Calculation on non-orthogonal curvelinear structured grids, finite-volume method
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| + | b^{\phi} = \left( J \Delta \xi \Delta \eta \right) \overline{S}^{\phi}_{P} - \left[ \frac{\Gamma \Delta \eta}{J} \left( \beta \frac{\partial \phi}{\partial \eta} \right) \right]^{e}_{w} - \left[ \frac{\Gamma \Delta \xi}{J} \left( \beta \frac{\partial \phi}{\partial \xi} \right) \right]^{n}_{s} | ||
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| + | </td><td width="5%">(15)</td></tr></table> | ||
Latest revision as of 10:24, 20 August 2010
2D case
For calculations in complex geometries boundary-fitted non-orthogonal curvlinear grids is usually used.
General transport equation is transformed from the physical domain 
into the computational domain 
as the following equation
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![\frac{\partial}{\partial \xi} \left( \rho U \phi \right) + \frac{\partial }{ \partial \eta } \left( \rho V \phi \right) = \frac{\partial}{\partial \xi} \left[ \frac{\Gamma }{J} \left( \alpha \frac{\partial \phi}{\partial \xi} - \beta \frac{\partial \phi}{ \partial \eta} \right) \right] + \frac{\partial}{\partial \eta} \left[ \frac{\Gamma}{J} \left( \gamma \frac{\partial \phi}{\partial \eta} - \beta \frac{\partial \phi}{ \partial \xi} \right) \right] + J S^{\phi}](/W/images/math/3/8/2/382456ea15e881910f1b040f17a347bd.png)
where
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Using the finite volume method the trnsformed equations can be integrated as follows:
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![\left[ \left( \rho U \Delta \eta \right) \right]^{e}_{w} + \left[ \left( \rho V \Delta \xi \right) \right]^{n}_{s} = \left[ \frac{\Gamma \Delta \eta}{J} \left( \alpha \frac{\partial \phi}{\partial \xi} - \beta \frac{\partial \phi}{ \partial \eta} \right) \right]^{e}_{w} + \left[ \frac{\Gamma \Delta \xi}{J} \left( \gamma \frac{\partial \phi}{\partial \eta } - \beta \frac{\partial \phi}{\partial \xi} \right) \right]^{n}_{s} + \left( J \Delta \xi \Delta \eta \right) \overline{S}^{\phi}_{P}](/W/images/math/c/9/b/c9bc323ba9595d8d85677016f4e53536.png)
The convection terms are approximated as described in section http://www.cfd-online.com/Wiki/Discretization_of_the_convection_term .
Diffusion terms are approximated by the second-oder central differencing scheme.
The standard form of the finite volume equation can be obtained as
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where
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![A^{\phi}_{E} = \left(\frac{\Gamma}{J} \alpha \frac{\Delta \eta}{\Delta \xi} \right)_{e} + max \left[ 0, - \left( \rho U \Delta \eta \right)_{e} \right]](/W/images/math/d/d/3/dd391b55e6d5ab853dfb8a363e1ad14e.png)
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![A^{\phi}_{W} = \left(\frac{\Gamma}{J} \alpha \frac{\Delta \eta}{\Delta \xi} \right)_{w} + max \left[ 0, \left( \rho U \Delta \eta \right)_{w} \right]](/W/images/math/0/d/b/0dbf08dd7c67f1ce5b898703ed51ba9e.png)
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![A^{\phi}_{N} = \left( \frac{ \Gamma }{J} \gamma \frac{\Delta \xi}{\Delta \eta} \right)_{n} + max \left[ 0, - \left( \rho V \Delta \xi \right)_{n} \right]](/W/images/math/7/c/1/7c191e197bd433da99e710d3972cb506.png)
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![A^{\phi}_{S} = \left( \frac{ \Gamma }{J} \gamma \frac{\Delta \xi}{\Delta \eta} \right)_{s} + max \left[ 0, \left( \rho V \Delta \xi \right)_{s} \right]](/W/images/math/3/8/3/383089c82dad52e5e81f6a38822a7428.png)
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![b^{\phi} = \left( J \Delta \xi \Delta \eta \right) \overline{S}^{\phi}_{P} - \left[ \frac{\Gamma \Delta \eta}{J} \left( \beta \frac{\partial \phi}{\partial \eta} \right) \right]^{e}_{w} - \left[ \frac{\Gamma \Delta \xi}{J} \left( \beta \frac{\partial \phi}{\partial \xi} \right) \right]^{n}_{s}](/W/images/math/6/7/9/679e9d836ee26246cc251d1718a29333.png)
