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September 27, 2004, 17:32 |
Convergence Difficulty
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#1 |
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Hello,
I am simulating diffusion of chlorine dioxide in a room (as steady state) using CFX 4.4 by solving mass fraction equation. Problem does not converge when the effects of buoyancy are included, but it converges well when the buyoncy effects are diregarded. Any light on this !! . I also tried using QUICK differencing scheme for MASS FRACTION1 but with no success. I am attaching my command file with this post with buoyancy effects commented out. Thanks , Sankalp __________________________________________________ ___ :>CFX4 :>SET LIMITS TOTAL CHARACTER WORK SPACE 5000000 MAXIMUM NUMBER OF PATCHES 20 END :>OPTIONS THREE DIMENSIONS TURBULENT FLOW RECTANGULAR GRID MASS FRACTION EQUATIONS 1 STEADY STATE COMPRESSIBLE FLOW /* BUOYANT FLOW*/ END :>MODEL DATA :>TITLE PROBLEM TITLE 'AIRFLOW IN APARTMENT' END :>PHYSICAL PROPERTIES >>STANDARD FLUID FLUID 'AIR' STANDARD FLUID REFERENCE TEMPERATURE 293.15 END >>COMPRESSIBILITY PARAMETERS UNIVERSAL GAS CONSTANT 8314.0 FLUID MOLECULAR WEIGHT 28.79 END /* >>BUOYANCY PARAMETERS GRAVITY VECTOR 0.0 -9.8 0.0 END */ >>MASS TRANSFER PARAMETERS >>MOLECULAR WEIGHTS MASS FRACTION1 71.5 END >>DIFFUSIVITIES MASS FRACTION1 1.0E-5 END :>SOLVER DATA :>PROGRAM CONTROL MAXIMUM NUMBER OF ITERATIONS 1000 PRESSURE REFERENCE POINT 1 1 1 OUTPUT MONITOR POSITION 1.25 1.25 0.5 MASS SOURCE TOLERANCE 1.0000E-06 END :>MODEL BOUNDARY CONDITIONS :>INLET BOUNDARIES PATCH NAME 'SUPPLY' U VELOCITY 0.1026 K 0.5 EPSILON 3.5 END :>INLET BOUNDARIES PATCH NAME 'DISINFECTANT' V VELOCITY -0.06 K 0.5 EPSILON 3.5 MASS FRACTION1 0.01 END :>STOP |
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