AIM-Simulate the flow over a cylinder and explain the phenomenon of Karman vortex street.

INTRODUCTION:

Ansys Fluent is the industry-leading fluid simulation software known for its advanced physics modeling capabilities and industry leading accuracy.Ansys Fluent gives you more time to innovate and optimize product performance. Trust your simulation results with a software that has been extensively validated across a wide range of applications. With Ansys Fluent, you can create advanced physics models and analyze a variety of fluids phenomena—all in a customizable and intuitive space.

OBJECTIVE:

PART-I

1. Simulate the flow with the steady and unsteady case and calculate the Strouhal Number for Re= 100.

PART-II

1. Calculate the coefficient of drag and lift over a cylinder by setting the Reynolds number to 10,100,1000,10000 & 100000. (Run with steady solver)
2. Discuss the effect of Reynolds number on the coefficient of drag. [ Results should be validated with any standard literature and error should be within 5 %]

PROVIDED DATA FOR ESCH SIMULATION SETUP.

1.COEFFICIENT OF DRAG

2.COEFFICIENT OF LIFT

3.Plots to show vortex shedding behind the cylinder.

THEORY:

In a mixing tee a fluid with 2 different temperature are coming through two inlets and is getting mixed inisde a pipe and the effectiveness of mixing is evaluated on parameters like velocity of cold and hot fluid. Also we perform this study to reach optimum cooling and good mixing. Now let us see the general setup of the experiments. Let us see which viscous model shall we use k-epsilon or k_omega.

FOR Re 10, 100, 1000 WE WILL USE LAMINAR MODEL IN FLUENT .

FOR Re 10000,100000 WE WILL USE k-epsilon MODEL FOR SIMULATION IN ANSYS.

DRAG COEFFICIENT.

LIFT COEFFICIENT.

SETTING UP CONDITION FOR THE MESH AND GEOMETRY IN SPACECLAIM AND MESHING.

MESH SIZE 0.250mm.

CYLINDER DIA 2m.

BOX DIMENSION 20m X 60m.

MESH SIZE IS CONSTANT IN ALL SIMULATION SETUPS.

LET US FIRST SETUP ALL THE BASIC GEOMETRY AND MESHING.

STEP 1- FIRST OPEN SPACE-CLAIM.

STEP 2- SKETCH ON ANY PLANE PREFERABLY CY PLANE AND DRAW A CIRCLE. FROM THERE DRAW CONSTRUCTIONLINE TO DRA THE INLET AT 20m TO LEFT OF CYLINDER AND OUTLET AT 40M TO RIGHT OF CYLINDER.

STEP 3-USE PULL TOOL TO GENERATE THE SURFACE AND THEN DELEAT THE CYLINDER PORTION AND EXIT SPACECLAIM.

STEP 4-NOW ENTER MESHING.

STEP 5- USE THE VALUE OF 250mm TO MINIMIZE THE SIZE OF MESH AND REFINE IT.

STEP 6-INSERT METHOD IN MESH TO TRANSFORM QUADRILATERAL MESH TO TRIANGULAR MESH.

STEP 7-ALSO INSERT SIZING TO CHANGE THE CYLINDER WALL TO SMOOTH LAYER BY ADDING SUITABLE DIVISION.

STEP 8- INSERT INFLATION TO REFINE THE MESH AT THE WALL OF CYLINDER.

STEP 9-THE INFLATION LAYER IS 6 AND GROWTH RATE IS 1.2.

STEP 10- A) SETUP THE METHOD TO LAMINAR FOR Re 10, 100, 1000.

B) SETUP THE MODEL TO k-epsilon FOR Re 10000, 100000.

STEP 11-THE INLET VELOCITIES AND SETUP CONDITIONS ARE GIVEN BELOW.

THE FLUID IN USE IS AIR WITH DENSITY 1.22KG/m^3

THE VISCOCITY OF AIR IS

STEP 12- WE WILL USE A MONITOR POINT AT X=10 AND Y=0 TO MONITOR THE VORTEX FORMATION OTHERWISE KNOWN AS Karman vortex street.

STEP 13-NOW WE WILL MONITOR THE VERTEX AVERAGE FOR VELOCITY AND ALSO PLOT VELOCITY CONTOUR AFTER INITIALIZATION.

STEP 14- NOW FOR STEADY STATE WE WILL JUST HIT CALCULATE FOR APPROXIMATELY 1500 ITERATION AND SEE WHEN THE VORTEX IS FORMED ADN WE WILL CONCLUDE THE STREAM TO CONVERGE WHEN THE PATTERN OF VORTEX BECOMES PERIODIC.

STEP 15- FOR TRANSIENT STEP WE WIL INPUT THE NUMBER OF TIMESTEPS AND SIZE OF TIMETEP AND HIT CALCULATE, IT WILL TAKE A LONG TIME FOR Re 100 TO ACHIEVE THE RESULT.

AFTER CALCULATING WE WILL SAVE THE LIFT AND DRAG COEFFICIENT PLOTS AND NOTE THE AVERAGE VALUES IN EXCEL SHEET.

LET US SEE THE RESULTS FOR STEP 2 FIRST.

FOR Re-10.

THERE IS NO VORTEX FORMATION.

DRAG COEFFICIENT PLOT LIFT COEFFICIENT PLOT

RESIDUAL PLOT

EVIDENCE OF NO VORTEX FORMATION AND CONVERGENCE

FOR Re-100(STEADY STATE)

THERE IS VORTEX FORMATION.

DRAG COEFFICIENT PLOT LIFT COEFFICIENT PLOT

RESIDUAL PLOT

EVIDENCE OF VORTEX FORMATION AND CONVERGENCE

FOR Re-1000(STEADY STATE)

THERE IS VORTEX FORMATION.

DRAG COEFFICIENT PLOT LIFT COEFFICIENT PLOT

RESIDUAL PLOT

EVIDENCE OF VORTEX FORMATION AND CONVERGENCE

FOR Re-10000(STEADY STATE TURBULANT MODEL)

THERE IS VORTEX FORMATION.

DRAG COEFFICIENT PLOT LIFT COEFFICIENT PLOT

RESIDUAL PLOT

EVIDENCE OF VORTEX FORMATION AND CONVERGENCE

FOR Re-100000(STEADY STATE TURBULANT MODEL)

THERE IS VORTEX FORMATION.

LIFT COEFFICIENT PLOT

RESIDUAL PLOT

EVIDENCE OF VORTEX FORMATION AND CONVERGENCE

THE REPORT FOR ALL THE ABOVE IS LISTED BELOW

THE STROUHALL NO GRAPH FOR Re 100 STEADY CASE IS AS FOLLOWS.

TRANSIENT CASE STUDY COULDNOT BE SOLVED AS THE CONVERGENCE AND VORTEX FORMATION WAS NOT HAPENNING EVEN AFTER 96000 ITERATIONS. MY SYSTEM WAS CRASHING ASN WAS STOPPING AND WAS LOOSING ALL RESULTS.

CONCLUSION:

1.THE NUMBER OF ITERATION CONVERGENCE DECREASES AS THE REYNOLDS NO INCREASES.

2.THE COEFFICIENT OF LIFT INCRESES AS THE REYNOLDS NO INCREASES.

3.THE COEFFICIENT OF DRAG INCRESES AS THE REYNOLDS NO INCREASES.

4.VERTEX AVERAGE VELOCITY ALSO INCREASES AS THE rRe INCREASES.

THE WHOLE WORKBENCH FILE IS ABOUT 4.44 GB .PLEASE SUGGEST HOW TO SHARE. I HAVE SHARED THE BASIC FILE.