Vamsi Spandan

A parallel interaction potential approach coupled with the immersed boundary method for fully resolved simulations of deformable interfaces and membranes

Abstract In this paper we show and discuss how the deformation dynamics of closed liquid–liquid interfaces (for example drops and bubbles) can be replicated with use of a phenomenological interaction potential model. This new approach to simulate liquid–liquid interfaces is based on the fundamental principle of minimum potential energy where the total potential energy depends on the extent of deformation of a spring network distributed on the surface of the immersed drop or bubble. Simulating liquid–liquid interfaces using this model require computing ad-hoc elastic constants which is done through a reverse-engineered approach. The results from our simulations agree very well with previous studies on the deformation of drops in standard flow configurations such as a deforming drop in a shear flow or cross flow. The interaction potential model is highly versatile, computationally efficient and can be easily incorporated into generic single phase fluid solvers to also simulate complex fluid–structure interaction problems. This is shown by simulating flow in the left ventricle of the heart with mechanical and natural mitral valves where the imposed flow, motion of ventricle and valves dynamically govern the behaviour of each other. Results from these simulations are compared with ad-hoc in-house experimental measurements. Finally, we present a simple and easy to implement parallelisation scheme, as high performance computing is unavoidable when studying large scale problems involving several thousands of simultaneously deforming bodies in highly turbulent flows.

Drag reduction in numerical two-phase Taylor-Couette turbulence using an Euler-Lagrange approach.

Two-phase turbulent Taylor-Couette (TC) flow is simulated using an Euler-Lagrange approach to study the effects of a secondary phase dispersed into a turbulent carrier phase (here bubbles dispersed into water). The dynamics of the carrier phase is computed using Direct Numerical Simulations (DNS) in an Eulerian framework, while the bubbles are tracked in a Lagrangian manner by modelling the effective drag, lift, added mass and buoyancy force acting on them. Two-way coupling is implemented between the dispersed phase and the carrier phase which allows for momentum exchange among both phases and to study the effect of the dispersed phase on the carrier phase dynamics. The radius ratio of the TC setup is fixed to

Deformation and orientation statistics of neutrally buoyant sub-Kolmogorov ellipsoidal droplets in turbulent Taylor–Couette flow

\eta=0.833

Deformable ellipsoidal bubbles in Taylor-Couette flow with enhanced Euler-Lagrangian tracking

, and a maximum inner cylinder Reynolds number of

AFiD-GPU: a versatile Navier-Stokes Solver for Wall-Bounded Turbulent Flows on GPU Clusters

Re_i=8000

Flow-induced dissolution of femtoliter surface droplet arrays

is reached. We vary the Froude number (

Physical mechanisms governing drag reduction in turbulent Taylor-Couette flow with finite-size deformable bubbles

Fr

A fast moving least squares approximation with adaptive Lagrangian mesh refinement for large scale immersed boundary simulations

), which is the ratio of the centripetal to the gravitational acceleration of the dispersed phase and study its effect on the net torque required to drive the TC system. For the two-phase TC system, we observe drag reduction, i.e., the torque required to drive the inner cylinder is less compared to that of the single phase system. The net drag reduction decreases with increasing Reynolds number

Life stages of wall-bounded decay of Taylor-Couette turbulence

Re_i

Growth dynamics of microbubbles on microcavity arrays by solvent exchange: Experiments and numerical simulations

, which is consistent with previous experimental findings (Murai et al. 2005, 2008). The drag reduction is strongly related to the Froude number: for fixed Reynolds number we observe higher drag reduction when