English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the zaia usage as premium feature

ZAIA

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the access of premium content as premium feature

Premium Content

Zendy Tools

Zendy Open

We present a novel moving immersed boundary method (IBM) and employ it indirect numerical simulations (DNS) of the closed-vessel swirling von Karmanflow in laminar and turbulent regimes. The IBM extends direct-forcingapproaches by leveraging a time integration scheme, that embeds the immersedboundary forcing step within a semi-implicit iterative Crank-Nicolson scheme.The overall method is robust, stable, and yields excellent results in canonicalcases with static and moving boundaries. The moving IBM allows us to reproducethe geometry and parameters of the swirling von Karman flow experiments in (F.Ravelet, A. Chiffaudel, and F. Daviaud, JFM 601, 339 (2008)) on a Cartesiangrid. In these DNS, the flow is driven by two-counter rotating impellers fittedwith curved inertial stirrers. We analyze the transition from laminar toturbulent flow by increasing the rotation rate of the counter-rotatingimpellers to attain the four Reynolds numbers 90, 360, 2000, and 4000. In thelaminar regime at Reynolds number 90 and 360, we observe flow features similarto those reported in the experiments and in particular, the appearance of asymmetry-breaking instability at Reynolds number 360. We observe transitionalturbulence at Reynolds number 2000. Fully developed turbulence is achieved atReynolds number 4000. Non-dimensional torque computed from simulations matchescorrelations from experimental data. The low Reynolds number symmetries, lostwith increasing Reynolds number, are recovered in the mean flow in the fullydeveloped turbulent regime, where we observe two tori symmetrical about themid-height plane. We note that turbulent fluctuations in the central region ofthe device remain anisotropic even at the highest Reynolds number 4000,suggesting that isotropization requires significantly higher Reynolds numbers.

Direct Numerical Simulations of the Swirling von Karman Flow Using a Semi-implicit Moving Immersed Boundary Method