Guru Kalyan Jayasingh

Guru Kalyan Jayasingh

Physics PhD student at UCSD

Talks and presentations

Tricritical Directed Percolation and Transitional Turbulence

October 18, 2025

Invited talk, JIFT Workshop on Strong Turbulence, Avalanching, and Structures in Boundary Plasma Turbulence, UC San Diego

This talk explores how body forces alter the canonical picture of the laminar–turbulent transition in pipe flow. By extending the standard framework of directed percolation to include external forcing, we identify a tricritical regime that interpolates between continuous and discontinuous transitions. The resulting phase diagram reveals how sufficiently strong body forces induce metastability, coexistence, and relaminarization—features observed in curved and centrifugal pipes. The analysis provides a unifying theoretical basis for diverse experimental and numerical observations of forced transitional turbulence.

Laminar-turbulent transition in pipes with body forces: continuous, discontinuous or both?

March 17, 2025

Contributed talk, APS Joint March and April Meeting Global Physics Summit 2025, Anaheim California

The laminar-turbulent transition in straight pipes is believed to occur through a continuous non-equilibrium phase transition in the directed percolation universality class. However, in curved pipes or in the presence of body forces it is possible to observe a discontinuous transition and other phenomenology which seem inconsistent with the emerging consensus. Here, we consider the perturbing effects of body forces and incorporate them into a minimal Landau theory of the transition. We calculate the phase diagram as a function of Reynolds number and body force strength, and show that above a threshold strength of the latter, there is a tricritical point which accounts for the observed discontinuity behavior, including spatially heterogeneous states. Our results are consistent with recent experiments in centrifugal pipes and direct numerical simulations of heated flows.