Transmission loss and noise reduction of reactive mufflers are determined by linear acoustic theory and unsteady flow field study, respectively. The effects of extending the inlet tube of the muffler, adding holes to the extension, and the number of holes on both transmission loss and noise reduction are investigated. In noise reduction analysis, the Navier-Stokes equations and k-ε model are us...

Title of dissertation: DEVELOPMENT OF A TIME-ACCURATE VISCOUS LAGRANGIAN VORTEX WAKE MODEL FOR WIND TURBINE APPLICATIONS Sandeep Gupta, Doctor of Philosophy, 2006 Dissertation directed by: Minta Martin Professor J. Gordon Leishman, Department of Aerospace Engineering A second-order accurate model has been developed and validated for modeling the unsteady aerodynamics of a wind turbine. The free...

A model was developed for the analysis of steady and unsteady bubble generation frequencies in a microfluidic flow-focusing device. In both cases, the generation frequency depends on the downstream influence of bubbles created by the flow-focusing device, which provides a source of feedback. For steady-state generation of bubbles, this feedback explains the relationships among frequency, gas pr...

Streamlines, contour lines, vector plots, and volume slices (cutting planes) are commonly used for flow visualization. These techniques are sometimes referred to as instantaneous flow visualization techniques because calculations are based on an instant of the flow field in time. Although instantaneous flow visualization techniques are effective for depicting phenomena in steady flows, they som...

The solution of time-dependent PDE-constrained optimization problems subject to unsteady flow equations presents a challenge to both algorithms and computers. In this paper we present an all-at-once approach where we solve for all time-steps of the discretized unsteady Stokes problem at once. The most desirable feature of this approach is that for all steps of an iterative scheme we only need a...

In this paper, the problem of unsteady stagnationpoint flow and heat transfer induced by a shrinking sheet in the presence of radiation effect is studied. The transformed boundary layer equations are solved numerically by the shooting method. The influence of radiation, unsteadiness and shrinking parameters, and the Prandtl number on the reduced skin friction coefficient and the heat transfer c...

1 Easy access to video imaging, digital frame grabbing and image processing technology has opened up exciting opportunities in fluid mechanics education. This paper presents several examples of student work, and discusses new curricula based on these new developments. Complex, unsteady flows can now be quantified using multi-dimensional techniques. Image sequences can be stored and used in prob...

We prove analytic criteria for the existence of finite-time attracting and repelling material surfaces and lines in threedimensional unsteady flows. The longest lived such structures define coherent structures in a Lagrangian sense. Our existence criteria involve the invariants of the velocity gradient tensor along fluid trajectories. An alternative approach to coherent structures is shown to l...

The vortex stretching process is relevant to energy transport at various scales in turbulent flow and in vortex reconnection. For these, reasons, exact solutions for vortex flow are useful. Robinson and Saffman [1] examined the Burgers vortex solution and found closed form steady solutions for special parameter values. Unsteady 2D Burgers vortex solutions have been used to model the spanwise st...

Performance analysis of a reversible micro-pump system is obtained by numerical simulations. The unsteady incompressible Navier–Stokes equations are solved in a moving micro-pump system using a spectral h/p element algorithm, employing an arbitrary Lagrangian Eulerian (ALE) formulation on structured/unstructured meshes. The performance of the micro-pump is evaluated as a function of the Reynold...