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12.4  Beam-Warming  Method                                            357



         12.4  Beam—Warming        Method

         The  Beam-Warming   (B-W) method   for  the  solution  of the  one-dimensional
         time-dependent  Euler  equations,  Eq. (5.1.2),  was discussed  in  Section  5.4 and
         its extension to the two-dimensional compressible viscous flows is discussed now,
         following [3].
            An  obvious  extension  of Eq.  (5.4.4)  to a two-dimensional  flow is,

                                                           5
         AQ n  =   6 At                           6At  1  f ( A F » U  °  (AF n
                   1 + e
                     At    d_ ( En    E%\    d_
                 +        dx\         Re/    dy    F  +  Re~
                    1 + C
                 +       AQ  n-\                                          (12.4.1)
                    1 + C
                                                           n
         The first term on the right-hand-side of Eq.  (12.4.1) AE  is given by Eq.  (5.4.7b)
         and,  similarly, the second  term  can be written as
                                                       2
                                 AF n  = BAQ n  +  0{At )                 (12.4.2)
         where
                                      *"(£*                               (12.4.3)


               1
         Since  E™ and  F™ are functions  of Q, Q x  and Q y,  they  can be written as
                                   = Vi(Q,Q x)  + V 2(Q,Q y)             (12.4.4a)
                                E v
                                  = W 1(Q,Q x)  + W 2(Q,Q y)             (12.4.4b)
                               F v
         where

                               0                              0
                             \\iu x
           Vi                                     V 2 =                  (12.4.5a)
                              fiv x                          flUy
                 HVV X +  \\±UU X  +  ^i^M^pj-Tx        fiVUy  — ^fXUVy J

                       0                                0
                                                      fiu y
          Wi  =                    w  =                                  (12.4.5b)
                      /J>V X        2                 t^Vy
                                         [fiUUy  +  zflVVy  +  J^fM£p- TTy
                 jJLUVx  —  ^)1VU X
         Then
                                d         9
                                  Arm        A.rn   9   ATrn             (12.4.6a)
                               -AE" V=-AV?       +   -AV?
                                                                         (12.4.6b)
                                       = l yAW?      l yAW?
                               l yA K
         As with  Eq.  (5.4.7a),  we can  write  +
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