Author: Tuncer Cebeci
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
Book Description
Recent developments and applications of an interactive boundary layer procedure for unsteady flows are reviewed. The emphasis is on a model problem corresponding to an oscillating thin airfoil in laminar flows and results are reported for different amplitudes and frequencies of oscillation. The use of the characteristic box scheme, with its stability criterion, are shown to allow the accurate calculation of reverse flows and the interaction procedure removes the singularity to allow calculation through regions of separated flow. Although the current focus of the interactive boundary layer procedure has been on the leading edge region, it has general applicability and, together with models for transition and turbulent flows, it can provide the basis for a method to deal with oscillation airfoils and wings and the rapid movement of fixed wing arrangements at angels of attack up to and beyond those of dynamic stall. Calculations at high angles of attack indicate that the behavior of the unsteady separated leading edge flow has similarities to steady flows down-stream of surface corrugations. The use of linear stability theory in the latter case shows that the locations of the onset of transition moves upstream with severity of corrugation and can move inside the separation bubble. In practice this means that the bubbles will be shortened and analogy with unsteady flows suggests that transition may play an important role and preclude the existence of the long separation bubbles determined by the laminar-flow calculations.
Oscillating Airfoils - Achievements and Conjectures
Author: Tuncer Cebeci
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
Book Description
Recent developments and applications of an interactive boundary layer procedure for unsteady flows are reviewed. The emphasis is on a model problem corresponding to an oscillating thin airfoil in laminar flows and results are reported for different amplitudes and frequencies of oscillation. The use of the characteristic box scheme, with its stability criterion, are shown to allow the accurate calculation of reverse flows and the interaction procedure removes the singularity to allow calculation through regions of separated flow. Although the current focus of the interactive boundary layer procedure has been on the leading edge region, it has general applicability and, together with models for transition and turbulent flows, it can provide the basis for a method to deal with oscillation airfoils and wings and the rapid movement of fixed wing arrangements at angels of attack up to and beyond those of dynamic stall. Calculations at high angles of attack indicate that the behavior of the unsteady separated leading edge flow has similarities to steady flows down-stream of surface corrugations. The use of linear stability theory in the latter case shows that the locations of the onset of transition moves upstream with severity of corrugation and can move inside the separation bubble. In practice this means that the bubbles will be shortened and analogy with unsteady flows suggests that transition may play an important role and preclude the existence of the long separation bubbles determined by the laminar-flow calculations.
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
Book Description
Recent developments and applications of an interactive boundary layer procedure for unsteady flows are reviewed. The emphasis is on a model problem corresponding to an oscillating thin airfoil in laminar flows and results are reported for different amplitudes and frequencies of oscillation. The use of the characteristic box scheme, with its stability criterion, are shown to allow the accurate calculation of reverse flows and the interaction procedure removes the singularity to allow calculation through regions of separated flow. Although the current focus of the interactive boundary layer procedure has been on the leading edge region, it has general applicability and, together with models for transition and turbulent flows, it can provide the basis for a method to deal with oscillation airfoils and wings and the rapid movement of fixed wing arrangements at angels of attack up to and beyond those of dynamic stall. Calculations at high angles of attack indicate that the behavior of the unsteady separated leading edge flow has similarities to steady flows down-stream of surface corrugations. The use of linear stability theory in the latter case shows that the locations of the onset of transition moves upstream with severity of corrugation and can move inside the separation bubble. In practice this means that the bubbles will be shortened and analogy with unsteady flows suggests that transition may play an important role and preclude the existence of the long separation bubbles determined by the laminar-flow calculations.
Scientific and Technical Aerospace Reports
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 666
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 666
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
On the Theory of Oscillating Airfoils of Finite Span in Subsonic Compressible Flow
Author: Eric Reissner
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 44
Book Description
The present report is concerned with the problem of the oscillating airfoil of finite span, within the frame of the linearized lifting surface theory. The aim of this study is the development of a theory which incorporates simultaneously the effects of three-dimensionality of the flow and of compressibility of the fluid. As an exact solution of this problem, even within the limitations of the linearized theory, presents very great difficulties, it is worth while to work toward an approximate theory which is valid provided the aspect ratio of the lifting surface is not too small.
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 44
Book Description
The present report is concerned with the problem of the oscillating airfoil of finite span, within the frame of the linearized lifting surface theory. The aim of this study is the development of a theory which incorporates simultaneously the effects of three-dimensionality of the flow and of compressibility of the fluid. As an exact solution of this problem, even within the limitations of the linearized theory, presents very great difficulties, it is worth while to work toward an approximate theory which is valid provided the aspect ratio of the lifting surface is not too small.
Demand Bibliography
Technical Reports Awareness Circular : TRAC.
Aeronautical Engineering
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 524
Book Description
A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA).
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 524
Book Description
A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA).
Aeronautical Engineering: A Cumulative Index to a Continuing Bibliography (supplement 235)
Government Reports Annual Index
Author:
Publisher:
ISBN:
Category : Research
Languages : en
Pages : 1428
Book Description
Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.
Publisher:
ISBN:
Category : Research
Languages : en
Pages : 1428
Book Description
Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.