## Steady state simulation of flow over a throttle body

OBJECTIVE:- STEADY STATE SIMULATION OF FLOW OVER A THROTTLE BODY .

SOFTWARE USED :-

1. CONVERGE STUDIO:- TO SETUP THE MODEL.

2. CYGWIN:- FOR RUNNING THE SIMULATION.

3. OPENFOAM:- TO VISUALIZE THE DIFFERENT POST-PROCESSED RESULT.

THEORY:-

HERE, WE HAVE DONE SIMULATION OF FLOW OVER A THROTTLE BODY IN STEADY STATE .

PRE-PROCESSING STEPS:-

HERE WE HAVE CONSIDER FOLLOWING THINGS FOR ELBOW IN CONVERGE STUDIO:-

(A) TYPE OF FLUID USED:- GAS(MIXTURE OF BASICALLY OXYGEN AND NITROGEN).

(B) TYPE OF CHANNEL:-

IT IS BASICALLY A THROTTLE BODY WHICH IS IN THE SHAPE OF ELBOW .

• OPEN FROM BOTH SIDE OF ELBOW.
• THROTTLE IS WALL .
• BODY IS WALL .

(C).DIMENSION OF CHANNEL:-

1. DIAMETER OF ELBOW =0.1 m (approx)

2. LENGTH OF ELBOW BODY= 0.0084 m (approx) .

(D).SIZE OF GRID USED:-0.01 FOR LENGTH  AND 0.001 FOR HEIGHT AND BREADTH.

(E). PRESSURE:-

AT INLET, 150000.PASCAL.

AT OUTLET, 100000 PASCAL.

(F). CRITERIA FOR RUNNING SIMULATION :-

1. INTIAL TIME STEP :- 1E-6 SECOND .

2. TIME PERIOD FOR SIMULATION :- 0.01 SECONDS .

3. NUMBER OF CYCLES FOR SIMULATION:- 15000 CYCLES .

(G).  GRID SIZE : - 2 milimeter (FOR ALL DIRECTION i.e LENGTH, BREATH AND HEIGHT) .

HERE , FIXED EMBBEDIING HAVE BEEN USED ON THE THROTTLE BODY.

(H). SOLVER TYPE USED:- PRESSURE BASED (STEADY) .

(I). PRE-PROCESSING STEPS:-

AFTER SETTING UP THE MODEL, WE SENT OUT DATA TO A PARTICULAR LOCATION WHERE ALL THE DETAIL OF CHANNEL IS AVAILABLE REQUIRED BY FURTHER SOFTWARE FOR SIMULATION.

THEN AFTER GENERATING AND STORING THE DATA, WE USED  CYGWIN SOFTWARE WHOSE WORK IS TO RUN SIMULATION.

PROCEDURE FOR RUNNING SIMULATION:-

1. OPEN "CYGWIN" IN COMMAND PROMPT.

2. THEN TRACE THE LOCATION WHERE DATA IS STORED FROM CONVERGE STUDIO.

3. NOW TYPE "converge.exe" FOR SERIES SIMULATION OR "mpiexec.exe -n 4 converge" FOR PARALLEL SIMULATION IN THAT FILE LOCATION.

4. AFTER DOING THIS, SIMULATION WILL START WORKING AND AND WILL STOP AFTER GIVEN NUMBER OF CYCLES (BOTH IMPLICITLY AND EXPLICITLY DEPANDING UPON SIMULATION PERIOD).

5. THIS IS HOW THE WORK OF CYGWIN COMPLETES. AFTER THIS USE POST_CONVERT COMMAND IN OUTPUT FILE IS USED WHICH IS GENERATED BY CYGWIN. IT WILL CONVERT THE GENERATED OUT FILE FROM CYGWIN INTO A COMPATIBLE            FROM WHICH WILL BE EASILY ACCESSED BY THE PARAFOAM.

NOW WE OPEN THE PARAFOAM SOFTWARE FOR POST PROCESSING TO VISUALIZE THE RESULT AND COMPARE IT.

POST-PROCESSING STEPS :-

1. IN OPENFOAM, CLICK ON OPEN FROM FILE MENU FROM DROP-DOWN MENU WHICH IS PRESENT AT TOP-LEFT OF THE SCREEN.

2. SEARCH FOR FILE WHERE FILE IS GENERATED BY POST CONVERT COMMAND AND OPEN IT. REMEMBER IT MUST HAVE ".vtm" DOMAIN AFTER FILE NAME.

3. CLICK ON APPLY, GEOMETRY WILL ORIGINATE. AFTER THIS CLICK ON SLICE OPTION TO SECTION THE GEOMETRY . NOW CLICK ON SURFACE WITH EDGES FROM TOP TOOLBAR OPTIONS . THIS WAY THE MESH WILL GENERATE .

4. AFTER IT, CLICK ON LINE PROBE OPTION TO SEE THE DIFFERNT PHYSICAL QUANTITES AND APPLY IT.

5. IN THIS WAY, THE GRAPH WILL GENERATE AND WE WILL BE SEE DIFFERENT PARAMETERS ACCORDING TO THAT APLLIED LINE PLOT.

6. IN THIS WAY, OUR POST-PROCESSING IS DONE.

MESH GRID  :-

PRESSURE PROFILE :-

HERE WE CAN OBSERVE VARIATION OF PRESSURE ACROSS WHOLE DOMAIN SPECIALLY NEAR THE THROTTLE PART .

PRESSURE IS VARYING ACROSS WHOLE DOMAIN BECAUSE WE HAVE PROVIDED A HUGE DIFFERENCE OF PRESSURE AT BOTH INLET AND OUTLET SECTION . AND SINCE PRESSURE IS DIFFERENT AT BOTH THE SECTIONS , IT IS QUITE REASONABLE   THAT PRESSURE WILL MOVE FROM HIGH PRESSURIC ZONE TO LOW PRESSURIC ZONE .

APART FROM THIS , WE OBSERVE THAT BOTH SHEAR AND NORMAL STRESS IS TAKING PLACE ON THE THROTTLE PART AND REASON FOR THIS STRESS GENERATION IS JUST ACT OF PRESSURE ON THROTTLE PART CAUSED DUE TO PRESSURE   DIFFERENCE BETWEEN BOTH SECTION .

VELOCITY PROFILE :-

HERE THE VELOCITY IS SOMEHOW CONSISTENT THROUGHOUT THE DOMAIN OF ELBOW PIPE WHICH PROVES VELOCITY IS STEADY OR INDEPENDENT OF TIME .

ALSO WE OBSERVED THAT VELOCITY IS LOW AT THROTTLE EDGE BECAUSE HERE THE THROTTLE PART IS OPPOSING THE FLOW OF DIRECTION OF VELOCITY DUE TO WHICH IT IS LOW .

THE VELOCITY IS MINIMUM AT ZONE OF BACK EDGE OF THROTTLE PART AND REASON BEHIND IS THAT THE PART IS ISOLATED FROM THE DIRECTION OF FLOW OF FLUID .

CONVERGE PLOT FOR MASS FLOW RATE:-

HERE , MASS FLOW RATE IS SAME AT BOTH INLET AND OUTLET SECTION OF THE DOMAIN OF ELBOW AND IT IS CONVERGING AT SAME LEVEL FROM BOTH SECTION . HENCE IT PROVES THAT MASS IS CONVERGED IN THE DOMAIN .

ALSO THE MASS FLOW RATE IS SHOWING NO VARIATION IN PLOT (IF WE LEAVE THE SHORT INTIAL PERIOD OF TIME) HENCE WE CAN ALSO SAY THAT MASS IS STEADY .

CONVERGE PLOT FOR VELOCITY :-

HERE VELOCITY IS SAME AT BOTH INLET AND OUTLET SECTION OF ELBOW AND AT BOTH END THE VALUE IS CONVERGING AND VARYING AT SAME LEVEL . HENCE AVERAGE VELOCITY IS BOTH CONVERGED AND CONSISTENT.

ALSO THE VELOCITY IS STEADY OVER THE SPAN OF SIMULATION TIME FOR BOTH THE SECTIONS BECAUSE THROTTLE PART IS AT CONSTANT POSITION DUE TO WHICH FLOW IS SAME AT OULET SECTION TOO. HENCE WE CAN'T SEE ANY CHANGE IN VALUE DUE TO IT'S SAME POSITION .

CONVERGE PLOT FOR PRESSURE :-

HERE IN THE PRESSURE PROFILE PICTURE, WE SEE THAT THERE IS DIFFERENCE BETWEEN THE ACTUAL PRESSURE AND PRESSURE PROVIDED BY US AS BOUNDARY CONDITION AT THE INLET SECTION WHEREAS THE PRESSURE AT OUTLET IS SAME AS WHAT WE HAVE PROVIDED A BOUNDARY CONDITION AT THE OUTLET SECTION .

THE REASON IS QUITE SIMPLE , ACTUALLY THE PRESSURE WHICH WE HAVE PROVIDED IS TOTAL PRESSURE AND WHAT WE ACTUALLY OBTAINING IN PICTURE IS STATIC PRESSURE . HERE AT INLET SECTION, PRESSURE IS DECREASED BELOW THE PRESSURE GIVEN BY US AS A BOUNDARY CONDITION BECAUSE WHEN PRESSURE ENTERS APPLIED BY US , IT GET RESISTED BY THE INTERNAL PRESSURE OF THE THROTTLE BODY AS A RESULT THE NET APPLIED PRESSURE DEGRADES AND WE GET THIS CURTAILED PRESSURE AS STATIC PRESSURE.

WHEREAS , THE PRESSURE AT OULET SECTION IS SAME WHAT HAVE PROVIDED BECAUSE THERE IS NO RESISTANCE AT OUTLET AS AT INLET DUE TO WHICH THE NET RESISTANCE REMAINS AS TOTAL PRESSURE IN THE FORM OF STATIC PRESSURE AND WE SEE NO SUCH DIFFERENCE HERE AT OUTLET .

CONVERGE PLOT FOR TOTAL CELL COUNT :-

HERE THE CELL COUNT IS 16000 WHICH MEANS THAT THE TOTAL GRID POINT IN MESH IS 16000 WHICH IS DIVIDED INTO FOUR RANKS WHICH MEANS SIMPLY PROCESSOR (FOUR) .

THE TOTAL GRID POINT IN DOMAIN IS DIVIDED AMONG PROCESSORS WHERE THE GRID POINT IS ASSIGNED TO EACH PROCESSOR ACCORDING TO IT'S POWER .

HERE TOTAL CELL COUNT IS CONSTANT ALL OVER SIMULATION TIME OR STEADY BEACUSE THERE IS NO THROTTLE MOVEMENT HENCE DUE TO WHICH MESH POINTS RELATED TO IT ALSO REMAIN STEADY WHICH REFLECTS BACK IN CELL COUNTS AND ALSO DEPICTED IN THE PLOT .

ANIMATION OF FLOW THROUGH THROTTLE BODY IN ELBOW PIPE IN TERMS OF PRESSURE :-

ANIMATION OF FLOW THROUGH THROTTLE BODY IN ELBOW PIPE IN TERMS OF VELOCITY :-

HERE IN BOTH CASE , YOU CAN SEE THAT TROTTLE IS STEADY IN BOTH CASE(PRESSURE AND VELOCITY) BECAUSE THROTTLE HAVE BEEN PUT ON STEADY IN BOTH CASE.

SO HERE ONLY WHAT CAN WE SEE HERE IS THAT FLOW WILL SIMPLY COME IN AND MOVE OUT FROM OUTLET WITHOUT ANY DISTURBENCE ..

SINCE IT IS A STEADY CASE , IT IS VERY DIFFICULT TO PREDICT OUT MUCH DIIFFERENCE IN PROFILE IN THE ANIMATION  AND OTHER REASON IS THAT MOTION OF FLUID IS TOO FURIOUS .

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