Problems for Stepped Spillways Modelling
 

Dear all
what models must be activated for investigating the influence of 1. Void Fraction 2. bubbles 3. Cavity length ?
i activated these models but it does NOT generate good results :
Air entrainment
Density evaluation
Drift-flux
Gravity
Surface tension
Viscosity
thank you

Hello Dear are you successful for simulation of water over stepped spillways ? we can cooperate for this simulation

How we cooperate? I also do this.

thank you so much for your reply im phd student i want make Scientific article about the flow over stepped spilways Using cfd ?

i am the same as you

So can you send my your email?

my email：flow3d@yeah.net

Dear Sayed (et al.),
you can find some description on models used for this type of simulation under the following link:

http://89.31.100.18/~iahrpapers/80300.pdf

There is also some discussion on the results: air entrainment, free surface roughness and velocity profiles.

Best regards,
D.

Thank you dear Davahue for your reply.
actually i simulated the stepped spillway before and i extracted the results too, but my problem is a big deviation between the experimental and numerical data.
the maximum values of spillway volume is 1 m , 1.4 m and 1.4 m on a Cartesian axis and i assume a 2.6* 1.6*1 m^3 mesh block using 0.5 to 1 cm mesh size for modelling , if you are curious about that.
i had to plot the air entertainment into the fluid flow over the spillway and i calculate that by fraction of fluid. when i compare the figures with the experimental figures, there is a deviation unfortunately.
i will be grateful if you share your experience with me.
thank you.

Dear Sayed,
my experience is: when using FLOW-3D's air entrainment model, you can reproduce the inception point location as shown in the above posted paper or in Bombardelli et al (2011). If you are interested in the velocity profiles, these 2 papers show also some comparison, and the one posted above also discusses on the free surface roughness.

If you want to reproduce accurately the air concentrations, you will have to do some calibration of C_{air}, this is also discussed in the above posted paper. If you want to get some more ideas on this type of calibrations, I carried out one for smooth spillways a few years ago which you can find in my Research Gate profile.

Best regards,
Daniel

Thank you dear Daniel for your helpful answer.

thanks daniel. I will read them carefully.

Hello,

I could not reach the link. Can you please send a new link to reach these documents?

Thank you in advance!
Yasemin

Hi,

Sorry, but still not available.

Thank you!
Yasemin

Hello,

I am trying to simulate a stepped spillway which ends with a stilling basin in FLOW-3D. I have confused about using one-phase model with activated air-entrainment model or two-phase model. I need to calculate cavitation risk through the spillway.

I have started with one-phase non-air entrainment model. After 30 seconds run, I added restart simulation with an air-entrainment model. Now, I am trying to add another restart simulation with two-fluids selection without air-entrainment model and it gives error below:

"Possible two-fluid velocity slip problem.
Density ratio greater than 10 to 1.
Consider using slip option. ifslip=1"

Also, I am curious about dividing geometry into small parts and run them one by one to save time. I read about it but I confused how to connect boundaries each other.

Could you please share your experiences?

Thank you in advance,
Yasemin

Thank you!
Yasemin

Hi every one.MY name is najam and I from Pakistan.I have just started using flow 3D.I am just a beginner in FLOW 3D.I am using flow 3D for my master thesis.My topic is ''Numerical modeling of stepped spillway using FLOW 3D".
For my first stage of my thesis I am doing model calibration where I am getting experimental results from a paper and I trying to validate it with my model results in flow 3D. The paper provides experimental pressure profiles at vertical and horizontal faces of steps. I am getting the values pressure at the mesh nodes closest to the horizontal and vertical face of steps.But i am getting significantly large values as compared to paper. I am using RNG model.Also I have used
Gravity and no inertial frame
Viscosity and turbulence

Can any one help me to figure out where I am doing the mistake.

Hello Najam,

Unfortunately, I am not familiar with the Flow 3D. However, your calibration step is the most difficult part for all numerical models. Did you do mesh independence analysis? I mean, is your mesh fine enough to solve the model? Also, have you checked enough points to decide that the gap is so large between experimental and numerical model?

Thank you,
Yasemin