[求助]请问如何在CFX中求表面摩擦系数Cf？

晴带雨伞

请问如何在CFX中求表面摩擦系数Cf？

wangzhibo

可以先求出摩擦力F,cf=F/2/density/velocity^2

wangzhibo

用CEL计算阻力系数(drag coefficient, cd)和升力系数(lift coefficient, cl)，并且在求解时实时显示cd和cl。
碰巧遇到一个例子，现在把CEL贴在下面。应该把这个CEL稍微修改一下，可以轻松应用到其他模型上。
在CFX-Pre里定义一个新的monitor point的方法是点击”Create Output Files and Monitor Points”图标，然后到Monitor tab下面把CEL表达式定义成一个monitor point。
LIBRARY:
CEL:
EXPRESSIONS:
DragForce = 2*(force_x()@DLRF6*cos(alpha)+force_z()@DLRF6*sin(alpha))
DynamicPres = 0.5*ReferenceDensity*Vinlet^2
LiftForce = max(2*(force_z()@DLRF6*cos(alpha)-force_x()@DLRF6*sin(alpha)), 1[N])
MachNumber = 0.75
PitchingMoment = torque_y()@DLRF6*2
PitchingMomentatQuaterChord=-1*(-torque_y()@DLRF6*2/LiftForce-QuaterChordLocation)*LiftForce QuaterChordLocation = 0.1579 [m]
ReferenceArea = 0.1453 [m^2]
ReferenceChord = 0.1412 [m]
ReferenceDensity = StaticPres/(287 [J K^-1 kg^-1]*Temp)
ReferenceViscosity = ReferenceDensity*ReferenceChord*Vinlet/ReynoldsNumber
ReynoldsNumber = 3000000
StaticPres = 119750 [Pa]
Temp = 293.0 [K]
Timestep = 1e-5 +TimeStepRamp(atstep)*2e-4
ToTemp = Temp*(1+ ((1.4 - 1)/2)*MachNumber^2)
TotalPres = StaticPres*(1.0+0.2*MachNumber^2)^3.5 - StaticPres
Vinlet = MachNumber*(1.4*287*Temp)^0.5/(1 [K^0.5]*1 )*1 [m]
alpha = 1.225 [degree]
cd = DragForce/(DynamicPres*ReferenceArea)
cl = LiftForce/(DynamicPres*ReferenceArea)
cm = PitchingMomentatQuaterChord/(DynamicPres*ReferenceArea*ReferenceChord)
END
END
END