Hybrid grids

CONSIDERATIONS RELATED TO FINITE ELEMENT MESH GENERATION 195 

It should be emphasized at this point that the basic requirements of compatibility and consistency of finite elements used in the discretization of the domain in a field problem cannot be arbitrarily violated. Therefore, application of the previously described classes of computational grids requires systematic data transfomiation procedures across interfaces involving discontinuity or overlapping. For example, by the use of specially designed mortar elements necessary communication between incompatible sections of a finite element grid can be established (Maday et ah, 1989). 

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Hybrid grids are used for very complex geometries where combination of structured mesh segments joined by zones of unstructured mesh can provide the best approach for discretization of the problem domain. The flexibility gained by combining structured and unstructured mesh segments also provides a facility to improve accuracy of the numerical solutions for field problems of a complicated nature. Figure 6.3 shows an example of this type of computational mesh. 

It was shown that a CFD model with periodicity, hybrid grid and MRF approach can be used for detailed studies on the design and operation of the Outokumpu flotation cell. 

As a result from computational model 1 a hybrid grid for a laboratory size OK flotation cell with unstructured cells in the rotor domain and structured cells in the stator and tank domain was generated. The tank was a cylindrical, unbaffled tank with Outokumpu s rotor-stator mixing device. Computational geometry is shown in figure 8. Geometrical details of the tank are given in table 2. 

The software packages ANSYS 12.0 up to 14.5 were used for the simulation of the air flow at different gas distributors and wheel geometries. Primarily, hybrid grids... 

Flows in 2D or 3D geometries using unstructured solution-adaptive triangular/tetrahedral, quadrilateral/hexahedral, or mixed (hybrid) grids that include prisms (wedges) or pyramids (Both conformal and hanging-node meshes are acceptable.) ... 

To resolve the problems associated with structured and unstructured grids, these fundamentally different approaches may be combined to generate mesh types which partially posses the properties of both categories. This gives rise to block-structured , overset and hybrid mesh types which under certain conditions may lead to more efficient simulations than the either class of purely structured or unstructured grids. Detailed discussions related to the properties of these classes of computational grid.s can be found in specialized textbooks (e.g, see Liseikin, 1999) and only brief definitions are given here. 

Automobile battery grids employ about 1—3 wt % antimony—lead alloys. Hybrid batteries use low (1.6—2.5 wt %) alloys for the positive grids and nonantimony alloys for the negative grids to give reduced or no water loss. The posts and straps of virtually all lead—acid batteries are made of alloys containing about 3 wt % antimony. 

Shaahid SM, El-Amin I, Rehman S, Al-Shehri A, Ahmad F, Bakashwain J. Dissemination of off-grid hybrid wind-diesel-battery power systems for electrification of isolated settlements of hot regions. International Journal of Sustainable Energy. 2007 26(2) 91-105. DOL10.1080/14786450701549873. 

Zhou K Lu W. Self-sustainable off-grid wind power generation systems with hybrid energy storage. In 37th Annual Conference on IEEE Industrial Electronics Society (IECON 2011) 7-10 November 2011 Melbourne, VIC IEEE pp. 3198-3202. DOL10. 1109/IECON. 2011. 6119822. 

Hravshat ES. Off-grid hybrid wind-diesel power plant for application in remote Jordanian settlements. Clean Technologies and Environmental Policy. 2009 11(4) 425-436. 

Chen J, Che Y, Zhao L. Design and research of off-grid wind-solar hybrid power generation systems. In 4th International Conference on Power Electronics Systems and Applications (PESA) 8-10 June 2011 Hong Kong IEEE pp. 1-5. DOLIO. 1109/PESA. 2011.5982922. 

Vick BD, Neal BA. Analysis of off-grid hybrid wind turbine/solar PV water pumping systems. Solar Energy. 2012 86(5) 1197-1207. DOLIO. 1016/j. solener. 2012. 01. 012. 

Brent AC, Rogers DE. Renewable rural electrification Sustainability assessment of mini-hybrid off-grid technological systems in the African context. Renewable Energy. 2010 35(1) 257-265. DOLIO. 1016/j. renene. 2009. 03. 028. 

Morea F, Viciguerra G, Cucchi D, Valencia C. Life cycle cost evaluation of off-grid PV-wind hybrid power systems. In 29th International Telecommunications Energy... 

Bekele G, Tadesse G. Feasibility study of small Hydro/PV/Wind hybrid system for off-grid mral electrification in Ethiopia. Applied Energy. 2012 97 5-15. DOI 10. 

If the battery pack of hybrid vehicles can additionally be charged with electricity from the public electricity grid, the vehicle is called plug-in hybrid. Batteries of plug-in hybrids have to be larger than those of a conventional hybrid vehicle. For short distance trips, plug-in hybrid vehicles can be operated in the electricity-only mode. Plug-in hybrids are not explicitly considered here, but addressed in more detail in Section 7.9. 

Kempton, W. (2007). Vehicle to grid power. IEEE Conference Plug-in Hybrids Accelerating Progress, Washington, DC. www.ieeeusa.org/policy/phev/ presentations/Tutorial%20Kempton.pdf. 

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