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How can it possible to change by itself in volumetric flow rate of velocity inlet BC |
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#1 |
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Onur Özcan
Join Date: Feb 2016
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Hi all,
I just wonder how to change volumetric flow rate in face cell of velocity inlet boundary condition ? velocity and temperature has been specified together with hydraulic diameter in velocity_inlet BC It has changed by itself following 50. iterations. Then, temperature of some regarding faces has not been steady as well. I am confusing how can it possible? |
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#2 | |
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Onur Özcan
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#3 |
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Has the size of the inlet changed? Because then the velocity could remain constant while the volumetric flow rate changes. Second, are there any UDFs or profiles hooked to the boundary?
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#4 | |
Senior Member
Onur Özcan
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Quote:
velocity inlet and pressure outlet are boundary conditions. Velocity inlet : Velocity magnitude: 1.4m/s, Supersonic/Initial Gauge Pressure (pascal) : 150000 Pa (1.5 bar) Temperature 300K , Operating pressure :101325 Pa (reference pressure location X,Y,Z=0, gravity is deactivated ) Pressure outlet : Gauge Pressure (pascal) =0 Backflow Total Temperature :323.15K Operating pressure :101325 Pa (reference pressure location X,Y,Z=0, gravity is deactivated ) |
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#5 | |
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Onur Özcan
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mass flow rate : rho x A x V ; (from continuity) equals to outlet_pressure all of them must be constant. Because I have specified that face as velocity_inlet BC. Volumetric flow rate need to be constant as well. |
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#6 |
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Onur Özcan
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Moreover, the problem always happen whenever I activate energy equation.
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#7 |
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Are you modelling compressible flow? Where are you measuring the volumetric flow rate (inlet and/or outlet boundaries?), and what are the values?
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#8 |
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Onur Özcan
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flow is defined as ''incompressible ideal gas ''. Well it is associated with density change . it arises from continuity equation.
But the thing I couldnt understand is that I have given a velocity and temperature inputs in velocity_inlet boundary condition. Well, coming from mass conservation, mass flow rate= rho x Wetted area x velocity, wetted area like velocity has been specified in velocity_inlet bc. Remaining is rho, it is just comply with temperature,So, temperature is constant as well. (because of giving in BC) I am really really confused what is going on during calculation ? I will be really appreciated if you help me out by the way I couldnt check inlet and outlet mass flow rate for this reason I have told you above |
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#9 | |
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Why? You can run a UDF over the inlet and outlet boundaries at each time step (DEFINE_AT_END) and compare the fluxes (calculated from the velocity etc). |
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#10 | |
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Onur Özcan
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Well, respectively. you can find attached whole geometry (consisting of 3 bodies in a part) Wall boundaries surrounds air inlets and heat flux =0 in wall boundary conditions tab. Exactly, whenever energy eq. is activated, that situation is to come true. problem is to solved in steady-state (not time). But yes,exactly, density changes not used UDF. |
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#11 | |
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Onur Özcan
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