《CFX5.5培训资料》（英文版）Boundary and Initial Conditions

CFX! Boundary and initial conditions CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-1 Boundary and Initial Conditions

CFX! Introduction Boundary conditions are required to set on all external domain boundaries Initial values/guess are required to set for all calculations Boundary conditions and initial values/guess can be either constants or expressions CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-2 Introduction Boundary conditions are required to set on all external domain boundaries Initial values/guess are required to set for all calculations Boundary conditions and initial values/guess can be either constants or expressions

CFX! Boundary conditions Default external boundary condition: adiabatic, no-slip wall Available boundary conditions: Inlets Outlets Openings Walls Symmetry Planes Periodic Pairs (ggi Periodic not support with Multi-phase flows) It is generally possible to specify different type options for different fluids on the same boundary condition with the same general boundary condition type CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-3 Boundary Conditions Default external boundary condition: adiabatic, no-slip wall Available boundary conditions: > Inlets > Outlets > Openings > Walls > Symmetry Planes > Periodic Pairs (GGI Periodic not support with Multi-phase flows) It is generally possible to specify different type options for different fluids on the same boundary condition with the same general boundary condition type

CFX! Boundary Condition Forms(single-phase) Actio Object Fluid Boundary Method New Existing Fluid Boundaries Specify name (will be referred to in post-processor) Domains Select boundary condition type Specify boundary condition values Type(nlet Refer Coordinate Frame Select surfaces on which to apply the boundary condition Auto Execute A CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-4 Boundary Condition Forms (single-phase) Specify name (will be referred to in post-processor) Select boundary condition type Select surfaces on which to apply the boundary condition Specify boundary condition values

CFX制 Boundary conditions a sample values form a Boundary Condition Values Flow Regime Values change according to bc type Mass and Momenturm Inlet- speed/velocity Normal Speed in pressure, mass flow Wall-No slip, free slip Turbulence moving, counter rotating, wall roughness rHeat Transfer Static Temperature pening -velocity, pressure Temperature K Also specify additional variables and mcF/2-Phase settings Some options governed b Additional variables domain settings Expression Editor CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-5 Boundary Conditions A sample values form Values change according to BC type Inlet - speed/velocity, pressure, mass flow Wall - No slip, free slip, moving, counter rotating, wall roughness Opening - velocity, pressure Also specify additional variables and MCF/2-Phase settings Some options governed by domain settings

FXI Boundary Conditions(multi-phase) Action 网回区 Component Detais for Fluid, mixture Fluid Boundary New Fluid Components Existing Fluid Boundaries VaL V Mass fraction Boundary Condition values Close Flow Regime Subsonic Mass and Momentum efer Coordinate Frame Normal Sp Coordi Val. V Normal Speed in values Default Intensity and Autocompute Length Scale List Edtor Auto Execute Additional variable Apply Close Expression Edtor CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-6 Boundary Conditions (multi-phase)

CFX! Inlet/outlet Bounday Condion Va油s Inlets/outlets Flow is allowed into domain for inlet or out of domain for outlet Artificial walls are built to Dfat identy wo Au carere Leram scaw prevent reverse flow Hea Transter Need to specify some of the E:tc lemerre following quantities at the inlet velocity, total/static pressure, mass flow rate, temperature turbulent quantities, additional scalars. mass fractions and a Boundary Condition Values volume fractions Flow Rear For rotating frame of reference Subsonic all velocities are in rotating Mass and Momentum Notmal Speed frame(except for the case when esian Velocity Component Val v total pressure in stationary Average Static Pressute frame is specified along with dose xpression Ector velocity component direction) CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-7 Inlet/Outlet Inlets/Outlets - Flow is allowed into domain for inlet or out of domain for outlet - Artificial walls are built to prevent reverse flow - Need to specify some of the following quantities at the inlet: velocity, total/static pressure, mass flow rate, temperature, turbulent quantities, additional scalars, mass fractions and volume fractions - For rotating frame of reference all velocities are in rotating frame (except for the case when total pressure in stationary frame is specified along with velocity component direction)

CFX! Degassing Outlet for Multi-phase Mixed boundary conditions are required to account for simulations where one fluid may flow out ofor Flow Regime into the domain through the Subsonic boundary but other fluids may not - Flow specifcation This is a typical requirement of bubble column applications where gas extraction occurs at a boundary c」 Expression E-」 Some settling and filtration applications require addition or removal of a continuous phase from a dispersed phase In practice, the boundary may be treated as an inlet or outlet for those fluids may move across the boundary, and a no flow boundary for those that may not CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-8 Degassing Outlet for Multi-phase Mixed boundary conditions are required to account for simulations where one fluid may flow out of or into the domain through the boundary but other fluids may not This is a typical requirement of bubble column applications where gas extraction occurs at a boundary Some settling and filtration applications require addition or removal of a continuous phase from a dispersed phase In practice, the boundary may be treated as an inlet or outlet for those fluids may move across the boundary, and a no flow boundary for those that may not

CFX! Opening BOundarycOndition Values 二回区 Openings Flow Regime Mixed flow permitted Mass and Momentum pecified pressure deemed total when flow is in Specified pressure deemed ow Direction Normal to Boundary static when flow is out Loss Coefficient Can also specify cartesian T Specify Loss Coefficient velocity components Turbulence Default Intensity and Autocompute Length Scale Useful when the exact flow Heat Transfer conditions are unknown Static Temperature Temperature Addtional variables Expression Editor CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-9 Opening Openings - Mixed flow permitted - Specified pressure deemed total when flow is in - Specified pressure deemed static when flow is out - Can also specify Cartesian velocity components - Useful when the exact flow conditions are unknown

CFX! Wall Wall type Boundary Condition Values External surface Wall Type Internal thin surface Exterior Wall Wallinfluence on flow Wall Influence On Flow no-slip(stationary) Wall Roughness no-slip(moving) Smooth Wal free slip Heat Transfer Wall Roughness Adiabatic V Smooth wall Rough wall Componerts Roughness height Additional Variables Conditions on temperature field adiabatic Close Expression Editor fixed temperature fixed heat flux convection coefficient and ambient temperature CFX5.5 V5.5.1H 2001AEA Technology

CFX 5.5 V5.5.1H © 2001AEA Technology 6-10 Wall Wall type - External surface - Internal thin surface Wall influence on flow - no-slip (stationary) - no-slip (moving) - free slip Wall Roughness - Smooth wall - Rough wall > Roughness height Conditions on temperature field - adiabatic - fixed temperature - fixed heat flux - convection coefficient and ambient temperature