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The results of balance aerodynamic tests on model straight wings with smooth and ribbed surfaces at an angle of attack =–4°–12°, Mach number M=0.15–0.63, and Reynolds number Re=2.4·106–3.5·106 are discussed. The nondimensional riblet spacings
+, which determines the effect of the riblets on the turbulent friction drag, and the effect of riblets on the upper and/or lower surface of a straight wing on its drag, lift, and moment characteristics are estimated.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 33–38, March–April, 1995. 相似文献
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In the current dynamic model of rotating truncated conical shells, the expressions of centrifugal and coriolis accelerations and initial hoop tension were incomplete and some terms were missing. This might cause the frequency characteristics of rotating conical shells to be overestimated (or underestimated). Therefore, the effects of rotation upon frequency characteristics of rotating truncated conical shell are studied in the paper. Accurate expressions of centrifugal and coriolis accelerations and initial hoop tension are derived, and then a modified dynamic model for the rotating truncated conical shell is presented. The generalized differential quadrature method is utilized to obtain the natural frequencies. The influences of various boundary conditions and rotating speed on the free vibration of the conical shell are discussed in detail. Through comparison analysis, the errors in current model are also pointed out. 相似文献
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以S809翼型为研究对象,用CFD数值模拟计算的方法研究了在失速条件下,风力机翼型上下表面同时开缝的被动控制策略对翼型空气动力学特性的影响。采用基于速度耦合的SIMPLEC算法进行数值模拟,将四种常用的湍流模型(Spalart-Allmaras、k-e、k-w、k-w-SST)在12°和24°攻角下的计算结果和实验数据对比,得出了最优于翼型计算的湍流模型为k-w-SST。分析了缝隙位置、宽度和斜率对翼型气动性能的影响。结果表明:当开缝位置位于分离点附近时,翼型气动性能最优;当缝隙宽度为弦长的2%时,翼型气动性能最优;当缝隙和弦线的夹角为75°时,翼型气动性能最优,且在攻角超过24°时开缝对翼型的气动性能有不利影响。 相似文献
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D. Levin 《Experiments in fluids》1989,7(8):566-568
Conclusion The use of a smooth surface, for small projectiles, may lead to a reduction of drag at zero angle of attack. However, for specific configurations, especially those with blunt aft sections, an adverse normal force characteristic may develop, causing stability problems, similar to the one described by Schneider (1978). On the other hand, a skilful use of the separation-zone motion could serve as a maneuvering tool for unguided projectiles that are required to perform a search motion, and a built-in instability could maintain the desired motion. 相似文献
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S. M. Aulchenko V. P. Zamuraev A. P. Kalinina 《Journal of Applied Mechanics and Technical Physics》2008,49(6):957-961
The possibility of controlling the aerodynamic characteristics of airfoils in transonic flight regimes by means of one-sided
pulsed-periodic energy supply is studied. Based on the numerical solution of two-dimensional unsteady gas-dynamic equations,
the change in the flow structure in the vicinity of a symmetric airfoil at different angles of attack and the aerodynamic
characteristics of the airfoil as functions of the amount of energy supplied asymmetrically (with respect to the airfoil)
are determined. The results obtained are compared with the data calculated for the flow past the airfoil at different angles
of attack without energy supply. It is found that a given lift force can be obtained with the use of energy supply at a much
better lift-to-drag ratio of the airfoil, as compared to the case of the flow past the airfoil at an angle of attack. The
moment characteristics of the airfoil are found.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 82–87, November–December, 2008. 相似文献
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V. M. Fomin V. I. Zapryagaev A. V. Lokotko V. F. Volkov 《Journal of Applied Mechanics and Technical Physics》2012,53(3):333-339
Results of experimental and numerical investigations of the effect of gas injection through a permeable porous surface on the drag coefficient of a cone-cylinder body of revolution in a supersonic flow with the Mach number range M h = 3–6 are presented. It is demonstrated that gas injection through a porous nose cone with gas flow rates being 6–8% of the free-stream flow rate in the mid-section leads to a decrease in the drag coefficient approximately by 5–7%. The contributions of the decrease in the drag force acting on the model forebody and of the increase in the base pressure to the total drag reduction are approximately identical. Gas injection through a porous base surface with the flow rate approximately equal to 1% leads to a threefold increase in the base pressure and to a decrease in the drag coefficient. Gas injection through a porous base surface with the flow rate approximately equal to 5% gives rise to a supersonic flow zone in the base region. 相似文献
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S. M. Aulchenko V. P. Zamuraev A. P. Kalinina 《Journal of Applied Mechanics and Technical Physics》2007,48(6):834-839
The possibility of controlling the aerodynamic characteristics of airfoils in transonic flight regimes by means of local pulsed
periodic energy supply is considered. The numerical solution of two-dimensional unsteady equations of gas dynamics allowed
determining the changes in the flow structure near a symmetric airfoil and its aerodynamic characteristics depending on the
magnitude of energy in the case of its asymmetric (with respect to the airfoil) supply. The results obtained are compared
with the calculated data for the flow around the airfoil at different angles of attack without energy supply. With the use
of energy supply, a prescribed lift force can be obtained with a substantially lower wave drag of the airfoil, as compared
with the flow around the airfoil at an angle of attack.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 70–76, November–December, 2007. 相似文献
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Using the Navier-Stokes equations in conjunction with the k-? model of turbulence, the characteristics of flow in the region downstream of a conical diffuser with 5° angle of inclination are calculated. Two representative stations 1D2 and 10D2 after the diffuser exit are selected for comparison against experimental results. The calculations indicate an underestimation of mean velocity and turbulence kinetic energy at the first station, while satisfactory agreement is obtained for the mean velocity at the second station. The use of a modified k-? model sensitive to adverse pressure conditions improves the predictions considerably. The effect of inlet properties and Reynolds number on the flow characteristics at the above stations is studied using various inlet profiles and a range of Reynolds numbers based on the inlet diameter from 50 000 to 280 000. 相似文献
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A. P. Alkhimov V. F. Kosarev S. V. Klinkov A. A. Sova 《Journal of Applied Mechanics and Technical Physics》2012,53(6):948-953
Results of an experimental and numerical study of the effect of conical separation regions artificially generated ahead of the target owing to impingement of a supersonic two-phase jet on the character of motion of particles smaller than 1 µm in diameter and on the process of cold gas-dynamic spraying as a whole are presented. Calculations predict a noticeable effect of the conical separation region artificially generated ahead of the target on the character of particle motion; in particular, the maximum velocity of the particle impact onto the target is found to be greater than that during spraying without the spike. Thus, the possibility of formation of a coating from particles smaller than 1 µm in diameter is demonstrated, and recommendations for implementation of the process in practice are given. 相似文献
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