Sunil Sathe

Preconditioning Techniques for Nonsymmetric Linear Systems in the Computation of Incompressible Flows

In this paper we present effective preconditioning techniques for solving the nonsymmetric systems that arise from the discretization of the Navier-Stokes equations. These linear systems are solved using either Krylov subspace methods or the Richardson scheme. We demonstrate the effectiveness of our techniques in handling time-accurate as well as steady-state solutions. We also compare our solvers with those published previously.

Aerodynamic Interactions Between Parachute Canopies

Aerodynamic interactions between parachute canopies can occur when two separate parachutes come close to each other or in a cluster of parachutes. For the case of two separate parachutes, our computational study focuses on the effect of the separation distance on the aerodynamic interactions, and also focuses on the fluid-structure interactions with given initial relative positions. For the aerodynamic interactions between the canopies of a cluster of parachutes, we focus on the effect of varying the number and arrangement of the canopies.

Modeling of Fluid-Structure Interactions with the Space-Time Techniques

We provide an overview of the space-time finite element techniques developed by the Team for Advanced Flow Simulation and Modeling (T AFSM) for modeling of fluid–structure interaction problems. The core method is the DeformingSpatial-Domain/Stabilized Space-Time formulation, complemented with the mesh update methods, including the Solid-Extension Mesh Moving Technique and MoveReconnect-Renode Mesh Update Method. Also complementing the core method are the block-iterative, quasi-direct and direct coupling methods for the solution of the fully-discretized, coupled fluid and structural mechanics equations. Additionally, the Surface-Edge-Node Contact Tracking technique is introduced as a contact algorithm for the purpose of protecting the quality of the fluid mechanics mesh between the structural surfaces coming into contact. We present mesh-moving tests and numerical examples with incompressible flows and membrane and cable structures.

Airdrop simulations of controlled parachute descents

Computational simulation tools have been applied to a variety of applications relating to the control of parachute descent. The simulation tools have three components: the computation of the structural dynamics (CSD); the computation of the fluid dynamics of the air stream (CFD); and the mutual interface between two that make up the fluid-structure interactions (FSI). In the area of CSD, element contact methodologies have been investigated and tested. FSI developments have focused on the application of line input controls and soft-landing techniques for round canopies. In addition, long duration simulation results have been performed and compared qualitatively with the results from experimental investigations.