Wave Propagation in 3‐D Poroelastic Media Accounting for Both Mesoscopic and Global Flow Effects

Biot's theory of poroelasticity is widely recognized as a fundamental framework for describing wave‐induced fluid flow in mesoscopic heterogeneous porous media. However, dynamic numerical modeling of velocity dispersion and attenuation in heterogeneous porous media remains challenging due to (a) the stiffness of Biot's equations and (b) the wavelength ‐dependent behavior relative to heterogeneity size . The former, arising from the contrasting discretization requirements for fast and slow P waves, has largely been mitigated by semi‐implicit schemes. The latter persists because accurate simulations require periodically repeated representative elementary volumes: when , the domain becomes prohibitively large; when , scattering masks mesoscale fluid‐flow effects. These constraints have led to a reluctant yet often questioned reliance on quasi‐static simulations neglecting inertial effect. We introduce a dimensionless framework enabling dynamic simulations in the same domain by directly controlling the diffusive process, eliminating frequency sweeps and reproducing quasi‐static analytical and numerical solutions while correctly including inertial effects. Our results demonstrate that quasi‐static approximations remain physically valid for modeling mesoscale fluid flow when the total contribution of global flow is very small. These results enable a more flexible and informed selection of modeling and measurement approaches. Meanwhile, our numerical framework can be used to model wave propagation in 3D heterogeneous porous media, accounting for both mesoscopic and global flow effects, which has been impossible until now.