Vortex shedding characteristics are investigated numerically for steady flow past two stationary cylinders of equal diameter at a critical gap spacing of 0.9 to 1.10 in increments of 0-05 and the analysis is extended to the study of flows around rotating cylinders. The Viscous Cell Boundary Element Method (VCBEM) developed by Tan et al. (1999) is modified to incorporate the study of rotating cylinder problems and this has proved successful in reproducing the detailed flow characteristics of experimental observations, correlation with theoretical predictions produced by other methods and experimental measurements of drag and lift coefficients over a range of Reynolds number. This has been achieved through a primitive variable formulation of the hybrid approach involving boundary element and finite element methods. The fluid domain is idealised by an unstructured mesh and the relevant boundary conditions for the rotating cylinder incorporated into the VCBEM code through development of suitable numerical schemes of study. Numerical predictions are presented for flow patterns involving different arrangements of twin rotating cylinders and the simulation results are discussed. A brief overview is presented describing reduced order modelling techniques applicable to Navier-Stokes equations with particular focus on the proper orthogonal decomposition technique and its application to rotating cylinders. A control function h is formulated for this class of problems and validation studies are conducted. Trust-region augmented reduced order modelling techniques are adopted for optimal control of vortex shedding in the wake of a cylinder by imposing a time dependent angular velocity on the cylinder. The application of these techniques to design feedforward and feedback controllers is examined to achieve vortex suppression.