Chpter20通用多相流模型(General Multiphase Models) 打印稿(7)

2． Select none if the secondary phase has the same velocity as the primary phase (i.e., no slip velocity).

3． Select user-defined to use a user-defined function for the slip velocity. See the separate UDF Manual for details. 20.6.10定义欧拉模型中的相（Defining Phases for the Eulerian Model）

在欧拉多相流计算中为主相和第二相指定必要的信息和它们的相互作用的说明由下面给出。 Defining the Primary Phase

在欧拉多相流计算中定义主相的步骤与在VOF计算中相同。详细内容见Section 20.6.8.

Defining a Non-Granular Secondary Phase

在欧拉多相流计算中定义非颗粒（即液体或气体）第二相的步骤如下： 1． Select the phase (e.g., phase-2) in the Phase list.

2． Click Set..., and the Secondary Phase panel (Figure 20.6.8) will open.

Figure 20.6.8: The Secondary Phase Panel for a Non-Granular Phase

3． In the Secondary Phase panel, enter a Name for the phase.

4． Specify which material the phase contains by choosing the appropriate material in the Phase Material drop-down

list. 5． Define the material properties for the Phase Material, following the same procedure you used to set the material

properties for the primary phase (see Section 20.6.8). 6． In the Secondary Phase panel, specify the Diameter of the bubbles or droplets of this phase.You can specify a

constant value, or use a user-defined function. See the separate UDF Manual for details about user-defined functions. 7． Click OK in the Secondary Phase panel.

Defining a Granular Secondary Phase

在欧拉多相流计算中定义颗粒第二相的步骤如下：

1． Select the phase (e.g., phase-2) in the Phase list.

2． Click Set..., and the Secondary Phase panel (Figure 20.6.9) will open.

Figure 20.6.9: The Secondary Phase Panel for a Granular Phase

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3． In the Secondary Phase panel, enter a Name for the phase.

4． Specify which material the phase contains by choosing the appropriate material in the Phase Material drop-down

list. 5． Define the material properties for the Phase Material, following the same procedure you usedgranular phase

(which must be placed in the fluid ma to set the material properties for the primary phase (see Section 20.6.8). For a terials category, as mentioned in Section 20.6.1), you need to specify only the density; you can ignore the values for the other properties, since they will not be used. 6． In the Secondary Phase panel, specify the following properties of the particles of this phase: Diameter

指定颗粒的直径。 You can select constant in the drop-down list and specify a constant value, or select user-defined to use a user-defined function. See the separate UDF Manual for details about user-defined functions. Granular Viscosity

指定颗粒的颗粒粘度的运动部分（?s,kinin Equation 20.4-50）。You can select constant (the default) in the drop-down list and specify a constant value, select yamlal-obrien to compute the value using Equation 20.4-52, select gidaspow to compute the value using Equation 20.4-53, or select user-defined to use a user-defined function. Granular Bulk Viscosity

specifies the solids bulk viscosity (?qin Equation 20.4-8). You can select constant (the default) in the drop-down list and specify a constant value, select lun-et-al to compute the value using Equation 20.4-54, or select user-defined to use a user-defined function. Frictional Viscosity

specifies a shear viscosity based on the viscous-plastic flow (?s,frin Equation 20.4-50). By none in the drop-down list. If you want to include the fric default, the frictional viscosity is neglected, as indicated by the default selection of tional viscosity, you can select Equation constant and specify a constant value, select schaeffer to compute the value using 20.4-55, or select user-defined to use a user-defined function. Angle of Internal Friction

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s

specifies a constant value for the angle ?used in Schaeffer's expression for frictional viscosity (Equation 20.4-55). This parameter is relevant only if you have selected schaeffer or user-defined for the Frictional Viscosity. Packing Limit

specifies the maximum volume fraction for the granular phase (?s,max). For monodispersed spheres the packing limit is about 0.63, which is the default value in FLUENT. In polydispersed cases, however, smaller spheres can fill the small gaps between larger spheres, so you may need to increase the maximum packing limit. 7． Click OK in the Secondary Phase panel.

Defining the Interaction Between Phases

对颗粒和非颗粒流动，你必须指定在动量交换系数的计算中使用的曳力函数。对颗粒流，你也必须指定颗粒碰

撞的归还系数（restitution coefficients）。为颗粒和非颗粒流动包含可选的升力和虚拟质量力（下面描述）也是可能的。

为指定这些参数，click Interaction... to open the Phase Interaction panel (Figure 20.6.10).

Figure 20.6.10: The Phase Interaction Panel for the Eulerian Model

Specifying the Drag Function

FLUENT允许你为一对相指定曳力函数，步骤如下：

1．Click the Drag tab to display the Drag Function inputs. 2. 对每一对相，从下面相应的列表中选择合适的曳力函数。

（1） Select schiller-naumann to use the fluid-fluid drag function described by Equation 20.4-19. The Schiller and

Naumann model is the default method, and it is acceptable for general use in all fluid-fluid multiphase calculations.

（2） Select morsi-alexander to use the fluid-fluid drag function described by Equation 20.4-23. The Morsi and

Alexander model is the most complete, adjusting the function definition frequently over a large range of Reynolds numbers, but calculations with this model may be less stable than with the other models. （3） Select symmetric to use the fluid-fluid drag function described by Equation …… 此处隐藏：8605字，全部文档内容请下载后查看。喜欢就下载吧 ……