SAE J 1594-2010 Vehicle Aerodynamics Terminology《车辆空气动力学术语》.pdf

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5、eding J512 DEC94 (R) Vehicle Aerodynamics Terminology RATIONALE This document has been revised to correct numerous errors and omissions in the previous (1994) revision. That revision, whose sole purpose was to place it into the new SAE Technical Standards Board format, was the only revision to the o

6、riginal (1987) issue. The current (2010) revision has also been used as an opportunity to update applicable references, delete those that are no longer readily available, improve the organization of the document, and modify the directional sense of the axes system as indicated below. The following i

7、s the rationale for selection of specific terminologies, conventions, and definitions. Axes System The SAE Road Vehicle Aerodynamics Committee agreed to modify the axes system in the original SAE J1594 issued in 1987, to have x positive rearward and z positive upward, to correspond with the positive

8、 directions of drag and lift, respectively. This change does not affect the positive sense of the aerodynamic forces and moments as defined in the previous version of SAE J1594, only their directional sense (specifically for drag, lift, yawing moment, and rolling moment) relative to the signs of the

9、 x and z axes in the new axes system. Resolving Center Center of gravity (c.g.) and body geometry-defined resolving centers used in vehicle dynamics (Reference 2.1.1.1) and aeronautics, respectively, are not satisfactory for road vehicle aerodynamics applications. A large portion of automotive aerod

10、ynamics development testing is performed before the vehicle c.g. is known. The c.g. location can also vary significantly with vehicle option content and loading. Relating the axis center to the body geometry is also problematic when major body geometry changes are explored during wind tunnel tests.

11、These situations are avoided by placing the resolving center at ground level, positioned at mid-wheelbase and mid-track. An added advantage of this location is the direct translation of aerodynamic loading to tire contact patch ground reactions. Forces and Moments The primary terminology for aerodyn

12、amic force and moment components (drag, lift, side force, pitching moment, yawing moment, and rolling moment) were adopted from aeronautical usage. The symbols for drag and lift (D & L) were also taken from aeronautics. To maintain consistency with the symbols for drag and lift, and to provide a mne

13、monic aid, the other component symbols (S,PM,YM and RM) were based on terminology. Attitude Angles Vehicle attitude angle definitions and symbols also correspond to existing aerodynamics terminology as used for aircraft development. Force and Moment Coefficients Aerodynamic coefficient definitions w

14、ere chosen consistent with aeronautical terminology, with one exception. Unlike typical aerodynamics convention, the wheelbase is used to compute moment coefficients. Although it makes more aerodynamic sense to use a body length dimension, this is more likely to change during wind tunnel development

15、 than wheelbase. Using wheelbase (WB) provides an additional advantage with the chosen axes system in simplifying the computation of axle loadings. For example, the lift coefficient for the front axle is then equal to CLF = CL/2 + CPM. However, if CPM were based on an overall length (OAL), a ratio o

16、f WB and OAL would have to be included in the computation. Vehicle Parameters The wheelbase designator (L) used in vehicle dynamics (Reference 2.1.1.1) was not adopted, since it is used for the aerodynamic lift force. Frontal area and scale factor symbols are consistent with aerodynamic usage. Provi

17、ded by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J1594 Revised JUL2010 Page 2 of 7Flow Parameters Symbols and definitions for air flow parameters were chosen consistent with aerodynamics terminology. The definition of equivalent full scale velocity (VE

18、Q) is included to provide a simple means of relating reduced scale model flow conditions to full scale. Standard day conditions were chosen to correspond to those defined at sea level conditions for the U.S. Standard Atmosphere adopted by NASA, NOAA and USAF in 1976 (Reference 2.1.3.1). For high-spe

19、ed (motorsports) and high-humidity (thermal) applications, references are cited to account for the effects of compressibility on dynamic pressure and relative humidity on air density, if deemed necessary. Yaw-Weighted Drag Coefficient Ambient wind magnitude, heading angle and vehicle path directions

20、 have an effect on the overall average aerodynamic drag of a vehicle during a particular duty cycle. The yaw-weighted drag coefficient is defined as the average drag coefficient during a particular driving schedule and ambient wind input. The wind and driving schedule factors affecting the wind-aver

21、aged drag coefficient have not been standardized. Some examples of yaw-weighted drag coefficient computations are given in References 2.1.1.2 - 2.1.1.4. FOREWORD The original SAE Road Vehicle Aerodynamics Terminology included in SAE J670 (ca. 1974) was found inadequate for use by vehicle aerodynamic

22、s engineers. The originating Vehicle Dynamics Committee therefore appointed F.N. Beuavais as chairman and organizer of a new Vehicle Aerodynamics Subcommittee. This subcommittee first met in October 1975 to begin work on a new Aerodynamics Terminology. A comprehensive survey of terminology used in N

23、orth America, Europe, and Japan showed that there was no standard set of nomenclature in use. The subcommittee in association with a number of non-member contributors used this survey, along with traditional (aircraft) aerodynamics and vehicle dynamics nomenclature, as inputs to a first draft docume

24、nt completed in 1977. The ever-increasing activity in ground vehicle aerodynamics led to the formation of a full committee, the Road Vehicle Aerodynamics Committee (RVAC), in 1983. The RVAC completed the final revisions of the terminology and voted its initial adoption in March 1986. 1. SCOPE This t

25、erminology is intended to provide a common nomenclature for use in publishing road vehicle aerodynamics data and reports. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest issue o

26、f SAE publications shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.2.1.1.1 SAE J670 Vehicle Dynamics Terminology 2.1.1.2 SAE J1252 SAE Wind Tu

27、nnel Test Procedure for Trucks and Buses Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J1594 Revised JUL2010 Page 3 of 72.1.1.3 SAE Paper No. 750704 Comparison of Effectiveness of Commercially Available Devices for the Reduction of Aerodynamic

28、Drag on Tractor Trailers, 1975. 2.1.1.4 SAE Paper No. 840298 The Effect of Ambient Wind on a Road Vehicles Aerodynamic Work Requirement and Fuel Consumption, 1984. 2.1.1.5 Aerodynamics of Road Vehicles, W.-H. Hucho, 4th Edition, 1998. 2.1.1.6 SAE Paper No. 2005-01-0870 Uncertainty Analysis of Aerody

29、namic Coefficients in an Automotive Wind Tunnel, 2005. 2.1.1.7 SAE TSB003 Rules for SAE use of SI (Metric) Units 2.1.2 NACA Publication Available online from NASA. 2.1.2.1 Report 1135 Equations, Tables, and Charts for Compressible Flow, 1953. 2.1.3 NOAA Publication Available online from the National

30、 Technical Information Service. 2.1.3.1 NOAA-S/T 76/1562U.S. Standard Atmosphere, 1976. Product Code ADA035728. 2.1.4 Wiley-interscience Publication Available from John S. Wiley and Sons, New York. 2.1.4.1 Low-Speed Wind Tunnel Testing, J.B. Barlow, W.H. Rae, and A. Pope, 3rd Edition, 1999. 2.2 Rela

31、ted Publications Not applicable. 3. AXES SYSTEM AND VEHICLE ANGLES 3.1 Orientation The stability axes system yaws with the vehicle or model (Figure 1). Axes form an orthogonal system, which is, as seen by the driver: a. x direction: positive rearward b. y direction: positive right c. z direction: po

32、sitive up 3.2 Resolving Center The origin of the axes system is located in the plane of the ground surface at mid-wheelbase and mid-track. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J1594 Revised JUL2010 Page 4 of 73.3 Vehicle Angles a. Pitc

33、h Angle (. ): Angle between the vehicle body longitudinal axis (x-direction) and the ground surface, positive nose-up.b. Yaw Angle (): Angle between the x-axis and the free-stream velocity vector (V ), positive nose-right (Figure 2). c. Roll Angle (): Angle between the vehicle body lateral axis (y-d

34、irection) and the ground surface, positive right side down.4. TERMINOLOGY 4.1 Vehicle Parameters a. Wheelbase (WB): Distance (in the x-direction) between the front and rear axles. b. Frontal Area (A): Vehicle area projection in the x-direction. c. Scale Factor (): Model dimensional fraction of full

35、scale vehicle. d. Vehicle Velocity ( V ): Vehicle velocity vector with magnitude V in the -x direction (Figure 2). 4.2 Flow Parameters a. Wind Velocity ( WV ): Ambient wind velocity vector, assumed to lie in the x-y plane, with magnitude VWwith direction relative to the x-axis (Figure 2).b. Wind Ang

36、le ( ): Angle of the wind velocity vector relative to the x-axis (Figure 2), positive when the wind approaches from the left. c. Free-stream Speed (V): Magnitude of the wind velocity vector relative to the vehicle velocity vector: VVVW=.d. Dynamic Pressure (q): q= 1/2V2NOTE: In wind tunnel applicati

37、ons, the dynamic pressure should be based on an empty-tunnel calibration. See References 2.1.1.5 and 2.1.4.1. At higher speeds (e.g., motorsports), compressibility corrections to dynamic pressure and velocity should be considered. See References 2.1.1.6 and 2.1.2.1. e. Air Density (): = 1.2250 kg/m3

38、at standard day conditions. f. Air Viscosity (): = 1.7894x10-5N.s/m2at standard day conditions. g. Standard Day Conditions: dry air at 15 C and 101.325 kPa NOTE: Dry air density and viscosity at other than standard day conditions can be computed from Equations 1 and 2: ()()3m/kg325.101/p)T15.273/(15

39、.2882250.1 += (Eq. 1) ()()25m/sNC60to0Tfor10T00460.07203.1 =+=(Eq. 2) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J1594 Revised JUL2010 Page 5 of 7where: T = Air temperature in degrees Celsius p = Atmospheric pressure in kiloPascals (Density

40、and viscosity data from Reference 2.1.3.1.) In environments where relative humidity is high, the calculation of moist-air density as a function of temperature, pressure, and relative humidity should be considered. See Reference 2.1.4.1. h. Boundary Layer Thickness (): Height above a surface where th

41、e local velocity u(z) is 99% of the free-stream speed (V).i. Displacement Thickness (*): * = 0(1-u(z)/V)dz j. Momentum Thickness (): = 0 u(z)/V(1-u(z)/V)dzk. Local Static Pressure (p) l. Free-Stream Static Pressure (p)m. Pressure Coefficient (Cp): Cp= (p-p)/qn. Reynolds Number per Unit Length (Re/ )

42、: Re/ = V/ o. Reynolds Number (Re): Re = VWB/p. Equivalent Velocity (VEQ): VEQ= V14.3 Forces and Moments The preferred designators for aerodynamic forces and moments are (see Figure 1): a. Drag (D): Aerodynamic force acting along the x-axis, positive rearward (Fx= D). b. Lift (L): Aerodynamic force

43、acting along the z-axis, positive upward (Fz= L). c. Side Force (S): Aerodynamic force acting along the y-axis, positive to the right (Fy= S). d. Pitching Moment (PM): Aerodynamic moment about the y-axis, positive nose-up (My= PM). e. Yawing Moment (YM): Aerodynamic moment about the z-axis, positive

44、 nose-right (Mz= -YM). f. Rolling Moment (RM): Aerodynamic moment about the x-axis, positive right side down (Mx= -RM). g. Front Lift (LF): Component of aerodynamic lift acting at the front axle (LF = L/2 + PM/WB). h. Rear Lift (LR): Component of aerodynamic lift acting at the rear axle (LR = L/2 -

45、PM/WB). i. Front Side Force (SF): Component of aerodynamic side force acting at the front axle (SF = S/2 + YM/WB). j. Rear Side Force (SF): Component of aerodynamic side force acting at the rear axle (SF = S/2 - YM/WB). Provided by IHSNot for ResaleNo reproduction or networking permitted without lic

46、ense from IHS-,-,-SAE J1594 Revised JUL2010 Page 6 of 74.4 Force and Moment Coefficients Nondimensional aerodynamic coefficients are designated by an upper case letter C with upper case subscripts identifying a force or moment component. a. Drag Coefficient: CD= D / (q A) b. Lift Coefficient: CL= L

47、/ (q A) c. Side Force Coefficient: CS= S / (q A) d. Pitching Moment Coefficient: CPM= PM / (q A WB)e. Yawing Moment Coefficient: CYM= YM / (q A WB) f. Rolling Moment Coefficient: CRM= RM / (q A WB) g. Front Lift Coefficient: CLF= CL/2 + CPMh. Rear Lift Coefficient: CLR= CL/2 - CPMi. Front Side Force

48、 Coefficient: CSF= CS/2 + CYMj. Rear Side Force Coefficient: CSR= CS/2 - CYMNOTE: Moment coefficients for vehicles with more than two axles may be based on a length parameter other than wheelbase (e.g., see Reference 2.1.1.2). In this case, the parameter should be specified. 4.5 Yaw-Weighted Drag Coefficient The yaw-weighted drag coefficient (DC ) is defined using an average aerodynamic drag force during a specified ambient wind input schedule, and normalized using the vehic