In premixed turbulent combustion, the Klimov–Williams criterion or Klimov–Williams limit, named after A.M. Klimov and Forman A. Williams, is the condition where  (assuming a Schmidt number of unity). When , the flame thickness is smaller than the Kolmogorov scale, thus the flame burning velocity is not affected by the turbulence field. Here, the burning velocity is given by the laminar flame speed and these laminar flamelets are called as wrinkled flamelets or corrugated flamelets, depending on the turbulence intensity. When , the turbulent transport penetrates into the preheat zone of the flame (thin reaction zone) or even into the reactive-diffusive zone (distributed flames).