hcrit.f File Reference

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Functions/Subroutines
subroutine	hcrit (xflow, rho, b, theta, dg, sqrts0, hk)

Function/Subroutine Documentation

hcrit()

subroutine hcrit	(	real*8	xflow,
		real*8	rho,
		real*8	b,
		real*8	theta,
		real*8	dg,
		real*8	sqrts0,
		real*8	hk
	)

!
!     determine the critical depth
!     
      implicit none
!      
      real*8 xflow,rho,b,dg,sqrts0,hk,theta,tth,c1,xflow2,
     &  a,dbbdh,dadh,bb,dhk
!
      hk=((xflow/(rho*b))**2/(dg*sqrts0))**(1.d0/3.d0)
!
      if(dabs(theta).lt.1.d-10) return
!
!     critical depth for trapezoid, non-rectangular cross section
!
      tth=dtan(theta)
      c1=rho*rho*dg*sqrts0
      xflow2=xflow*xflow
!
      do
         a=hk*(b+hk*tth)
         dbbdh=2.d0*tth
         dadh=b+hk*dbbdh
         bb=dadh
         dhk=(xflow2*bb-c1*a**3)/(xflow2*dbbdh-3.d0*c1*a*a*dadh)
         if(dabs(dhk)/dhk.lt.1.d-3) exit
         hk=hk-dhk
      enddo
!
      return