Johnson King Turbulence Model
 

On the 1985 paper by Johnson & King, they derive the Reynolds shear stress ODE equation, then to obtain a useable version of the ODE they make a substitution: g=(-u'v'm)^(-1/2)and a similar one for g.eq. I've done the same derivation as them, but in the multiplier where they get (a1)/(2Um.Lm) I get (a1)/(Um.Lm). Where has this '2' come from in their equation? If anyone has worked with JKM and can solve this for me, I'd be grateful. Thanks in advance, Steve