//--------------------------------------------------------------------------
//-------- execute ---------------------------------------------------------
//--------------------------------------------------------------------------
void
AssembleMomentumEdgeSolverAlgorithm::execute()
{

  stk::mesh::MetaData & meta_data = realm_.meta_data();

  const int nDim = meta_data.spatial_dimension();

  const double small = 1.0e-16;

  // extract user advection options (allow to potentially change over time)
  const std::string dofName = "velocity";
  const double alpha = realm_.get_alpha_factor(dofName);
  const double alphaUpw = realm_.get_alpha_upw_factor(dofName);
  const double hoUpwind = realm_.get_upw_factor(dofName);
  const bool useLimiter = realm_.primitive_uses_limiter(dofName);

  // one minus flavor
  const double om_alpha = 1.0-alpha;
  const double om_alphaUpw = 1.0-alphaUpw;

  // space for LHS/RHS; always edge connectivity
  const int nodesPerEdge = 2;
  const int lhsSize = nDim*nodesPerEdge*nDim*nodesPerEdge;
  const int rhsSize = nDim*nodesPerEdge;
  std::vector<double> lhs(lhsSize);
  std::vector<double> rhs(rhsSize);
  std::vector<stk::mesh::Entity> connected_nodes(2);

  // area vector; gather into
  std::vector<double> areaVec(nDim);

  // pointer for fast access
  double *p_lhs = &lhs[0];
  double *p_rhs = &rhs[0];
  double *p_areaVec = &areaVec[0];

  // space for dui/dxj. This variable is the modified gradient with NOC
  std::vector<double> duidxj(nDim*nDim);

  // extrapolated value from the L/R direction 
  std::vector<double> uIpL(nDim);
  std::vector<double> uIpR(nDim);
  // limiter values from the L/R direction, 0:1
  std::vector<double> limitL(nDim,1.0); 
  std::vector<double> limitR(nDim,1.0);
  // extrapolated gradient from L/R direction
  std::vector<double> duL(nDim);
  std::vector<double> duR(nDim);
  
  // pointers for fast access
  double *p_duidxj = &duidxj[0];
  double *p_uIpL = &uIpL[0];
  double *p_uIpR = &uIpR[0];
  double *p_limitL = &limitL[0];
  double *p_limitR = &limitR[0];
  double *p_duL = &duL[0];
  double *p_duR = &duR[0];

  // deal with state
  VectorFieldType &velocityNp1 = velocity_->field_of_state(stk::mesh::StateNP1);
  ScalarFieldType &densityNp1 = density_->field_of_state(stk::mesh::StateNP1);

  // define some common selectors
  stk::mesh::Selector s_locally_owned_union = meta_data.locally_owned_part()
    & stk::mesh::selectUnion(partVec_) 
    & !(realm_.get_inactive_selector());

  stk::mesh::BucketVector const& edge_buckets =
    realm_.get_buckets( stk::topology::EDGE_RANK, s_locally_owned_union );
  for ( stk::mesh::BucketVector::const_iterator ib = edge_buckets.begin();
        ib != edge_buckets.end() ; ++ib ) {
    stk::mesh::Bucket & b = **ib ;
    const stk::mesh::Bucket::size_type length   = b.size();

    // pointer to edge area vector and mdot
    const double * av = stk::mesh::field_data(*edgeAreaVec_, b);
    const double * mdot = stk::mesh::field_data(*massFlowRate_, b);

    for ( stk::mesh::Bucket::size_type k = 0 ; k < length ; ++k ) {

      // zeroing of lhs/rhs
      for ( int i = 0; i < lhsSize; ++i ) {
        p_lhs[i] = 0.0;
      }
      for ( int i = 0; i < rhsSize; ++i ) {
        p_rhs[i] = 0.0;
      }

      stk::mesh::Entity const * edge_node_rels = b.begin_nodes(k);

      // pointer to edge area vector
      for ( int j = 0; j < nDim; ++j )
        p_areaVec[j] = av[k*nDim+j];
      const double tmdot = mdot[k];

      // sanity check on number or nodes
      ThrowAssert( b.num_nodes(k) == 2 );

      // left and right nodes
      stk::mesh::Entity nodeL = edge_node_rels[0];
      stk::mesh::Entity nodeR = edge_node_rels[1];

      connected_nodes[0] = nodeL;
      connected_nodes[1] = nodeR;

      // extract nodal fields
      const double * coordL = stk::mesh::field_data(*coordinates_, nodeL);
      const double * coordR = stk::mesh::field_data(*coordinates_, nodeR);

      const double * dudxL = stk::mesh::field_data(*dudx_, nodeL);
      const double * dudxR = stk::mesh::field_data(*dudx_, nodeR);

      const double * vrtmL = stk::mesh::field_data(*velocityRTM_, nodeL);
      const double * vrtmR = stk::mesh::field_data(*velocityRTM_, nodeR);

      const double * uNp1L = stk::mesh::field_data(velocityNp1, nodeL);
      const double * uNp1R = stk::mesh::field_data(velocityNp1, nodeR);

      const double densityL = *stk::mesh::field_data(densityNp1, nodeL);
      const double densityR = *stk::mesh::field_data(densityNp1, nodeR);

      const double viscosityL = *stk::mesh::field_data(*viscosity_, nodeL);
      const double viscosityR = *stk::mesh::field_data(*viscosity_, nodeR);

      // copy in extrapolated values
      for ( int i = 0; i < nDim; ++i ) {
        // extrapolated du
        p_duL[i] = 0.0;
        p_duR[i] = 0.0;
        const int offSet = nDim*i;
        for ( int j = 0; j < nDim; ++j ) {
          const double dxj = 0.5*(coordR[j] - coordL[j]);
          p_duL[i] += dxj*dudxL[offSet+j];
          p_duR[i] += dxj*dudxR[offSet+j];
        }
      }

      // compute geometry
      double axdx = 0.0;
      double asq = 0.0;
      double udotx = 0.0;
      for ( int j = 0; j < nDim; ++j ) {
        const double axj = p_areaVec[j];
        const double dxj = coordR[j] - coordL[j];
        axdx += axj*dxj;
        asq += axj*axj;
        udotx += 0.5*dxj*(vrtmL[j] + vrtmR[j]);
      }

      const double inv_axdx = 1.0/axdx;

      // ip props
      const double viscIp = 0.5*(viscosityL + viscosityR);
      const double diffIp = 0.5*(viscosityL/densityL + viscosityR/densityR);

      // Peclet factor
      const double pecfac = pecletFunction_->execute(std::abs(udotx)/(diffIp+small));
      const double om_pecfac = 1.0-pecfac;

      // determine limiter if applicable
      if ( useLimiter ) {
        for ( int i = 0; i < nDim; ++i ) {
          const double dq = uNp1R[i] - uNp1L[i];
          const double dqMl = 2.0*2.0*p_duL[i] - dq;
          const double dqMr = 2.0*2.0*p_duR[i] - dq;
          p_limitL[i] = van_leer(dqMl, dq, small);
          p_limitR[i] = van_leer(dqMr, dq, small);
        }
      }

      // final upwind extrapolation; with limiter
      for ( int i = 0; i < nDim; ++i ) {
        p_uIpL[i] = uNp1L[i] + p_duL[i]*hoUpwind*p_limitL[i];
        p_uIpR[i] = uNp1R[i] - p_duR[i]*hoUpwind*p_limitR[i];
      }

      /*
        form duidxj with over-relaxed procedure of Jasak:

        dui/dxj = GjUi +[(uiR - uiL) - GlUi*dxl]*Aj/AxDx
        where Gp is the interpolated pth nodal gradient for ui
      */
      for ( int i = 0; i < nDim; ++i ) {

        // difference between R and L nodes for component i
        const double uidiff = uNp1R[i] - uNp1L[i];

        // offset into all forms of dudx
        const int offSetI = nDim*i;

        // start sum for NOC contribution
        double GlUidxl = 0.0;
        for ( int l = 0; l< nDim; ++l ) {
          const int offSetIL = offSetI+l;
          const double dxl = coordR[l] - coordL[l];
          const double GlUi = 0.5*(dudxL[offSetIL] + dudxR[offSetIL]);
          GlUidxl += GlUi*dxl;
        }

        // form full tensor dui/dxj with NOC
        for ( int j = 0; j < nDim; ++j ) {
          const int offSetIJ = offSetI+j;
          const double axj = p_areaVec[j];
          const double GjUi = 0.5*(dudxL[offSetIJ] + dudxR[offSetIJ]);
          p_duidxj[offSetIJ] = GjUi + (uidiff - GlUidxl)*axj*inv_axdx;
        }
      }

      // lhs diffusion; only -mu*dui/dxj*Aj contribution for now
      const double dlhsfac = -viscIp*asq*inv_axdx;

      for ( int i = 0; i < nDim; ++i ) {

        // 2nd order central
        const double uiIp = 0.5*(uNp1R[i] + uNp1L[i]);

        // upwind
        const double uiUpwind = (tmdot > 0) ? alphaUpw*p_uIpL[i] + om_alphaUpw*uiIp
          : alphaUpw*p_uIpR[i] + om_alphaUpw*uiIp;

        // generalized central (2nd and 4th order)
        const double uiHatL = alpha*p_uIpL[i] + om_alpha*uiIp;
        const double uiHatR = alpha*p_uIpR[i] + om_alpha*uiIp;
        const double uiCds = 0.5*(uiHatL + uiHatR);

        // total advection; pressure contribution in time term expression
        const double aflux = tmdot*(pecfac*uiUpwind + om_pecfac*uiCds);

        // divU
        double divU = 0.0;
        for ( int j = 0; j < nDim; ++j)
          divU += p_duidxj[j*nDim+j];

        // diffusive flux; viscous tensor doted with area vector
        double dflux = 2.0/3.0*viscIp*divU*p_areaVec[i]*includeDivU_;
        const int offSetI = nDim*i;
        for ( int j = 0; j < nDim; ++j ) {
          const int offSetTrans = nDim*j+i;
          const double axj = p_areaVec[j];
          dflux += -viscIp*(p_duidxj[offSetI+j] + p_duidxj[offSetTrans])*axj;
        }

        // residal for total flux
        const double tflux = aflux + dflux;
        const int indexL = i;
        const int indexR = i + nDim;

        // total flux left
        p_rhs[indexL] -= tflux;
        // total flux right
        p_rhs[indexR] += tflux;

        // setup for LHS
        const int rowL = indexL * nodesPerEdge*nDim;
        const int rowR = indexR * nodesPerEdge*nDim;

        //==============================
        // advection first
        //==============================
        const int rLiL = rowL+indexL;
        const int rLiR = rowL+indexR;
        const int rRiL = rowR+indexL;
        const int rRiR = rowR+indexR;

        // upwind advection (includes 4th); left node
        double alhsfac = 0.5*(tmdot+std::abs(tmdot))*pecfac*alphaUpw
          + 0.5*alpha*om_pecfac*tmdot;
        p_lhs[rLiL] += alhsfac;
        p_lhs[rRiL] -= alhsfac;

        // upwind advection (incldues 4th); right node
        alhsfac = 0.5*(tmdot-std::abs(tmdot))*pecfac*alphaUpw
          + 0.5*alpha*om_pecfac*tmdot;
        p_lhs[rRiR] -= alhsfac;
        p_lhs[rLiR] += alhsfac;

        // central; left; collect terms on alpha and alphaUpw
        alhsfac = 0.5*tmdot*(pecfac*om_alphaUpw + om_pecfac*om_alpha);
        p_lhs[rLiL] += alhsfac;
        p_lhs[rLiR] += alhsfac;
        // central; right
        p_lhs[rRiL] -= alhsfac;
        p_lhs[rRiR] -= alhsfac;

        //==============================
        // diffusion second
        //==============================
        const double axi = p_areaVec[i];

        //diffusion; row IL
        p_lhs[rLiL] -= dlhsfac;
        p_lhs[rLiR] += dlhsfac;

        // diffusion; row IR
        p_lhs[rRiL] += dlhsfac;
        p_lhs[rRiR] -= dlhsfac;

        // more diffusion; see theory manual
        for ( int j = 0; j < nDim; ++j ) {
          const double lhsfacNS = -viscIp*axi*p_areaVec[j]*inv_axdx;

          const int colL = j;
          const int colR = j + nDim;

          // first left; IL,IL; IL,IR
          p_lhs[rowL + colL] -= lhsfacNS;
          p_lhs[rowL + colR] += lhsfacNS;

          // now right, IR,IL; IR,IR
          p_lhs[rowR + colL] += lhsfacNS;
          p_lhs[rowR + colR] -= lhsfacNS;
        }

      }
      
      apply_coeff(connected_nodes, rhs, lhs, __FILE__);

    }
  }
}
//--------------------------------------------------------------------------
//-------- execute ---------------------------------------------------------
//--------------------------------------------------------------------------
void
AssembleRadTransEdgeUpwindSolverAlgorithm::execute()
{

  stk::mesh::MetaData & meta_data = realm_.meta_data();

  const int nDim = meta_data.spatial_dimension();

  // extract current ordinate direction
  std::vector<double> Sk(nDim,0.0);
  radEqSystem_->get_current_ordinate(&Sk[0]);
  const double *p_Sk = &Sk[0];
  intensity_ = radEqSystem_->get_intensity();

  // space for LHS/RHS; always nodesPerEdge*nodesPerEdge and nodesPerEdge
  std::vector<double> lhs(4);
  std::vector<double> rhs(2);
  std::vector<int> scratchIds(2);
  std::vector<double> scratchVals(2);
  std::vector<stk::mesh::Entity> connected_nodes(2);

  // area vector; gather into
  std::vector<double> areaVec(nDim);

  // pointers for fast access
  double *p_lhs = &lhs[0];
  double *p_rhs = &rhs[0];
  double *p_areaVec = &areaVec[0];

  // define some common selectors
  stk::mesh::Selector s_locally_owned_union = meta_data.locally_owned_part()
    &stk::mesh::selectUnion(partVec_);

  stk::mesh::BucketVector const& edge_buckets =
    realm_.get_buckets( stk::topology::EDGE_RANK, s_locally_owned_union );
  for ( stk::mesh::BucketVector::const_iterator ib = edge_buckets.begin();
        ib != edge_buckets.end() ; ++ib ) {
    stk::mesh::Bucket & b = **ib ;
    const size_t length   = b.size();

    // pointer to edge area vector
    const double * av = stk::mesh::field_data(*edgeAreaVec_, b);

    for ( size_t k = 0 ; k < length ; ++k ) {

      // set ordinal for edge
      unsigned edge_ordinal = k;
      // sanity check on number or nodes
      ThrowAssert( b.num_nodes(edge_ordinal) == 2 );

      stk::mesh::Entity const * edge_node_rels = b.begin_nodes(edge_ordinal);

      // pointer to edge area vector
      for ( int j = 0; j < nDim; ++j )
        p_areaVec[j] = av[k*nDim+j];

      // left and right nodes
      stk::mesh::Entity nodeL = edge_node_rels[0];
      stk::mesh::Entity nodeR = edge_node_rels[1];

      connected_nodes[0] = nodeL;
      connected_nodes[1] = nodeR;

      // extract nodal fields
      const double intensityL = *stk::mesh::field_data(*intensity_, nodeL);
      const double intensityR = *stk::mesh::field_data(*intensity_, nodeR);

      // compute sj*njdS
      double sjaj = 0.0;
      for ( int j = 0; j < nDim; ++j ) {
        sjaj += p_Sk[j]*p_areaVec[j];
      }

      // upwind; left node
      double lhsfac = 0.5*(sjaj+std::abs(sjaj));
      p_lhs[0] = +lhsfac;
      p_lhs[2] = -lhsfac;

      // upwind; right node
      lhsfac = 0.5*(sjaj-std::abs(sjaj));
      p_lhs[3] = -lhsfac;
      p_lhs[1] = +lhsfac;

      // residual
      const double intensityIp = (sjaj > 0.0) ? intensityL : intensityR;
      p_rhs[0] = -sjaj*intensityIp;
      p_rhs[1] = +sjaj*intensityIp;
      
      apply_coeff(connected_nodes, scratchIds, scratchVals, rhs, lhs, __FILE__);

    }
  }
}
//--------------------------------------------------------------------------
//-------- execute ---------------------------------------------------------
//--------------------------------------------------------------------------
void
AssembleContinuityEdgeSolverAlgorithm::execute()
{

  stk::mesh::MetaData & meta_data = realm_.meta_data();

  const int nDim = meta_data.spatial_dimension();

  // extract noc
  const std::string dofName = "pressure";
  const double nocFac
    = (realm_.get_noc_usage(dofName) == true) ? 1.0 : 0.0;

  // time step
  const double dt = realm_.get_time_step();
  const double gamma1 = realm_.get_gamma1();
  const double projTimeScale = dt/gamma1;

  // deal with interpolation procedure
  const double interpTogether = realm_.get_mdot_interp();
  const double om_interpTogether = 1.0-interpTogether;
  
  // space for LHS/RHS; always nodesPerEdge*nodesPerEdge and nodesPerEdge
  std::vector<double> lhs(4);
  std::vector<double> rhs(2);
  std::vector<stk::mesh::Entity> connected_nodes(2);

  // area vector; gather into
  std::vector<double> areaVec(nDim);

  // pointers for fast access
  double *p_lhs = &lhs[0];
  double *p_rhs = &rhs[0];
  double *p_areaVec = &areaVec[0];

  // mesh motion
  std::vector<double> vrtmL(nDim);
  std::vector<double> vrtmR(nDim);
  double * p_vrtmL = &vrtmL[0];
  double * p_vrtmR = &vrtmR[0];

  // deal with state
  VectorFieldType &velocityNp1 = velocity_->field_of_state(stk::mesh::StateNP1);
  ScalarFieldType &densityNp1 = density_->field_of_state(stk::mesh::StateNP1);

  // define some common selectors
  stk::mesh::Selector s_locally_owned_union = meta_data.locally_owned_part()
    &stk::mesh::selectUnion(partVec_);

  stk::mesh::BucketVector const& edge_buckets =
    realm_.get_buckets( stk::topology::EDGE_RANK, s_locally_owned_union );
  for ( stk::mesh::BucketVector::const_iterator ib = edge_buckets.begin();
        ib != edge_buckets.end() ; ++ib ) {
    stk::mesh::Bucket & b = **ib ;
    const stk::mesh::Bucket::size_type length   = b.size();

    // pointer to edge area vector
    const double * av = stk::mesh::field_data(*edgeAreaVec_, b);

    for ( stk::mesh::Bucket::size_type k = 0 ; k < length ; ++k ) {

      // sanity check on number or nodes
      ThrowAssert( b.num_nodes(k) == 2 );

      stk::mesh::Entity const * edge_node_rels = b.begin_nodes(k);

      // pointer to edge area vector
      for ( int j = 0; j < nDim; ++j )
        p_areaVec[j] = av[k*nDim+j];

      // left and right nodes
      stk::mesh::Entity nodeL = edge_node_rels[0];
      stk::mesh::Entity nodeR = edge_node_rels[1];

      connected_nodes[0] = nodeL;
      connected_nodes[1] = nodeR;

      // extract nodal fields
      const double * coordL = stk::mesh::field_data(*coordinates_, nodeL);
      const double * coordR = stk::mesh::field_data(*coordinates_, nodeR);

      const double * GpdxL = stk::mesh::field_data(*Gpdx_, nodeL);
      const double * GpdxR = stk::mesh::field_data(*Gpdx_, nodeR);

      const double * velocityNp1L = stk::mesh::field_data(velocityNp1, nodeL);
      const double * velocityNp1R = stk::mesh::field_data(velocityNp1, nodeR);

      const double pressureL = *stk::mesh::field_data(*pressure_, nodeL);
      const double pressureR = *stk::mesh::field_data(*pressure_, nodeR);

      const double densityL = *stk::mesh::field_data(densityNp1, nodeL);
      const double densityR = *stk::mesh::field_data(densityNp1, nodeR);

      // copy to velcoity relative to mesh
      for ( int j = 0; j < nDim; ++j ) {
        p_vrtmL[j] = velocityNp1L[j];
        p_vrtmR[j] = velocityNp1R[j];
      }

      // deal with mesh motion
      if ( meshMotion_ ) {
        const double * meshVelocityL = stk::mesh::field_data(*meshVelocity_, nodeL );
        const double * meshVelocityR = stk::mesh::field_data(*meshVelocity_, nodeR );
        for (int j = 0; j < nDim; ++j ) {
          p_vrtmL[j] -= meshVelocityL[j];
          p_vrtmR[j] -= meshVelocityR[j];
        }
      }

      // compute geometry
      double axdx = 0.0;
      double asq = 0.0;
      for ( int j = 0; j < nDim; ++j ) {
        const double axj = p_areaVec[j];
        const double dxj = coordR[j] - coordL[j];
        asq += axj*axj;
        axdx += axj*dxj;
      }

      const double inv_axdx = 1.0/axdx;
      const double rhoIp = 0.5*(densityR + densityL);

      //  mdot
      double tmdot = -projTimeScale*(pressureR - pressureL)*asq*inv_axdx;
      for ( int j = 0; j < nDim; ++j ) {
        const double axj = p_areaVec[j];
        const double dxj = coordR[j] - coordL[j];
        const double kxj = axj - asq*inv_axdx*dxj; // NOC
        const double rhoUjIp = 0.5*(densityR*p_vrtmR[j] + densityL*p_vrtmL[j]);
        const double ujIp = 0.5*(p_vrtmR[j] + p_vrtmL[j]);
        const double GjIp = 0.5*(GpdxR[j] + GpdxL[j]);
        tmdot += (interpTogether*rhoUjIp + om_interpTogether*rhoIp*ujIp + projTimeScale*GjIp)*axj 
          - projTimeScale*kxj*GjIp*nocFac;
      }

      const double lhsfac = -asq*inv_axdx;

      /*
        lhs[0] = IL,IL; lhs[1] = IL,IR; IR,IL; IR,IR
      */

      // first left
      p_lhs[0] = -lhsfac;
      p_lhs[1] = +lhsfac;
      p_rhs[0] = -tmdot/projTimeScale;

      // now right
      p_lhs[2] = +lhsfac;
      p_lhs[3] = -lhsfac;
      p_rhs[1] = tmdot/projTimeScale;

      apply_coeff(connected_nodes, rhs, lhs, __FILE__);

    }
  }
}
Esempio n. 4
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//--------------------------------------------------------------------------
//-------- execute ---------------------------------------------------------
//--------------------------------------------------------------------------
void
ComputeMdotEdgeAlgorithm::execute()
{

  stk::mesh::MetaData & meta_data = realm_.meta_data();

  const int nDim = meta_data.spatial_dimension();

  // extract noc
  const std::string dofName = "pressure";
  const double nocFac
    = (realm_.get_noc_usage(dofName) == true) ? 1.0 : 0.0;

  // time step
  const double dt = realm_.get_time_step();
  const double gamma1 = realm_.get_gamma1();
  const double projTimeScale = dt/gamma1;

  // deal with interpolation procedure
  const double interpTogether = realm_.get_mdot_interp();
  const double om_interpTogether = 1.0-interpTogether;

  // area vector; gather into
  std::vector<double> areaVec(nDim);

  // pointers for fast access
  double *p_areaVec = &areaVec[0];

  // deal with state
  ScalarFieldType &densityNp1 = density_->field_of_state(stk::mesh::StateNP1);

  // define some common selectors
  stk::mesh::Selector s_locally_owned_union = meta_data.locally_owned_part()
    &stk::mesh::selectUnion(partVec_);

  stk::mesh::BucketVector const& edge_buckets =
    realm_.get_buckets( stk::topology::EDGE_RANK, s_locally_owned_union );
  for ( stk::mesh::BucketVector::const_iterator ib = edge_buckets.begin();
        ib != edge_buckets.end() ; ++ib ) {
    stk::mesh::Bucket & b = **ib ;
    const stk::mesh::Bucket::size_type length   = b.size();

    // pointer to edge area vector and mdot
          const double * av = stk::mesh::field_data(*edgeAreaVec_, b);
          double * mdot     = stk::mesh::field_data(*massFlowRate_, b);

    for ( stk::mesh::Bucket::size_type k = 0 ; k < length ; ++k ) {

      stk::mesh::Entity const * edge_node_rels = b.begin_nodes(k);

      // sanity check on number or nodes
      ThrowAssert( b.num_nodes(k) == 2 );

      // pointer to edge area vector
      for ( int j = 0; j < nDim; ++j )
        p_areaVec[j] = av[k*nDim+j];

      // left and right nodes
      stk::mesh::Entity nodeL = edge_node_rels[0];
      stk::mesh::Entity nodeR = edge_node_rels[1];

      // extract nodal fields
      const double * coordL = stk::mesh::field_data(*coordinates_, nodeL );
      const double * coordR = stk::mesh::field_data(*coordinates_, nodeR );

      const double * GpdxL = stk::mesh::field_data(*Gpdx_, nodeL );
      const double * GpdxR = stk::mesh::field_data(*Gpdx_, nodeR );

      const double * vrtmL = stk::mesh::field_data(*velocityRTM_, nodeL );
      const double * vrtmR = stk::mesh::field_data(*velocityRTM_, nodeR );

      const double pressureL = *stk::mesh::field_data(*pressure_, nodeL );
      const double pressureR = *stk::mesh::field_data(*pressure_, nodeR );

      const double densityL = *stk::mesh::field_data(densityNp1, nodeL );
      const double densityR = *stk::mesh::field_data(densityNp1, nodeR );

      // compute geometry
      double axdx = 0.0;
      double asq = 0.0;
      for ( int j = 0; j < nDim; ++j ) {
        const double axj = p_areaVec[j];
        const double dxj = coordR[j] - coordL[j];
        asq += axj*axj;
        axdx += axj*dxj;
      }

      const double inv_axdx = 1.0/axdx;
      const double rhoIp = 0.5*(densityR + densityL);

      //  mdot
      double tmdot = -projTimeScale*(pressureR - pressureL)*asq*inv_axdx;
      for ( int j = 0; j < nDim; ++j ) {
        const double axj = p_areaVec[j];
        const double dxj = coordR[j] - coordL[j];
        const double kxj = axj - asq*inv_axdx*dxj; // NOC
        const double rhoUjIp = 0.5*(densityR*vrtmR[j] + densityL*vrtmL[j]);
        const double ujIp = 0.5*(vrtmR[j] + vrtmL[j]);
        const double GjIp = 0.5*(GpdxR[j] + GpdxL[j]);
        tmdot += (interpTogether*rhoUjIp + om_interpTogether*rhoIp*ujIp + projTimeScale*GjIp)*axj 
          - projTimeScale*kxj*GjIp*nocFac;
      }
      // scatter to mdot
      mdot[k] = tmdot;
    }
  }
}
//--------------------------------------------------------------------------
//-------- execute ---------------------------------------------------------
//--------------------------------------------------------------------------
void
AssembleScalarEdgeSolverAlgorithm::execute()
{

  stk::mesh::BulkData & bulk_data = realm_.bulk_data();
  stk::mesh::MetaData & meta_data = realm_.meta_data();

  const int nDim = meta_data.spatial_dimension();

  const double small = 1.0e-16;

  // extract user advection options (allow to potentially change over time)
  const std::string dofName = scalarQ_->name();
  const double hybridFactor = realm_.get_hybrid_factor(dofName);
  const double alpha = realm_.get_alpha_factor(dofName);
  const double alphaUpw = realm_.get_alpha_upw_factor(dofName);
  const double hoUpwind = realm_.get_upw_factor(dofName);
  const bool useLimiter = realm_.primitive_uses_limiter(dofName);

  // one minus flavor
  const double om_alpha = 1.0-alpha;
  const double om_alphaUpw = 1.0-alphaUpw;

  // space for LHS/RHS; always edge connectivity
  const int nodesPerEdge = 2;
  const int lhsSize = nodesPerEdge*nodesPerEdge;
  const int rhsSize = nodesPerEdge;
  std::vector<double> lhs(lhsSize);
  std::vector<double> rhs(rhsSize);
  std::vector<stk::mesh::Entity> connected_nodes(2);

  // area vector; gather into
  std::vector<double> areaVec(nDim);

  // pointer for fast access
  double *p_lhs = &lhs[0];
  double *p_rhs = &rhs[0];
  double *p_areaVec = &areaVec[0];

  // deal with state
  ScalarFieldType &scalarQNp1  = scalarQ_->field_of_state(stk::mesh::StateNP1);
  ScalarFieldType &densityNp1 = density_->field_of_state(stk::mesh::StateNP1);

  // define some common selectors
  stk::mesh::Selector s_locally_owned_union = meta_data.locally_owned_part()
    & stk::mesh::selectUnion(partVec_) 
    & !(realm_.get_inactive_selector());

  stk::mesh::BucketVector const& edge_buckets =
    realm_.get_buckets( stk::topology::EDGE_RANK, s_locally_owned_union );
  for ( stk::mesh::BucketVector::const_iterator ib = edge_buckets.begin();
        ib != edge_buckets.end() ; ++ib ) {
    stk::mesh::Bucket & b = **ib ;
    const stk::mesh::Bucket::size_type length   = b.size();

    // pointer to edge area vector and mdot
    const double * av = stk::mesh::field_data(*edgeAreaVec_, b);
    const double * mdot = stk::mesh::field_data(*massFlowRate_, b);

    for ( stk::mesh::Bucket::size_type k = 0 ; k < length ; ++k ) {

      // zeroing of lhs/rhs
      for ( int i = 0; i < lhsSize; ++i ) {
        p_lhs[i] = 0.0;
      }
      for ( int i = 0; i < rhsSize; ++i ) {
        p_rhs[i] = 0.0;
      }

      // get edge
      stk::mesh::Entity edge = b[k];

      stk::mesh::Entity const * edge_node_rels = bulk_data.begin_nodes(edge);

      // sanity check on number or nodes
      ThrowAssert( bulk_data.num_nodes(edge) == 2 );

      // pointer to edge area vector
      for ( int j = 0; j < nDim; ++j )
        p_areaVec[j] = av[k*nDim+j];
      const double tmdot = mdot[k];

      // left and right nodes
      stk::mesh::Entity nodeL = edge_node_rels[0];
      stk::mesh::Entity nodeR = edge_node_rels[1];

      connected_nodes[0] = nodeL;
      connected_nodes[1] = nodeR;

      // extract nodal fields
      const double * coordL = stk::mesh::field_data(*coordinates_, nodeL);
      const double * coordR = stk::mesh::field_data(*coordinates_, nodeR);

      const double * dqdxL = stk::mesh::field_data(*dqdx_, nodeL);
      const double * dqdxR = stk::mesh::field_data(*dqdx_, nodeR);

      const double * vrtmL = stk::mesh::field_data(*velocityRTM_, nodeL);
      const double * vrtmR = stk::mesh::field_data(*velocityRTM_, nodeR);

      const double qNp1L = *stk::mesh::field_data(scalarQNp1, nodeL);
      const double qNp1R = *stk::mesh::field_data(scalarQNp1, nodeR);

      const double densityL = *stk::mesh::field_data(densityNp1, nodeL);
      const double densityR = *stk::mesh::field_data(densityNp1, nodeR);

      const double diffFluxCoeffL = *stk::mesh::field_data(*diffFluxCoeff_, nodeL);
      const double diffFluxCoeffR = *stk::mesh::field_data(*diffFluxCoeff_, nodeR);

      // compute geometry
      double axdx = 0.0;
      double asq = 0.0;
      double udotx = 0.0;
      for ( int j = 0; j < nDim; ++j ) {
        const double axj = p_areaVec[j];
        const double dxj = coordR[j] - coordL[j];
        asq += axj*axj;
        axdx += axj*dxj;
        udotx += 0.5*dxj*(vrtmL[j] + vrtmR[j]);
      }

      const double inv_axdx = 1.0/axdx;

      // ip props
      const double viscIp = 0.5*(diffFluxCoeffL + diffFluxCoeffR);
      const double diffIp = 0.5*(diffFluxCoeffL/densityL + diffFluxCoeffR/densityR);

      // Peclet factor
      double pecfac = hybridFactor*udotx/(diffIp+small);
      pecfac = pecfac*pecfac/(5.0 + pecfac*pecfac);
      const double om_pecfac = 1.0-pecfac;

      // left and right extrapolation; add in diffusion calc
      double dqL = 0.0;
      double dqR = 0.0;
      double nonOrth = 0.0;
      for ( int j = 0; j < nDim; ++j ) {
        const double dxj = coordR[j] - coordL[j];
        dqL += 0.5*dxj*dqdxL[j];
        dqR += 0.5*dxj*dqdxR[j];
        // now non-orth (over-relaxed procedure of Jasek)
        const double axj = p_areaVec[j];
        const double kxj = axj - asq*inv_axdx*dxj;
        const double GjIp = 0.5*(dqdxL[j] + dqdxR[j]);
        nonOrth += -viscIp*kxj*GjIp;
      }

      // add limiter if appropriate
      double limitL = 1.0;
      double limitR = 1.0;
      const double dq = qNp1R - qNp1L;
      if ( useLimiter ) {
        const double dqMl = 2.0*2.0*dqL - dq;
        const double dqMr = 2.0*2.0*dqR - dq;
        limitL = van_leer(dqMl, dq, small);
        limitR = van_leer(dqMr, dq, small);
      }
      
      // extrapolated; for now limit
      const double qIpL = qNp1L + dqL*hoUpwind*limitL;
      const double qIpR = qNp1R - dqR*hoUpwind*limitR;

      //====================================
      // diffusive flux
      //====================================
      double lhsfac = -viscIp*asq*inv_axdx;
      double diffFlux = lhsfac*(qNp1R - qNp1L) + nonOrth;

      // first left
      p_lhs[0] = -lhsfac;
      p_lhs[1] = +lhsfac;
      p_rhs[0] = -diffFlux;

      // now right
      p_lhs[2] = +lhsfac;
      p_lhs[3] = -lhsfac;
      p_rhs[1] = diffFlux;

      //====================================
      // advective flux
      //====================================

      // 2nd order central
      const double qIp = 0.5*( qNp1L + qNp1R );

      // upwind
      const double qUpwind = (tmdot > 0) ? alphaUpw*qIpL + om_alphaUpw*qIp
          : alphaUpw*qIpR + om_alphaUpw*qIp;

      // generalized central (2nd and 4th order)
      const double qHatL = alpha*qIpL + om_alpha*qIp;
      const double qHatR = alpha*qIpR + om_alpha*qIp;
      const double qCds = 0.5*(qHatL + qHatR);

      // total advection
      const double aflux = tmdot*(pecfac*qUpwind + om_pecfac*qCds);

      // upwind advection (includes 4th); left node
      double alhsfac = 0.5*(tmdot+std::abs(tmdot))*pecfac*alphaUpw
        + 0.5*alpha*om_pecfac*tmdot;
      p_lhs[0] += alhsfac;
      p_lhs[2] -= alhsfac;

      // upwind advection; right node
      alhsfac = 0.5*(tmdot-std::abs(tmdot))*pecfac*alphaUpw
        + 0.5*alpha*om_pecfac*tmdot;
      p_lhs[3] -= alhsfac;
      p_lhs[1] += alhsfac;

      // central; left; collect terms on alpha and alphaUpw
      alhsfac = 0.5*tmdot*(pecfac*om_alphaUpw + om_pecfac*om_alpha);
      p_lhs[0] += alhsfac;
      p_lhs[1] += alhsfac;
      // central; right; collect terms on alpha and alphaUpw
      p_lhs[2] -= alhsfac;
      p_lhs[3] -= alhsfac;

      // total flux left
      p_rhs[0] -= aflux;
      // total flux right
      p_rhs[1] += aflux;

      apply_coeff(connected_nodes, rhs, lhs, __FILE__);

    }
  }
}