Part II: Steady aerofoil-spoiler characteristics

1987 ◽  
Vol 91 (908) ◽  
pp. 359-366
Keyword(s):  
Separated Flow ◽  
Experimental Results ◽  
Surface Singularity ◽  
Separation Region ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Singularity Method ◽  
Total Head ◽  
Low Speeds ◽  
Theoretical Results

Summary A surface singularity method has been formulated to predict two-dimensional spoiler characteristics at low speeds. Vorticity singularities are placed on the aerofoil surface, on the spoiler surface, on the upper separation streamline from the spoiler tip and on the lower separation streamline from the aerofoil trailing edge. The separation region is closed downstream by two discrete vortices. The flow inside the separation region is assumed to have uniform total head. The downstream extent of the separated wake is an empirical input. The flows both external and internal to the separated regions are solved. Theoretical results have been obtained for a range of spoiler-aerofoil configurations which compare reasonably with experimental results. The model is deficient in that it predicts a higher compression ahead of the spoiler than obtained in practice. Furthermore, there is a minimum spoiler angle below which a solution is not possible; it is thought that this feature is related to the physical observation that at small spoiler angles, the separated flow from the spoiler reattaches on the aerofoil upper surface ahead of the trailing edge.

Theoretical Study on the Flow About Savonius Rotor

1984 ◽  
Vol 106 (1) ◽  
pp. 85-91 ◽  
Author(s):  
Takenori Ogawa
Keyword(s):  
Dimensional Analysis ◽  
Theoretical Study ◽  
Separated Flow ◽  
Vortex Method ◽  
Experimental Results ◽  
Two Dimensional ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Savonius Rotor ◽  
Singularity Method

A method for the two-dimensional analysis of the separated flow about Savonius rotors is presented. Calculations are performed by combining the singularity method and the discrete vortex method. The method is applied to the simulation of flows about a stationary rotor and a rotating rotor. Moreover, torque and power coefficients are computed and compared with the experimental results presented by Sheldahl et al. Theoretical and experimental results agree well qualitatively.

An Investigation of the Predicting Capabilities of a Variable Flow Stress Machining Theory

2001 ◽  
Author(s):  
P. Mathew
Keyword(s):  
Flow Stress ◽  
Material Flow ◽  
Three Dimensional ◽  
Experimental Results ◽  
Two Dimensional ◽  
Variable Flow ◽  
Comparative Results ◽  
Intermittent Cutting ◽  
Theoretical Results ◽  
Modelling Approach

Abstract The Oxley Machining Theory, which has been developed over the last 40 years, is presented in this paper. The capability of the model is described with its initial two-dimensional machining approach followed by the extension to the generalised model for three-dimensional machining. The theoretical results from the model are compared with the experimental results to determine the model capability. A brief description of the work associated with the effect of strain hardening at the interface is presented and comparative results are shown. A further extension of the model to intermittent cutting process of reaming is also presented and a comparison with the experimental results indicates the model developed is quite capable of predicting cutting forces for reaming. In explaining the results obtain, the assumptions made are explained and the inputs required. The limitations of the modelling approach are presented. It is pointed out that the Oxley model is a versatile model as long as proper description of the material flow stress properties is presented.

An Experimental Study of Rectilinear Jet-Flap Cascades

1972 ◽  
Vol 94 (1) ◽  
pp. 97-104 ◽  
Author(s):  
T. J. Landsberg ◽  
E. Krasnoff
Keyword(s):  
Experimental Study ◽  
Momentum Flux ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Tangential Blowing ◽  
Theoretical Results ◽  
Good Agreement

The performance of two-dimensional jet-flap cascades is determined experimentally. Stream deflection angles are presented as a function of the ratio of jet to mainstream momentum flux at chord spacing ratios of 0.375 and 0.75. Results obtained with conventional jet-flap airfoils (normal blowing near trailing edge) are in good agreement with published theoretical results. Tangential blowing jet-flap airfoils (tangential blowing over a rounded trailing edge) are shown to approximately double the turning effectiveness of the cascade.

Part I: Some experiences on simple panel methods applied to attached and separated flows

1987 ◽  
Vol 91 (908) ◽  
pp. 350-359 ◽  
Author(s):  
H. B. Tou ◽  
G. J. Hancock
Keyword(s):  
Piecewise Linear ◽  
Separated Flows ◽  
Surface Singularity ◽  
List Type ◽  
Trailing Edge ◽  
Kutta Condition ◽  
First Order ◽  
Panel Methods ◽  
Total Head ◽  
Order Surface

Summary Simple first order surface singularity methods based on: (i) Smith and Hess uniform source panels plus a uniform vorticity around aerofoil profile, (ii) piecewise linear vorticity around aerofoil profile, with different assumption for Kutta condition, have been applied to attached flows and separated flows past an aerofoil/spoiler configuration, assuming an inviscid model. For separated flows, piecewise linear vorticity methods give reasonable results as long as small panel elements are taken in the region of the separations at the spoiler tip and aerofoil trailing edge. The Smith and Hess method gives results which do not agree too closely with the vorticity methods. There is doubt concerning uniqueness. Results have been compared using two different wake models; in one, the total head inside the wake is taken to be uniform, in the second, the static pressures along the separation streamlines are taken to be uniform. There appears to be a difference of about 5% in CL. It is not known why.

scholarly journals Flow Past a Flat Plate With a Vortex/Sink Combination

1996 ◽  
Vol 63 (2) ◽  
pp. 543-550 ◽  
Author(s):  
N. J. Mourtos ◽  
M. Brooks
Keyword(s):  
Flat Plate ◽  
Current Model ◽  
Angle Of Attack ◽  
Separated Flow ◽  
Leading Edge ◽  
Classical Solutions ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Kutta Condition ◽  
Attached Flow

This paper presents a potential flow model for the leading edge vortex over a two-dimensional flat plate at an angle of attack. The paper is an extension of a model by Saffman and Sheffield (1977). A sink has been added in this model in an effort to satisfy the Kutta condition at both the leading edge and the trailing edge of the plate. The introduction of the sink was inspired by the fact that most steady vortices in nature appear in combination with a flow feature which can be interpreted as a sink at their cores when the flow is analyzed in a two-dimensional observation plane. As in the Saffman and Sheffield model, the presence of a vortex results in increased lift; however, in the current model a unique vortex/sink position is found at each angle of attack. A comparison has also been made between the lift and the drag of this model and the corresponding results for two classical solutions of flow over a flat plate: (a) the fully attached flow with the Kutta condition satisfied at the trailing edge only and (b) the Helmholtz solution of fully separated flow.

Part V: Steady and oscillatory aerofoil-spoiler-flap characteristics

1987 ◽  
Vol 91 (910) ◽  
pp. 479-492 ◽  
Author(s):  
H. B. Tou ◽  
G. J. Hancock
Keyword(s):  
Experimental Data ◽  
Small Amplitude ◽  
Separated Flow ◽  
Separation Point ◽  
Two Dimensional ◽  
Harmonic Motion ◽  
Simple Harmonic Motion ◽  
Attached Flow ◽  
Flow Through ◽  
Low Speeds

Summary An inviscid model for a steady two-dimensional aerofoil-spoiler at low speeds is applied to an aerofoil-spoiler-plain flap configuration. The model is extended to an aerofoil-spoiler-slotted flap configuration. The flow through a slotted flap can result in either attached flow or separated flow about the flap. The location of the separation point on the flap has to be assumed, it is taken empirically to fit experimental data. The inviscid model is extended to the aerofoil-spoiler-slotted flap configuration with the spoiler oscillating in small amplitude simple harmonic motion about a mean spoiler angle. Although both the steady and unsteady models for the aerofoil-spoiler-flap configuration are crude, the results look encouraging.

Nonlinear Interaction of Two Lifting Bodies in Arbitrary Unsteady Motion

1968 ◽  
Vol 90 (3) ◽  
pp. 387-394 ◽  
Author(s):  
J. P. Giesing
Keyword(s):  
Nonlinear Interaction ◽  
Potential Flow ◽  
Unsteady Motion ◽  
The Body ◽  
Surface Singularity ◽  
Vortex Wake ◽  
Two Dimensional ◽  
Singularity Method ◽  
Body Shapes ◽  
Two Bodies

A Method is developed for the exact calculation of the two-dimensional potential flow about two bodies, either or both of which are lifting, in nonlinear-unsteady flight. No restrictions are placed on either the body shapes or their motions. Pressures, forces, moments, and vortex-wake shapes are determined by applying a surface singularity method step by step in time. Calculated results for a variety of flow situations are presented.

Two-Dimensional Flow at Right Angles to a Flexible Membrane

1981 ◽  
Vol 32 (3) ◽  
pp. 243-269 ◽  
Author(s):  
B.G. Newman ◽  
H.T. Low
Keyword(s):  
Strouhal Number ◽  
Incompressible Flow ◽  
Separated Flow ◽  
Experimental Results ◽  
Two Dimensional ◽  
Flexible Membrane ◽  
Dimensional Flow ◽  
Two Dimensional Flow ◽  
Universal Correlation ◽  
Membrane Density

SummaryIncompressible flow perpendicular to a flexible, impervious membrane has been studied for two-dimensional conditions. The membrane was mounted on relatively thin supports spaced c apart. Measurements of drag, base pressure and the frequency of membrane oscillation are presented for various lengths ℓ, and for two densities, of membrane. These parameters are related to one another theoretically and in particular Bearman′s universal correlation for Strouhal number agrees with the experimental results. It is found that for values of< 0.50 the drag is independent of membrane density. The drag decreases at larger values ofand this is related to a periodic reattachment of the separated flow to the back of the membrane. For a given ℓ the drag is greatest whenis very small and the membrane is almost flat.

Comments on Milgram: “Calculation of Attached or Partially Separated Flow Around Airfoil Sections”

1978 ◽  
Vol 22 (01) ◽  
pp. 64-65
Author(s):  
Fabio R. Goldschmied
Keyword(s):  
Experimental Verification ◽  
A Priori ◽  
Separated Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Separated Flows ◽  
Two Dimensional ◽  
The Subject ◽  
Edge Separation ◽  
Theoretical Results

The title paper presents a relatively unified potential flow theory for attached and partially separated (trailing-edge separation) two-dimensional, incompressible airfoil sections. The partially separated flows are characterized by nonreattaching flow separation from a point on the suction side of the airfoil downstream from the leading edge; it is required that the location of this separation point and the corresponding separation pressure be specified a priori. Figures 5 and 6 of the subject paper present the test data and the theoretical results for the NACA 63–018 airfoil at 15- and 18-deg angle of attack, respectively, as the only experimental verification for partially separated flows.

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