That never changes if there is no air drag or air friction of any kind.
它未曾变过,如果没有空气阻力,或任何摩擦力。
2
A testing system was designed and implemented to figure out the frictiondrag of an underwater axisymmetrical vehicle model.
为了研究轴对称回转体水下航行器模型所受到的壁面摩擦阻力，设计并实施了一套测试系统。
3
Experimental and analytical results show that the system can be used to study the frictiondrag of the vehicle models at certain speed range, which full-fills the design demand.