Hi,
I am working on solving the flow as show in the attached image. there is flow into the pipe due to suction created by cross flow happening at the outlet. In other words the air perpendicular to the outlet(in fig) creates a vacuum and draws in air from inlet to combine and flow out. How could I simulate the perpendicular cross flow on the outlet in 2D. Please advice. Thank you.
No. Thats a closed end. I am trying to use the cross flow wind at the inlet to create a negative pressure and pull air through the small inlet.
What is the problem? This is a very standard flow problem with one inflow and one outflow and standard BC.s can be prescribed. You just need to differentiate the BCs. depending on incompressible or not flow model.
I am real new to CFD. Can you please advice on how to specify the cross wind of velocity 35m/s at the outlet. This wind is flowing perpendicular to outlet. Need you guidance to set up my model.
That means you need to know first a physical condition for the inlet velocity. In your case what do you know about the physics ? Is the velocity at the outlet fully developed? Is it turbulent?
Just as example for incompressible flow with standard inflow/outflow, a laminar developed velocity inlet profile is a parabola for the y-component and zero for the x-component. But if the flow is turbulent, the profile is different. At the outlet you can set a pressure value if the flow goes in an environment, otherwise you can set convective BC.s. In your flow problem, you want to prescribe the outlet velocity but you need to prescribe the profile along the outlet. Then, the inflow velocity must be computed accordingly to the mass conservation, that is the same flow rate must be prescribed.
In case of compressible flow assumption, the BCs. are more complex
.
In any case, you need to study some CFD textbook.
Thank you for guiding me in the right direction. I am in a need to complete this project and request you to help me solve this. I could give you my problem definition which states what I am trying to solve and my know values. I would really appreciate if you could help me with the physics. I am attaching a photo of the problem definition and my know values. Thank you for your time and support.
Something is not congruent, how do you think to get suction if there is no pressure difference between inlet and outlet?
The fast moving cross air will create a low pressure region at the outlet of the vent. The air pressure inside the box would be higher than that is my understanding. Hence air will flow out. I am trying to use concept of a venturi pump. All i want to obtain is a suction effect and draw air out.
You wrote atmospheric pressure at the outlet, that is the same you wrote at inlet. That cannot be prescribed to generate a pressure difference that drives the flow. Without further knowledge of outlet conditions, the pressure is not determined, At a first and rude approximation you need of the Bernoulli relation to determine the static pressure at the outlet. This way p=p0 - 1/2 rho*v^2 could be used.
Otherwise, you have to simulate the full 3D model with the external cross flow.
I am trying to substitute values in the Bernoulli equation p=p0 - 1/2 rho*v^2 , where p0=101.325Kpa rho=1.225kg/m3 and v=35m/s. the value comes out to be -648.98Kpa which looks absurd to me.
If i am using a 3d model with external cross flow what would my boundary conditions be?
Setting atmospheric pressure you have p0 about 10^5 N/m^2, rho*v^2=1500 N/m^2, how do you compute the value??
Thank you again for your constant support Mr. Filippo. Yes now i get the value 98500 N/m^2 as the pressure at the outlet. I know I am asking too much of you. Would you mind sharing a little time as per your convenience to help me with this problem. I have got few more doubts on handling this problem and believe this would make the thread too long. My email address is [email protected]. Can we have a call or video chat if you feel fine with it?
- Badges
- Science topic