Unsteady aerodynamics of blade rows

The requirements placed on an unsteady aerodynamic theory intended for turbomachinery aeroelastic or aeroacoustic applications are discussed along with a brief description of the various theoretical models that are available to address these requirements. The major emphasis is placed on the description of a linearized inviscid theory which fully accounts for the affects of a nonuniform mean or steady flow on unsteady aerodynamic response. Although this linearization was developed primarily for blade flutter prediction, more general equations are presented which account for unsteady excitations due to incident external aerodynamic disturbances as well as those due to prescribed blade motions. The motivation for this linearized unsteady aerodynamic theory is focused on, its physical and mathematical formulation is outlined and examples are presented to illustrate the status of numerical solution procedures and several effects of mean flow nonuniformity on unsteady aerodynamic response

Development of an unsteady aerodynamic analysis for finite-deflection subsonic cascades

An unsteady potential flow analysis, which accounts for the effects of blade geometry and steady turning, was developed to predict aerodynamic forces and moments associated with free vibration or flutter phenomena in the fan, compressor, or turbine stages of modern jet engines. Based on the assumption of small amplitude blade motions, the unsteady flow is governed by linear equations with variable coefficients which depend on the underlying steady low. These equations were approximated using difference expressions determined from an implicit least squares development and applicable on arbitrary grids. The resulting linear system of algebraic equations is block tridiagonal, which permits an efficient, direct (i.e., noniterative) solution. The solution procedure was extended to treat blades with rounded or blunt edges at incidence relative to the inlet flow

Refus de justice et identité nobiliaire. L'affaire Hugues de Baux contre Pelet de Mimet. Roquevaire, 1298-1303

L'affaire judiciaire mettant aux prises deux coseigneurs du village de Roquevaire, près de Marseille, entre la fin du XIIIe et le début du XIVe siècle offre la possibilité de donner à voir les stratégies d'identité mises en œuvre par les seigneurs, quel que soit leur niveau dans la hiérarchie nobiliaire, qui mobilisent toutes les ressources judiciaires qu'offrent les procédures mises en place par les Angevins en Provence. Loin d'être démuni face à un grand seigneur récalcitrant, Pelet de Mimet réclame justice pendant une dizaine d'années sur des droits de juridiction qui lui sont déniés par Hugues de Baux et mène en parallèle une politique de regroupement des parts de coseigneurie sur ce lieu qui se révèle, au final, payante. Face à ces stratégies, Hugues de Baux se place, quant à lui, sur le terrain de la familiarité avec le souverain angevin et de la protection de ses droits que le prince se doit de garantir

Using microseismic data recorded at the Weyburn CCS-EOR site to assess the likelihood of induced seismic activity

Since 2000, CO2 has been successfully injected for the purposes of both enhanced oil recovery (EOR) and carbon capture and storage (CCS) at the Weyburn oilfield. A component of the geophysical monitoring program at Weyburn has included the use of downhole geophones to monitor microseismic activity. Microseismic events have already been used to assess the likelihood of CO2 leakage through the caprock at Weyburn. However, in recent years, the focus with respect to CCS and geomechanics has shifted to the concern that fluid injection will trigger induced seismicity. Therefore, in this paper we reanalyse the microseismic observations at Weyburn with respect to concerns regarding induced seismicity. We assess the population statistics of the Weyburn microseismic events, both in terms of the Gutenberg–Richter b-values and the correlation between moment release and injection/production volumes. Our observa- tions serve to corroborate previous studies that considered the geomechanical cause of the microseismic events: namely that the events are not directly triggered by fluid injection, but in response to stress transfer through the rock frame in response to both production and injection. We observe that the b- value at Weyburn is close to 1, the value expected for stress-driven, tectonic seismicity, and significantly lower than values observed in cases where the microseismicity is directly driven by fluid injection (during hydraulic fracturing, for example). We also note little to no correlation between fluid volume changes and induced seismicity – either injection volume alone or net volume change (produced–injected). Finally, we use the observed event statistics to forecast the likelihood that current operations at Weyburn will lead to larger events of sufficient magnitude to be of concern to local populations. We find that the probability of inducing such events is very unlikely

Development of a steady potential solver for use with linearized, unsteady aerodynamic analyses

A full potential steady flow solver (SFLOW) developed explicitly for use with an inviscid unsteady aerodynamic analysis (LINFLO) is described. The steady solver uses the nonconservative form of the nonlinear potential flow equations together with an implicit, least squares, finite difference approximation to solve for the steady flow field. The difference equations were developed on a composite mesh which consists of a C grid embedded in a rectilinear (H grid) cascade mesh. The composite mesh is capable of resolving blade to blade and far field phenomena on the H grid, while accurately resolving local phenomena on the C grid. The resulting system of algebraic equations is arranged in matrix form using a sparse matrix package and solved by Newton's method. Steady and unsteady results are presented for two cascade configurations: a high speed compressor and a turbine with high exit Mach number