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In-cylinder flow characteristics in a four-stroke diesel engine were studied experimentally by instantaneous measurements of swirl and squish flow velocity distribution with particle image velocimetry (PIV). The triple-exposed PIV films were interrogated on a self-made system to get the velocity distribution. The measured velocities were analyzed by spatially high-pass and low-pass filtering techniques. Vorticity distributions were also calculated using the measured data. As results, vortex structure of the flow field was clearly visualized. Spatially averaged in-cylinder flow energy was found decaying at high rate but the less-scaled flow components at much lower rate. Clearly visualized squish and reverse squish movements around the top dead center (TDC) during the compression stroke were found strongly affecting the swirl flow field. making the in-bowl flow energy increased.

At the collision moment, a driver’s lower extremity will be in different foot position, which leads to the different posture of the lower extremity with various muscle activations. These will affect the driver’s injury during collision, so it is necessary to investigate further. A simulated collision scene was constructed, and 20 participants (10 male and 10 female) were recruited for the test in a driving simulator. The braking posture and muscle activation of eight major muscles of driver’s lower extremity (both legs) were measured. The muscle activations in different postures were then analyzed. At the collision moment, the right leg was possible to be on the brake (male, 40%; female, 45%), in the air (male, 27.5%; female, 37.5%) or even on the accelerator (male, 25%; female, 12.5%). The left leg was on the floor all along.