Objectives  In this paper, an improved third-order WENO scheme named 'WENO-N+3' is constructed by adding a suitable term to the weights of the conventional WENO-N3 scheme.

  Methods  The precision near the critical points of WENO-N3 and the WENO-N+3 schemes is derived using the Taylor expansion, and accuracy tests are also conducted. Shock-entropy wave interaction, interacting blast waves and Rayleigh-Taylor instability problems are selected in order to verify that the improved scheme WENO-N+3 has less dissipation than the conventional WENO-JS3, WENO-Z3 or WENO-N3 schemes, with high-resolution flow field structures. Finally, the proposed WENO-N+3 scheme is applied to simulations of explosion loads in a confined space.

  Results  The simulation results indicate that the present scheme can provide a higher shockwave peak.

  Conclusions  The findings of this paper can provide valuable references for research into the numerical calculation of internal explosion loads.