petals under the function of vortexes. Fig. 3 shows the temperature field and flow field structure when C0 gets larger, we can find that the number of vortexes is six and they are closer to the tube wall. The temperature field appears a shape of three petals. When C0 is set larger values, the temperature field and flow field structure are show in Figs. 4 and 5. The numbers of vortexes are eight and ten respectively and the influence of vortexes is weak in the core flow and strong near the tube wall. The form of temperature fields is changed into four or five petals. Temperature field gets more uniform in the core flow and the temperature gradient gets steeper near the tube wall. Average temperature gets higher and the temperature difference between fluid and tube is reduced. As the value of C0 grows larger, the intensity of virtual heat field becomes stronger, and the temperature field and flow field structure are in different form. The larger value of C0 leads to more vortexes and more uniform fluid temperature. As a consequence, convective heat transfer in the tube is enhanced.