Butterfly LES delta model


hi all,
i recently want to use butterfly to conduct LES modeling. however OpenFOAM come across a fatal error “cuberootvol coeffs is undefined”. i found that the component “LES turbulence model” can only define the name of LES model and delta,but can not define cuberootvol coeffs. the “turbulenceProperties” files created by butterfly also has no defination of the cuberootvol coeffs. so could anyone add definiton of the cuberootvol coeffs in turbulenceProperties like standard files?