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Experimental results on a liquid metal magnetohydrodynamic (MHD) turbulent flow through a circular conductive pipe subject to a uniform transversal magnetic field are summarized in this paper. The results of the MHD turbulent velocity distributions inside the conductive pipe are obtained. The velocity profiles along the center line of the middle cross section of the pipe are given. There are no big velocity jets in the Robert layers. The velocity distribution agrees well with the numerical simulation result. The transient turbulent velocity of one point in above mentioned line changing with times are measured in the experiment, it is found that the transient velocity varies dramatically compared to the average velocity at high Reynolds number (Re). The strong magnetic field suppresses the turbulent velocity fluctuation. The velocity profiles varying with the different Reynolds numbers at the same Hartmann number (Ha) are also presented in this paper. It is shown that the velocity in the center fluid area decreases with the Reynolds numbers increasing. The Reynolds stresses at different Reynolds numbers and Hartmann numbers are also derived from experimental data. The Reynolds stresses decrease with the increasing of Hartmann numbers. The map of laminar-turbulent transition for MHD circular conductive pipe flows at high Reynolds and Hartmann numbers are also presented. A different fluid instability from the theoretical prediction in Refs. Lielausis (1975) and Moresco et al. (2004) is observed and the transition condition is Re/Ha > 20.

Liquid metal magnetohydrodynamic (MHD) flows through the electrical coupling rectangular ducts are investigated based on a fully developed modeling. Numerical simulations of four different coupling MHD duct flows are carried out to get the results of the MHD pressure drop and the velocity distribution. The first and second cases are that the coupling rectangular ducts are arranged along the direction of external magnetic field, the flow direction in the two ducts is the same in case 1 but it is opposite in case 2; in the third and fourth cases, another coupling duct is extended along the perpendicular direction of the external magnetic field, the flow direction is identical in case 3, but it is opposite in case 4. Numerical results of the velocity and the induced electrical current distributions in the cross sections of the coupling ducts are given in those four different cases, it is indicated that the external magnetic field has a different effect on the flow pattern in those four cases. The MHD pressure drop in those four different cases is compared with the result of one normal rectangular duct flow, the MHD pressure drop of case 1 is reduced compare with the result of one normal duct MHD flows and result of case 4 is closed to one normal duct case, but the results of cases 2 and 3 are larger than it, especially for case 2 it is several times larger than the result of one normal duct flow. In addition, the MHD pressure gradients in those four cases decrease with the increase of the wall conductance ratios when the other conditions are the same. In the case, the three coupling duct flows when the flow direction of the middle duct is opposite, the strong magnetic field has very significant effect on the flow pattern in the middle coupling duct, and the MHD pressure gradient in the middle duct can be dozens of times bigger than that of one normal single duct flow. These results should be considered in the future liquid blanket design.

Up to now, no a real full-cover liquid metal (LM) free surface flow have been successfully used in magnetic fusion devices as MHD instability and unavoidable rivulet flow. Recently, after we carried out a guidable free curve-surface flow on theoretically and experimentally, seeking for other way to get a full-cover free surface flow is also in implementing. The superficial layer MHD effect in free surface flow is experimentally observed. After compared and analyzed the characteristic parameters of the free surface flow, the conditions of full-cover free surface flow are found. Meanwhile, the new two parameters of surface cover ratio and rivulet flow index are introduced to characterize the flowing characteristic of the full-cover free surface flow under magnetic field. According to the analysis rule, for different liquid metal, there are the different unique conditions to meet full-cover free surface flow under magnetic field. This may be a way to solve free surface flow major MHD key issue for LM PFCs.

Effect of contact resistance on magnetohydrodynamic (MHD) laminar flows through circular pipes are investigated by numerical simulations. A numerical method is proposed to investigate this issue. This method is that the induced magnetic field is individually calculated through two different governing equations in the liquid and the solid domains, special boundary conditions are given considering effects of the contact resistance. This method is validated by comparing with analytical solution and another numerical method. Numerical results of the velocity distribution and the MHD pressure drop affected by the contact resistance through circular pipes are given. It is shown that the contact resistance has a significant impact on the MHD pressure drop under the conditions of the fusion liquid metal blanket , and normally, the big contact resistance as a result of poor wetting can cause the MHD pressure drop to be several times lower than no contact resistance case. In addition, non-uniform contact resistance will cause the jet instability in the Robert layer and form a larger jet near the area of contact resistance. In the end, numerical results are compared with experimental results which include the effect of non-uniform contact resistance on the velocity distribution; it is indicated that numerical results are in good agreement with experimental results and validates that the larger velocity jet will be caused by the non-uniform contact resistance from experimental results.

Magnetohydrodynamics (MHD) laminar flows through circular pipes are studied in this paper by numerical simulation under the conditions of Hartmann numbers from 18 to 10000. The code is developed based on a fully developed modeling and validated by Samad's analytical solution and Chang's asymptotic results. After the code validation, numerical simulation is extended to high Hartmann number for MHD circular pipe flows with conducting walls, and numerical results such as velocity distribution and MHD pressure gradient are obtained. Typical M-type velocity is observed but there is not such a big velocity jet as that of MHD rectangular duct flows even under the conditions of high Hartmann numbers and big wall conductance ratio. The over speed region in Robert layers becomes smaller when Hartmann numbers increase. When Hartmann number is fixed and wall conductance ratios change, the dimensionless velocity is through one point which is in agreement with Samad's results, the locus of maximum value of velocity jet is same and effects of wall conductance ratio only on the maximum value of velocity jet. In case of Robert walls are treated as insulating and Hartmann walls as conducting for circular pipe MHD flows, there is big velocity jet like as MHD rectangular duct flows of Hunt's case 2.

Consequent on MHD geometry sensibility phenomena was measured in an accident case; the more detail experiments have been conducted at the liquid metal experimental loop upgrade facility (LMEL-U). The experimental results indicate that MHD pressure drop can be greatly reduced in the special designed ducts. Base on the experimental data, an innovation channel concept (tentatively called as the secondary flow channel, short in “S-channel”) is addressed as a reducing MHD pressure drop channel for the application of a liquid metal blanket system in fusion reactor. It may be a dawn for solving MHD pressure drop key issue of liquid metal blanket system.

The duct with a flow channel insert (FCI) which is made of silicon carbon composite (SiC f /SiC) is a key element in dual coolant lead lithium (DCLL) blanket, and the most important problems of FCI is the magnetohydrodynamics (MHD) issues. In this paper it is presented the study of MHD issues in FCI duct flow using Fluent code, the modification of the FCI with a pressure equalization slot (PES) has been considered in this simulation. Numerical and experimental results of velocity distribution and MHD pressure drop of FCI were given in this paper, then compare and discuss the difference between them. From the experimental and numerical results it indicated that the FCI with insulating material could greatly reduce MHD pressure drop. For fully developed MHD duct flow a general second-order simple method has been developed which solve the unsteady equations and let the steady state be approached asymptotically at large times. Using this method can get accurate result for MHD duct flow in the condition of high Hartmann number without FCI. Then using this method numerical simulation was performed with MHD duct flow with FCI.

Up to now, no a real liquid metal (LM) free surface flow have been successfully used in magnetic fusion devices as MHD instability and unavoidable rivulet flow. Recently, after we carried out a guidable free curve-surface flow on theoretically and experimentally, seeking for other way to get a full-cover free surface flow is also in implementing. The superficial layer MHD effect in free surface flow is experimentally observed. After compared and analyzed the characteristic parameters of the free surface flow, the new two parameters of surface cover ratio and rivulet flow index are introduced to characterize the flowing characteristic of the full-cover free surface flow under magnetic field. According to the analysis rule, for different liquid metal, there are the different unique conditions to meet full-cover free surface flow under magnetic field.

MHD phenomena in a duct flow were studied experimentally by using copper electrodes inserted into the wall of a perfectly insulated duct. The electrodes were connected using a copper wire to imitate different insulator coating imperfection conditions. The experimental results show instabilities of electric potential at the wall (surface instabilities) as well as instabilities in the pressure and velocity (bulk instabilities). The instabilities are strongly dependent on the scale of the copper wire. Three different cases were studied (at the same flow regimes, but with different electrode connections), where the potential at the duct wall is smaller, equal to or higher than the product of duct diameter 2a0 and transverse magnetic field B0 and average velocity V0. MHD pressure drop ΔP also exhibits significant changes.

Liquid metal free surface flows (films, jets and droplets) are considered as prospective coolants in diverter/limiter system and first wall in fusion reactor, but the knowledge of liquid metal free surface, particularly jet flows, is very limited. In this article, the stability of a jet flow under a gradient magnetic field is investigated, and its MHD effects are the top concern. Firstly, a simplified model is developed to analyze the MHD effects of the jet flow and to explain the reason why it can keep stable, and the examination of the induced electric potential and currents of the jet flow is also included. Secondly, numerical simulation based on the approach of solving the electric potential equation was proceeded to support the theoretical analysis. Finally, experiments with different value of B0 (maximum value of the magnetic field) and v 0 (average fluid velocity at the nozzle exit), and different kind of nozzle were performed on the Liquid Metal Experimental Loop (LMEL) in Southwestern Institute of Physics (SWIP), and there's a good agreement with experimental data and theoretical results. Qualitatively, a jet flow under a gradient magnetic field can keep its shape stable due to electromagnetic (EM) force in its direction and the compressed EM force in its cross-section, meanwhile, the reduction in velocity leads to a shorter range distance and a lager radius of cross-section of the jet flow. These effects are closely related to the parameters of the radius of the nozzle, the values of B0 and v 0 .

The advanced limiter-divertor plasma-facing system (ALPS) has been studied for several years, but the magnetohydrodynamic (MHD) stability of free surface jet flow in a gradient transverse magnetic field is one of the key remaining issues. Recently, some experiments on jet flow were performed with a 0.2- to 1.95-T gradient magnetic field and 2.9, 3.24, and 4.10 m/s velocities for a flow diameter of 6 mm. The results indicated that the transverse gradient magnetic field strongly shortens the jet flow range and the shape of the cross section of the jet flow deforms from round to elliptical and finally becomes a bowed-down shape in the jet flow downstream under these experimental conditions. This paper includes simple modeling of jet flow MHD stability in a gradient transverse magnetic field, which derives the velocity and the area of the cross section of the jet flow along the flow path. The theoretical expected values are in good agreement with experimental results.

It is important that the magnetohydrodynamic (MHD) flow velocity in the cross section of the junction region of a manifold pipe be related to materials compatibility, heat transfer, and MHD pressure drop. Experimental results are given of the velocity distribution across the circular pipe on the center plane in the region of the junction of a manifold pipe and the MHD pressure drop due to the junction MHD effects. The results show that both the boundary layer and core velocity distribution on the center plane of the cross section of the junction region of the manifold pipe increase with an increase of the Hartmann number M and that the velocity at the boundary is jet flow and in the core is flat flow. However, the approach theory expects the core velocity distribution to decrease with an increase of M and never in jet flow at the boundary layer. For the downstream case, the velocity distribution is strongly affected by the junction of the manifold pipe only in a half area of the cross section and for the upstream case in the whole cross-section area. The factor for MHD pressure drops due to the junction MHD effects is also carried out,more » which explains the experimental data.« less

It is important that magnetohydrodynamic (MHD) flow velocity distribution in the cross section ofa duct be related to materials compatibility, heat transfer, and MHD pressure drop. The first experimental results are given of the velocity distribution across the rectangular duct on the center plane and of the two-dimensional (2-D) MHD pressure drop effect due to the 2-D velocity distribution. The results show that both the boundary and core velocity distributions on the center plane of the duct increase with an increase of the Hartmann number M. However, the approach theory expected the core velocity distribution to decrease with an increase of M. The 2-D effect factor for the MHD pressure drop due to the 2-D velocity distribution was also carried out. This explains why the numerical results of the MHD pressure drop gradient are lower than in the experiments. Theoretical analysis of the 2-D and three-dimensional effects on the velocity distribution and MHD pressure drop is also included.

Liquid metal magnetohydrodynamic (MHD) flows through the electrical coupling rectangular ducts are investigated based on a fully developed modeling. Numerical simulations of four different coupling MHD duct flows are carried out to get the results of the MHD pressure drop and the velocity distribution. The first and second cases are that the coupling rectangular ducts are arranged along the direction of external magnetic field, the flow direction in the two ducts is the same in case 1 but it is opposite in case 2; in the third and fourth cases another coupling duct is extended along the perpendicular direction of the external magnetic field, the flow direction is identical in case 3 but it is opposite in case 4. Numerical results of the velocity and the induced electrical current distributions in the cross sections of the coupling ducts are given in those four different cases, it is indicated that the external magnetic field has a different effect on the flow pattern in those four cases. The MHD pressure drop in those four different cases are compared with the result of one normal rectangular duct flow, the MHD pressure drop of case 1 is reduced compare to the result of one normal duct MHD flows and result of case 4 is almost the same as one normal duct but the results of case 2 and 3 are larger than it, especially in case 2 it is several times larger than the result of one normal duct flow, in addition, the MHD pressure gradient decreases with the increase of the wall conductance ratio. These results are very important and should be considered in the future liquid blanket design.