[flow_CH]

Hello

I am new in CFD and fluent.
I am simulating a 2 meters long open channel with water velocity= 4 m/s.
So in field or laboratory, every particle in flow cross into channel after 0.5 second.
I am viewing flow after 0.5 second in fluent (the time that fluent shows), but flow does not yet arrive to outlet. My question is what the mean of time in fluent?
Thanks

[rayan24]

Normally if your channel made 2m and your flow velocity equal to 4m/s so after 0.5s each fluid particle traveled the distance (d = 4m / s * 0.5s = 2m), so if the fluid does not reach the outlet after 0.5s I think it's just a problem of viewing no more!! tries to reduce the maximum value of velocity in the scale color. if the probleme is not resolved try to change your "time step" (maybe it is not enough)

[flow_CH]

Originally Posted by rayan24

Normally if your channel made 2m and your flow velocity equal to 4m/s so after 0.5s each fluid particle traveled the distance (d = 4m / s * 0.5s = 2m), so if the fluid does not reach the outlet after 0.5s I think it's just a problem of viewing no more!! tries to reduce the maximum value of velocity in the scale color. if the probleme is not resolved try to change your "time step" (maybe it is not enough)

Thanks for your reply
I do not understand.
The flow is in middle of channel but i have pressure and velocity and etc in downer than that point.

[rayan24]

By a 3D visualization as you presented we can not draw conclusions .. try to present massqiue fraction and velocity on a one plane (just a plane)that intersects the inlet in the middle and through the channel..(The figures that you show are from a stationary simulation and not unsteady? non)

[flow_CH]

I will do that but this is unsteady simulation. Why you think this is steady?

[rayan24]

It's just a feeling .. One question when you started the unsteady simulation, are you part of a solution that already exists? or just after defining your BC you cast the unsteady simulation??

[flow_CH]

After defining BCs and initialize and patch, i started unsteady simulation. what is your purpose?

[rayan24]

oouh ..OK, I see where your problem comes!
So to make an unsteady simulation it is necessary to start with a solution already exists (ie its the solution at the initial time (t = 0))

[flow_CH]

Originally Posted by rayan24

oouh ..OK, I see where your problem comes!
So to make an unsteady simulation it is necessary to start with a solution already exists (ie its the solution at the initial time (t = 0))

I define velocity and k and epsilon in initial panel. They are in t=0

[rayan24]

The stationary solution converged well be your initial case (its the solution at t=0)

[flow_CH]

So you are saying first i should model in steady state then unsteady sate?( in the end of convergence i change steady to unsteady?)

[rayan24]

Just when you get the convergence of steady state, you save this result then you use this result as the initial case (t=0) (not initialized your converged solution)

[rayan24]

Is your problem has been solved?

[flow_CH]

Yes. But i have another problem.
I want to find p/gamma in model but the static pressures(p) are very large. I defined reference pressure location in top of water flow(where the air always exist). It is 101325 pa

[flow_CH]

I want to find free surface height (Water height). I am plotting density for air and water(mixture) in a line. But in plot which density in closer to air i should choose for finding water height? (choosing (998) kg/s for water and (......) kg/s for interface between water and air)

Thanks

[rayan24]

Sorry but I did not understand your question

[flow_CH]

Just i want to find Water height in channel (from bottom of channel to free surface)

[rayan24]

Normalement la hauteur d'eau c'est toi qui le définit en se basant sur la visuatlisation de ta simulation!