风阻系数小，风阻就小？

Core Viewpoint - The pursuit of low drag coefficients (Cd) in the automotive industry is prevalent, but a lower Cd does not necessarily equate to lower overall drag due to the influence of other variables such as frontal area, air density, and speed [4][9]. Summary by Sections What is Drag? - Drag is the resistance experienced by an object moving through air, consisting of impact drag, friction drag, and shape drag [2][3]. Drag Coefficient (Cd) - The drag coefficient (Cd) is a dimensionless number that quantifies the drag force experienced by an object in a fluid, reflecting the energy loss efficiency as fluid flows around it [4]. Frontal Area (A) - The frontal area refers to the projected area of an object facing the wind, which is a controllable parameter that directly affects drag [6]. Air Velocity (v) - Drag is proportional to the square of the vehicle's speed, meaning that as speed doubles, drag increases exponentially, highlighting the significant impact of speed on energy consumption [8]. Air Density (ρ) - Air density varies with altitude, temperature, and humidity, affecting the actual drag experienced by a vehicle, even if the Cd and speed remain constant [8]. Misconceptions about Low Cd - A lower Cd does not guarantee lower overall drag, as other factors like frontal area and speed play crucial roles. For instance, a Boeing 787 has a much lower Cd than a Mercedes AMG GT, yet its total drag can be higher due to its larger frontal area [9].