Published online by Cambridge University Press: 25 June 2020
Kaneda’s (J. Fluid Mech., vol. 107, 1981, pp. 131–145) Lagrangian renormalized approximation was extended to single-time spectral closure under two assumptions: (i) Markovianization and (ii) the Lagrangian velocity response function is expressed by $G(k,\unicode[STIX]{x1D70F})=\exp (-C_{1}(k)\unicode[STIX]{x1D70F}-C_{2}(k)\unicode[STIX]{x1D70F}^{2}/2)$. The unknown functions $C_{1}(k)$ and $C_{2}(k)$ are theoretically derived to be consistent with the exact short-time behaviour of $G(k,\unicode[STIX]{x1D70F})$ and the asymptotic short-time behaviour of assumed exponential form of $G(k,\unicode[STIX]{x1D70F})$, i.e. the present closure is derived from the Navier–Stokes equation without introduction of any adjustable parameters and it can calculate the statistical quantities by theory. The results show that the present closure has good agreement with direct numerical simulation for single- and two-point statistics.