How do I set a particle injection rate at a frequency less other then every time step in a transient simulation?
In this case, particles are not injected at every time step, but are injected at every nth timestep or some other frequency. In order to accomplish this, the particle mass flow rate should be specified as a function of time using an expression ( step function will have to be used ), and then set the number of particles per unit time dependent on the mass flow rate. (That is why this option exists.) Alternatively, you may wish to use a particle injection region with User Fortran. For example, if we are running a transient case with time step of 0.01 [s] and we want a particle to be injected at t = 0.1 [s] and t = 0.2 [s] the setup would appear as follows: ##------------------------------------------------------------------------------ # # Creating an expression to turn the particle injection on and off # ##------------------------------------------------------------------------------ LIBRARY: CEL: EXPRESSIONS: particle mass flow = 0.0037418 [kg/s]* (step((t-0.099[s])/1[s])*step((0.101[s]-t)/1[s]) +step((t-0.199[s])/1[s])*step((0.201[s]-t)/1[s]))total time = 0.5[s] tstep = 0.01 [s] END END END ##------------------------------------------------------------------------------ # # Using the CEL expression for particle mass flow: # particle mass flow = 0.0037418 [kg/s] @ t = 0.01 [s], 0.02 [s] # otherwise, particle mass flow = 0 [kg/s] # # Note 0.0037418 kg/s is equivalent to 100 copper particles per second. # ##------------------------------------------------------------------------------ FLOW: SIMULATION TYPE: Option = Transient INITIAL TIME: Option = Automatic with ValueTime = 0 [s] END TIME DURATION: Option = Total Time Total Time = total time END TIME STEPS: Option = Timesteps Timesteps = tstep END END DOMAIN: Domain 1 Domain Type = Fluid Fluids List = Water Particles List = Copper BOUNDARY: In1 Boundary Type = INLET Location = in1 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Normal Speed = 1 [m s^-1] Option = Normal Speed END TURBULENCE: Option = Medium Intensity and Eddy Viscosity Ratio END END FLUID: CopperBOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = Zero Slip Velocity END PARTICLE MASS FLOW RATE: Mass Flow Rate = particle mass flow END PARTICLE POSITION: Option = Uniform Injection ##------------------------------------------------------------------------------ # # One particle will be injected: # Since there will be 100 injection points per kg: # - when the flow rate is 0 kg/s, there will be no injection points # - when the flow rate is 0.0037418 kg/s, at a timestep of 0.01 [s] # 3.7418e-5 kg will be injected. So the number of injection points will be # 100 points/kg * 3.7148e-5 kg = 0.0037148 injection points. Since the # number of injection points is rounded up to the nearest integer, # a value of 1 is assigned to the number of injection point. # ##------------------------------------------------------------------------------ NUMBER OF POSITIONS: Number per Unit Time and Mass Flow Rate = 100 [kg^-1] Option = Proportional to Mass Flow Rate END END END END END BOUNDARY: Outlet Boundary Type = OUTLET Location = outBOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Average Static Pressure Relative Pressure = 0 [Pa] END PRESSURE AVERAGING: Option = Average Over Whole Outlet END END END FLUID: Copper FLUID MODELS: MORPHOLOGY: Option = Dispersed Particle Transport Fluid ##------------------------------------------------------------------------------ # # 1 [mm] particle injected # ##------------------------------------------------------------------------------ PARTICLE DIAMETER DISTRIBUTION: Diameter = 1 [mm] Option = Specified Diameter END END END END END END |
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