[Falcon35]

How can i get velocity profile on a flat plate with FLUENT like this ?

[CeesH]

LIke mentioned before, set up lines normal to the surface at the locations you want to plot, and plot the x-velocity vectors on those lines

Cheers,
Cees

[Falcon35]

Originally Posted by CeesH

LIke mentioned before, set up lines normal to the surface at the locations you want to plot, and plot the x-velocity vectors on those lines

Cheers,
Cees

i did it but i get this nonsense thing ? :/

[CeesH]

well, I wouldn't worry too much about the plot itself. more about your results; why is there a peak in your velocity profile? Discretization schemes maybe?

Regarding the plot, you apperantly want a vector plot rather than an x-y plot. That can be done. Use graphics and animations > vectors rather than reports > plot. Think about the length of your line too, because you now plot a large part of the bulk which compresses the boundary layer. Doesn't mean the plot is wrong, but it compromises clarity.

[Falcon35]

Originally Posted by CeesH

well, I wouldn't worry too much about the plot itself. more about your results; why is there a peak in your velocity profile? Discretization schemes maybe?

Regarding the plot, you apperantly want a vector plot rather than an x-y plot. That can be done. Use graphics and animations > vectors rather than reports > plot. Think about the length of your line too, because you now plot a large part of the bulk which compresses the boundary layer. Doesn't mean the plot is wrong, but it compromises clarity.

i got this now , what didn't happen again ?

[CeesH]

that's a contour plot. Not a vector plot. Also, this is on the whole body, not just on the lines you made.

[Falcon35]

Originally Posted by CeesH

that's a contour plot. Not a vector plot. Also, this is on the whole body, not just on the lines you made.

then how can i do it vector plot ? i pushed vector plot ?

[CeesH]

graphics and animations menu, option 3 is 'vectors'. Click this one, and select the created lines as plot regions

[Falcon35]

Originally Posted by CeesH

graphics and animations menu, option 3 is 'vectors'. Click this one, and select the created lines as plot regions

okay i got it now how can i zoom it ? i pushed zoom button but it doesn't work, plot seems so small so how can i got 0,99 Uinlet velocity from this plot ?

[CeesH]

You can't zoom in. What you can do is make new lines, which have a short y-component - close to what you expect the boundary layers to be.

Edit: sorry, of course you can zoom in using the zoom tool in the top menu. My bad.

[Falcon35]

Originally Posted by CeesH

You can't zoom in. What you can do is make new lines, which have a short y-component - close to what you expect the boundary layers to be.

i got it and someone got it why ?

[CeesH]

because you are plotting over the whole domain height. You need to make a line that doesn't extend all the way from top to bottom, but instead only to say, Y = 2D where D is the estimated boundary layer thickness.

[Falcon35]

Originally Posted by CeesH

because you are plotting over the whole domain height. You need to make a line that doesn't extend all the way from top to bottom, but instead only to say, Y = 2D where D is the estimated boundary layer thickness.

then which type line should i plot ? i plotted from bottom to top ?

[CeesH]

make a new line/rake, and enter the x and y coordinates you want.

for x, maybe you want L/2 again?
for y, take 0 to some that is more in line with the size of the boundary layer. Maybe something like H/10, where H is the total height in the y-direction

[Falcon35]

Originally Posted by CeesH

make a new line/rake, and enter the x and y coordinates you want.

for x, maybe you want L/2 again?
for y, take 0 to some that is more in line with the size of the boundary layer. Maybe something like H/10, where H is the total height in the y-direction

i did it and i got it this time ...

Why couldn't i get this again ?

[CeesH]

If you use the + button on the screen now to zoom your view?

click on the zoom icon, and draw a box around the profile you made.


(sorry, when I said 'you can't zoom' before, I meant you cannot plot only the boundary layer piece. of course you can still zoom the view; my mistake)

[Falcon35]

Originally Posted by CeesH

If you use the + button on the screen now to zoom your view?

click on the zoom icon, and draw a box around the profile you made.


(sorry, when I said 'you can't zoom' before, I meant you cannot plot only the boundary layer piece. of course you can still zoom the view; my mistake)

thank you but why aren't they STRAIGHT ? o.O

[CeesH]

Unfortunately, that's not a plotting question. It seems there is a y-component in your velocity as well (of course, you can check this) - and the vector direction is based on the velocity direction. This also causes a local maximum at the edge of your boundary layer. So there seems to be an error in your simulation. Do you use laminar or turbulent flow (and what is your reynolds number?) Did the simulation converge? Which momentum discretization scheme did you use?

[Falcon35]

Originally Posted by CeesH

Unfortunately, that's not a plotting question. It seems there is a y-component in your velocity as well (of course, you can check this) - and the vector direction is based on the velocity direction. This also causes a local maximum at the edge of your boundary layer. So there seems to be an error in your simulation. Do you use laminar or turbulent flow (and what is your reynolds number?) Did the simulation converge? Which momentum discretization scheme did you use?

i have only x velocity of 1 m/s , my Re number 1000 and yes it's same a tutorial from cornell university, it converged why did happen it ?

[CeesH]

I just looked at the Cornell results, and they do see the same overshoot in velocity at the edge of the boundary layer there. With that, I assume there is a small y-velocity component as well. Because in your case, it is there in the solution. If you color by the y-velocity instead of x-velocity, you'll see.