You could look at systems_of_equations_ex6.C. Look for the comment "Apply a traction" in the code (around line 500)
David On 05/17/2014 10:50 AM, walter kou wrote: > Hi John, > > Sorry for the further trouble, > > Specifically, on the boundary surface, I need to compute d(xyz)/dxi, > d(xyz)/deta to apply the traction, what is the best way to do? > > > Thanks, > > Walter > > > On Fri, May 16, 2014 at 2:20 PM, John Peterson <[email protected]> wrote: > >> The derivatives of the Lagrange shape functions are nonzero on the element >> faces. This is why you are seeing dphi_face != 0 >> >> >>> On May 16, 2014, at 12:07 PM, walter kou <[email protected]> wrote: >>> >>> Hi all, >>> >>> Really appreciate it if any one can tell what get_dphi() is for the >> element >>> at the boundary, and point out the reason for my issue. >>> >>> >>>> On Thu, May 15, 2014 at 10:58 PM, walter kou <[email protected]> >> wrote: >>>>> Hi all, >>>>> >>>>> For the 2D boundary element of the 3D domain, what is dphi_face = >>>>> fe_face->get_dphi(); ?? >>>>> >>>>> The strange thing to me is as below: >>>>> >>>>> 1) I use Hex8 for the 3D box, thus get 2D quad4 at the boundary face >>>>> (i.e. side element) . Notice the side element is shown below with >> nodes on >>>>> the x-y plane: >>>>> >>>>> /************ show the nodes on boundary element: side-element >>>>> [side-elem]:node: 0 coordinates:(x,y,z)=1,0,0 >>>>> [side-elem]:node: 1 coordinates:(x,y,z)=1,1,0 >>>>> [side-elem]:node: 2 coordinates:(x,y,z)=2,1,0 >>>>> [side-elem]:node: 3 coordinates:(x,y,z)=2,0,0 >>>>> >>>>> 2) I print out the Jxw- face, phi_face dphi_face. >>>>> >>>>> 3) Why do I get non-zero dphi_face[*][*](2)? should dphi/dz ==0 since >> the >>>>> 2D face is on the x-y plane? >>>>> >>>>> 4) Why is dphi_face[7][3](2) is non-zero, even nodes 4-7 are not on the >>>>> face? >>>>> >>>>> 5) Is dphi-face[*][*](0,1,2) = dphi/d(x,y,z) for both bulk and >> boundary >>>>> elements? >>>>> >>>>> Thanks >>>>> >>>>> /*************** show Jxw_face, phi, dphi >>>>> >>>>> Jxw_face[0]:=0.25 >>>>> Jxw_face[1]:=0.25 >>>>> Jxw_face[2]:=0.25 >>>>> Jxw_face[3]:=0.25 >>>>> >>>>> phi_face[0][0]:0.622008 dphi_face[0][0]:(x,y,z)=(-0.788675, -0.788675, >>>>> -0.622008) >>>>> phi_face[0][1]:0.166667 dphi_face[0][1]:(x,y,z)=(-0.211325, -0.788675, >>>>> -0.166667) >>>>> phi_face[0][2]:0.166667 dphi_face[0][2]:(x,y,z)=(-0.788675, -0.211325, >>>>> -0.166667) >>>>> phi_face[0][3]:0.0446582 dphi_face[0][3]:(x,y,z)=(-0.211325, >> -0.211325, >>>>> -0.0446582) >>>>> phi_face[1][0]:0.166667 dphi_face[1][0]:(x,y,z)=(0.788675, -0.211325, >>>>> -0.166667) >>>>> phi_face[1][1]:0.0446582 dphi_face[1][1]:(x,y,z)=(0.211325, -0.211325, >>>>> -0.0446582) >>>>> phi_face[1][2]:0.622008 dphi_face[1][2]:(x,y,z)=(0.788675, -0.788675, >>>>> -0.622008) >>>>> phi_face[1][3]:0.166667 dphi_face[1][3]:(x,y,z)=(0.211325, -0.788675, >>>>> -0.166667) >>>>> phi_face[2][0]:0.0446582 dphi_face[2][0]:(x,y,z)=(0.211325, 0.211325, >>>>> -0.0446582) >>>>> phi_face[2][1]:0.166667 dphi_face[2][1]:(x,y,z)=(0.788675, 0.211325, >>>>> -0.166667) >>>>> phi_face[2][2]:0.166667 dphi_face[2][2]:(x,y,z)=(0.211325, 0.788675, >>>>> -0.166667) >>>>> phi_face[2][3]:0.622008 dphi_face[2][3]:(x,y,z)=(0.788675, 0.788675, >>>>> -0.622008) >>>>> phi_face[3][0]:0.166667 dphi_face[3][0]:(x,y,z)=(-0.211325, 0.788675, >>>>> -0.166667) >>>>> phi_face[3][1]:0.622008 dphi_face[3][1]:(x,y,z)=(-0.788675, 0.788675, >>>>> -0.622008) >>>>> phi_face[3][2]:0.0446582 dphi_face[3][2]:(x,y,z)=(-0.211325, 0.211325, >>>>> -0.0446582) >>>>> phi_face[3][3]:0.166667 dphi_face[3][3]:(x,y,z)=(-0.788675, 0.211325, >>>>> -0.166667) >>>>> phi_face[4][0]:0 dphi_face[4][0]:(x,y,z)=( 0, 0, >> 0.622008) >>>>> phi_face[4][1]:0 dphi_face[4][1]:(x,y,z)=( 0, 0, >> 0.166667) >>>>> phi_face[4][2]:0 dphi_face[4][2]:(x,y,z)=( 0, 0, >> 0.166667) >>>>> phi_face[4][3]:0 dphi_face[4][3]:(x,y,z)=( 0, 0, >> 0.0446582) >>>>> phi_face[5][0]:0 dphi_face[5][0]:(x,y,z)=( 0, 0, >> 0.166667) >>>>> phi_face[5][1]:0 dphi_face[5][1]:(x,y,z)=( 0, 0, >> 0.0446582) >>>>> phi_face[5][2]:0 dphi_face[5][2]:(x,y,z)=( 0, 0, >> 0.622008) >>>>> phi_face[5][3]:0 dphi_face[5][3]:(x,y,z)=( 0, 0, >> 0.166667) >>>>> phi_face[6][0]:0 dphi_face[6][0]:(x,y,z)=( 0, 0, >> 0.0446582) >>>>> phi_face[6][1]:0 dphi_face[6][1]:(x,y,z)=( 0, 0, >> 0.166667) >>>>> phi_face[6][2]:0 dphi_face[6][2]:(x,y,z)=( 0, 0, >> 0.166667) >>>>> phi_face[6][3]:0 dphi_face[6][3]:(x,y,z)=( 0, 0, >> 0.622008) >>>>> phi_face[7][0]:0 dphi_face[7][0]:(x,y,z)=( 0, 0, >> 0.166667) >>>>> phi_face[7][1]:0 dphi_face[7][1]:(x,y,z)=( 0, 0, >> 0.622008) >>>>> phi_face[7][2]:0 dphi_face[7][2]:(x,y,z)=( 0, 0, >> 0.0446582) >>>>> phi_face[7][3]:0 dphi_face[7][3]:(x,y,z)=( 0, 0, >> 0.166667) >> ------------------------------------------------------------------------------ >>> "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE >>> Instantly run your Selenium tests across 300+ browser/OS combos. >>> Get unparalleled scalability from the best Selenium testing platform >> available >>> Simple to use. 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