# Synthetic Jet Boundary Condition

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 September 15, 2001, 01:59 Synthetic Jet Boundary Condition #1 Karthikeyan D. Guest   Posts: n/a Hi all, I am trying to simulate viscous flow over an airfoil with mass suction/blowing on the surface. I would like to impose this as a surface boundary condition. Right now, i extrapolate density to the wall, give the appropriate velocities (of the jet) and (thus getting all but one of the conserved variables), then get the pressure using: dp/d(eta) = -rho*(dv/dt).eta_n where 'eta' is the normal direction and eta_n is the unit normal. Can anybody suggest a better solution for pressure - the normal momentum equation perhaps? Or can anybody suggest where i can look for this?..Am using a structured curvilineat mesh. Thanks, Karthik.

 August 18, 2010, 07:17 hi #2 Senior Member     Morteza Join Date: May 2010 Location: Iran,Islamic Republic of Posts: 161 Rep Power: 9 hi I am trying to model suction over an airfoil in fluent and gambit. but i encountered some problems that i can not find the solutions for since 2 weeks ago. first:: i have read many articles that model continous suction or suction using a synthetic jet. all of the articles give us the suction velocity ,but when i choose the outer boundary as pressure far field ,i see some warnings. some body tolds me that i have to use the pressure outlet boundary condition for suction hole... but i can not calculate the pressure for my low renolds number model... in other words when i am trying to re-do an earlier numerical work in fluent that used velocity inlet for suction,i also have tobe able to do it.. 2; the drag coefficient is negative in nearly all cases and the lift coefficient has a big variation with the exact value..and sometimes has a negative value. 3.i have modeled more than 7 different cases in gambit with differen meshes. i do not know where do the problems come from? please answer these questions : a: which type of mesh is better for modelling a base airfoil and suction-including airfoil.. C-H grid....O-grid....boundary layer mesh or .... please send me a dbs file of mesh over a base airfoil and a dbs file of mesh over a sutioned airfoil... b: please tell me which boundary conditions i have touse in gambit... pressure far field,symmetry,wall or ...... for a typical C-H grid over airfoil please express the boundary cond. detailed. c: which solver and discretization schemes is better to model a base airfoil and suctioned airfoil. tell me the appropriate turbulance model and any other things you things is good to better model an airfoil. d: to calculatethe darg and lift coefficients in fluent , is it needed to change the default value of area in refrence value? elease send me by email useful file(tyrorial,mesh file,dbs file ,case and data file ,fortrn code,or..) thatcan help me to do this...thanks i am ready to send you my works to tell me my faults.. but it isan emergency ..please sooner... thanks f:: please answer me,,,,,, i'm stock...

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