Rebekka Zimmermann | Searcharxiv

arXiv2025

Weak solutions of the two-dimensional incompressible inhomogeneous Navier-Stokes equations in the presence of variable odd viscosity

We consider the two-dimensional incompressible inhomogeneous Navier-Stokes equations with odd viscosity, where the shear and the odd viscosity coefficients depend continuously on the unknown density function. We establish the existence of weak solutions in both the evolutionary and stationary cases. Furthermore, we investigate the limit of the weak solutions as the odd viscosity coefficient converges to a constant. Lastly, we consider examples of stationary solutions for parallel, concentric and radial flows.

math.AP↗

arXiv2024

Global-in-time well-posedness for the two-dimensional incompressible Navier-Stokes equations with freely transported viscosity coefficient

We establish the global-in-time well-posedness of the two-dimensional incompressible Navier-Stokes equations with freely transported viscosity coefficient, under a scaling-invariant smallness condition on the initial data. The viscosity coefficient is allowed to exhibit large jumps across $W^{2,2+ε}$-interfaces. The viscous stress tensor $μSu$ is carefully analyzed. Specifically, $(R^\perp\otimes R):(μSu)$, where $R$ denotes the Riesz operator, defines a ``good unknown'' that satisfies time-weighted $H^1$-energy estimates. Combined with tangential regularity, this leads to the $W^{1,2+ε}$-regularity of another ``good unknown'', $(\barτ\otimes n):(μSu)$, where $\barτ$ and $n$ denote the unit tangential and normal vectors of the interfaces, respectively. These results collectively provide a Lipschitz estimate for the velocity field, even in the presence of significant discontinuities in $μ$. As applications, we investigate the well-posedness of the Boussinesq equations without heat conduction and the density-dependent incompressible Navier-Stokes equations in two spatial dimensions.

math.AP↗