Drag-divergence Mach number (original) (raw)
阻力发散马赫数（英語：drag divergence Mach number）是指当飞行器的马赫数达到该马赫数后阻力开始急剧增大，此时阻力系数可达低速时的十倍以上。 通常阻力发散马赫数大于0.6，属跨音速效应。同时，阻力发散马赫数一定大于临界马赫数。 一般而言，阻力系数会在马赫数为1左右达到最大值，进入超音速后在马赫数约为1.2时开始下降。 對於一族的螺旋槳翼型，阻力發散馬赫數 Mdd 可以用Korn's relation 求得: 其中 是阻力發散馬赫數, 是翼型中特定某一段的升力係數,t 是給定翼型段的厚度,c 是給定翼型段的翼弦長, 是藉由計算流體力學分析 (CFD analysis) 給予的一個係數:K = 0.87 可以用在傳統翼型 (NACA 6系列),K = 0.95 則可以用在超臨界翼型
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| dbo:abstract | The drag-divergence Mach number (not to be confused with critical Mach number) is the Mach number at which the aerodynamic drag on an airfoil or airframe begins to increase rapidly as the Mach number continues to increase. This increase can cause the drag coefficient to rise to more than ten times its low-speed value. The value of the drag-divergence Mach number is typically greater than 0.6; therefore it is a transonic effect. The drag-divergence Mach number is usually close to, and always greater than, the critical Mach number. Generally, the drag coefficient peaks at Mach 1.0 and begins to decrease again after the transition into the supersonic regime above approximately Mach 1.2. The large increase in drag is caused by the formation of a shock wave on the upper surface of the airfoil, which can induce flow separation and adverse pressure gradients on the aft portion of the wing. This effect requires that aircraft intended to fly at supersonic speeds have a large amount of thrust. In early development of transonic and supersonic aircraft, a steep dive was often used to provide extra acceleration through the high-drag region around Mach 1.0. This steep increase in drag gave rise to the popular false notion of an unbreakable sound barrier, because it seemed that no aircraft technology in the foreseeable future would have enough propulsive force or control authority to overcome it. Indeed, one of the popular analytical methods for calculating drag at high speeds, the Prandtl–Glauert rule, predicts an infinite amount of drag at Mach 1.0. Two of the important technological advancements that arose out of attempts to conquer the sound barrier were the Whitcomb area rule and the supercritical airfoil. A supercritical airfoil is shaped specifically to make the drag-divergence Mach number as high as possible, allowing aircraft to fly with relatively lower drag at high subsonic and low transonic speeds. These, along with other advancements including computational fluid dynamics, have been able to reduce the factor of increase in drag to two or three for modern aircraft designs. Drag-divergence Mach numbers Mdd for a given family of propeller airfoils can be approximated by Korn's relation: where is the drag-divergence Mach number, is the coefficient of lift of a specific section of the airfoil,t is the airfoil thickness at a given section,c is the chord length at a given section, is a factor established through CFD analysis:K = 0.87 for conventional airfoils (6 series),K = 0.95 for supercritical airfoils. (en) 阻力发散马赫数（英語：drag divergence Mach number）是指当飞行器的马赫数达到该马赫数后阻力开始急剧增大，此时阻力系数可达低速时的十倍以上。 通常阻力发散马赫数大于0.6，属跨音速效应。同时，阻力发散马赫数一定大于临界马赫数。 一般而言，阻力系数会在马赫数为1左右达到最大值，进入超音速后在马赫数约为1.2时开始下降。 對於一族的螺旋槳翼型，阻力發散馬赫數 Mdd 可以用Korn's relation 求得: 其中 是阻力發散馬赫數, 是翼型中特定某一段的升力係數,t 是給定翼型段的厚度,c 是給定翼型段的翼弦長, 是藉由計算流體力學分析 (CFD analysis) 給予的一個係數:K = 0.87 可以用在傳統翼型 (NACA 6系列),K = 0.95 則可以用在超臨界翼型 (zh) |
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| dbo:wikiPageWikiLink | dbr:Sound_barrier dbr:Critical_Mach_number dbr:Shock_wave dbr:Computational_fluid_dynamics dbr:Speed_of_sound dbr:Subsonic_flight dbr:Supercritical_airfoil dbc:Aircraft_wing_design dbr:Transonic dbr:Drag_coefficient dbr:Critical_Mach dbr:Airfoil dbr:Aircraft dbr:Aircraft_flight_control_system dbr:Airframe dbr:Drag_(physics) dbr:Flow_separation dbr:Adverse_pressure_gradient dbr:Aerodynamics dbr:Coffin_corner_(aerodynamics) dbr:Thrust dbc:Drag_(physics) dbr:Infinity dbr:Mach_number dbr:Supersonic dbr:Wave_drag dbr:Aircraft_propulsion dbr:Whitcomb_area_rule dbr:Prandtl–Glauert_rule |
| dcterms:subject | dbc:Aircraft_wing_design dbc:Drag_(physics) |
| rdfs:comment | 阻力发散马赫数（英語：drag divergence Mach number）是指当飞行器的马赫数达到该马赫数后阻力开始急剧增大，此时阻力系数可达低速时的十倍以上。 通常阻力发散马赫数大于0.6，属跨音速效应。同时，阻力发散马赫数一定大于临界马赫数。 一般而言，阻力系数会在马赫数为1左右达到最大值，进入超音速后在马赫数约为1.2时开始下降。 對於一族的螺旋槳翼型，阻力發散馬赫數 Mdd 可以用Korn's relation 求得: 其中 是阻力發散馬赫數, 是翼型中特定某一段的升力係數,t 是給定翼型段的厚度,c 是給定翼型段的翼弦長, 是藉由計算流體力學分析 (CFD analysis) 給予的一個係數:K = 0.87 可以用在傳統翼型 (NACA 6系列),K = 0.95 則可以用在超臨界翼型 (zh) The drag-divergence Mach number (not to be confused with critical Mach number) is the Mach number at which the aerodynamic drag on an airfoil or airframe begins to increase rapidly as the Mach number continues to increase. This increase can cause the drag coefficient to rise to more than ten times its low-speed value. Drag-divergence Mach numbers Mdd for a given family of propeller airfoils can be approximated by Korn's relation: where (en) |
| rdfs:label | Drag-divergence Mach number (en) 阻力发散马赫数 (zh) |
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