The spatial relationship between the energy dissipation slabs and the vortex tubes is investigated based on the direct numerical simulation（DNS） of the channel flow. The spatial distance between these two structures...The spatial relationship between the energy dissipation slabs and the vortex tubes is investigated based on the direct numerical simulation（DNS） of the channel flow. The spatial distance between these two structures is found to be slightly greater than the vortex radius. Comparison of the core areas of the vortex tubes and the dissipation slabs gives a mean ratio of 0.16 for the mean swirling strength and that of 2.89 for the mean dissipation rate. These results verify that in the channel flow the slabs of intense dissipation and the vortex tubes do not coincide in space. Rather they appear in pairs offset with a mean separation of approximately 10η.展开更多
Turbulence kinetic energies in confined vortex flows have been studied. The studies were based on the experiments performed in a vortex chamber. In the experiments, a Laser Doppler Anemometry (LDA) was used to perform...Turbulence kinetic energies in confined vortex flows have been studied. The studies were based on the experiments performed in a vortex chamber. In the experiments, a Laser Doppler Anemometry (LDA) was used to perform flow measurements inside the vortex chamber, which provided the data for the kinetic energy analysis. The studies concentrated on the influences of the contraction ratio and the inlet air flow rate on the kinetic energy, and analyzed the characteristics of the kinetic energy in the confined vortex flows, including the distributions of the tangential component, radial component and total turbulence kinetic energy. In the paper, both the experimental techniques and the experimental results were presented. Based on a similarity analysis and the experimental data, an empirical scaling formula was proposed so that the tangential component of the turbulence kinetic energy was dependent only on the parameter of the contraction ratio.展开更多
Sound particle velocity is irrotational and achve sound intensity may sometimes be rotational. With the development of the measurement of sound intensity and the active noise control, the interest of studying the rota...Sound particle velocity is irrotational and achve sound intensity may sometimes be rotational. With the development of the measurement of sound intensity and the active noise control, the interest of studying the rotational characteristics of sound intensity and the sound energy vortex has been increasing. In this paper, we discussed the sound image method for rectangular room with light-absorption walls, derived a method for computation of number of sound images and their positions, and gave equations for sound field variables. As an example, we computed sound pressures and the phases of sound pressure waves on a cross-section of a room, and drew diagrams to show sound energy streamlines on the cross-section. The diagrams show that some energy streamlines roll up to form energy vortexes. Around vortex point is a rotational sound wave. The dimensions of vortexes are dependent on sound frequency and decrease with the increase of frequency. It can be predicted that the vortexes would disappear at higher frequencies.展开更多
基金Project supported by the National Natural Science Foun-dation of China(Grant No.51127006)
文摘The spatial relationship between the energy dissipation slabs and the vortex tubes is investigated based on the direct numerical simulation（DNS） of the channel flow. The spatial distance between these two structures is found to be slightly greater than the vortex radius. Comparison of the core areas of the vortex tubes and the dissipation slabs gives a mean ratio of 0.16 for the mean swirling strength and that of 2.89 for the mean dissipation rate. These results verify that in the channel flow the slabs of intense dissipation and the vortex tubes do not coincide in space. Rather they appear in pairs offset with a mean separation of approximately 10η.
文摘Turbulence kinetic energies in confined vortex flows have been studied. The studies were based on the experiments performed in a vortex chamber. In the experiments, a Laser Doppler Anemometry (LDA) was used to perform flow measurements inside the vortex chamber, which provided the data for the kinetic energy analysis. The studies concentrated on the influences of the contraction ratio and the inlet air flow rate on the kinetic energy, and analyzed the characteristics of the kinetic energy in the confined vortex flows, including the distributions of the tangential component, radial component and total turbulence kinetic energy. In the paper, both the experimental techniques and the experimental results were presented. Based on a similarity analysis and the experimental data, an empirical scaling formula was proposed so that the tangential component of the turbulence kinetic energy was dependent only on the parameter of the contraction ratio.
文摘Sound particle velocity is irrotational and achve sound intensity may sometimes be rotational. With the development of the measurement of sound intensity and the active noise control, the interest of studying the rotational characteristics of sound intensity and the sound energy vortex has been increasing. In this paper, we discussed the sound image method for rectangular room with light-absorption walls, derived a method for computation of number of sound images and their positions, and gave equations for sound field variables. As an example, we computed sound pressures and the phases of sound pressure waves on a cross-section of a room, and drew diagrams to show sound energy streamlines on the cross-section. The diagrams show that some energy streamlines roll up to form energy vortexes. Around vortex point is a rotational sound wave. The dimensions of vortexes are dependent on sound frequency and decrease with the increase of frequency. It can be predicted that the vortexes would disappear at higher frequencies.
