Resources

Author(s): Lukas Bentkamp and Michael Wilczek The comprehensive statistics of a turbulent flow field can in principle be captured by Hopf’s functional approach; however, the resulting functional equations have remained largely intractable. We here study a simplified passive vector model, whose Hopf equation is solved exactly by an ensemble of Gaussian fields. Based on both theory and simulations, we find that the model displays a fluctuating energy...

Author(s): Hongsik Kim and Sunghwan Jung Put a soap bubble in an electric field and it stretches into a taller, smooth dome. Turn the field up and, past a critical point, the top sharpens into a pointed cone that fires off a thin jet. Imaging the bubble from the side, we follow this whole sequence in one experiment and find two things. Bubbles of different sizes deform along the same curve once the field is rescaled by bubble size and surface...

Author(s): Yatin Darbar, Ahmed Said Ismail, Thomas C. Sykes, David Harbottle, Harvey M. Thompson, and Mark C. T. Wilson Droplet mixing is vital in many practical applications, yet the underlying physical mechanisms remain poorly understood. This work uses carefully validated numerical simulations to investigate the mixing dynamics of inkjet printed droplets. Our results show that impact-driven flows contribute only weakly to mixing, while molecular...

Author(s): Suresh Behara Rotating bluff bodies are widely used to control wake instabilities and fluid forces, but the role of wake–body interactions in multi-body configurations remains less understood. Direct simulations of isolated and tandem transversely rotating spheres show that rotation can suppress classical shedding and reorganize the wake into double-threaded vortical structures. However, tandem interactions can overturn this stabilizing...

Author(s): Luis H. Hatashita, Pranav Nathan, and Suhas S. Jain High-fidelity simulations have become indispensable for uncovering the physics of turbulent two-phase flows, yet quantitative guidelines for the grid and time-step requirements needed to accurately resolve interface dynamics have been lacking. We derive scaling laws that predict these computational requirements as functions of Reynolds, Weber, and Capillary numbers; identify distinct...

Author(s): Wouter J. T. Bos Invariants, such as energy or enstrophy, are central to turbulence theory. Some systems behave in a sub-space between two well-known limits where invariants are known. Here, we demonstrate that invariants can also be defined for these intermediate cases. Knowledge of the invariants enables the development of simple models for the multiscale dynamics of such systems. [Phys. Rev. Fluids 11, 074605] Published Fri Jul...

Author(s): Naoya Okamoto, Takashi Ishihara, Mitsuo Yokokawa, and Yukio Kaneda Using direct numerical simulations of incompressible turbulence at Taylor-scale Reynolds numbers Rλ up to about 1740, we examine spectra, two-point correlations, and second-order local-average moments of the energy dissipation rate ϵ and enstrophy Ω. Correlations and local-average moments exhibit larger scaling exponents for fluctuating fields than for total fields over...