A double perturbation strategy is presented to solve the asymptotic solutions of a Johnson-Segalman （J-S） fluid through a slowly varying pipe. First, a small parameter of the slowly varying angle is taken as the sma...A double perturbation strategy is presented to solve the asymptotic solutions of a Johnson-Segalman （J-S） fluid through a slowly varying pipe. First, a small parameter of the slowly varying angle is taken as the small perturbation parameter, and then the second-order asymptotic solution of the flow of a Newtonian fluid through a slowly varying pipe is obtained in the first perturbation strategy. Second, the viscoelastic parameter is selected as the small perturbation parameter in the second perturbation strategy to solve the asymptotic solution of the flow of a J-S fluid through a slowly varying pipe. Finally, the parameter effects, including the axial distance, the slowly varying angle, and the Reynolds number, on the velocity distributions are analyzed. The results show that the increases in both the axial distance and the slowly varying angle make the axial velocity slow down. However, the radial velocity increases with the slowly varying angle, and decreases with the axial distance. There are two special positions in the distribution curves of the axial velocity and the radial velocity with different Reynolds numbers, and there are different trends on both sides of the special positions. The double perturbation strategy is applicable to such problems with the flow of a non-Newtonian fluid through a slowly varying pipe.展开更多
This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the conditi...This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the condition of unsteady state long-term continuous running, analyzes the change of soil temperature filed around underground pipe and performance of underground pipe heat exchange between single U and double U pipe system. The results show that double U pipe system is better than single U system, which can improve unit depth heat exchange efficiency, reduce the number of wells and reduce the initial investment.展开更多
Twin vortices flow behavior with out-of-plane angle effect in double bent pipe system is studied numerically and experimentally. Double bent pipe system generates very complicated flow behavior including twin vortices...Twin vortices flow behavior with out-of-plane angle effect in double bent pipe system is studied numerically and experimentally. Double bent pipe system generates very complicated flow behavior including twin vortices in the downstream of the double bent. Moreover, angle from the plane of the double bent forms more complicated flow behavior due to the flow twist by out-of-plane angle. In this study, numerical analysis is examined for this double bent system using three-dimensional CFD code, FLUENT, to reproduce those complicated flow behaviors with twin vortices. Numerical results are compared with experimental results obtained by Ultrasonic Velocity Profiler (UVP). Discrepancy between numerical and experimental result is discussed changing out-of- plane angle, α. Velocity profiles obtained by numerical results are converted into UVP profiles, and they are compared with the experimental results by UVP. Consequently, velocity behavior especially around the pipe wall obtained by numerical results is agreed with experimental results.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11572203 and11332006)
文摘A double perturbation strategy is presented to solve the asymptotic solutions of a Johnson-Segalman （J-S） fluid through a slowly varying pipe. First, a small parameter of the slowly varying angle is taken as the small perturbation parameter, and then the second-order asymptotic solution of the flow of a Newtonian fluid through a slowly varying pipe is obtained in the first perturbation strategy. Second, the viscoelastic parameter is selected as the small perturbation parameter in the second perturbation strategy to solve the asymptotic solution of the flow of a J-S fluid through a slowly varying pipe. Finally, the parameter effects, including the axial distance, the slowly varying angle, and the Reynolds number, on the velocity distributions are analyzed. The results show that the increases in both the axial distance and the slowly varying angle make the axial velocity slow down. However, the radial velocity increases with the slowly varying angle, and decreases with the axial distance. There are two special positions in the distribution curves of the axial velocity and the radial velocity with different Reynolds numbers, and there are different trends on both sides of the special positions. The double perturbation strategy is applicable to such problems with the flow of a non-Newtonian fluid through a slowly varying pipe.
文摘This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the condition of unsteady state long-term continuous running, analyzes the change of soil temperature filed around underground pipe and performance of underground pipe heat exchange between single U and double U pipe system. The results show that double U pipe system is better than single U system, which can improve unit depth heat exchange efficiency, reduce the number of wells and reduce the initial investment.
文摘Twin vortices flow behavior with out-of-plane angle effect in double bent pipe system is studied numerically and experimentally. Double bent pipe system generates very complicated flow behavior including twin vortices in the downstream of the double bent. Moreover, angle from the plane of the double bent forms more complicated flow behavior due to the flow twist by out-of-plane angle. In this study, numerical analysis is examined for this double bent system using three-dimensional CFD code, FLUENT, to reproduce those complicated flow behaviors with twin vortices. Numerical results are compared with experimental results obtained by Ultrasonic Velocity Profiler (UVP). Discrepancy between numerical and experimental result is discussed changing out-of- plane angle, α. Velocity profiles obtained by numerical results are converted into UVP profiles, and they are compared with the experimental results by UVP. Consequently, velocity behavior especially around the pipe wall obtained by numerical results is agreed with experimental results.
