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As a simulation of road driving, wind tunnel testing of full-size vehicles produces certain errors in the aerodynamic forces, aerodynamic moments, and surface pressures. The magnitude of these errors, in general, depends on the following: a.) Flow quality, b.) Determination of the reference dynamic pressure, c.) Wind tunnel floor boundary layer, d.) Test section geometry and position of the car within that geometry, e.) Shape of the vehicle, f.) Blockage ratio: The ratio of the cross-sectional area of the vehicle to the cross-sectional area of the wind tunnel nozzle, g.) Wheel rotation, and h.) Internal flow in the model. The SAE Standards Committee, Open Throat Wind Tunnel Adjustments, had as a goal to document the knowledge of the influence of model interference on wind tunnel test results for automotive open jet wind tunnels. This document contains the following information related to this subject: a.) Design data of open throat wind tunnels, b.)

As a simulation of road driving, wind tunnel testing of full-size vehicles produces certain errors in the aerodynamic forces, aerodynamic moments, and surface pressures. The magnitude of these errors, in general, depends on the following: a Flow quality b Determination of the reference dynamic pressure c Wind tunnel floor boundary layer d Test section geometry and position of the car within that geometry e Shape of the vehicle f Blockage ratio: The ratio of the cross-sectional area of the vehicle to the cross-sectional area of the wind tunnel nozzle g Wheel rotation h Internal flow in the model The SAE Standards Committee, Open Throat Wind Tunnel Adjustments had as a goal to document the knowledge of the influence of model interference on wind tunnel test results for automotive open jet wind tunnels.

As a simulation of road driving, wind tunnel testing of full-size vehicles produces certain errors in the aerodynamic forces, aerodynamic moments, and surface pressures. The magnitude of these errors, in general, depends on the following: a Flow quality b Determination of the reference dynamic pressure c Wind tunnel floor boundary layer d Test section geometry and position of the car within that geometry e Shape of the vehicle f Blockage ratio: The ratio of the cross-sectional area of the vehicle to the cross-sectional area of the wind tunnel nozzle g Wheel rotation h Internal flow in the model The SAE Standards Committee, Open Throat Wind Tunnel Adjustments had as a goal to document the knowledge of the influence of model interference on wind tunnel test results for automotive open jet wind tunnels.

The scope of this SAE Information Report is confined to wind-tunnel testing, although it is recognized that many aspects of the aerodynamic characteristics of road vehicles can be investigated in other test facilities (such as water-tanks) or, especially, on the road. For example, coastdown testing is often used to determine aerodynamic drag (either in isolation or as part of the total resistance), and artificial gust generators are used to investigate the sensitivity of vehicles to cross-wind gusts. Also excluded from the present Report are climatic wind-tunnel tests of road vehicles, which are defined in more detail in Section 3. The Report covers the aerodynamic requirements of a wind-tunnel for automotive testing, together with the facility equipment needed and the requirements affecting the test vehicle or model.

The scope of this SAE Information Report is confined to wind-tunnel testing, although it is recognized that many aspects of the aerodynamic characteristics of road vehicles can be investigated in other test facilities (such as water-tanks) or, especially, on the road. For example, coastdown testing is often used to determine aerodynamic drag (either in isolation or as part of the total resistance), and artificial gust generators are used to investigate the sensitivity of vehicles to cross-wind gusts. Also excluded from the present Report are climatic wind-tunnel tests of road vehicles, which are defined in more detail in Section 3. The Report covers the aerodynamic requirements of a wind-tunnel for automotive testing, together with the facility equipment needed and the requirements affecting the test vehicle or model.

This SAE Information Report has been prepared by the Standards Committee on Cooling Flow Measurement (CFM) at the request of the SAE Road Vehicle Aerodynamics Forum Committee (RVAC). The committee was formed in January 1985 for the purpose of investigating what measuring techniques are used by automotive product manufacturers to determine air cooling air flow rates and, if possible, to synthesize these into a recommended practice report. Although a great deal is already known about engine cooling, recent concern with fuel conservation has resulted in generally smaller air intakes whose shape and location are dictated primarily by low vehicle drag/high forward speed requirements. The new vehicle intake configurations make it more difficult to achieve adequate cooling under all conditions. They cause cooling flow velocity profiles to become distorted and underhood temperatures to be excessively high.

This SAE Information Report has been prepared at the request of the SAE Road Vehicle Aerodynamics Forum Committee (RVAC), incorporating material from earlier revisions of the document first prepared by the Standards Committee on Cooling Flow Measurement (CFM). Although a great deal is already known about engine cooling, recent concern with fuel conservation has resulted in generally smaller air intakes whose shape and location are dictated primarily by low vehicle drag/high forward speed requirements. The new vehicle intake configurations make it more difficult to achieve adequate cooling under all conditions. They cause cooling flow velocity profiles to become distorted and underhood temperatures to be excessively high. Such problems make it necessary to achieve much better accuracy in measuring cooling flows.