Aerodynamics of Engine-Airframe Interaction

The report describes progress in research directed towards the efficient solution of the inviscid Euler and Reynolds-averaged Navier-Stokes equations for transonic flows through engine inlets, and past complete aircraft configurations, with emphasis on the flowfields in the vicinity of engine inlets. The research focusses upon the development of solution-adaptive grid procedures for these problems, and the development of multi-grid algorithms in conjunction with both, implicit and explicit time-stepping schemes for the solution of three-dimensional problems. The work includes further development of mesh systems suitable for inlet and wing-fuselage-inlet geometries using a variational approach. Work during this reporting period concentrated upon two-dimensional problems, and has been in two general areas: (1) the development of solution-adaptive procedures to cluster the grid cells in regions of high (truncation) error;and (2) the development of a multigrid scheme for solution of the two-dimensional Euler equations using a diagonalized alternating direction implicit (ADI) smoothing algorithm

Numerical calculation of the transonic flow past a swept wing

A numerical method is presented for analyzing the transonic potential flow past a lifting, swept wing. A finite difference approximation to the full potential equation is solved in a coordinate system which is nearly conformally mapped from the physical space in planes parallel to the symmetry plane, and reduces the wing surface to a portion of one boundary of the computational grid. A coordinate invariant, rotated difference scheme is used, and the difference equations are solved by relaxation. The method is capable of treating wings of arbitrary planform and dihedral, although approximations in treating the tips and vortex sheet make its accuracy suspect for wings of small aspect ratio. Comparisons of calculated results with experimental data are shown for examples of both conventional and supercritical transport wings. Agreement is good for both types, but it was found necessary to account for the displacement effect of the boundary layer for the supercritical wing, presumably because of its greater sensitivity to changes in effective geometry

Recent experiences with three-dimensional transonic potential flow calculations

Some recent experiences with computer programs capable of solving finitie-difference approximations to the full potential equation for the transonic flow past three dimensional swept wings and simple wing-fuselage combinations are discussed. The programs used are a nonconservative program for swept wings, a quasi-conservative finite-volume program capable of treating swept wings mounted on fuselages of slowly varying circular cross section, and a fully conservative finite volume scheme capable of treating swept wings and wing-cylinder combinations. The present capabilities of these codes are reviewed. The relative merits of the conservative and nonconservative formulations are discussed, and the results of calculations including corrections for the boundary-layer displacement effect are presented

Measurements for the rotordynamic shroud forces for centrifugal pumps

An experiment was designed to measure the rotordynamic shroud forces on a centrigual pump impeller. The measurements were doen for various whirl/impeller ratios and for different flow rates. A destabilising tangential force was measured for small positive whirl ratios and this force decreased with increasing flow rate

A Test Program to Measure Fluid Mechanical Whirl-Excitation Forces in Centrifugal Pumps

Much speculation has surrounded the possible unsteady hydrodynamic forces which could be responsible for the excitation of whirl instabilities in turbomachines. However there exist very few measurements of these forces which would permit one to evaluate the merits of the existing fluid mechanical analyses. In keeping with the informal nature of this workshop we will present details of a proposed test program for the measurement of the unsteady forces on centrifugal impellers caused by either (i) azimuthal asymmetry in the volute geometry or (ii) an externally imposed whirl motion of the impeller. In the second case the forces resulting from the imposed whirl motions with frequencies ranging from zero to synchronous will be measured by means of a force balance upon which the impeller is mounted. This work is presently being carried out under contract with the NASA George Marshall Space Flight Center, Huntsville, Alabama (Contract NAS 8-33108)

The Effect of Inlet Swirl on the Rotordynamic Shroud Forces in a Centrifugal Pump

The role played by fluid forces in determining the rotordynamic stability of a centrifugal pump is gaining increasing attention. The present research investigates the contributions to the rotordynamic forces from the discharge-to-suction leakage flows between the front shroud of the rotating impeller and the stationary pump casing. In particular, the dependency of the rotordynamic characteristics of leakage flows on the swirl at the inlet to the leakage path was examined. An inlet guide vane was designed for the experiment so that swirl could be introduced at the leakage flow inlet. The data demonstrate substantial rotordynamic effects and a destabilizing tangential force for small positive whirl ratios: this force decreased with increasing flow rate. The effect of swirl on the rotordynamic forces was found to be destabilizing

DISQUIETUDE

ARTIST STATEMENT In a post 9/11 world, the global war on terrorism influences our thinking and casts a perpetual shadow that is inescapable. We live in a state of disquietude. Amidst unspeakable events and traumas, we experience censored media, invasion of privacy in the name of heightened homeland security, eroded freedom of speech, and constant rhetoric serving the politics of fear. Art in the age of terrorism is an attempt to bring interpretation and meaning to these timely issues by portraying multiple perspectives, which address the philosophical, social, political and cultural interventions that the war against terrorism has created. It encourages dialogue between various world views and political sources. When images promote meaningful discussion and contemplation, we are given the opportunity to better understand situations that are beyond words. I was inspired to explore the ramifications of terrorism when thinking about personal encounters with terrorism related to places our family had lived or visited. Shortly before my husband attended a conference in Madrid, Spain, terrorists bombed the commuter train system, killing almost 200 people in 2004. When suicide bombers attacked the London Underground between the Kings Cross and Russell Square stations in 2005, the location was unnervingly close to home; my husband and I had lived for more than a year between these two stations, right above the explosions. And, with close relatives in Nagasaki, I have also been keenly aware of the destructive power of atomic weapons: bodies vaporized by the nuclear bomb left permanent afterimages of human shadows etched on building walls in both Nagasaki and Hiroshima. For the above reasons, I found myself drawn to the topic of terrorism, and began to ask myself questions. This body of work seeks to respond to and answer just some of them. Disquietude seeks to explore the wide range of psychological, social, and global ramifications of living in the age of terrorism. The unifying thread running through the work is the ambiguity in each piece, offering a safe haven for each viewer to consider and reflect upon the many repercussions of terrorism, before, during and after it has occurred. The imagery represents the dualities we must face in today’s climate; life vs. death, security vs. vulnerability, anxiety vs. peace, hope vs. despair. My interest in diverse forms of artistic expression has resulted in a wide range of visual stimuli. My aim is to present a multi-faceted approach to the many ways we interpret the status of our well-being at any given time, amidst a constant barrage of media referencing the last, current or impending attack from terrorists--at home or abroad. Pamela Caughe

A Brief Note on the Interaction of an Actuator Cascade with a Singularity

We have recently become concerned with making estimates of steady forces that may be exerted between moving blade rows and stationary blade rows or volutes. Our present interest is with time averaged forces for estimation of shaft loads and flow asymmetry forces rather than with transient processes. For this purpose we have adopted the well-known "actuator" model for the blade row in which the flow leaving the row or cascade is assumed to have a constant leaving angle. The disturbances external to this row such as a volute may be represented by distributions of vortex elements as was done for example by Domm and Hergt [1]