[jeevan]

can anyone help me out how to start for creating a mixing tank model with impeller, i am new to cfd.

thanks in advance.

[vidhya]

hi,
i am also new to cfd..
still you can start by first designing the geometry in design modeller or importing a cad geometry..
u have to create two domains if u ought to design a tank with impeller. one is the stationary tank domain and the other is the rotating domain for impeller.
no tutorials wil be available for these. so u can go through some of basic to know about all the tools available if u are using ansys design modeller..
by the way what cfd package are u using?
i can help u out with the steps if its design modeller...

[jeevan]

thank u vidhya for your reply..

i will explain what i have done. i considered a rectangular tank with rectangular blade inside..i modeled and imported to icem cfd for meshing..
how do i start abt it for meshing. i want the blade to rotate simulating the mixing..

waiting for your reply..

[vidhya]

hi jeevan,
the best way to start is to learn the tutorials of 3d pipe junction and pipe blade... if u want to simulate and see ur results then tetra meshing will be the easiest though its nt very accurate..

and meshing has nothing to do with the blade rotating.. you will define all that in the fluent or cfx whichever software u use.. meshing is mainly to discretise the whole geometry into small volumes so tat the equations are solved in all the control volumes..

actuallly the easiest way to start with hexa or tetra meshing is to do meshing separately for tank and impeller...
cos tank is stationary domain.. and impeller is another (rotating)..
so u first export ur geometry to icem cfd.. define parts individually like baffles, shaft, periodicity, interface and all that.. yu can refer mixing tank simulation tutorials so that u will get an idea about different parts to be defined..
u can delete the impler domain.. (blades, hub)
similarly for impeller meshing, delete tank domain and mesh separately..
this is how we go about it... hope u can understand..

[jeevan]

hi vidhya,
let me put wat i understood,

first i will mesh the tank removing the blade by a block with o grid..then i will take another block and mesh the blade alone.. so i will have 2 bodies with 2 meshes...is that what u meant.

[vidhya]

yeh,
by the way i dont know if u had created a domain around your blade or not...
for ur reference see this..
this is how ur pic should luk like... an eg..
now see in the pic..
the two domains..
blade should be inside a domain..
then as u understood carry on with meshing
good luck...

[jeevan]

hi vidhya,
thanks for the reply...i saw those images...how do i create domains...i dont know the domain concept...i will upload the geometry pic...have a look..

[vidhya]

wel i dont get how u had exactly designed ur blade..
see u can create domains by using extrude options..
i guess u had used only ansys.. create a circle around the blade (close enuf so that there wont be changes in the equation values once it is solved in solver) and use extrude option=> cut material.. then again use extrude=>add frozen.. this will help u create a domain around ur blade..
why we use domain is... see u cant solve equations in ur blade as it is rotating.. like we normally use multiple reference frame model..
so for tank which is stationary jus assume like u stand in tank and monitor the variables in each cell(mesh)..
same way in impeller.. if u create a domain and assign same rotation speed for it as that of the blade then it will be like u standing in the domain and watching the blade..
so what happens... domain also rotates, blade also rotates.. so it will stationary to u.. so equations can be easily solved. that is why we create domains around blades.
now hope u understood y we create domains.
and rectangle also create using extrude option=>add material.
then it will be easy for u.
good luck

[jeevan]

thnk u vidhya,

sorry that i couldn't reply...let me try and get back to you...

[gajendra]

I am using ansys 13.