Author: M. Maina Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
An investigation into the application of transition prediction methods for hybrid laminar flow control for military aircraft has been carried out. Linear stability theory and the "e" criterion are commonly used for predicting the onset of transition. Although a great deal of experience has been gained in their use over the years, there are still issues involved in the use of these methods which affect the accuracy of transition prediction The investigation has shown the importance of the inclusion of negatively oriented oblique waves in the calculation of the N-factors. The effect of these waves on the predicted N-factor values and hence transition onset has been shown to be significant and cannot be ignored. These effects are more marked for the combination of adverse pressure gradients and high angles of sweep which are relevant to military aircraft. A parametric study has been carried out to investigate the effect of surface suction or cooling on transition and to determine the appropriate suction quantities or cooling rates required to suppress the various instability modes in order to delay transition for military aircraft Trends in the possible extents of laminar flow achievable for different pressure distributions and flow conditions with various suction and/or cooling distributions are shown and their implications for design are discussed.
Author: National Aeronautics and Space Adm Nasa Publisher: Independently Published ISBN: 9781730927997 Category : Science Languages : en Pages : 102
Book Description
A study was conducted to evaluate the application of hybrid laminar flow control (HLFC) to global range military transport aircraft. The global mission included the capability to transport 132,500 pounds of payload 6500 nautical miles, land and deliver the payload and without refueling return 6500 nautical miles to a friendly airbase. The preliminary design studies show significant performance benefits obtained for the HLFC aircraft as compared to counterpart turbulent flow aircraft. The study results at M=0.77 show that the largest benefits of HLFC are obtained with a high wing with engines on the wing configuration. As compared with the turbulent flow baseline aircraft, the high wing HLFC aircraft shows 17 percent reduction in fuel burned, 19.2 percent increase in lift-to-drag ratio, an insignificant increase in operating weight, and a 7.4 percent reduction in gross weight. Lange, Roy H. Unspecified Center...
Author: Siegfried Wagner Publisher: Springer Science & Business Media ISBN: 3540450602 Category : Technology & Engineering Languages : en Pages : 334
Book Description
The 24 papers presented at the international concluding colloquium of the German priority programme (DFG-Verbundschwerpunktprogramm) "Transition", held in April 2002 in Stuttgart. The unique and successful programme ran six years, starting April 1996, and was sponsored mainly by the Deutsche Forschungsgemeinschaft, DFG, but also by the Deutsches Zentrum für Luft-und Raumfahrt, DLR, the Physikalisch-Technische Bundesanstalt Braunschweig, PTB, and Airbus Deutschland. The papers summarise the results of the programme and cover transition mechanisms, transition prediction, transition control, natural transition and measurement techniques, transition - turbulence - separation, and visualisation issues. Three invited papers are devoted to mechanisms of turbulence production, to a general framework of stability, receptivity and control, and a forcing model for receptivity analysis. Almost every transition topic arising in subsonic and transonic flow is covered.
Author: National Aeronautics and Space Administration Publisher: CreateSpace ISBN: 9781493794324 Category : History Languages : en Pages : 86
Book Description
Laminar-flow control is an area of aeronautical research that has a long history at NASA's Langley Research Center, Dryden Flight Research Center, their predecessor organizations, and elsewhere. In this monograph, Albert L. Braslow, who spent much of his career at Langley working with this research, presents a history of that portion of laminar-flow technology known as active laminar-flow control, which employs suction of a small quantity of air through airplane surfaces. This important technique offers the potential for significant reduction in drag and, thereby, for large increases in range or reductions in fuel usage for aircraft. For transport aircraft, the reductions in fuel consumed as a result of laminar-flow control may equal 30 percent of present consumption. Given such potential, it is obvious that active laminar-flow control with suction is an important technology. In this study, the author covers the early history of the subject and brings the story all the way to the mid-1990s with an emphasis on flight research, much of which occurred at Dryden.
Author: Simha S. Dodbele Publisher: ISBN: Category : Airplanes Languages : en Pages : 24
Book Description
An optimization method has been developed to design axisymmetric body shapes such as fuselages, nacelles, and external fuel tanks with increased transition Reynolds numbers in subsonic compressible flow. The new design method involves a constraint minimization procedure coupled with analysis of the inviscid and viscous flow regions and linear stability analysis of the compressible boundary-layer. In order to reduce the computer time, Granville's transition criterion is used to predict boundary-layer transition and to calculate the gradients of the objective function, and linear stability theory coupled with the e(exp n)-method is used to calculate the objective function at the end of each design iteration. Use of a method to design an axisymmetric body with extensive natural laminar flow is illustrated through the design of a tiptank of a business jet. For the original tiptank, boundary layer transition is predicted to occur at a transition Reynolds number of 6.04 x 10(exp 6). For the designed body shape, a transition Reynolds number of 7.22 x 10(exp 6) is predicted using compressible linear stability theory coupled with the e(exp n)-method.
Author: M. Maina
Author: National Aeronautics and Space Adm Nasa
Author: 
Author: R.H. Lange
Author: M. Choudhari
Author: Siegfried Wagner
Author: National Aeronautics and Space Administration
Author: Simha S. Dodbele
Author: G. L. Goglia
Author: Hansgeorg Riedel