flow counterexample and positive small-d speed change
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

The authors explain the periodic-orbit average, the variational selection argument and why the two-dimensional ODE slowdown mechanism does not transfer.

Correction and publication history