P. S. Gurugubelli

Bio: P. S. Gurugubelli is an academic researcher from Birla Institute of Technology and Science. The author has contributed to research in topics: Flapping & Reynolds number. The author has an hindex of 8, co-authored 24 publications receiving 309 citations. Previous affiliations of P. S. Gurugubelli include National University of Singapore.

Self-induced flapping dynamics of a flexible inverted foil in a uniform flow

Abstract: We present a numerical study on the self-induced flapping dynamics of an inverted flexible foil in a uniform flow. A high-order coupled fluid–structure solver based on fully coupled Navier–Stokes and nonlinear structural dynamic equations has been employed. Unlike a conventional flexible foil flapping where the leading edge is clamped, the inverted elastic foil is fixed at the trailing edge and the leading edge is allowed to oscillate freely. We investigate the evolution of flapping instability of an inverted foil as a function of the non-dimensional bending rigidity, , Reynolds number, , and structure-to-fluid mass ratio, , and identify three distinct stability regimes, namely (i) fixed-point stable, (ii) deformed steady and (iii) unsteady flapping state. With the aid of a simplified analytical model, we show that the fixed-point stable regime loses its stability by static-divergence instability. The transition from the deformed steady state to the unsteady flapping regime is marked by a flow separation at the leading edge. We also show that an inverted foil is more vulnerable to static divergence than a conventional foil. Three distinct unsteady flapping modes have been observed as a function of decreasing : (i) inverted limit-cycle oscillations, (ii) deformed flapping and (iii) flipped flapping. We characterize the transition to the deformed-flapping regime through a quasistatic equilibrium analysis between the structural restoring and the fluid forces. We further examine the effects of on the post-critical flapping dynamics at a fixed . Finally, we present the net work done by the fluid and the bending strain energy developed in a flexible foil due to the flapping motion. For small , we demonstrate that the flapping of an inverted flexible foil can generate times more strain energy in comparison to a conventional flexible foil flapping, which has a profound impact on energy harvesting devices.

Added Mass and Aeroelastic Stability of a Flexible Plate Interacting With Mean Flow in a Confined Channel

Abstract: This work presents a review and theoretical study of the added-mass and aeroelastic instability exhibited by a linear elastic plate immersed in a mean flow. We first present a combined added-mass result for the model problem with a mean incompressible and compressible flow interacting with an elastic plate. Using the Euler–Bernoulli model for the plate and a 2D viscous potential flow model, a generalized closed-form expression of added-mass force has been derived for a flexible plate oscillating in fluid. A new compressibility correction factor is introduced in the incompressible added-mass force to account for the compressibility effects. We present a formulation for predicting the critical velocity for the onset of flapping instability. Our proposed new formulation considers tension effects explicitly due to viscous shear stress along the fluid-structure interface. In general, the tension effects are stabilizing in nature and become critical in problems involving low mass ratios. We further study the effects of the mass ratio and channel height on the aeroelastic instability using the linear stability analysis. It is observed that the proximity of the wall parallel to the plate affects the growth rate of the instability, however, these effects are less significant in comparison to the mass ratio or the tension effects in defining the instability. Finally, we conclude this paper with the validation of the theoretical results with experimental data presented in the literature.

Introduction to the Mechanics of Solids

Abstract: A. M. Freudenthal London: John Wiley. 1966. Pp. xv + 492. Price £5 13s. Although written in modern idiom with a currently fashionable title, the book deals with a subject formerly called 'Strength of materials', and covers what engineers are expected to know about stresses in simple structures and mechanical properties of materials. The Introduction admirably discusses how the theoretical and experimental approaches to the behaviour of mechanical systems are to be reconciled with each other.

Numerical Approximation Of Partial Differential Equations

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Mathematical Modeling in Continuum Mechanics

Abstract: Part I. Fundamental Concepts in Continuum Mechanics: 1. Describing the motion of a system: geometry and kinematics 2. The fundamental law of dynamics 3. The Cauchy stress-tensor. Applications 4. Real and virtual powers 5. Deformation tensor. Deformation rate tensor. Constitutive laws 6. Energy equations. Shock equations Part II. Physics of Fluids: 7. General properties of Newtonian fluids 8. Flows of perfect fluids 9. Viscous fluids and thermohydraulics 10. Magnetohydrodynamics and inertial confinement of plasmas 11. Combustion 12. Equations of the atmosphere and of the ocean Part III. Solid Mechanics: 13. The general equations of linear elasticity 14. Classical problems of elastostatics 15. Energy theorems. Duality. Variational formulations 16. Introduction to nonlinear constitutive laws and to homogenization Part IV. Introduction to Wave Phenomena: 17. Linear wave equations in mechanics 18. The soliton equation: the Korteweg-de Vries equations 19. The nonlinear Schrodinger equation Appendix A.