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352 AIRCRAFT ENGINEERIN G December, 1943 Translations Issued by the N.A.C.A. Technical Memorandum No. 1036. Aero übertragung in glatten und rauhen Rohren." Technical Memorandum No. 1,040. Piezo dynamics of the Fuselage. By H. Multhopp. Forschung auf dem Gebiete des Ingenieurwesens electric Instruments of High Natural Frequency ("Zur Aerodynamik des Flugzeugrumpfes." Bd. 11, No . 4, July-August, 1940, pp . 149-158.) Vibration Characteristics and Protection against Luftfahrtforschung, Vol. 18, Nos. 2-3, March Interference by Mass Forces. By Werner Th e heat transfer accompanying turbulent flow in tubes is treate d by a new theory of wall turbul 29, 1941, pp . 52-56.) Gohlke. ("Quarzdruckmessgeräte hoher Eigen- ence, and a formula for smooth tubes has been de frequenz Schwingungseigenschaften und Ab- Th e present report deals with a number of prob rived (equation 39) which is asymptotic at lems, particularly with the interaction of the fuse hilfe gegen die Stoning durch Massenkråfte." Re→ ∞ . It agrees ver y well with th e dat a available lage with the wing and tail, on the basis of simple VDI, Forschungsheft 407, XII Bd., March- t o date. The formula also holds for th e flow along calculatin g methods derived from greatly idealized a flat plate if A is based on the velocity far away. April, 1941, pp . 1-25.) concepts . Fo r rough tubes, the unit conductance is shown to Th e exploration of the processes accompanying Fo r the fuselage alone it affords, in variance with b e a function of kv v; the two empirical constants * engine combustion demands quick-responding pres potentia l theory, a certain frictional lift in yawed (Δ , n) which appear in equation (52) canno t yet be r sure-recording instruments, among which th e piezo flow, which, similar to the lift of a wing of small determine d because of lack of experiemental data. electric type has found widespread use because of aspec t ratio, is no longer linearly related to the it s specially propitious properties as a vibration- angle of attack. Nevertheless there exists for this recording instrumen t for high frequencies. Lacking frictional lift something like a neutra l stability point Technical Memorandum No. 1038. The appropriat e test methods, the potential errors of th e position of which on oblong fuselages appears to Performance of a Vaneless Diffuser Fan. By piezoelectric recorders in dynamic measurements b e associated with the lift increase of th e fuselage in V. Polikovsky and M. Nevelson. (Report No. could only be estimated up to now. proximity to th e zero lift, according t o the present 224, of the Central Aero-Hydrodynamical I n the present report a test method is described experiments. by means of which th e resonance curves of th e piezo The pitching moments of the fuselage can be Institute, Moscow, 1935.) electric picku p can be determined ; hence an instru determined with comparatively great reliability so Th e present paper is devoted to the theoretical menta l appraisal of the vibration characteristics of far as the flow conditions in the neighbourhood of an d experimental investigation of one of th e station piezo-electric recorders is obtainable. the axis of the fuselage can be approximated if the ar y elements of a fan, namely, th e vaneless diffuser. fuselage were absent, which, in general, is not very Technical Memorandum No. 1,041. Tail Th e method of computation is based on th e prin- difficult. ciples developed by Pfleiderer (Forschungsarbeiten Buffeting. By G. Abdrashitov. (Report No. For the unstable contribution of the fuselage to No. 295). The practical interest of this investiga 395 of the Central Aero-Hydrodynamical the static longitudinal stability of the aeroplane it tio n arises from the fact tha t th e design of th e fan affords comparatively simple formulae, the evalua Institute, Moscow, 1939.) guide elements—vaneless diffusers, guide vanes, tion of which offers little difficulty. On the engine An approximate theory of buffeting is here pre spira l casing—is far behind the design of the im nacelles ther e is, i n addition , a ver y substantial wing sented , based on the assumption of harmonic dis peller as regards accuracy and reliability. The moment contribution induced by the non-uniform turbin g forces. Two cases of buffeting are con computation s conducted by the method here pre distribution of the transverse displacement flow of sidered : namely, for a tail angle of attac k greater sented have shown sufficiently good agreement with the nacelle along th e wing chord ; this also can be an d less than the stalling angle, respectively. On th e experimental dat a and indicate th e limits within represented by a simple formula. A check on a th e basis of the tests conducted and the results of which th e values of the coefficient of friction lie. large number of dissimilar aircraft types regarding foreign investigators, a general analysis is given of the unstable fuselage and nacelle moment s disclosed th e nature of the forced vibrations, the possible an agreement with the wind-tunnel tests, which Technical Memorandum No. 1039. Pres load limits on th e tail, and the methods of elimina should be sufficient for practical requirements. The tion of buffeting. sure Distribution in Nonuniform Two- errors remained throughout within the scope of Dimensional Flow. By M. Schwabe. ("Über Technical Memorandum No, 1,042. The instrumental accuracy. Druckermittlung in der nichtstationären oretical Determination of Axial Fan Perform For th e determination of th e fuselage effect on th e ebenen Strömung." Ingenieur-Archiv, Vol. 6, lift distribution of the wing the flow transverse to ance. By E. Struve. (Report No. 295, of the the fuselage was assumed to be two-dimensional; No. 1, February 1935, pp. 34-50.) Central Aero-Hydrodynamical Institute, Mos then all th e mathematica l difficulties, which th e fuse Th e two-dimensional flow pas t a circular cylinder cow, 1937.) lage of itself would entail, can be removed by a con- is mad e visible on th e surface of wate r by scattered Th e repor t present s a metho d for the computation formal transformation of the fuselage cross section particle s and recorded under long exposure by a of axial fan characteristics. The method is based to a vertical slit. Then the calculation of the lift movin g picture camera. The velocity of flow is de on the assumption that the law of constancy of the distribution for a wing-fuselage combination reduces duced from the path lengths of the particles, the circulation along th e blade holds, approximately, for to tha t of an equivalent wing, wherein the fuselage radiu s of curvature of the paths is defined, the all fan conditions for which the blade elements effect is represented by a change in chord distribu pressure along a streamline is determined according operat e a t normal angles of attac k (up t o th e stalling tion and also, t o some extent , in th e angle-of-attack t o Bernoulli's general formula (p=p0 — ½ρw2 — angles). Pressure head coefficient K and power distribution. Then the conventional methods of ρ∂Φ/∂t), and transverse to the stream-lines accord coefficient K for the force components in the axial computing the lift distribution of a wing are fully u ing to the centrifugal force formula (p—p + an d tangential directions, respectively, and analo applicable. In particular, it again affords two basic 0 pfv2/rds'). The pressure distribution formulae for gous t o the lift and drag coefficients C and C are distributions from which the lift distributions for y x different stages of development of the vortex pair conveniently introduced. the different ca values of th e wing can be found by an d for one stat e of th e vorte x stree t is indicated , th e Th e report can be divided into five parts : linear combination, as is customary on a wing with pressure field determined, th e pressure drop behind 1. Exposition of the blade element theory based out fuselage effect. The portion of lift taken over th e cylinder analyzed and th e variation of th e pres on th e general laws of mechanics and on th e funda by th e fuselage itself is easily estimate d from th e lift sur e drag coefficient with respect t o time demon menta l coefficients of experimental aerodynamics, distribution so determined. The air load distribu strated . It reaches a value about twice as high as respectively. tions determined for the wing-fuselage combination i n th e th e steady state . The asymmetrica l pressure 2. Discussion of th e physical basis of th e phenom by this method differ considerably from those ob distributio n on the cylinder is demonstrate d for one en a in fan operation and generalization to different tained by the orthodox method when th e measured stag e of development of th e vortex street and the operatin g conditions. ca differences were directly distributed as positive force transverse to the flow direction defined; it 3 . Explanation of the new modification of axial or negative fuselage lift across th e fuselage width. amount s to more than 40 per cent of the drag in fan computation, whereby use is made of the pres I n the case of sideslip, th e displacement flow of thi s instance. sure and power coefficients. the fuselage causes an additional anti-symmetrical I n th e theoretical treatmen t th e customar y poten 4. Method of determination of axial fan perform lift distribution along the wing (for a high- or low- tia l flow is superposed by a source-sink flow, the ance. wing arrangement) with an attendant rolling potentia l of which is secured by series development, 5. Comparison of theoretical with experimental moment of considerable magnitude. The simple from which the velocity components are deduced. results and discussion of several conclusions drawn formula evolved for thi s rolling momen t on elliptical I n the pressure formula p0 = ½iρw2+p+ρ ∂ Φ/ ∂ t th e therefrom. fuselage sections is very satisfactorily confirmed by tim e variable f(t)/a and its derivation are solved Comparison with experiment shows that the the few available measurements. from the recorded motion of the free stagnation metho d presented permits construction of that As regards the effect of the fuselage on the flow point . portio n of th e axial fan characteristic lying within conditions at the tail surfaces the sideslip of the A comparison of theory and experiment indicates th e range of maximum efficiency with an accuracy fuselage for a high- or low-wing arrangement pro good agreement in the streamline pattern. The sufficient for practical purposes. There is brought duces a sidewash at the vertical fin and rudder and approximatio n of th e theoretica l t o th e experimental ou t the need for further detailed study of a n air foil leads to appreciable changes in directional stability pressure distribution on the zero streamline for an situate d in a flow having a rotational component and damping in yaw. earl y stat e of development of th e vorte x pair is also an d of the mutual interference of the blades of a A few measurements demonstrating this pheno satisfactory. Subsequent calculation indicates pro cascade in order to obtain further accuracy in the menon ver y distinctl y ar e intende d t o rive t attention nounced departures from the test data. The metho d described. In this connexion a method is t o the results of this phenomenon in th e mechanics theoretica l pressure field is compared with the ex outlined for obtaining the aerodynamic characteris of unsymmetrical flight motions. perimental , the theoretical pressure curve on the tics of th e airfoil from the fan characteristic?. An line of symmetry behind the free stagnation point approximat e method for plotting th e fan character- Technical Memorandum No. 1037. Theory an d the pressure drop in i t dependent on the time istics, that does not involve much computation of Heat Transfer in Smooth and Rough Pipes. is obtained in satisfactory approximation with the work and may be used for tentative computation, tes t data. By G. D. Mattioli. ("Theorie der Wärme- is also presented.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Dec 1, 1943
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