The Cauchy Problem For A Non Strictly Hyperbolic 3×3 System Of Conservation Laws Arising In Polymer Flooding

We Study The Cauchy Problem Of A 3×3 System Of Conservation Laws Modeling Two–Phase Flow Of Polymer Flooding In Rough Porous Media With Possibly Discontinuous Permeability Function. The System Loses Strict Hyperbolicity In Some Regions Of The Domain Where The Eigenvalues Of Different Families Coincide, And Bv Estimates Are Not Available In General. For A Suitable 2×2 System, A Singular Change Of Variable Introduced By Temple [B. Temple, Adv. Appl. Math., 3(3):335–375, 1982], [E.L.Isaacson And J.B. Temple, J. Diff. Eqs., 65(2):250–268, 1986] Could Be Effective To Control The Total Variation [W. Shen, J. Diff. Eqs., 261(1):627–653, 2016]. An Extension Of This Technique Can Be Applied To A 3×3 System Only Under Strict Hypotheses On The Flux Functions [G.M. Coclite And N.H. Risebro, Siam J. Math. Anal., 36(4):1293–1309, 2005].