Homogeneous Venturi-effect concentrators for creeping flows: Magnifying flow velocities and heat fluxes simultaneously

Although thermal metamaterials have received considerable attention for approximately a decade, previous studies have so far focused on heat conduction or thermal convection in porous media, hampering applications related to moving in media. Based on transformation heat transfer, here we have analytically designed Venturi effect concentrators by simultaneously manipulating the dynamic viscosity and the thermal conductivity. Further based on this theory and integral median theorem, inhomogeneous concentrators metamaterials simplified to homogeneous counterparts are proposed. Noteworthily, the proposed method can be employed to simplify not only thermal metamaterials, but also other inhomogeneous metamaterials, such as optical metamaterials, electromagnetic metamaterials, acoustic metamaterials, among others. Numerical simulations demonstrate that these Venturi-effect concentrators can not only amplify both flow velocities and heat fluxes in thermal-flow fields, but also achieve cloaking effects in thermal-flow systems. Since these Venturi-effect concentrators do not interfere with the thermal-flow field outside the concentrators, they secure advantages over conventional Venturi tubes and will facilitate potential applications related to Venturi effects.