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Getting Down to Laminar Flow

Getting Down to Laminar Flow Aircraft Engineering THE MONTHLY SCIENTIFIC AND TECHNICAL ORGAN OF THE AERONAUTICAL ENGINEERING PROFESSION VOL XX No 231 MAY 1948 The Practical Aspect S some of our readers will be aware, PROFESSOR GOLDSTEIN'S Although PROFESSOR GOLDSTEIN only incidentally mentions com­ Wright-Brothers lecture appears in the April issue of the mercial aeroplanes it is important to remember that he is dealing AJournal of the Aeronautical Sciences, which has reached this throughout with wings suitable for subsonic flight and is not con­ country just at the time when we are going to press, and it was, in cerned with compressibility and the problems of supersonic flow. fact, in accordance with the usual practice that, at the request of the Indeed, the difficulties with which he deals are mainly those affecting Institute, we postponed the start of our own publication of it until wings of thick section rather than the thin wings fitted to aeroplanes this priority had been ensured. A comparatively small proportion of of the fighter class. Consequently, the information he makes public our readers, however, even in the United States of America, is of considerable practical interest to designers of transport aero­ receive the Journal; whereas it is, in our opinion, very necessary that planes and heavy bombers. It is, perhaps, as well to emphasize this this lecture should reach as wide a circle of aerodynamicists and in view of the fact that high speed flight is at the present time so much designers as possible. It is the first authoritative statement on a sub­ more in the limelight owing to its greater dramatic appeal. A point ject on which practically nothing has been published and as to which that is of great import is that the postponement of the stall of these widespread ignorance prevails outside the privileged few who have low-drag wings is entirely dependent on the suction effect and that themselves been connected with the work—as is evidenced by the the change from unstalled to stalled flight is therefore largely out of number of references to unpublished A.R.C. Reports given in the control of the pilot. This dependence on power-operated suction PROFESSOR GOLDSTEIN'S bibliography. It carries the cachet of having devices incorporated to maintain laminar flow consequently in­ been prepared and delivered by the chairman of the British Aero­ volves a new peril in that sudden failure of engines at a critical nautical Research Council and is therefore on that account, as well moment, such as during the operation of landing, may have dis­ as by reason of its own intrinsic merit, a quite outstanding contribu­ astrous results. It is important that the undoubtedly attractive tion to knowledge. We are sure for all these reasons that the possibilities of this ingenious method of controlling the flow of air bulk of our readers will agree with our decision to make it available over a wing should not obscure this very real drawback from the to them in AIRCRAFT ENGINEERING. It is, in fact, in accordance with pilot's point of view. our regular practice to make these lectures delivered in America by British authors available to our readers—we, for instance, published DR ROXBEE Cox's contribution on 'British Aircraft Gas-Turbine The Financial Side Practice' two years ago. One aspect of these developments that is disquieting is their very obvious effect on the cost of aeroplanes that are to embody them. On the Surface It is abundantly clear that a great deal of work, both of a research and experimental nature, has to be done. PROFESSOR GOLDSTEIN It would be easy to be humorous about the flies to which some himself mentions the need for 'controlled experiment' and full-scale space is devoted, but in fact of course they offered a very serious ob­ trials and, at the other end of the picture, refers to the fact that we stacle to the pursuit of knowledge and may well continue to present a in England do not possess a suitable low-turbulence wind-tunnel— difficult problem for the users of these new types of wing. A way of operating at, say, a Reynolds number of 30 ×106—from which could circumventing the trouble will certainly have to be found and a possi­ be obtained the necessary data to provide some of the information bility which occurs to us is to adopt a system already in use for de- needed. All three of these desiderata imply the need for considerable icing and fit a porous strip through which a suitable fluid would be expenditure and the question arises where the money is to come sprayed to which the corpses would stick, to be subsequently washed from and by whom it is to be provided. The Government already, off by water. This obviously has the disadvantage of involving the quite rightly, bears the burden of the long-scale fundamental research addition of quite considerable weight to the aeroplane—though as the work but the later experiment and full-scale trials should appropri­ trouble disappears at 5,000 feet this may not be too serious—but we ately be carried out by the firms. This means, of necessity, that the can think of no more satisfactory method. It may be, on the other money they spend will have to be recovered; which in its turn in­ hand, that with the very highly polished surfaces envisaged the flies volves Government orders for prototype aeroplanes for commercial may just slide off without disintegrating into the small parts which are use—a principle that has already been adopted in this country in the most potent cause of disturbance. Incidentally, it is a considerable regard to aeroplanes such as the Brabazon and Saunders Roe boat practical relief to learn that once a wing has been specially treated to purely in view of their size—or the burden being spread over sub­ obtain the requisite smoothness of surface this condition persists sequent production machines. In either case, it appears unhappily and does not deteriorate even after quite a considerable period of that the day of the cheap aeroplane is indefinitely postponed. exposure to the elements—even up to two years. Actually, this accords with the experience of careful motorists who already know We are afraid that it is in fact inevitable that as they continue to that a car that has a good wax polish applied to it periodically has grow in complexity and scientific efficiency aeroplanes will tend to the capacity of throwing off rain and does not get dirty in the way become more and more costly; in view, particularly, of the heavy that a less well cared-for vehicle will suffer. overhead expenses of design. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

Getting Down to Laminar Flow

Aircraft Engineering and Aerospace Technology , Volume 20 (5): 1 – May 1, 1948

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb031631
Publisher site
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Abstract

Aircraft Engineering THE MONTHLY SCIENTIFIC AND TECHNICAL ORGAN OF THE AERONAUTICAL ENGINEERING PROFESSION VOL XX No 231 MAY 1948 The Practical Aspect S some of our readers will be aware, PROFESSOR GOLDSTEIN'S Although PROFESSOR GOLDSTEIN only incidentally mentions com­ Wright-Brothers lecture appears in the April issue of the mercial aeroplanes it is important to remember that he is dealing AJournal of the Aeronautical Sciences, which has reached this throughout with wings suitable for subsonic flight and is not con­ country just at the time when we are going to press, and it was, in cerned with compressibility and the problems of supersonic flow. fact, in accordance with the usual practice that, at the request of the Indeed, the difficulties with which he deals are mainly those affecting Institute, we postponed the start of our own publication of it until wings of thick section rather than the thin wings fitted to aeroplanes this priority had been ensured. A comparatively small proportion of of the fighter class. Consequently, the information he makes public our readers, however, even in the United States of America, is of considerable practical interest to designers of transport aero­ receive the Journal; whereas it is, in our opinion, very necessary that planes and heavy bombers. It is, perhaps, as well to emphasize this this lecture should reach as wide a circle of aerodynamicists and in view of the fact that high speed flight is at the present time so much designers as possible. It is the first authoritative statement on a sub­ more in the limelight owing to its greater dramatic appeal. A point ject on which practically nothing has been published and as to which that is of great import is that the postponement of the stall of these widespread ignorance prevails outside the privileged few who have low-drag wings is entirely dependent on the suction effect and that themselves been connected with the work—as is evidenced by the the change from unstalled to stalled flight is therefore largely out of number of references to unpublished A.R.C. Reports given in the control of the pilot. This dependence on power-operated suction PROFESSOR GOLDSTEIN'S bibliography. It carries the cachet of having devices incorporated to maintain laminar flow consequently in­ been prepared and delivered by the chairman of the British Aero­ volves a new peril in that sudden failure of engines at a critical nautical Research Council and is therefore on that account, as well moment, such as during the operation of landing, may have dis­ as by reason of its own intrinsic merit, a quite outstanding contribu­ astrous results. It is important that the undoubtedly attractive tion to knowledge. We are sure for all these reasons that the possibilities of this ingenious method of controlling the flow of air bulk of our readers will agree with our decision to make it available over a wing should not obscure this very real drawback from the to them in AIRCRAFT ENGINEERING. It is, in fact, in accordance with pilot's point of view. our regular practice to make these lectures delivered in America by British authors available to our readers—we, for instance, published DR ROXBEE Cox's contribution on 'British Aircraft Gas-Turbine The Financial Side Practice' two years ago. One aspect of these developments that is disquieting is their very obvious effect on the cost of aeroplanes that are to embody them. On the Surface It is abundantly clear that a great deal of work, both of a research and experimental nature, has to be done. PROFESSOR GOLDSTEIN It would be easy to be humorous about the flies to which some himself mentions the need for 'controlled experiment' and full-scale space is devoted, but in fact of course they offered a very serious ob­ trials and, at the other end of the picture, refers to the fact that we stacle to the pursuit of knowledge and may well continue to present a in England do not possess a suitable low-turbulence wind-tunnel— difficult problem for the users of these new types of wing. A way of operating at, say, a Reynolds number of 30 ×106—from which could circumventing the trouble will certainly have to be found and a possi­ be obtained the necessary data to provide some of the information bility which occurs to us is to adopt a system already in use for de- needed. All three of these desiderata imply the need for considerable icing and fit a porous strip through which a suitable fluid would be expenditure and the question arises where the money is to come sprayed to which the corpses would stick, to be subsequently washed from and by whom it is to be provided. The Government already, off by water. This obviously has the disadvantage of involving the quite rightly, bears the burden of the long-scale fundamental research addition of quite considerable weight to the aeroplane—though as the work but the later experiment and full-scale trials should appropri­ trouble disappears at 5,000 feet this may not be too serious—but we ately be carried out by the firms. This means, of necessity, that the can think of no more satisfactory method. It may be, on the other money they spend will have to be recovered; which in its turn in­ hand, that with the very highly polished surfaces envisaged the flies volves Government orders for prototype aeroplanes for commercial may just slide off without disintegrating into the small parts which are use—a principle that has already been adopted in this country in the most potent cause of disturbance. Incidentally, it is a considerable regard to aeroplanes such as the Brabazon and Saunders Roe boat practical relief to learn that once a wing has been specially treated to purely in view of their size—or the burden being spread over sub­ obtain the requisite smoothness of surface this condition persists sequent production machines. In either case, it appears unhappily and does not deteriorate even after quite a considerable period of that the day of the cheap aeroplane is indefinitely postponed. exposure to the elements—even up to two years. Actually, this accords with the experience of careful motorists who already know We are afraid that it is in fact inevitable that as they continue to that a car that has a good wax polish applied to it periodically has grow in complexity and scientific efficiency aeroplanes will tend to the capacity of throwing off rain and does not get dirty in the way become more and more costly; in view, particularly, of the heavy that a less well cared-for vehicle will suffer. overhead expenses of design.

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: May 1, 1948

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