Simultaneous Multiple-Location Separation Control

A method of controlling a shear layer for a fluid dynamic body introduces first periodic disturbances into the fluid medium at a first flow separation location. Simultaneously, second periodic disturbances are introduced into the fluid medium at a second flow separation location. A phase difference between the first and second periodic disturbances is adjusted to control flow separation of the shear layer as the fluid medium moves over the fluid dynamic body

Vortex control for rotor blade devices

To control vortices originating at the tips of a rotor's blades rotating through the air at a revolution frequency f, separation control device(s) are actuated to periodically introduce perturbations into the airflow moving over the blades. The periodic introduction of perturbations is controlled in accordance with a periodic modulating frequency of introduction f.sub.0 while the frequency of the perturbations so-introduced is designated as f.sub.e. Vortex control is achieved when the periodic modulating frequency of introduction f.sub.0 satisfies the relationship nf.ltoreq.f.sub.0.ltoreq.f.sub.e where n is the number of blades

Better Late than Never: Publication of the Decisions from the 1845 Term of the Republic of Texas Supreme Court

Two years ago, this column featured the rediscovery of a full year\u27s worth of decisions issued by the Supreme Court of the Republic of Texas that had never been printed. Paulsen & Hambleton, Whatever Happened to 7845? The Missing Decisions of the Texas Supreme Court, 48 Tex. B.J. 830 (1985). Those decisions now have been collected and will appear in the December 1986 issue of the Texas Law Review (The Missing Cases of the Republic, 65 Texas L. Rev. 377 (1986)). Although none of the missing cases are likely to have any direct bearing on the outcome of the Texaco-Pennzoil appeal or any other great legal issue of our day, the opinions nevertheless should be of considerable interest to attorneys, law librarians, and historians

Better Late than Never: Publication of the Decisions from the 1845 Term of the Republic of Texas Supreme Court

Two years ago, this column featured the rediscovery of a full year\u27s worth of decisions issued by the Supreme Court of the Republic of Texas that had never been printed. Paulsen & Hambleton, Whatever Happened to 7845? The Missing Decisions of the Texas Supreme Court, 48 Tex. B.J. 830 (1985). Those decisions now have been collected and will appear in the December 1986 issue of the Texas Law Review (The Missing Cases of the Republic, 65 Texas L. Rev. 377 (1986)). Although none of the missing cases are likely to have any direct bearing on the outcome of the Texaco-Pennzoil appeal or any other great legal issue of our day, the opinions nevertheless should be of considerable interest to attorneys, law librarians, and historians

Flow Control Predictions using URANS Modeling: A Parametric Study

A computational study was performed for steady and oscillatory flow control over a hump model with flow separation to assess how well the steady and unsteady Reynolds-averaged Navier-Stokes equations predict trends due to Reynolds number, control magnitude, and control frequency. As demonstrated previously, the hump model case is useful because it clearly demonstrates a failing in all known turbulence models: they under-predict the turbulent shear stress in the separated region and consequently reattachment occurs too far downstream. In spite of this known failing, three different turbulence models were employed to determine if trends can be captured even though absolute levels are not. The three turbulence models behaved similarly. Overall they showed very similar trends as experiment for steady suction, but only agreed qualitatively with some of the trends for oscillatory control

Parametric Study of Flow Control Over a Hump Model Using an Unsteady Reynolds- Averaged Navier-Stokes Code

This is an expanded version of a limited-length paper that appeared at the 5th International Symposium on Turbulence and Shear Flow Phenomena by the same authors. A computational study was performed for steady and oscillatory flow control over a hump model with flow separation to assess how well the steady and unsteady Reynolds-averaged Navier-Stokes equations predict trends due to Reynolds number, control magnitude, and control frequency. As demonstrated in earlier studies, the hump model case is useful because it clearly demonstrates a failing in all known turbulence models: they under-predict the turbulent shear stress in the separated region and consequently reattachment occurs too far downstream. In spite of this known failing, three different turbulence models were employed to determine if trends can be captured even though absolute levels are not. Overall the three turbulence models showed very similar trends as experiment for steady suction, but only agreed qualitatively with some of the trends for oscillatory control

Managing Flap Vortices via Separation Control

A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management by means of boundary layer separation control. Passive control was achieved using a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressures, was used to predict vortex characteristics based on inviscid rollup relations and vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over either outboard or inboard edge vortices while producing small lift and moment excursions. Unsteady surface pressures indicated that dynamic separation and attachment control can be exploited to perturb vortices at wavelengths shorter than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading

The interplay between technology and politics : a case study analysis of financial reporting practices in Winchester, Massachusetts

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2002.Includes bibliographical references (p. 80-82).The purpose of this study is to explore the interplay between technology and politics by analyzing how recent revisions in the governmental financial reporting model - promulgated in Governmental Accounting Standards Board, Statement 34 - are translated into practice at the local governmental level. The recent reduction in cost and subsequent proliferation of desktop database and mapping technologies has the potential to provide users of governmental financial statements with new ways of watching over entities entrusted with public resources. Similarly, these same "asset management system" technologies offer local governments an invaluable internal decision-support tool for optimizing future planning decisions. However, as evidenced in the Town of Winchester, Massachusetts, the realization of this enhanced monitoring and planning potential extends beyond the realm of information technology concerns. Indeed, (1) without a long-term governmental accounting focus, (2) without the internal governmental capacity to effectively deploy and maintain information technology-driven asset management tools, and (3) without an understanding of the political logic that drives information technology implementation and public disclosure decisions in the local government context, the types and detail of information included in governmental financial statements may continue to lag behind the demands of financial statement users.by David Scott Greenblatt.M.C.P