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Old   March 6, 2016, 04:51
Default particles leave domain
  #1
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Hello,

why are some particles leaving the domain (see image)

Cheers,

Steffen
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File Type: gif particles.gif (56.0 KB, 86 views)
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Old   March 6, 2016, 18:29
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Glenn Horrocks
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I have no idea. If you explain what you are doing we might have some idea of how to help you.

Please post your CCL and a image of your geometry.
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Old   March 7, 2016, 05:13
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I just want to simulate the particle travelling time. Seems some times they dont interact with the geometry, sometimes they do
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File Type: zip particles fly out.zip (6.2 KB, 7 views)
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Old   March 7, 2016, 05:19
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sorry, I don't open *.zip files from random people from the internet
Did you set the boundary conditions correctly to that surface at the bottom?
Please paste your ccl in an [CODE]-Environment
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Old   March 7, 2016, 05:26
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FLOW: Flow Analysis 1
SOLUTION UNITS:
Angle Units = [rad]
Length Units = [m]
Mass Units = [kg]
Solid Angle Units = [sr]
Temperature Units = [K]
Time Units = [s]
END
ANALYSIS TYPE:
Option = Transient
EXTERNAL SOLVER COUPLING:
Option = None
END
INITIAL TIME:
Option = Automatic with Value
Time = 0 [s]
END
TIME DURATION:
Option = Total Time
Total Time = 15 [s]
END
TIME STEPS:
Option = Timesteps
Timesteps = 3 [s]
END
END
DOMAIN: Default Domain
Coord Frame = Coord 0
Domain Type = Fluid
Location = B460
BOUNDARY: Default Domain Default
Boundary Type = WALL
Location = F462.460,F463.460,F464.460
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
FLUID: particle
BOUNDARY CONDITIONS:
PARTICLE WALL INTERACTION:
Option = Equation Dependent
END
VELOCITY:
Option = Restitution Coefficient
Parallel Coefficient of Restitution = 1
Perpendicular Coefficient of Restitution = 0.8
END
END
END
END
BOUNDARY: Default Domain Inlet
Boundary Type = INLET
Location = Inlet
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Mass Flow Rate = 7 [kg s^-1]
Mass Flow Rate Area = As Specified
Option = Mass Flow Rate
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
FLUID: particle
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Normal Speed = 0.172 [m s^-1]
Option = Normal Speed
END
PARTICLE MASS FLOW RATE:
Mass Flow Rate = 0.1 [kg s^-1]
END
PARTICLE POSITION:
Option = Uniform Injection
Particle Locations = Equally Spaced
NUMBER OF POSITIONS:
Number per Unit Time = 100 [s^-1]
Option = Direct Specification
END
END
END
END
END
BOUNDARY: Default Domain Outlet
Boundary Type = OUTLET
Location = Outlet
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Average Static Pressure
Pressure Profile Blend = 0.05
Relative Pressure = 0 [Pa]
END
PRESSURE AVERAGING:
Option = Average Over Whole Outlet
END
END
END
BOUNDARY: Default Domain Symmetrie
Boundary Type = SYMMETRY
Location = Symmetrie
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Option = Stationary
END
MESH DEFORMATION:
Option = None
END
REFERENCE PRESSURE:
Reference Pressure = 1 [atm]
END
END
FLUID DEFINITION: Fluied 1
Material = Water
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID DEFINITION: particle
Material = Water
Option = Material Library
MORPHOLOGY:
Option = Dispersed Particle Transport Solid
PARTICLE DIAMETER DISTRIBUTION:
Maximum Diameter = 2 [mm]
Mean Diameter = 1.5 [mm]
Minimum Diameter = 1 [mm]
Option = Normal in Diameter by Mass
Standard Deviation in Diameter = 0.25 [mm]
END
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
FLUID: particle
EROSION MODEL:
Option = None
END
PARTICLE ROUGH WALL MODEL:
Option = None
END
END
HEAT TRANSFER MODEL:
Fluid Temperature = 25 [C]
Option = Isothermal
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = k epsilon
END
TURBULENT WALL FUNCTIONS:
Option = Scalable
END
END
FLUID PAIR: Fluied 1 | particle
Particle Coupling = One-way Coupling
MOMENTUM TRANSFER:
DRAG FORCE:
Option = Schiller Naumann
END
PRESSURE GRADIENT FORCE:
Option = None
END
TURBULENT DISPERSION FORCE:
Option = None
END
VIRTUAL MASS FORCE:
Option = None
END
END
END
INITIALISATION:
Option = Automatic
INITIAL CONDITIONS:
Velocity Type = Cartesian
CARTESIAN VELOCITY COMPONENTS:
Option = Automatic with Value
U = 0 [m s^-1]
V = 0 [m s^-1]
W = 0 [m s^-1]
END
STATIC PRESSURE:
Option = Automatic with Value
Relative Pressure = 0 [Pa]
END
TURBULENCE INITIAL CONDITIONS:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
END
PARTICLE INJECTION REGION: Particle Injection Region 1
Coord Frame = Coord 0
FLUID: particle
INJECTION CONDITIONS:
INJECTION METHOD:
Option = Cone
CONE DEFINITION:
Injection Centre = 2 [m], 0 [m], -0.25 [m]
Inner Radius of Injection Plane = 2 [cm]
Option = Ring Cone
Outer Radius of Injection Plane = 5 [cm]
INJECTION DIRECTION:
Injection Direction X Component = -2
Injection Direction Y Component = 0
Injection Direction Z Component = 0
Option = Cartesian Components
END
END
INJECTION VELOCITY:
Cone Angle = 1 [deg]
Injection Velocity Magnitude = 0.172 [m s^-1]
Option = Velocity Magnitude
END
NUMBER OF POSITIONS:
Number per Unit Time = 100 [s^-1]
Option = Direct Specification
END
END
PARTICLE DIAMETER DISTRIBUTION:
Diameter = 1 [mm]
Option = Specified Diameter
END
PARTICLE MASS FLOW RATE:
Mass Flow Rate = 0.007 [kg s^-1]
END
END
END
END
END
OUTPUT CONTROL:
EXPORT RESULTS: Export Results 1
Option = Particle Track Data
EXPORT FORMAT:
Filename Prefix = particle track
Option = CFX CSV
END
EXPORT FREQUENCY:
Option = Every Timestep
END
EXPORT TRACK DATA:
Option = Selected Variables
Output Boundary = Default Domain Outlet
Output Variables List = particle.Particle Time
Particle Definition = particle
END
END
PARTICLE TRACK FILE:
Keep Track File = On
Option = Specified Time Spacing
Track File Format = Formatted
Track Printing Interval = 1
Track Time Spacing = 20 [s]
END
RESULTS:
File Compression Level = Default
Option = Standard
END
TRANSIENT RESULTS: Transient Results 1
File Compression Level = Default
Option = Standard
OUTPUT FREQUENCY:
Option = Timestep Interval
Timestep Interval = 0
END
END
TRANSIENT RESULTS: Transient Results 2
File Compression Level = Default
Option = Standard
OUTPUT FREQUENCY:
Option = Timestep Interval
Timestep Interval = 1
END
END
TRANSIENT RESULTS: Transient Results 3
File Compression Level = Default
Option = Standard
OUTPUT FREQUENCY:
Option = Every Timestep
END
END
END
SOLVER CONTROL:
Turbulence Numerics = First Order
ADVECTION SCHEME:
Option = High Resolution
END
CONVERGENCE CONTROL:
Maximum Number of Coefficient Loops = 20
Minimum Number of Coefficient Loops = 1
Timescale Control = Coefficient Loops
END
CONVERGENCE CRITERIA:
Residual Target = 1.E-4
Residual Type = RMS
END
PARTICLE CONTROL:
PARTICLE INTEGRATION:
Maximum Particle Integration Time Step = 1.0E10 [s]
Option = Forward Euler
END
PARTICLE SOURCE SMOOTHING:
Option = Smooth
END
PARTICLE TERMINATION CONTROL:
Maximum Number of Integration Steps = 2000
Maximum Tracking Distance = 15 [m]
Maximum Tracking Time = 17 [s]
END
END
TRANSIENT SCHEME:
Option = Second Order Backward Euler
TIMESTEP INITIALISATION:
Option = Automatic
END
END
END
END
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Old   March 7, 2016, 05:28
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the other bit would have been the step file
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Old   March 7, 2016, 06:25
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Your simulation time step is 3s and you have no limit to the particle tracking time step. Have you tried reducing either of these numbers?
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Old   March 7, 2016, 06:39
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And do you have a reason why you have set 20 as the 'Maximum Number of Coefficient Loops'? That seems quite high to me. Suggested is usually 3-5. Sometimes you need 10.
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Old   March 7, 2016, 07:01
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I guess its the time step, if thats a snapshot in time, the particles will not find the wall. Just wanted to reduce computing time and file size.
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Old   March 7, 2016, 17:19
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If you set the time step size to keep the file size to a minimum then you are completely on the wrong track.

Time step size must be set from the results of a sensitivity analysis where you determine what time step size you need. Likewise convergence tolerance and mesh resolution. Otherwise the result you get are rubbish. And the computing time and file size gets to whatever size it needs to, and you just need to make sure you have a computing system big enough to handle it.
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