Flow symmetry-breaking in porous media induces opposing viscous and pressure transverse drag forces

Turbulent flow in porous media with porosity less than 80% is susceptible to macroscale symmetry-breaking depending on the solid obstacle shape and Reynolds number. Macroscale symmetry breaking introduces a unique behavior in the drag force on the solid obstacle in the transverse direction where the pressure and viscous drag forces have equal magnitude and act in opposing directions. Large Eddy Simulation of the microscale turbulent flow shows that symmetry-breaking is caused by an imbalance in the microscale pressure distribution resulting in a net macroscale pressure drag force in the transverse direction. Opposing viscous and pressure drag forces emerge in the Reynolds averaged flow due to asymmetric pressure and shear stress distributions on the solid obstacle surface. A shift in the flow stagnation point and the microscale vortices from the plane of geometric symmetry yields a resultant transverse pressure drag force. The tortuosity of the flow streamlines increases due to this shift causing high shear stress in the locations in between the stagnation point and the microscale vortices. Macroscale flow symmetry-breaking influences the turbulence length and time scales, and increases the turbulence anisotropy.