Global L∞ Solutions to System of Isentropic Gas Dynamics in a Divergent Nozzle with Friction

In this article, we study the global L∞ entropy solutions for the Cauchy problem of system of isentropic gas dynamics in a divergent nozzle with a friction. Especially when the adiabatic exponent γ = 3, we apply for the maximum principle to obtain the L∞ estimates w(ρδ,ε, uδ,ε) ≤ B(t) and z(ρδ,ε, uδ,ε) ≤ B(t) for the viscosity solutions (ρδ,ε, uδ,ε), where B(t) is a nonnegative bounded function for any finite time t. This work, in the special case γ ≥ 3, extends the previous works, which provided the global entropy solutions for the same Cauchy problem with the restriction w(ρδ,ε, uδ,ε) ≤ 0 or z(ρδ,ε, uδ,ε) ≤ 0.