船底凹槽气层流动特征及影响因素研究

Study on Characteristics of Air Layer and Its Influencing Factors on 2D Bottom Hollow

采用VOF方法,通过求解RANS方程数值研究了船底凹槽中的气层运动形态及其影响因素,模拟了气层在凹槽中的发展过程,分析了气流量、断阶高度、来流速度对气层形态的影响规律,分析了气层波长与来流速度之间的函数关系.研究结果表明:向凹槽中喷气可形成长气穴;存在一个气流量的临界值,当气流量小于该值时,仅在凹槽首部形成长度有限的局部气穴;当气流量大于该值时,气穴迅速向尾部延伸,并呈波动特征;凹槽深度对气层波动的波长影响甚微,对气层厚度的影响较大;凹槽深度增加,气层的平均厚度增大;气层的波长随来流速度增加而增大,波长近似为速度平方的63.6%.

The air layer formation and its influencing factor on 2D bottom hollow was revealed numeri‐cally by VOF method and solving RANS equations .The effects of some factors ,such as air flow rate , step height and velocity on air layer shapes were studied ,the formula between wave length and veloci‐ty is obtained .T he numerical results show s that a long air cavity is obtained by injecting air into hol‐low if air flow rate is larger than the critical value ,but a short and small local air cavity is presented if air flow is lower than the value .The large and long air cavity shows itself as wave pattern .The hol‐low height has little effect on wave length ,but has some effect on air layer thickness .The air layer thickness is increase as the increase of velocity .The wave length is up as the speed up ,and the wave length is equal to 0 .636 times of the square of velocity .