# Why is my fluent simulation giving Cp values above 1???

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 March 24, 2010, 15:01 Why is my fluent simulation giving Cp values above 1??? #1 New Member   Join Date: Mar 2010 Posts: 2 Rep Power: 0 hello to everyone on the forum Im a newbie!! can anyone help?? I have recently carried out some fluent simulations of an aerofoil in a wind tunnel. details; 2D steady flow simulation standard k-epsilon turbulence model with standard wall functions pressure correction technique simple algorithm disecretisation pressure, second order momentum, second order upwind turbulent kinetic energy, first order upwind turbulent dissipation rate, first order upwind inlet is a pressure inlet, outlet right hand wall is pressure outlet zero gauge pressure. aerofoil is given wall boundary conditions. the simulation agrees with experimental results when the aerofoil is set at zero incidence but with higher incidences around 10 degrees the Cp value goes above 1 which cannot be correct... Does anyone have any idea why this is occuring?? thanks

 March 24, 2010, 15:23 #2 Senior Member   Join Date: Jul 2009 Posts: 357 Rep Power: 18 Are you sure you're not computing -Cp?

 March 24, 2010, 15:40 #3 New Member   Join Date: Mar 2010 Posts: 2 Rep Power: 0 well I was computing Cp values over the aerofoils top and bottom surfaces using the static pressures that the simulation gave, for comparisson to the Cp values calculated from experimental results. So really I am asking why would the simulation find static pressures at the leading edge of the aerofoil that are greater than the inlet pressure (total pressure)???

 March 26, 2010, 09:12 Hi #4 Member   Dynampally Pavitran Join Date: Mar 2010 Location: India Posts: 74 Rep Power: 16 The Cp values can be more than 1 for compressible flows. 1. I guess the flow in your simulation is incompressible. Take correct inlet velocity(V) value, for computing Free stream Dynamic Pressure(0.5*density*V^2).