An Approach to the Constrained Design of Natural Laminar Flow Airfoils PDF Download
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722177904
Category :
Languages : en
Pages : 78
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Book Description
A design method has been developed by which an airfoil with a substantial amount of natural laminar flow can be designed, while maintaining other aerodynamic and geometric constraints. After obtaining the initial airfoil's pressure distribution at the design lift coefficient using an Euler solver coupled with an integral turbulent boundary layer method, the calculations from a laminar boundary layer solver are used by a stability analysis code to obtain estimates of the transition location (using N-Factors) for the starting airfoil. A new design method then calculates a target pressure distribution that will increase the laminar flow toward the desired amount. An airfoil design method is then iteratively used to design an airfoil that possesses that target pressure distribution. The new airfoil's boundary layer stability characteristics are determined, and this iterative process continues until an airfoil is designed that meets the laminar flow requirement and as many of the other constraints as possible. Green, Bradford E. Langley Research Center...
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722177904
Category :
Languages : en
Pages : 78
Get Book Here
Book Description
A design method has been developed by which an airfoil with a substantial amount of natural laminar flow can be designed, while maintaining other aerodynamic and geometric constraints. After obtaining the initial airfoil's pressure distribution at the design lift coefficient using an Euler solver coupled with an integral turbulent boundary layer method, the calculations from a laminar boundary layer solver are used by a stability analysis code to obtain estimates of the transition location (using N-Factors) for the starting airfoil. A new design method then calculates a target pressure distribution that will increase the laminar flow toward the desired amount. An airfoil design method is then iteratively used to design an airfoil that possesses that target pressure distribution. The new airfoil's boundary layer stability characteristics are determined, and this iterative process continues until an airfoil is designed that meets the laminar flow requirement and as many of the other constraints as possible. Green, Bradford E. Langley Research Center...
Author: Bradford E. Green
Publisher:
ISBN:
Category :
Languages : en
Pages : 188
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 82
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Author: Richard Lawson Campbell
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 28
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The objective of inverse airfoil design has traditionally been the determination of the airfoil shape that results in desired aerodynamic characteristics. Under this general classification, inverse methods have progressed a great deal over the past few decades. With modern inverse methods, it is possible to prescribe velocity and/or boundary-layer characteristics along with desired geometric constraints in the design of airfoils. In spite of these advances, inverse airfoil design still involves a certain amount of trial and error when a designer attempts to fine tune the drag polar of the airfoil or when attempting to tailor the airfoil for a particular application. The research presented in this thesis makes two specific advances to the state of the art in inverse design. The first part of the research describes the development of an approach by which a desired boundary-layer transition curve can be specified as an input to inverse design. The second part presents an approach for incorporating aircraft performance considerations in the inverse design process. The two advances can help reduce the design cycle time for airfoil and aircraft design by reducing the amount of trial and error in the design process. The motivation factor for the first part of the research (inverse design via specification of the boundary-layer transition curve) was the strong connection between the transition curve and the airfoil drag polar. In the approach developed, a multidimensional Newton iteration is used to adjust the velocity distribution until the transition lift coefficient at several locations on the airfoil are within a given tolerance of the specifications. It is shown that the shape of the drag bucket as well as the camber and extents of laminar flow on the airfoil can be controlled through the specification of the transition-curve. This method represents an enhancement over previous inverse airfoil design methods since it allows for a single specification that spans multipl.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722063139
Category :
Languages : en
Pages : 26
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An approach was developed for incorporating flow and geometric constraints into the Direct Iterative Surface Curvature (DISC) design method. In this approach, an initial target pressure distribution is developed using a set of control points. The chordwise locations and pressure levels of these points are initially estimated either from empirical relationships and observed characteristics of pressure distributions for a given class of airfoils or by fitting the points to an existing pressure distribution. These values are then automatically adjusted during the design process to satisfy the flow and geometric constraints. The flow constraints currently available are lift, wave drag, pitching moment, pressure gradient, and local pressure levels. The geometric constraint options include maximum thickness, local thickness, leading-edge radius, and a 'glove' constraint involving inner and outer bounding surfaces. This design method was also extended to include the successive constraint release (SCR) approach to constrained minimization. Campbell, Richard L. Langley Research Center RTOP 505-59-10-03...
Author: R. W. Barnwell
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 432
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Book Description
Research on laminar flow and its transition to turbulent flow has been an important part of fluid dynamics research during the last sixty years. Since transition impacts, in some way, every aspect of aircraft performance, this emphasis is not only understandable but should continue well into the future. The delay of transition through the use of a favorable pressure gradient by proper body shaping (natural laminar flow) or the use of a small amount of suction (laminar flow control) was recognized even in the early 1930s and rapidly became the foundation of much of the laminar flow research in the U.S. and abroad. As one would expect, there have been many approaches, both theoretical and experimental, employed to achieve the substantial progress made to date. Boundary layer stability theories have been formu lated and calibrated by a good deal of wind tunnel and flight experiments. New laminar now airfoils and wings have been designed and many have been employed in aircraft designs. While the early research was, of necessity, concerned with the design of subsonic aircraft interest has steadily moved to higher speeds including those appropriate to planetary entry. Clearly, there have been substantial advances in our understanding of transition physics and in the development and application of transition prediction methodolo gies to the design of aircraft.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 96
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Author: Dan M. Somers
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 132
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A flapped natural laminar flow airfoil for general aviation applications, the NLF(1)-0215F, has been designed and analyzed theoretically and verified experimentally in the Langley Low Turbulence Pressure Tunnel. The basic objective of combining the high maximum lift of the NASA low speed airfoils with the low cruise drag of the NACA 6 series airfoils has been achieved. The safety requirement that the maximum lift coefficient not be significantly affected with transition fixed near the leading edge has also been met. Comparisons of the theoretical and experimental results show generally good agreement.
Author: Dan M. Somers
Publisher:
ISBN:
Category :
Languages : en
Pages : 108
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