Research Article | Open Access
On Existence, Uniform Decay Rates, and Blow-Up for Solutions of a Nonlinear Wave Equation with Dissipative and Source
This paper studies the blow-up and existence, and asymptotic behaviors of the solution of a nonlinear hyperbolic equation with dissipative and source terms. By using Galerkin procedure and the perturbed energy method, the local and global existence of solution is established. In addition, by the concave method, the blow-up of solutions can be obtained.
In this paper, we investigate the following nonlinear wave equation: where is a bounded domain in with smooth boundary , is a Laplace operator, and indicates derivative of in outward normal direction of . In addition to, if and if , then . is a constant, are given in (A1) later.
In 1968, Greenberg et al.  first suggested and studied the following equation: Under the condition and higher smooth conditions on and initial data, they claimed the global existence of classical solutions for the initial boundary value problem of (1.2).
The multidimensional form of the following: was first studied by Clement [2, 3]. Exploiting the monotone operator method, he obtained the global existence of weak solutions for the initial boundary value problem of (1.2).
Our model comes from . In , Yang has studied the global existence, asymptotic behavior, and blow-up of solutions for a nonlinear wave equations with dissipative term: with the same initial and boundary conditions as that of (1.1). In our model, we add damping and source terms which enhance the difficulty of proving the existence and decay of solution of (1.2).
The paper is organized as follows. In Section 2, we present some notations, and results needed later and main results. Section 3 contains the statement and the proofs of the decay of solutions. Section 4 gives the statement and the proofs of the blow-up of solutions.
We first introduce the following abbreviations: Let () denote the -inner product. We denote the dual of by , with , and . Now we make the following assumptions:) and for some , if , else if , then , so that , , where is the optimal embedding constant.() The initial data (); If , then and if , then . () If , and if , then . Without loss of generality, we assume that .
And(), and for some , if , else if , then , so that , . where is the optimal embedding constant, and .() If , then and if , then .(), and if , then and if , then .
Throughout this paper, we use the embedding which implies when where is an optimal embedding constant. We introduce the following functionals: Because , we have
Theorem 2.1. Assume that ()–() hold, then problem (1.1) has a unique solution satisfying where .
Theorem 2.2. Assume that ()–() hold, is the local solution of the problem (1.1). And where , then is a global bounded solution, moreover, where is a constant.
Theorem 2.5. Assume that ()–(), () hold, and there exist some , then the solution of the problem (1.1) blows-up at the limited time .
3. Decay of Solutions
Lemma 3.1 (see ). Let be any bounded domain in , be an orthogonal basis in . Then for any , there exists a positive number such that for all .
Proof of Theorem 2.1. We look for approximate solutions of problem (1.1) of the form
where is an orthogonal basis in , and also in , and the coefficients satisfy with
Since is dense in and , we choose such that
The above system of o.d.e. has a local solution defined in some interval . The following will prove that the can be substituted by some .
Multiply (3.3) by and summing up about , we get A simple integration of (3.5) over leads to where .
We now estimate the last two terms at the right-hand side of (3.6). Using Hӧlder inequality, Young's inequality, and the embedding theorem, we know there exist , satisfying that where Consider the following: assuming that .
Similarly, Using (3.6)–(3.10), we have Choosing in (3.11), we have where . Assuming , we have A simple integration of (3.13) over leads to this implies that Though may blow up, there exists satisfying where is independent of .
Moreover, By (3.17), By (3.16), From (3.16)–(3.19), we have So the solution of problem (3.3) exists on for each . On the other hand, we can extract a subsequence from , still denoted by , such that as . By (3.21), the Sobolev embedding theorem and the continuity of , for , as . By Lemma 3.1, (3.21)-(3.22), for any , there exist positive constant and independent of and , respectively, such that, as ,
By the arbitrariness of we get From the continuity of and (3.25) we know that a.e. on . With the same methods used above we easily get a.e. on . Integrating (3.3) over gets Exploiting (3.16)-(3.17), we have
Let in (3.26) and we deduce from (3.23), (3.27) and the Lebesgue-dominated convergence theorem that This implies is a local weak solution of problem (1.1). The proof of Theorem 2.1 is completed.
Secondly, we prove Theorem 2.2. First we give two lemmas. It is easy to prove what follows.
Lemma 3.2. The modified energy functional satisfies, along solutions of (1.1),
Lemma 3.3. Assume that ()–() hold, satisfying Then .
Proof. Since , then there exists (by continuity) such that , this gives
By using (2.8), (2.9), (3.31), and Lemma 3.2, we easily have
We then exploit (2.12), and (3.32) to obtain
Using (3.33), we have
Therefore, for all . By repeating this procedure, and using the fact that the proof is completed.
Lemma 3.4. Assume that ()–() hold, (2.12) satisfy. Then the solution is global existence. More, exist positive constant has
Proof. It suffices to show that is bounded independently of . To achieve this, we use (2.9), (3.31), and Lemma 3.2 to get Since are positive. Therefore, Moreover, where is a positive constant, which depends only on .
Lemma 3.5. Assume that ()–() hold, (2.12) satisfy. Then exist has
Lemma 3.6. Assume that ()–() hold, (2.12) satisfy. Then there exists a , having
Proof of Theorem 2.2. First, is also absolutely continuous, and we have
A simple integration of (3.52) over leads to
Using the upper inequality, (3.45), (3.46), and (3.52), we have
Apply (3.42), (3.47), we can get (2.13).
Using (3.31) and Lemma 3.3, we get . (2.13) implies . So when , we have and . It is that (2.14) is satisfied. Theorem 2.2 is complete.
Following we will prove Theorem 2.3. For this purpose we set where is a positive constant and
Lemma 3.7. Let be small enough. Then there exist two positive constants and such that
Proof. By Lemma 3.4 and Young's inequality, a direct computation gives Similarly, we have provided that is small enough.
Proof. Applying equations of (1.1), we see Exploiting the assumption () and Young's inequality, we have Exploiting (3.63) and (3.62), we get Choosing satisfies and satisfies at the above; the proof of (3.61) is completed.