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-   -   SIMULATION OFNATURAL CONVECTION :WAVY CHANNEL (2D) (http://www.cfd-online.com/Forums/fluent/50313-simulation-ofnatural-convection-wavy-channel-2d.html)

 AKI January 17, 2009 18:55

SIMULATION OFNATURAL CONVECTION :WAVY CHANNEL (2D)

Hi friends, I am doing simulation of natural convection on 2D wavy curve surface. Please please help me in clearly certain doubts: I am using realisable k-epsilon model 1)The Grash-off number is of 10^9 order ....... can i use turbulent model for this buoyancy convection 2)In define -operating condition - one unchecked block for operating density is there , I am using INCOMPRESSIBLE IDEAL GAS,do i need to check the operatind density box or leave it 3)1)the continuity equation in not converging (over 6000 iterations), which under relaxation factors I need to alter ,should I decrease or increase the under relaxation factors plz tell exactly or atleast their combinations. PLZ PLZ PLZ HELP.

 AKI January 17, 2009 19:09

Re: TRUE CNVERGENCE:TTAL HEATTRANSFER FLUX REPORT

Hi friends, please tell 1)..If the solution has converged , and when the generated flux report of sum of all surface boundaries is nearly equal to zero .Does that necessary mean that a true solution has been obtained....

2)..ALSO DOES THE TOTAL FLUX REPORT FOR ALL SURFACES NEAR TO BE EXACTLY ZERO AFTER CONVERGE OCCURS OR IT CAN BE NEARLY ZERO VALUE,TO INDICATE THAT TRUE SOLUTION HAS BEEN GOT AFTER CONVERGENCE......

3)..IS THE TOTAL FLUX REPORT VALUE HAS TO BE necesarily near zero after converge, or we may have true solution after convergence even total total flux sum across all surface boundary has to be nearly zero.(NO HEAT GENERATION INSIDE) PLZ PLZ TEL REPLY FAST.....

 AKI January 17, 2009 19:24

USING NEW MATERIAL ie.NOT IN THE FLUENT DATABASE

Hi friends I need to you use ASBESTOS material AS WALL in natural covection simulation which is not in the database.

CAN I SIMPLY EDIT THE MATERIAL PROPERTIES OF SAY ALUMINIUM as that of ASBESTOS PROPERTIES and use it in the boundary condition panel (I am using ABSESTOS as wall material . OR, DUE I NEED ANY USER DEFINED CODES FOR THAT ,PLEASE EXPLAIN BECAUSE I DONT HAVE ANY EXPOSURE IN USING UDF YET. PLEASE EXPLAIN OR PLEASE SEND ME THE CODE IF THAT IS REQUIRED IN THIS CASE. PLEASE EXPLAIN OR SEND ME SOME MATERIAL OR LINK HOW TO USE USER DEFINED FUNCTIONS ...aki.mech@gmail.com PLEASE PLEASE REPLY SOON URGENT

 AKI January 17, 2009 19:39

REGARDING CONVERGENCE

please tell IF THE SOLUTION IS NOT GETTING CONVERGED FOR A LONG NUMBER OF ITERATIONS,(((THE FLUX REPORT SHOWING TOTAL SUM OF FLUX ACCROSS THE BOUNDARIES NEARLY EQUAL TO ZERO) DOES THAT MEAN THE SOLUTION HAS CONVERGED OR CORRECT SOLUTION HAS BEEN GOT.

ALSO IN HIS CASE THE TEMPERATURE VALUE OF BOUNDARIES AND THE SURAFACE HEAT CO-EFFICIENTS VARYING VERY VERY SLIGHTLY

DOES THIS MEAN CORRECT SOLUTION

 AKI January 17, 2009 19:50

REVERSE FLOW IN ITERATION REPORT

HI FRIENDS IN NATURAL CONVECTION OVER WAVY CURVE SURFACE, THE BOTTOM WALL BOUNDARY IS AT CONSTANT FLUX WHILE OTHER DOMAIN BOUNDARY ARE PRESSURE INLETS.

PLEASE EXPLAIN WHAT DOES 1>>>.... THE REVERSE FLOW IN THE ITERATION REPORT PHYSICALLY MEAN .IS THERE ANY PROBLEM IS I GET THE REVERSE FLOW IN THE FINAL CONVERGED ITERATION REPORT.. 3>>>....... PLEASE TELL WHAT IS THE PHYSICAL MEANING OF CIRCULAR STREAMLINES, QUITE DENSE AND LOCALISED STREAM LINES AND THE SPARSE STREAMLINES.

PLEASE PLEASE EXPLAIN THEM FROM POINT OF VIEW OF PHYSICS BEHIND THE FLOW ALSO...

 AKI January 17, 2009 19:58

WHICH MODEL TO BE USED GENERALLY

HI FRIENDS I AM SIMULATING NATURAL CONVECTION FLOW

THE GRASHOFF NUMBER IS OF ORDER 10^9 PLEASE TELL WHICH MODEL I SHOULD USE- LAMINAR OR TUBULENT MODELS IN CASE IF I USE TURBULENT MODEL ,WHICH MODEL SHOULD I USE A)...IF I USE TURBULENT MODEL...WHICH ONE B) WHICH WALL TREATMENT OPTION SHOULD I USE... C) WHEN AND WHY SHOULD I USE THE FULL BUOYANCY OPTION .. DOES THAT AFFECTS THE FINAL SOLUTION COMPREHENSIVELY

 AKI January 17, 2009 20:05

FULL BUOYANCY OPTION AND VISCOUS HEATING OPTION

HI FRIENDS IF I AM USING K-EPSILON TURBULENCE MODEL PLEASE TELL WHEN AND WHY TO USE THE FULL BUOYANCY EFFECT OPTION AND THE VISCOUS HEATING OPTION. PLEASE EXPLAIN WHEN TO USE THESE OPTIONS DO I NEED TO USE THE FULL BUOYANCE OPTION IN CASE OF NATURAL CONVECTION..THAT IS DRIVEN BY BUOYANCY

 AKI January 17, 2009 20:12

OPERATING DENSITY AND OPERATING PRESSURE

HI FRIENDS I AM USING A FIXED DOMAIN FOR NATURAL CONVECTION THE EQUATION OF STATE FOR DENSITY IS-----INCOMPRESSIBLE IDEAL GAS

PLEASE TELL ME . A)WHAT VALUE SHOULD I GIVE FOR OPERATING PRESSURE AND THE GUAGE PRESSURE B)SHOULD I NEED TO CHECK THE OPERATING DANSITY VALE BOX WHICH IS IN THE DEFINE - OPERATING CONDITION PANEL IN GENERAL WHEN DO I NEED TO APPLY THEM .PLEASE TELL