In order to investigate the distribution law of the air velocity in the sudden expansion roadway and accurately ascertain the boundary of the recirculation zone of the flow field, the particle image velocimetry ( PIV) was applied to test the flow field in a rectangular and straight sudden expansion roadway, and the numerical simulation was carried out on the flow field of the sudden expansion roadway under the conditions of different sudden expansion ratio and different inlet air velocity. The research results showed that the streamlines changed from smooth line to mutations while the air flowing through the sudden expansion roadway, the circumfluence whirlpool areas were formed in the upper and lower corner behind the sudden expansion roadway, the existence of the negative wind velocity in the recirculation zone made the velocity distribution in the recirculation zone present a "Ω" type, then the velocity distribution gradually tended to be stable in a "∩" type with the increase of the distance from the sudden expansion transition surface, the position of the sectional air velocity transited from the "Ω" type distribution to the "∩" type distribution was the boundary of the recirculation zone of the sudden expansion roadway;the boundary position of the recirculation zone varied greatly with the increase of the air velocity when the air velocity was in the range of 0. 1 m/s to 2. 5 m/s, and the boundary position of the recirculation zone had little change with the increase of the air velocity when the air velocity was in the range of 2. 5 m/s to 25. 0 m/s; when the air velocity was constant, the boundary position of the recirculation zone was farther away from the sudden expansion transition surface with the the incease of the sudden expansion ratio, that was, the recirculation zone became longer.%为探究突扩巷道断面风速分布规律,准确确定流场回流区边界,利用粒子图像测速仪(PIV)对矩形均直突扩巷道流场进行测试,并对不同突扩比和不同入口风速条件下突扩流场进行数值模拟.研究结果表明:风流经过突扩巷道后流线由平滑直线发生突变,在突扩位置后上下隅角形成回流旋涡区,回流区域负值风速的存在使得回流区内速度分布呈现"Ω"型,随着距离的增加速度分布逐渐趋于稳定并呈"∩"型,断面风速由"Ω"型分布向"∩"型分布的过渡位置即为突扩巷道流场回流区边界位置;在风速0.1～2.5 m/s内,回流区边界位置随着风速的增大有较大变化,而在风速2.5～25.0 m/s内,回流区位置随风速的增大变化较小;当风速一定时,回流区边界位置随着突扩比的增大而距突扩过渡面越远,即回流区越长.
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