bluuebunny/crossref_metadata_2025 huggingface dataset:
The Calculation of the Three-Dimensional Turbulent Boundary Layer: Part III. Comparison of Attachment-Line Calculations with Experiment
Authors: Cumpsty N. A. , Head M. R.
Published: July 2016

Wind tunnel measurements have been made of the attachment-line boundary layer on a swept wing. The combination of a 4-5 in (114 mm) nose radius and 60° angle of sweep enabled a wide range of values of the parameter V2/(v dU/dx) (denoted here by C*), to be covered, and gave a thick enough boundary layer for the velocity profiles to be accurately measured. Pitot traverses were performed for values of C* from 0·59 × 105 to 3·7 × 105. Without a trip wire fitted the attachment-line flow was laminar over the full range and the measured velocity profiles agreed closely with the theory for an infinite swept wing. With a large trip wire fitted, a transition régime was observed in the range 0·6 × 105 < C* < 1·4 × 105, and at higher values of C* the flow was fully turbulent and showed good agreement with the earlier calculations of Cumpsty and Head. Preston tubes were used for skin friction measurements in fully turbulent conditions and a hot wire was used to explore the development of turbulence in the transition régime.
Vibrations of Tapered Cantilever Beams and Shafts
Authors: Murty A. V. Krishna , Prabhakaran K. R.
Published: July 2016

Vibration characteristics of a linearly tapered cantilever beam and a shaft have been studied by using the lumped inertia force method; a linear displacement distribution is considered over each element. The results are compared with some of those in the literature and with experimental observations. These comparisons indicate that, even using a few elements, a reasonable degree of accuracy can be obtained in the natural frequency, although it is essential to consider more elements in order to determine mode shape accurately.
An Improved Reversed-Flow Formulation of the Galerkin-Kantorovich-Dorodnitsyn Multi-Moment Integral Method
Authors: Bethel Howard E.
Published: July 2016

An improved reversed-flow formulation of the Galerkin-Kantorovich-Dorodnitsyn multi-moment integral method is presented in this paper. Convergence and accuracy properties of the approximate solutions of the Stewartson lower branch similar flows are given. The approximate solutions obtained with the new formulation for the lower branch similar flows are, in general, more accurate than those obtained with the classical Pohlhausen method or either of the previous formulations used with the GKD method.
Effect of a Continuous Area Convergence on the Motion of a Shock Wave
Authors: Wilcox P. L.
Published: July 2016

The transient motion of a shock wave is investigated during its passage through ducts containing various area convergences. The method of characteristics has been used to follow the unsteady motion of the shock wave in an inviscid, non-conducting gas. The strength of the shock is taken to be large enough so that initially both sets of characteristics face downstream. The results are found to be in good agreement with unsteady and quasi-steady theories. A comparison is made between the characteristics results and experimental results obtained in a 1 ft (0·305 m) diameter shock tube. This shock tube incorporates a 3·75:1 linear area change in the low pressure section length. Good agreement is found between experiment and theory. A comparison is also made with other experimental work.
Reduction of Base Drag by Boat-Tailed Afterbodies in Low-Speed Flow
Authors: Mair W. A.
Published: July 2016

Drag measurements were made on a blunt-based body of revolution with the addition of several alternative boat-tailed afterbodies. The best of these afterbodies, with a length of only 60 per cent of the maximum diameter, gave almost as much reduction of drag as a conventional streamline tail. The pressure distribution on this body was measured for various lengths. It does not seem to be possible at present to predict quantitatively the drag of this type of body but some qualitative design principles have been suggested.
Simplification of the Razor Blade Technique and its Application to the Measurement of Wall-Shear Stress in Wall-Jet Flows
Authors: Pai B. R. , Whitelaw J. H.
Published: July 2016

Experiments in a in (6-35 mm) channel have yielded further information on the precision and convenience of the razor blade technique. It is shown that adhesive tape or carefully located cement can be used to secure a segment of razor blade over a static pressure hole: the resulting calibration for shear stress remains valid if the blade is removed and relocated over the same or a different, similar sized hole. Razor blade segments, calibrated in this manner, have been used to measure wall-shear stress in a turbulent boundary layer with tangential, secondary injection: the results indicate that V. C. Patel’s law of the wall is valid for such flows.
Some Extensions of Thin-Shock-Layer Theory
Authors: Squire L C
Published: July 2016

In the usual form of thin-shock-layer theory it is assumed that the flow about a lifting body can be expanded in terms of the inverse density ratio across a basic oblique shock wave lying in the plane of the leading edges of the body. In this paper it is shown that more accurate results can be obtained by moving the basic shock closer to the calculated shock wave below the body. The results obtained show why the original form of thin-shock-layer theory often gave good agreement with experiment in conditions which appeared to be outside the range of validity of the theory.
Non-Linear Vibration Analysis of a Rectangular Plate on a Viscoelastic Foundation
Authors: Kishor B , Rao J S
Published: July 2016

An analysis is presented for the non-linear vibrations of an elastic rectangular plate resting on a viscoelastic foundation. Hamilton’s principle is used for obtaining coupled non-linear partial differential equations of the system. These equations are uncoupled with the help of Berger’s approximation and the Galerkin method is used to obtain the solution of the resulting equations. Particular cases of the plates on an elastic foundation are also discussed.
Effects of Yaw on a Gothic Wing at Supersonic Speeds
Authors: Narayan K Yegna
Published: July 2016

Results are presented of an experimental study of the pressures on the flat windward surface of a Gothic wing at a free-stream Mach number of 3.5 and at moderately high angles of attack, including the effects of yaw. The results show that the perturbation in pressure due to yaw is almost independent of the streamwise distance from the vertex. As a result, it has been possible to calculate the pressure distribution on the yawed wing using the appropriate yawed conical wing results, the zero yaw results being calculated by the “equivalent” delta wing method. The calculations show reasonable agreement with the experiments and confirm that the perturbation due to yaw generates a stabilising rolling moment.
Extensional Effects in Constrained Viscoelastic Layer Damping
Authors: Nakra B C , Grootenhuis P
Published: July 2016

The vibration damping in unsymmetrical, multi-layer beams is obtained by the combined effects of extensional and shear stresses in the viscoelastic layer. The shear stress distribution is not constant across such a layer, although previous work has ignored this. The error in an estimate based on the previous work of the overall loss factor can be large, in particular for the lower resonant modes of long beams with a stiff damping layer.
Governing Equations for Thick Sandwich Shells with Honeycomb Cores and Laminated Faces
Authors: Webber J P H
Published: July 2016

The governing elasticity equations for sandwich shells of double curvature are discussed. No restriction is placed on the thickness of the honeycomb core, and the faces are taken to be made up from fibre reinforced plastic laminations. Some numerical results are given for a circular cylinder subjected to uniform internal radial loading. The results show the importance of treating the core as a thick shell, and of including the bending effects and coupling terms in the laminated faces.
Rotational Cut-Off and Anharmonicity Effects on Thermodynamic Properties of Gases at High Temperatures
Authors: Reddy N M
Published: July 2016

The exact expressions for the partition function Q and the coefficient of specific heat at constant volume Cv for a rotating-anharmonic oscillator molecule, including coupling and rotational cut-off, have been formulated and values of Q and Cv have been computed in the temperature range of 100°K to 100 000°K for O2, N2 and H2 gases. The exact Q and Cv values are also compared with the corresponding rigid-rotator harmonic-oscillator (infinite rotational and vibrational levels) and rigidrotator anharmonic-oscillator (infinite rotational levels) values. The rigid-rotator harmonic-oscillator approximation can be accepted for temperatures up to about 5000°K for O2 and N2. Beyond these temperatures the error in Cv will be significant, owing to anharmonicity and rotational cut-off effects. For H2, the rigid-rotator harmonic-oscillator approximation becomes unacceptable even for temperatures as low as 2000°K.
Similarities in Pressure Distribution in Separated Flow Behind Backward-Facing Steps
Authors: Badri Narayanan M A , Khadgi Y N , Viswanath P R
Published: July 2016

Static pressures have been measured in the separated flow region behind backward-facing steps in a wind tunnel, suitable corrections being applied for the model blockage. The results indicate a reasonably well defined similarity in the pressure distribution.
Experiment on Turbulent Boundary Layers on a Concave Wall
Authors: M C So Ronald , Mellor George L
Published: July 2016

The present experiment describes the behaviour of a turbulent boundary layer on a concave wall. At the onset of curvature there appears a fairly coherent wavelike transverse profile of mean velocity. This disturbance might be interpreted as a kind of large scale Taylor-Görtler type instability superimposed on a conventional turbulent boundary layer; further downstream the coherence degenerates as the turbulence level increases. Boundary-layer profile measurements were made at positions of maxima and minima of transverse profiles of (U-component) mean velocity. The boundary layer at the minima positions is found to be twice as thick as that at the maxima positions. Also, turbulent intensities inside the boundary layer are substantially increased as a result of the concave curvature of the surface.
Calculation of a Turbulent Boundary Layer Downstream of a Small Step Change in Surface Roughness
Authors: Antonia R A , Wood D H
Published: July 2016

Measurements of mean velocity and Reynolds shear stress have been made in a turbulent boundary layer downstream of a small step change in surface roughness. Upstream of the step the surface is smooth, while downstream it consists of a d-type rough wall made up by a series of two-dimensional elements of square cross section placed transversely across the flow and spaced one element width apart in the direction of the flow. The calculated mean velocity and Reynolds shear stress profiles obtained using the method of Bradshaw, Ferriss and Atwell are in good agreement with the measurements throughout the relaxation region of the layer. Well downstream the calculation method adequately reproduces the self-preserving features of a d-type rough wall.
Vibration and Buckling of Cross-Ply Laminated Circular Cylindrical Panels
Authors: Sinha P K , Rath A K
Published: July 2016

The paper deals with the free transverse vibration and stability analysis of circular cylindrical composite panels. The panels are assumed to be composed of an arbitrary sequence of 0° and 90° layers. The non-dimensional vibration and buckling parameters are computed for simply-supported panels consisting of antisymmetric crossply graphite-epoxy laminates. The influence of the coupling between bending and extension, shear deformation, the panel curvature, and the aspect ratio are then discussed.
Eddy Viscosity and Entrainment in Equilibrium Boundary Layers
Authors: Head M R , Galbraith R A McD
Published: July 2016

The properties of equilibrium turbulent boundary layers have been examined using Thompson’s family of velocity profiles along with alternative π – G relationships. The relationship which is in best agreement with measurements of equilibrium layers confirms an earlier suggestion that (νT/Uδ*)max is not a universal constant for such layers but decreases for small and negative values of π. A close relationship is established between eddy viscosity and entrainment, and it is shown that veδ/νT is effectively constant for π > 2.
Wake Curvature and the Kutta Condition in Laminar Flow
Authors: Brown S N , Stewartson K
Published: July 2016

The velocity defect in the wake and its curvature lead to a pressure jump across it. As a result the pressure distribution on the aerofoil and the lift are modified.
Buckling and Post-buckling Behaviour of Plates with Holes
Authors: Ritchie D , Rhodes J
Published: July 2016

This paper gives details of theoretical and experimental investigations into the behaviour of simply-supported uniformly compressed square and rectangular plates with central circular holes. The theoretical analysis employs an approximate approach using a combination of Rayleigh-Ritz and finite-element methods. The experimental investigation consisted of a number of experiments on plates with hole diameters from one- to seven-tenths of the plate width. Agreement between experiment and theory is shown to be good at buckling. In the post-buckling range it is found that the theoretical analysis is reasonably accurate for small holes, but loses accuracy when dealing with large holes.
Large Deflection of Axisymmetrically Loaded Spherical Caps
Authors: Chia Chuen-Yuan
Published: July 2016

This study is an investigation of the non-linear behaviour of an elastic spherical cap under the assumption of axisymmetric deformation. The types of axisymmetric loading under consideration are partially loaded uniform pressure, line load, “cosine” load with the maximum intensity at the apex and the combined action of uniform pressure and line load. The edge of the cap is assumed to be rigidly clamped, hinged, and unrestrainedly simply-supported. The method of solution is an extension of the iterative procedure for the integral equations formulated by Budiansky for uniformly loaded, clamped caps. In the cases of hinged and unrestrainedly simply-supported edges, the critical loads for the axisymmetric snap-buckling are presented for different types of loading and various values of the geometrical cap parameter. In the case of a clamped edge the load-deflection curves are established until no solution can be found for further increasing the load. The load corresponding to the limit point on the load-deflection curve is the critical load if the axisymmetric snap-buckling exists. The graphical results are presented for load-deflection curves, deflection profiles, bending moments, transverse shear and interaction of buckling pressures and buckling line loads. The present results are in good agreement with available data for uniform pressure distributed over the entire surface of the cap with three sets of edge conditions and over the central portion of a clamped cap.
The Pressure at the Reattachment Point in Subsonic Two-Dimensional Steady Base Flow
Authors: Tanner M
Published: July 2016

A theory is developed for the prediction of the pressure at the reattachment point in subsonic two-dimensional steady base flow. Theoretically estimated values of the reattachment pressure seem to agree well with experimental ones.
Remarks on Unsteady Newtonian Flow Theory
Authors: Mahood G E , Hui W H
Published: July 2016

Unsteady high Mach number flows past oscillating cones and oscillating wedges are studied according to Newtonian impact theory, with and without centrifugal force corrections. It is found that, contrary to existing theories, the centrifugal force contribution in unsteady flow is significant and not negligible; for example, it contributes one-half to the dynamic stability derivatives of an oscillating wedge and one-third to that of an oscillating cone. It is also shown that in both cases the dynamic stability derivatives calculated by Newtonian impact theory with centrifugal force correction agree exactly with those obtained by gas-dynamic theory in the double limit γ → 1 and M∞ → ∞, independently. These conclusions are expected to hold for more general three-dimensional unsteady Newtonian flow when the Newtonian shock layer is attached.
Supersonic Turbulent Boundary Layers: Some Comparisons Between Experiment and a Simple Theory
Authors: Stollery J L
Published: July 2016

Comparisons are made between some measurements of skin friction and heat transfer over five axisymmetric bodies and the predictions of a simple theory. The development of the theory is outlined and explicit expressions obtained for all the gross turbulent boundary-layer characteristics (δ*,θ,H,Cf and St).
Golf Ball Aerodynamics
Authors: Bearman P W , Harvey J K
Published: July 2016

A wind tunnel technique has been developed to measure the aerodynamic forces acting on golf balls over a wide range of Reynolds number and spin rate. Balls with round dimples and hexagonal dimples have been investigated. The dimples are found to induce a critical Reynolds number behaviour at a lower value of Reynolds number than that experienced by a smooth sphere and beyond this point, unlike the behaviour of a sand-roughened sphere, there is little dependence of the forces on further increases in Reynolds number. A hexagonally-dimpled ball has a higher lift coefficient and a slightly lower drag coefficient than a conventional round-dimpled ball. Trajectories are calculated using the aerodynamic data and the ranges are compared with data obtained from a driving machine on a golf course.
General Solution of the Problem of Large Deflection of an Annular Membrane under Pressure
Authors: Na T Y , Kurajian G M , Chiou J P
Published: July 2016

The non-linear boundary-value problem resulting from an analysis of the stresses and deflections of an annular membrane is transformed into an initial-value problem, replacing the iterative and series methods of Pifko and Goldberg. A general solution valid for the complete range of values of the ratio of inner and outer radii is obtained and tabulated by this non-iterative method.
Measurements in an Axisymmetric Turbulent Boundary Layer Along a Circular Cylinder
Authors: Afzal Noor , Singh K P
Published: July 2016

In an axisymmetric turbulent boundary layer along a circular cylinder at constant pressure, measurements have been made of mean velocity profile and turbulence characteristics: longitudinal velocity fluctuations, Reynolds shear stress, transverse correlation and spectrum. It has been found that the qualitative behaviour of an axisymmetric turbulent boundary layer is similar to that of a two-dimensional boundary layer in the wall region, where as in the outer region the effects of transverse curvature are observed.
Aerodynamic Throttling of a Two-Dimensional Flow by a Thick Jet
Authors: Stek J B , Brandt H
Published: July 2016

The velocity and pressure distributions in a flow generated by a thick air jet that throttles a confined airstream have been studied analytically and experimentally. Velocity and pressure measurements were made in a duct with a rectangular cross section of 102 mm height and 19 mm depth, through which air flowed at velocities ranging from 65 to 80 m/s. The airstream was throttled by a thick air jet having velocities ranging from 130 to 150 m/s that entered the mainstream at angles ranging from 60° to 135°. The jet-mainstream contour was found to be elliptical and agreement within six per cent was obtained between the theoretically and experimentally determined maximum height of the contour. Jet spreading was found to be linear. The theory permits determination of the velocity profile in the jet and gives velocities that deviate less than ten per cent from values obtained experimentally.
An Experimental Study of the Static and Dynamic Behaviour of a Tensioned Sheet with a Rectangular Opening
Authors: Datta P K
Published: July 2016

The results of an experimental study of the buckling and vibration behaviour of tensioned sheets with a rectangular opening are presented. The buckling phenomenon involves the existence of a non-uniform pre-buckle stress state in the vicinity of the opening. The local buckling load has been estimated on the basis of the modified Southwell method. The effect of parameters like cut-out size, sheet width, sheet thickness and cut-out corner radius has been investigated. The data from the vibration experiments indicate that the load versus frequency behaviour is dependent on the size of the test specimen and the opening shape. It has been observed that, for certain combinations of plate and opening parameters, the load versus frequency plot has a minimum corresponding to the local buckling of the free edge of the hole. For other plate and opening parameters it shows only a kink corresponding to the local buckling of the free edge of the cut-out. The buckling load for the opening shapes obtained from both the static and dynamic experiments are compared, showing good agreement.
Two-Dimensional Aft Bodies for Minimum Pressure Drag in Supersonic Flow
Authors: Viswanath P R , Narasimha R
Published: July 2016

The base pressure correlation proposed earlier by the authors, to take into account the effects of the boundary layer and of the boat-tail angle, is utilised in the design of two-dimensional aft bodies for minimum drag in supersonic flow. The general advantages of boat-tailing are indicated and charts of optimum profile parameters and minimum drag are provided for use in preliminary design. The effects on aft-body drag of possible reversion of the boundary layer at a sudden expansion are discussed, and the relevance of the optimum shapes found to the lifting case is indicated. The calculated optimum geometry is in good agreement with the experimental results of Fuller and Reid.
An Alternative Analytical Method for Ground-Effect Aerofoils
Authors: Kida T , Miyai Y
Published: July 2016

An alternative analytical method is applied to interference problems of an aerofoil very close to the ground, such as a free surface, a solid wall, and a slipstream. The method of matched asymptotic expansions on the small ground clearance is used in the governing integral equation and this analysis is different from Widnall and Barrows’s analysis. They used the matched asymptotic method in the differential equation. To show that the present method is reasonable, the problem of a ground-effect aerofoil in uniform fluid flow is considered and it is found possible to obtain the same results as those of Widnall and Barrows for the case of small ground clearance. By comparing with some earlier studies, it is found that the asymptotic method used with small ground clearance is valid for a clearance less than about 0.3 of the chord length. Next, the interference of ground-effect aerofoils in the channel wall, in a free jet stream, and in a slipstream are examined, and it is found that the present method can be easily applied to these problems.
The Aerodynamic Efficiency of Windmills
Authors: Lilley G M
Published: July 2016

The paper reproduces the results of an earlier report on the vortex theory of windmills and follows that theory through to establish the aerodynamic design procedure for a horizontal axis windmill. The results are shown to differ considerably from those given in a recent paper by Griffith and the differences are explained. The main conclusion is that, when full allowance is made for the drag of the blades, hub and tip losses, and losses due to interference with the support tower, the power output coefficient or efficiency of a horizontal axis windmill cannot exceed 30 to 35 per cent, as compared to an ideal efficiency of 59 per cent.
On the Calculation of the Incompressible Flow Past an Aerofoil with a Jet Flap
Authors: O’Mahoney R. , Smith F.T.
Published: July 2016

The incompressible planar flow past a wing with a jet issuing from the trailing edge is calculated by two separate methods, both adaptations of conformal mapping routines that are numerically exact in the jet-free case. These are the well-known circle mapping method and the halfplane method. The former is rendered inexact by the jump conditions across the jet and an approximation is necessary. The halfplane method, however, remains exact in principle, and a range of results is presented below. The most accurate of the previous calculations is verified, and comparisons between the halfplane and circle methods are also made. The halfplane scheme seems well suited for such wake-controlled flows and has been extended to transonic conditions in a related study.
Experiments on the Laminar Flow in a Rectangular Streamwise Corner
Authors: El-Gamal H.A. , Barclay W.H.
Published: July 2016

The results of measurements in the flow along a rectangular corner are presented in the form of velocity profiles. The profiles form two sets: one for flow in a slightly favourable streamwise pressure gradient and one for flow when the pressure gradient is ‘practically zero’. The appearance of the profiles is quite different from that of previously reported experimental work and it is suggested here that the primary cause of this is the different type of corner leading edges used in each case. The flow appears to be only marginally stable and even very slightly changed entry conditions caused by alterations in the leading edge geometry may have a marked effect on the profiles further downstream. The new results are consistent with the notion of corner layer similarity (an implication in every attempted theoretical solution) but there remains a significant difference between the experimental results and the more reliable theoretical solutions available.
Two Different Theoretical Approaches to the Base Pressure Problem in Two-Dimensional Supersonic Flow
Authors: Tanner M.
Published: July 2016

The basic physical idea underlying the theories based on the flow model of CHAPMAN and KORST is that the base pressure can be predicted if the pressure at the reattachment point is known. In the new theory of TANNER the fundamental idea is the connection between the drag of the body and the entropy increase in the flow. This paper presents the essence of both theories together with theoretical and experimental results.
The Aerodynamic Performance of a Freely Hinged Door between Two Flows
Authors: Hunt B.L. , Bizon S.A. , Taylor S.A. , Wilson D.A.
Published: July 2016

This paper reports experimental results for the performance of a freely hinged door between two incompressible air flows of different total pressures and different velocities. The apparatus used is a laboratory idealisation of the tertiary door system for an aircraft propulsion nozzle. The governing parameters are identified and the performance is presented in terms of the equilibrium door angle and the relative magnitude of the mass flow admitted. Three doors of different shapes were used and results are also presented for a plain opening. The main aerodynamic parameters are shown to be the velocity ratio and a non-dimensional pressure difference across the door. The shape of the downstream door jamb is found to have a considerable influence on the operation of the door at low angles. Removal of the door results in a lower entry mass flow over most of the operating range. It is shown that the mass flow ratio can be predicted quite well from the measured door angles by means of a simple theory.
An Improved Version of the Cebeci-Smith Eddy-Viscosity Model
Authors: Nituch M.J. , Sjolander S. , Head M.R.
Published: July 2016

Although the Cebeci-Smith method of calculating turbulent boundary layers is widely used and generally gives acceptably accurate results, highly inaccurate skin-friction values are obtained for relaxing flows and equilibrium layers in strong adverse pressure gradient. In the present paper, these anomalies are removed by suitable modifications to the basic eddy-viscosity model.
A Surface Source and Vorticity Panel Method
Authors: Petrie J.A.H.
Published: July 2016

A panel method for solving potential flow problems of arbitrary geometry is presented. It is very easy to apply and should be very quick to run. Unlike most other panel methods this one does not require a specification of the vorticity distribution in advance, but obtains it as part of the solution. The method is applied to three test cases chosen for their difficult and varied nature.
Vortex Shedding from Smooth and Roughened Cylinders in Cross-Flow near a Plane Surface
Authors: Buresti G. , Lanciotti A.
Published: July 2016

The characteristics of the flow field around a circular cylinder in cross-flow placed at various distances from a plane, parallel both to the flow and to the cylinder axis, were analysed using a hot wire anemometer. Experiments were performed in a wind tunnel with Reynolds numbers ranging from 0.85×105to 3×105. The spectra of the hot wire signals were obtained using a Fast Fourier Transform technique programmed on a PDP 11/40 computer. As regards a smooth cylinder, the main features of the vortex shedding mechanism in the subcritical regime remained unaltered for distances from the plane greater than approximately 0.4 diameters; in particular the Strouhal frequency did not show any significant variation relative to the typical value for an isolated cylinder. As for lower values of the distance from the plane, the regular vortex shedding disappeared and the hot wire spectra showed typical turbulent features. The possibility of obtaining supercritical conditions by roughening the cylinder surface was confirmed together with the importance of the Reynolds number based on the typical roughness size, Rk, in the evaluation of the flow regime around the cylinder. In the case of roughened cylinders, and with values of Rkbelow-350, the regular vortex shedding disappeared at a distance from the plane smaller than 0.3 diameters. This fact suggests that, at least in part of the supercritical regime, the influence of the plane can be smaller than in the subcritical regime.
Aerodynamic Interaction Between Two Spheres at Reynolds Numbers Around 104
Authors: Lee K.C.
Published: July 2016

The behaviour of streams of solid particles when ejected into a fluid crossflow suggests that there are considerable forces caused by aerodynamic interaction between closely spaced particles. The overall effect is a dispersion of the solids normal to the fluid flow direction and a bunching up along the axis. This effect is apparent in aerial work where particulate solids are released from aircraft and also in dilute two phase flow especially at the onset of choking or saltation. The experimental work reported here contrives to measure these forces for spheres at the appropriate Reynolds numbers. The results are considered to be sufficiently accurate and comprehensive to give some understanding of the phenomena occurring and to permit an explanation, at least qualitatively, of the behaviour mentioned.
Aerodynamics of Airfoils with Porous Trailing Edges
Authors: Ventres C. Samuel , Barakat Richard
Published: July 2016

The aerodynamics of a thin airfoil of arbitrary camber having a porous trailing edge in steady, subsonic, compressible potential flow is investigated. In the special case of a flat plate airfoil with a porous trailing edge, an exact, closed form solution is obtained using complex variable theory. The pressure loading on the airfoil, the lift and pitching moments are exhibited explicitly along with typical numerical results. The corresponding situation in supersonic flow is also considered.
Incompressible Flow Past a Wing-Body Combination Using General Curvilinear Coordinates
Authors: Murray J.C.
Published: July 2016

It is shown, by the successive application of coordinate transformations involving complex analytic functions, how a general curvilinear coordinate system can be constructed which is suitable for geometries consisting of a finite surface together with two semi-infinite cylinders. A typical example of such a geometry is considered which comprises a wing-body combination in which two semi-infinite unswept wings are attached to a finite body. The potential problem associated with non-lifting incompressible flow past the wing-body combination is formulated in the general curvilinear coordinate system and is solved numerically. The distribution of the pressure coefficient over the wing-body surface is presented.
Pressure Gradient and Leading Edge Effects on the Corner Boundary Layer
Authors: Zamir M. , Young A.D.
Published: July 2016

Results are presented of velocity and pressure measurements made in the initially laminar boundary layer in a streamwise corner formed by two flat plates at 90° to each other set at various incidences. The leading edges of the plates were sharp in contrast to earlier tests with an aerofoil type leading edge. It was found impossible to obtain a steady enough flow for useful measurements to be made at zero incidence and pressure gradient, a small incidence associated with a favourable pressure gradient was necessary. This is believed to be because of the development of separation bubbles at the sharp leading edge at very small incidences due to small variations of flow direction to be expected in a wind tunnel. The profiled nose used in earlier tests afforded flow conditions much closer to the ideal theoretical model involving zero pressure gradient, but it is argued that any nose however shaped may introduce disturbances in the form of characteristic secondary flows that may well determine the downstream response of the boundary layer. In any case the corner flow is highly unstable at all but very low Reynolds numbers, and in the absence of a region of favourable pressure gradient a Reynolds number in terms of distance downstream of the leading edge greater than about 105is unlikely to be attained in practice with the flow remaining smooth and laminar.
Linear Stability of a Radial Wall Jet
Authors: Tsuji Y , Morikawa Y
Published: July 2016

A linear stability analysis was made for a radial wall jet. A perturbation method against the two-dimensional wall jet was used for the formulation, from which a non-homogeneous Orr-Sommerfeld equation was derived. The computation showed that disturbances are more unstable in the radial wall jet than in the two-dimensional case, which agrees qualitatively with an experimental evidence.
Influence of the Wake Component on Turbulent Skin Friction at Subsonic and Supersonic Speeds
Authors: Mabey D.G.
Published: July 2016

Some velocity profile and skin friction measurements for turbulent boundary layers at subsonic and supersonic speeds are reviewed to derive the magnitude of the wake component and the effects of its variation with Reynolds number on predictions of skin friction. As Reynolds number increases the wake component increases rapidly, reaches a maximum and then decreases. The measurements considered suggest that this maximum may be higher at supersonic speeds than at subsonic speeds. This wake component variation has a significant influence on predictions of skin friction in the Reynolds number range of interest on wind tunnel models.
Calculation of Subsonic Normal Force and Centre of Pressure Position of Bodies of Revolution Using a Slender Body Theory – Boundary Layer Method
Authors: Thomson K.D.
Published: July 2016

The aim of this paper is to present a method for predicting the aerodynamic characteristics of slender bodies of revolution at small incidence, under flow conditions such that the boundary layer is turbulent. Firstly a panel method based on slender body theory is developed and used to calculate the surface velocity distribution on the body at zero incidence. Secondly this velocity distribution is used in conjunction with an existing boundary layer estimation method to calculate the growth of boundary layer displacement thickness which is added to the body to produce the effective aerodynamic profile. Finally, recourse is again made to slender body theory to calculate the normal force curve slope and centre of pressure position of the effective aerodynamic profile. Comparisons made between predictions and experiment for a number of slender bodies extending from highly boattailed configurations to ogive-cylinders, and covering a large range of boundary layer growth rates, indicate that the method is useful for missile design purposes.
Design of Aerofoils for Prescribed Pressure Distribution in Viscous Incompressible Flows
Authors: Dutt H.N.V. , Sreekanth A.K.
Published: July 2016

A design procedure has been developed to generate aerofoil shapes for prescribed pressure distributions in an incompressible viscous attached flow. It is based on the method of singularities, originally proposed by Chen and later modified by Kennedy and Marsden, for inviscid flows. The classical approach of adding the displacement thickness of the boundary layer and wake to the aerofoil contour is used to account for viscous effects. Several numerical examples are worked out and are compared with the inviscid flow results. Significant changes in aerofoil contours due to viscous effects are observed and these are discussed.
The Pressure Distribution on the Surface of an Ellipsoid in Inviscid Flow
Authors: Band Edward G.U. , Payne Peter R.
Published: July 2016

The classic equations for inviscid flow about an ellipsoid are employed to compute the corresponding static pressure distribution which can then be applied to a number of practical problems. The tension in the skin of a dirigible, the gross pressure distribution around a man in an open ejection seat, the aerodynamic lift on an air cushion vehicle, automobile or high speed boat, the “squatting” of a ship, are all examples of practical applications. A remarkable result from the theory is that the lowest pressure, that around the equator normal to the flow, is always constant around the equator, no matter how much disparity there is between the semi-axes b and c.
Re-Circulating Flows Associated with Two-Dimensional Steps
Authors: Moss W.D. , Baker S.
Published: July 2016

This paper describes measurements made in the regions of separated flow associated with three simple sharpedged two-dimensional geometries, a rear-facing step, a front-facing step and a rectangular block. The use of the pulsed-wire anemometer made possible the measurement of the three components of mean velocity and turbulence; earlier techniques, such as the hot-wire anemometer, were not well suited to the accurate determination of these quantities either in regions of continually reversing flows such as the re-circulatory zone or in regions of very high turbulence such as the shear layers bounding these zones. Supplementary measurements of surface pressure and shear stresses are also presented and comparison is made between these shear layers and the plane mixing layer. The work forms the first part of an extended programme for the investigation of bluff body flows but its principal immediate value will probably help in providing data with which to test the validity of mathematical models of turbulence as applied to re-circulating flows.
An Investigation of Turbulent Boundary Layer on a Flat Plate With a Small Step Change in Surface Roughness
Authors: Narayana P.A. Aswatha
Published: July 2016

The response of turbulent boundary layer to sudden change in surface roughness have been studied experimentally. Mean velocity measurements have been made in the boundary layer on a flat plate, downstream of a small step change in surface roughness under 3 different pressure gradients. The surface upstream of the step consisted of ‘k* type ‘large roughness’ wall (or ‘small roughness’ wall) and downstream of the step consisted of smooth surface (or ‘small roughness’ wall). Velocity profiles after the step change have been analysed on the basis of the two layer model. The inner region responds very quickly to the new boundary condition while the outer region takes more time to attain equilibrium or a state of local self-preservation. The skin-friction coefficient initially increased after the step change and gradually reached towards a constant value except for a particular roughness combination under adverse pressure gradient wherein the change in the roughness function is gradual over the transition.
Non-Equilibrium Flow of an Ideal Dissociating Gas Behind an Attached Shock Wave
Authors: Sharma V.D.
Published: July 2016

The curvature of an attached shock wave and the flow variable gradients at the tip of a straight edged wedge caused by non-equilibrium effects are determined for a steady plane flow. The specific source of non-equilibrium effects considered here is the dissociation-recombination reaction in a symmetrical diatomic gas. An oxygen like idea dissociating gas is used as an example in calculating the desired quantities. The qualitative behaviour of the exact results is compared with those obtained by using approximate methods.
Miniature Pressure Probe for Measuring the Surface-Shear-Stress Vector in Turbulent Flow
Authors: Pontikos N. , Bradshaw P.
Published: July 2016

If two small fences are arranged approximately at right angles in plan view, the magnitude and direction of surface shear stress can be deduced from measurements of the pressure difference across each fence. Fence heights as small as 0.05 mm are easily achieved. The device is simpler to use than null-seeking arrangements, and is accurate even in the presence of strong pressure gradients, which are shown to have large effects on other types of surface obstacle in three-dimensional flow.
A Numerical Study of Vortex Shedding From One and Two Circular Cylinders
Authors: Stansby P.K.
Published: July 2016

A discrete-vortex representation of the wake of a circular cylinder, in which vortices are convected in a potential-flow calculation and maintain their identities unless they approach one another or a surface closely, predicts many of the unsteady flow features and is computationally more efficient than other schemes. The mean rate of shedding of vorticity is adjusted to be compatible with experiments at a high subcritical Reynolds number of 3 × 104 and the model gives reasonable predictions of separation, drag, lift, Strouhal number and vorticity loss in the formation region. The method is extended to accommodate a second cylinder and many of the surprising features which have been observed experimentally with two cylinders in a side-by-side arrangement are reproduced.
Comparisons Between Inverse Boundary-Layer Calculations and Detailed Measurements in Laminar Separated Flows
Authors: Horton H.P.
Published: July 2016

A brief description is given of an accurate numerical method for the inverse calculation of both attached and separated laminar, two-dimensional, incompressible boundary-layers with prescribed displacement thickness. The method employs downstream-marching, using an approximation to the convection terms in the reverse-flow region to stabilise the computation. Results of three calculations made by this method, using measured distributions of displacement thickness as input, are presented and compared with the corresponding measured velocity profiles and distributions of external velocity. Very close agreement between theory and experiment is found in general, giving further evidence of the validity of the boundary-layer approximation in separated flows of limited extent.
On the Non-Linear Vibrations of a Projectile
Authors: Rath P.C. , Sharma S.M.
Published: July 2016

The Nonlinear Magnus effect on the nutational oscillations of a missile has been studied. In particular the existence of self-sustained vibrations has been proved. A numerical method is suggested to obtain the limit cycles wherever they exist.
An Integral Method for the Oscillating Turbulent Boundary Layer
Authors: Patel M.H.
Published: July 2016

The linearised time dependent momentum integral equation is used in conjunction with assumed velocity profiles and a quasi-static skin friction approximation to predict the turbulent boundary layer response to sinusoidal streamwise velocity fluctuations in the freestream. The mean zero pressure gradient case, corresponding to flat plate flow, is presented in detail and verified by comparison with experimental data and alternative calculations. The asymptotic turbulent boundary layer response to very high frequency perturbations is also derived. It is shown that a travelling wave component in the freestream, with its associated time dependent streamwise pressure gradient, has a dominant effect on the turbulent boundary layer response.
Skin Friction and Heat Transfer at an Infinite Swept Attachment Line
Authors: Poll D.I.A.
Published: July 2016

Simple, yet reasonably accurate, expressions have been developed for the prediction of skin friction and heat transfer coefficient at an infinite swept attachment line using the concepts of ‘reference temperature’ and ‘Reynolds analogy’. The formulae have then been used to investigate the effect of varying sweep angle with constant undisturbed free stream conditions in the limits of very low and very high Mach number.
The Stiffness of a Two-Cell Anisotropic Tube
Authors: Mansfield E.H.
Published: July 2016

An analysis is made of the general two-cell thin-walled cylindrical tube subjected to longitudinal tension, bending and torsion. The walls of the tube may be of fibre composite with an asymmetric lay-up resulting in a coupling between direct and shear stresses and strains. The two-cell tube differs from the single-cell tube in that the tension axis and the principal axes of bending are not necessarily aligned to the c.g. and the principal moments of inertia of the longitudinal stress bearing material.
An Investigation of the Swirl in an S-Duct
Authors: Guo R.W. , Seddon J.
Published: July 2016

Measurements are presented of the static pressure, total pressure, swirl and three-dimensional turbulence in the flow through an S-curved rectangular duct mounted in a wind tunnel at different incidences, yaw angles and mass flow ratios. The results show that at high incidence there is a large vortex around an area of flow separation after the first bend and a pair of contra-rotating vortices in the flow after the second bend. The distortion of total pressure at the exit of the S-duct is significantly high, and the corresponding three-dimensional turbulence is up to 16.7%. Appreciation of the existence of this type of flow is important in the field of air intake design for jet aircraft.
The Importance of Secondary Shedding in Two-Dimensional Wake Formation at Very High Reynolds Numbers
Authors: Stansby P.K. , Dixon A.G.
Published: July 2016

Uncertainties in the use of the discrete-vortex method in modelling the time development of the wake of a circular cylinder at very high Reynolds numbers are investigated. It is shown that simply introducing vorticity at generally accepted separation positions at a rate of ½Us2, Us being the velocity at separation, gives wholly unrealistic wake predictions. In the base region pressure fields occur which would promote separation in steady flow and so a first approximation for ‘secondary’ separation is incorporated into the model. This brings pressure distributions and vorticity structures at subcritical and supercritical Reynolds numbers into good agreement with experiment. The convection of the vortices is calculated using the cloud-in-cell technique and comparisons are made with direct summation methods.
Thermal Stresses in Polygonal Plates Due to Localised Heating
Authors: Wah Thein
Published: July 2016

A general procedure for the analysis of thermal stresses in a polygonal elastic plate due to heating over a small circular or rectangular area is presented. The method employs eigenfunctions of angular regions together with a least squares procedure to establish continuity. Numerical results are given.
The Effect of Nose Blunting on the Wave Drag of Ogive Forebodies
Authors: Partington R. , Baker T.J.
Published: July 2016

A theoretical method is used to predict the surface pressure distribution and drag-rise characteristics of blunted ogive forebodies. The results confirm the observation that a moderate degree of nose blunting can reduce wave drag relative to that of a pointed body of the same fineness ratio. An analysis of the theoretical data provides a simple explanation of this phenomenon.