1、BRITISH STANDARD BS 185-4: 1969 Incorporating Amendment No. 1 Glossary of Aeronautical and astronautical terms Section 4: Aerodynamics UDC 001.4:629.7.015:533.6BS185-4:1969 This British Standard, having been approved by the AerospaceIndustry Standards Committee, was published underthe authority of t
2、he Executive Board of the Institutionon 31July1969 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference ACE/1 Draft for comment 67/19252 ISBN 580 05940 5 A British Standard does not purport to include all the necessary provisions of a contract. Users of B
3、ritish Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 16 and a back cover. This standard h
4、as been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue Comments 1033 November 1972 Indicated by a sideline in the marginBS185-4:1969 BSI 12-1999
5、 i Contents Page Section 4. Aerodynamics 1 Subsection 41. General 1 Subsection 42. Stability and control 4 Subsection 43. Performance 5 Subsection 4445. Fluid motion 7 Subsection 46. Model testing 13ii blankBS185-4:1969 BSI 12-1999 1 (Notes on the arrangement and scope of the glossary are contained
6、in the Foreword to Section 1.) Section 4. Aerodynamics BS M 31, “Symbols for flight dynamics”, lists the recommended terms, with explanatory text and symbols, to be used in mathematical analysis and is designed to meet a more specialized need than is this glossary. However, care has been taken to en
7、sure that, as far as is possible, there is no conflict between the glossary and the other standard. Subsection 41. General No. Term Definition 4101 aerodynamic centre The point about which the rate of change of pitching moment with incidence is zero. 4102 aerodynamic twist Variation of the zero-lift
8、 line along the span of a wing or other aerofoil. (Cf. 5228.) 4103 airspeed The speed of an object relative to the ambient undisturbed air. angles 4104 angle of attack ANGLE OF INCIDENCE The angle between a reference line in a body (for an aerofoil the chord is usually used) and the projection of th
9、e velocity relative to the ambient undisturbed air on to the place of symmetry. NOTENot to be confused with rigging angle of incidence, 5236. 4105 effective angle of attack The angle between a reference line on a body and the mean direction of a non-uniform disturbed airstream ahead of the body. 410
10、6 angle of downwash/upwash The angle between the projections on to the plane of symmetry of the local and undisturbed flow directions. 4107 angle of sideslip The angle between the direction of the undisturbed flow and the plane of symmetry. 4108 angle of sidewash The angle between the projections of
11、 the local and undisturbed flow directions on to a plane perpendicular to the plane of symmetry and parallel to the undisturbed flow. 4109 area rule, sonic The approximation that the wave drag at the speed of sound is the same for all bodies with the same longitudinal distribution of cross-sectional
12、 area. In particular, it is equal to that of a body of revolution of that area distribution. 4110 area rule, supersonic A method of estimating the wave drag in inviscid supersonic flow for smooth bodies in terms of the areas of sections taken obliquely at the Mach angle. 4111 autorotation Continuous
13、 rotation of a body resulting from the action of air forces and not sustained by control inputs. (See also 5728.) axes 4112 body axes A system of rectangular co-ordinate axes fixed in the aircraft, usually with the origin at the centre of gravity. The x-axis is usually forward of and in (or parallel
14、 to) the plane of symmetry, the y-axis is to starboard, and the z-axis perpendicular to these so as to form a righthanded system. 4113 aerodynamic-body axes WIND-BODY AXES Body axes in which the x-axis coincides with (or is parallel to) the projection on to the plane of symmetry of some datum veloci
15、ty of the origin relative to the ambient undisturbed air. 4114 principal body axes Body axes that coincide with the principal axes of inertia through the centre of gravity. 4115 longitudinal axes The x-axis of a system of body axes in which the xz-plane is the plane of symmetry.BS185-4:1969 2 BSI 12
16、-1999 No. Term Definition 4116 normal axis The z-axis of a system of body axes in which the xz-plane is the plane of symmetry. 4117 transverse axis LATERAL AXIS The y-axis of a system of body axes in which the xz-plane is the plane of symmetry. 4118 cross-wind axis The straight line through the cent
17、re of gravity perpendicular to the lift and drag axes. The positive direction is to port. 4119 drag axis The straight line through the centre of gravity parallel to the direction of the undisturbed flow. The positive direction is downstream. 4120 lift axis The straight line through the centre of gra
18、vity in the plane of symmetry and perpendicular to the drag axis. The positive sense is in the dorsal direction. 4121 centre of pressure The point on some reference line (e.g. the chord of an aerofoil) about which the pitching moment is zero. drag a 4122 cooling drag Drag associated with the cooling
19、 of the power plant, etc. 4123 form drag For shock-free flow, the normal-pressure drag less the vortex drag. 4124 lift-dependent drag The difference between the drag at a given lift coefficient and the drag at some specified datum lift coefficient. 4125 normal-pressure drag Drag arising from the res
20、olved components of the pressures normal to the surface. 4126 post-exit drag The force in the drag direction deduced from the resolved components of the normal pressures on the outside of the equivalent post-exit streamtube. 4127 pre-entry drag The force in the drag direction deduced from the resolv
21、ed components of the normal pressures on the outside of the pre-entry streamtube. 4128 profile drag BOUNDARY-LAYER DRAG Drag associated with losses in total pressure and total temperature in the boundary layers. It is the sum of the form drag and the skin-friction drag. 4129 ram drag The force, acti
22、ng in the downstream direction, which would arise if the momentum of the internal flow at infinity of a body were destroyed. It is the effective sink drag of an air intake. 4130 sink drag Drag arising from the removal of fluid from the flow. 4131 spillage drag The difference between the drag at a gi
23、ven intake flow and the drag at some specified intake flow. 4132 skin-friction drag SURFACE-FRICTION DRAG Drag arising from the resolved components of the tangential forces on the surface of a body. 4133 wave drag SHOCK-WAVE DRAG Drag arising from the formation of shock waves. 4134 vortex drag TRAIL
24、ING-VORTEX DRAG Drag arising from the formation of trailing vortices. Formerly called induced drag. 4135 external surface A surface that forms a boundary of the external flow. flows 4136 datum intake flow The intake flow that would occur if the boundary of the pre-entry streamtube were unaffected by
25、 the presence of the intake. 4137 external flow The flow of fluid which passes around a body. a See also 4141.BS185-4:1969 BSI 12-1999 3 No. Term Definition 4138 full intake flow The intake flow that occurs when, with a pre-entry compression body in position, the boundary of the pre-entry streamtube
26、 is unaffected by the presence of the remainder of the intake. If there is no pre-entry compression body, then full intake flow is the same as datum intake flow. 4139 internal flow The flow of fluid which passes through a duct of a body. forces 4140 cross-wind force The component of the total aerody
27、namic force in the direction of the cross-wind axis. 4141 drag a The component of the total aerodynamic force in the direction of the undisturbed flow. In powered flight, contributions to this component arising from thrust are excluded. 4142 lift The component of the total aerodynamic force in the d
28、irection of the lift axis. 4143 longitudinal force AXIAL FORCE The component of the total aerodynamic force along the x-axis (orlongitudinal axis). 4144 normal force The component of the total aerodynamic force along the z-axis (ornormal axis). 4145 transverse force LATERAL FORCE SIDE FORCE The comp
29、onent of the total aerodynamic force along the y-axis (ortransverse axis). 4146 thrust The aerodynamic force attributed to the propulsive system. 4147 post-exit thrust The force in the direction of motion deduced from the resolved components of the normal pressures on the inside of the post-exit str
30、eamtube. 4148 pre-entry thrust The force in the direction of motion deduced from the resolved components of the normal pressures on the inside of the pre-entry streamtube. 4149 ground effect The effect of the proximity of the ground or other surface on the aerodynamic qualities of an aircraft. 4150
31、hinge moment The moment about the hinge axis of a control or other hinged surface due to aerodynamic forces. 4151 industrial aerodynamics Aerodynamics of non-aeronautical engineering applications, such as buildings, bridges, stacks, vehicles, duct flows, fans, ventilation, combustion. 4152 interfere
32、nce The aerodynamic influence of bodies on one another. 4153 internal surface A surface that forms a boundary of the internal flow. 4154 limiting velocity The steady velocity attainable by an aircraft along a straight flight path at any specified angle to the horizontal under given atmospheric and p
33、ropulsive conditions. 4155 post-exit streamtube The hypothetical streamtube, extending from the body to infinity downstream, that is assumed to separate the internal flow from the external flow in the absence of mixing. 4156 pre-entry streamtube The streamtube extending to the entry of a ducted body
34、 from infinity upstream and separating the internal flow from the external flow. 4157 scale effect The effect upon any non-dimensional aerodynamic coefficient of a change in the size of a body, other conditions remaining unchanged. More generally, the effect of a change in the Reynolds number. a See
35、 also 4122 to 4134.BS185-4:1969 4 BSI 12-1999 No. Term Definition 4158 sound barrier A popular term for the large changes in the aerodynamic characteristics of an aircraft approaching the speed of sound, formerly believed to make supersonic flight unattainable. 4159 spillage The amount by which the
36、intake flow is less than some specified intake flow. 4160 stall The progressive breakdown of attached flow over an aerofoil, leading to marked changes in aerodynamic characteristics, in particular loss of lift. (Cf. 2225.) 4161 terminal velocity 1. The highest value of the limiting velocity. 2. The
37、velocity for which the drag of a freely falling body just balances the weight at a given altitude. 4162 vertical thrust margin (VTM) The amount, on a VTOL aircraft, by which the vertical thrust exceeds the aircraft weight. 4163 zero-lift line A line through the trailing edge of an aerofoil section p
38、arallel to the direction of the relative air stream when the lift is zero. Subsection 42. Stability and control 4201 aerodynamic damping That part of the damping of a system which is contributed by the aerodynamic forces and/or moments called into play by the motion. 4202 aerodynamic stiffness That
39、part of the stiffness of a system which is contributed by the aerodynamic forces and moments called into play by the motion. 4203 disturbance A displacement from steady state conditions. 4204 divergence A disturbance which increases without oscillation (Cf. 4234.) 4205 lateral divergence A divergenc
40、e involving rolling, yawing, sideslipping, or any combination of these. 4206 longitudinal divergence A divergence in the plane of symmetry. 4207 spiral divergence SPIRAL INSTABILITY A lateral divergence which tends to a spiral descent with increasing rate of turn. 4208 instability The quality whereb
41、y any disturbance from steady motion tends to increase. An aircraft is unstable if, following a disturbance from a given type of steady motions, it does not return to its initial steady motion without movement of the controls by the pilot (Cf. 4223.) motions 4209 lateral motion Motion involving roll
42、ing, yawing, sideslipping, or any combination of these. 4210 longitudinal motion Motion in the plane of symmetry. 4211 coupled motion Motion of an aircraft involving both lateral and longitudinal motion at the same time. 4212 inertia coupling Coupled motion due to the inertial properties of the airc
43、raft. 4213 manoeuvre margin with stick fixed The distance of the centre of the gravity forward of the manoeuvre point with stick fixed, expressed as a fraction of the longitudinal reference dimension. It is a measure of the displacement of the control column necessary to produce a given normal accel
44、eration in a steady pull-out. 4214 manoeuvre margin with stick free The distance of the centre of gravity forward of the manoeuvre point with stick free, expressed as a fraction of the longitudinal reference dimension. It is a measure of the force on the control column necessary to produce a given n
45、ormal acceleration in a steady pull-out.BS185-4:1969 BSI 12-1999 5 No. Term Definition 4215 manoeuvre point with stick fixed The position of the centre of gravity for which the displacement of the control surface required to maintain a steady normal acceleration does not depend on the acceleration.
46、4216 manoeuvre point with stick free The position of the centre of gravity for which the force on the control column required to maintain a steady normal acceleration does not depend on the acceleration. 4217 neutral point with stick fixed The centre of gravity position for which the static margin w
47、ith stick fixed is zero. 4218 neutral point with stick free The centre of gravity position for which the static margin with stick free is zero. oscillations 4219 lateral oscillation An oscillation involving rolling, yawing, sideslipping, or any combination of these. 4220 longitudinal oscillation An
48、oscillation in the plane of symmetry. 4221 phugoid oscillation The long-period longitudinal oscillation involving predominantly changes in airspeed. 4222 short-period longitudinal oscillation An oscillation, in which the aircrafts forward speed remains substantially constant, involving predominantly
49、 changes in incidence and attitude. It is so called because the period is usually, but not necessarily, small compared with that of the phugoid. 4223 stability The quality whereby any disturbance of steady motion tends to decrease. A given type of steady motion is stable if the aircraft will return to that state of motion after disturbance without movement of the controls by the pilot. (Cf. 4208.) 4224 directional stability Stability of motion involving yawing, sideslipping, or any combination of these. 4225 dynamic stability Complete stability of motion when aerodynamics for
