Numerical Simulation And Experiment Study Of The Noise Radiated By A Cavity Flow

Self-sustained oscillation can be caused by a low-speed turbulent flow over an open cavity, as well as noise radiation. In the aerospace industry, the understanding of cavity flow phenomena has received considerable attention, with a significant amount of research being carried out. For recent years, vehicle noise has received considerable attention. Cavity noise is a common source of noise in vehicle aerodynamic noise due to the flow over cavities such as open windows or door seals. The reduction of such noise can give a comfortable in-car condition and reduce noise radiation to the surroundings, all which can offer social and commercial advantages.The flow mechanism and radiated noise by a low-speed turbulent flow over an open cavity has been investigated computationally. After acquired the flow field data which is obtained by using Large Eddy Simulation, hybrid method that couples numerical flow computations with an implementation of the Ffowcs Williams-Hawkings equation is used to capture the flow induced noise. Hybrid method, which split the computational domain into a source region and a propagation region, can separate different length scales, and reduce computational demanding. In order to investigate the influence of incoming flow velocity, different flow speeds (such as 30m/s, 50m/s, 70m/s) are used for the cavity with which the length L=16mm an the depth D=4mm. And different cavity lengths (such as L=16mm, L=12mm, L=8mm) are also used to investigate the influence of cavity configuration while the velocity of incoming flow is 70m/s. Self-sustained oscillation in cavity and the coupling between flow field and radiated noise are observed in all these computations. For cavity configuration L=16mm and D=4mm, the time of one cavity oscillation period decrease while the sound pressure level (SPL) increase when the velocity of incoming flow changing from 30m/s to 50m/s, and at last 70m/s. when the velocity of incoming flow is 70m/s the sound pressure level of radiated noise is up to 97dB which is higher than limitation. As the cavity length L changing from 16mm to 8mm, the time of one oscillation period decrease as well as the sound pressure level (SPL) of flow radiated noise. The velocity of incoming flow of these computations is 70m/s. When the velocity of incoming flow is 70m/s, the maximum SPL of the cavity with the length L=8mm is 70dB while the cavity with the length L=16mm is 97dB. The transition of flow mode is the main cause of such reduction. The reduction of cavity noise is also discussed in this article. Cavity noise experiment is conducted in wind tunnel and the result is shown good agreement with numerical simulation...