Tunable porous and patterned surfaces for turbulence control

Control of wall-bounded turbulent flows has been an active area of research for several decades. However, the development of effective control techniques has been hindered by the limited availability of computationally tractable models that can guide design and optimization. This talk describes extensions of the resolvent formalism that seek to address this limitation. Under the resolvent formulation, the turbulent velocity field can be expressed as a superposition of propagating modes identified via a gain-based decomposition of the Navier-Stokes equations. Control is introduced into this framework via changes to the boundary conditions or through additional forcing terms. These changes alter the structure and gain of resolvent modes, whereby a reduction in gain is shown to be indicative of mode suppression and drag reduction. This approach reproduces previous observations for passive control techniques such as sharkskin-inspired riblets, compliant walls, and anisotropic porous materials with minimal computation. Ongoing work aims to develop optimization routines for riblet shape, and to design, fabricate, and test porous materials that can passively control turbulent flows.

Live Zoom Event: <https://caltech.zoom.us/j/84737586094>

Box Recordings for Caltech: <https://caltech.box.com/s/ktk4t67cwdgqp2eky4duoxcahqqmt9hk>