gas combustion

[Yuan Huang]

hi,
  I am learning to use Code_Saturne  and I have some trouble in gas combustion.
 1. how to set the value of temperture on wall and outlet.
 2. It can only set the the direction of speed s eparately， and can't set the normal speed in the usd3pi file. So when there are several inlet, it is inconvenient to set.
 3. The heat capacity and dynamic viscosity is constant default, how to set them in variety?
thanks very much!

[Marcus Charwath]

Dear Yuan Huang, Being a member of Code Saturne's Combustion R&D team, I'd like to answer to your questions. 1. At a first glance, the definition of a fixed temperature at the OUTLET of a combustion chamber seems to be very particular wish. Nevertheless, the standard boundary condition types named as IPAROI (i.e. wall) and ISOLIB (i.e. outlet) do not allow to set a certain temperature. However, a modification of these standard types is possible allowing the user to impose free chosen temperatures at the corresponding faces. Because the implementation of  these modifications is rather complex I'd be glad to assist you. 2. The incoming massflow can be set in two different ways. a) It is evdient, providing a certain mass flow as the inlet condition the user must additionally define the different FLOW DIRECTIONS . The latter represent indispensable information, which are needed to solve the flow field properly in the physical space. b) The provided VELOCITY VECTORS are used to deduce an incoming mass flow by means of the lateral surface and the fluid density. Again, in order to properly solve the flow field in the physical space three velocity vectors have to be provided. These methods have been proven to be applicalbe to a variety of different inlet conditions and work very well. Indeed, it does not exist a SINGLE keyword setting the incoming mass flow normal to the inlet face surface. However, I'd be glad to show a very simple and fast approach, which avoids long term settings of inlet velocity vectos normal to the inlet face surface. 3. No matter which combustion model (gas, oil and coal combustion) is used, the specific heat capacity is calculated according to data taken from a table called "JANAF". These data are tabulated as function of the temperature. Thus, the constant values provided in usini1.XXX are not used anymore.   Well, I hope my answers will help you to improve your knowledge about Code Saturne. Please, do not hesitate to contact me if further questions occur.   Best regards Marcus Charwath

[Yuan Huang]

hi,
  Thanks very much for you help Marcus Charwath.
  I am clear for what you say about question 1 ,2, and  the specific heat capacity of question 3, but what about the dynamic viscosity?
  And how to set the initial temperture and pressure? I only see the initial of components.
 

[Marcus Charwath]

Hi there,
 
The initial temperature T0 and initial pressure p0 are set in usini1.f90.
 
 
Marcus

[Yuan Huang]

T0 and p0  set in usini1.f90 aren't the reference  temperature and pressure?

[Alexandre Douce]

Yes there are.

[Yuan Huang]

thanks all!