Waves induced by a submerged moving dipole in a two-layer fluidof finite depth

The waves induced by a moving dipole in a two-fluid system are analytically and experimentally investigated. The velocity potential of a dipole moving horizontally in the lower layer of a two-layer fluid with finite depth is derived by superposing Greens functions of sources (or sinks). The far-field waves are studied by using the method of stationary phase. The effects of two resulting modes, i.e. the surface- and internal-wave modes, on both the surface divergence field and the interfacial elevation are analyzed. A laboratory study on the internal waves generated by a moving sphere in a two-layer fluid is conducted in a towing tank under the same conditions as in the theoretical approach. The qualitative consistency between the present theory and the laboratory study is examined and confirmed.

SURFACE EFFECTS OF INTERNAL WAVE GENERATED BY A MOVING SOURCE IN A TWO-LAYER FLUID OF FINITE DEPTH

Based on the potential flow theory of water waves, the interaction mechanism between the free_surface and internal waves generated by a moving point source in the lower layer of a two_layer fluid was studied. By virtue of the method of Green's function, the properties of the divergence field at the free surface were obtained, which plays an important role in the SAR (Synthetic Aperture Radar) image. It is shown that the coupling interaction between the surface_wave mode and internal_wave mode must be taken into account for the cases of large density difference between two layers, the source approaching to the pynocline and the total Froude number Fr close to the critical number Fr 2. The theoretical analysis is qualitatively consistent with the experimental results presented by Ma Hui_yang.

Comparison of double layer in argon helicon plasma and magnetized DC discharge plasma

We present in this paper the comparison of an electric double layer(DL)in argon helicon plasma and magnetized direct current(DC)discharge plasma.DL in high-density argon helicon plasma of 13.56 MHz RF discharge was investigated experimentally by a floating electrostatic probe and local optical emission spectroscopy(LOES).The DL characteristics at different operating parameters,including RF power(300-1500 W),tube diameter(8-60 mm),and external magnetic field(0-300 G),were measured.For comparison,DL in magnetized plasma channel of a DC discharge under different conditions was also measured experimentally.The results show that in both cases,DL appears in a divergent magnetic field where the magnetic field gradient is the largest and when the plasma density is sufficiently high.DL strength(or potential drop of DL)increases with the magnetic field in two different structures.It is suggested that the electric DL should be a common phenomenon in dense plasma under a gradient external magnetic field.DL in magnetized plasmas can be controlled properly by magnetic field structure and discharge mode(hence the plasma density).