Cfd modeling of ram air intake

pdewcfd · February 8, 2018, 08:26

Hi,
I am trying to simulate a ram air intake but I have some confusions regarding the boundary conditions at the inlet and outlet.
lets say my bike is running at 200kmph.
1. At this speed I can calculate my stagnation inlet BC and give to inlet whereas for the outlet I am not clear, I can give pressure outlet BC but it would then fix the pressure in the system.
2. if I give mass flow rate outlet BC by assuming a volumetric efficiency, RPM of engine and density of air then I am only modelling a particular condition of operation.
How can I simulate this case holistically? Since the moment I mount this ram intake on my throttle body, the system pressure itself changes.
Please suggest something.

fluid23 · February 8, 2018, 14:11

Perhaps I don't understand your question, but any single CFD analysis will only address one specific operating condition. You have to change boundary conditions to get results for each condition you need to know about. If you can determine system mass flow for each condition of interest, I would setup a pressure outlet boundary with mass flow specification option activated. This will adjust your back pressure in response to your flow to achieve a specific flow rate.

If I am off the mark on your question, please clarify your intent.

February 8, 2018, 08:26	Cfd modeling of ram air intake	#1
pdewcfd New Member Join Date: Feb 2018 Posts: 2 Rep Power: 0	Hi, I am trying to simulate a ram air intake but I have some confusions regarding the boundary conditions at the inlet and outlet. lets say my bike is running at 200kmph. 1. At this speed I can calculate my stagnation inlet BC and give to inlet whereas for the outlet I am not clear, I can give pressure outlet BC but it would then fix the pressure in the system. 2. if I give mass flow rate outlet BC by assuming a volumetric efficiency, RPM of engine and density of air then I am only modelling a particular condition of operation. How can I simulate this case holistically? Since the moment I mount this ram intake on my throttle body, the system pressure itself changes. Please suggest something.

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February 8, 2018, 14:11		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	Perhaps I don't understand your question, but any single CFD analysis will only address one specific operating condition. You have to change boundary conditions to get results for each condition you need to know about. If you can determine system mass flow for each condition of interest, I would setup a pressure outlet boundary with mass flow specification option activated. This will adjust your back pressure in response to your flow to achieve a specific flow rate. If I am off the mark on your question, please clarify your intent.