Analysis of coupling aerodynamics and acoustics are performed to investigate the self-sustained oscillation and aerodynamic noise in two-dimensional flow past a cavity with length to depth ratio of 2 at subsonic speed...Analysis of coupling aerodynamics and acoustics are performed to investigate the self-sustained oscillation and aerodynamic noise in two-dimensional flow past a cavity with length to depth ratio of 2 at subsonic speeds. The large eddy simulation (LES) equations and integral formulation of Ffowcs-Williams and Hawings (FW-H) are solved for the cavity with same conditions as experiments. The obtained density-field agrees well with Krishnamurty’s experimental schlieren photograph, which simulates flow-field distributions and the direction of sound wave radiation. The simulated self-sustained oscillation modes inside the cavity agree with Rossiter’s and Heller’s predicated results, which indicate frequency characteristics are obtained. Moreover, the results indicate that the feedback mechanism that new shedding-vortexes induced by propagation of sound wave created by the impingement of the shedding-vortexes in the shear-layer and rear cavity face leads to self-sustained oscillation and high noise inside the cavity. The peak acoustic pressure occurs in the first oscillation mode and the most of sound energy focuses on the low-frequency region.展开更多
于2013年5月利用带宽为20 Hz^100 k Hz的水听器测量系统对大连市周边近岸海域的大黑石、付家庄、星海湾、塔河湾、海之韵5个典型站位的水下噪声进行了测量,获取各站点海洋环境噪声数据以及风速、海况等环境要素,然后进行噪声平均声压级(...于2013年5月利用带宽为20 Hz^100 k Hz的水听器测量系统对大连市周边近岸海域的大黑石、付家庄、星海湾、塔河湾、海之韵5个典型站位的水下噪声进行了测量,获取各站点海洋环境噪声数据以及风速、海况等环境要素,然后进行噪声平均声压级(Sound pressure level,SPL)的计算和20 Hz^100 k Hz带宽的噪声频谱分析。结果表明:付家庄、星海湾海区噪声平均声压级分别为126.58、123.39 d B(以1μPa为参考声压,下同),船舶航行、近岸工程建设等人为噪声是该海区的主要噪声源;大黑石、塔河湾海域的海洋噪声较低,平均声压级分别为115.66、122.17 d B,潮汐和风浪等自然噪声是该海域的主要海洋噪声源;货运港口及航道附近的海之韵海域平均声压级最高,为132.53 d B,船舶航行等为主要噪声源。总体上,大连周边近岸海域海洋噪声受人类活动因素影响较大,在港口航道、海洋工程等区域显示了较高的噪声水平,而地处渤海的养殖海域噪声最低。本次测量的平均声压级处于鱼类和海洋哺乳动物的听力范围之内,但因声压级相对较低,对当地海水养殖业和海洋哺乳动物应该不会产生显著影响。展开更多
文摘Analysis of coupling aerodynamics and acoustics are performed to investigate the self-sustained oscillation and aerodynamic noise in two-dimensional flow past a cavity with length to depth ratio of 2 at subsonic speeds. The large eddy simulation (LES) equations and integral formulation of Ffowcs-Williams and Hawings (FW-H) are solved for the cavity with same conditions as experiments. The obtained density-field agrees well with Krishnamurty’s experimental schlieren photograph, which simulates flow-field distributions and the direction of sound wave radiation. The simulated self-sustained oscillation modes inside the cavity agree with Rossiter’s and Heller’s predicated results, which indicate frequency characteristics are obtained. Moreover, the results indicate that the feedback mechanism that new shedding-vortexes induced by propagation of sound wave created by the impingement of the shedding-vortexes in the shear-layer and rear cavity face leads to self-sustained oscillation and high noise inside the cavity. The peak acoustic pressure occurs in the first oscillation mode and the most of sound energy focuses on the low-frequency region.
文摘于2013年5月利用带宽为20 Hz^100 k Hz的水听器测量系统对大连市周边近岸海域的大黑石、付家庄、星海湾、塔河湾、海之韵5个典型站位的水下噪声进行了测量,获取各站点海洋环境噪声数据以及风速、海况等环境要素,然后进行噪声平均声压级(Sound pressure level,SPL)的计算和20 Hz^100 k Hz带宽的噪声频谱分析。结果表明:付家庄、星海湾海区噪声平均声压级分别为126.58、123.39 d B(以1μPa为参考声压,下同),船舶航行、近岸工程建设等人为噪声是该海区的主要噪声源;大黑石、塔河湾海域的海洋噪声较低,平均声压级分别为115.66、122.17 d B,潮汐和风浪等自然噪声是该海域的主要海洋噪声源;货运港口及航道附近的海之韵海域平均声压级最高,为132.53 d B,船舶航行等为主要噪声源。总体上,大连周边近岸海域海洋噪声受人类活动因素影响较大,在港口航道、海洋工程等区域显示了较高的噪声水平,而地处渤海的养殖海域噪声最低。本次测量的平均声压级处于鱼类和海洋哺乳动物的听力范围之内,但因声压级相对较低,对当地海水养殖业和海洋哺乳动物应该不会产生显著影响。
