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Neste trabalho estudamos a existência de soluções de equações do tipo Navier-Stokes com retardo na força externa e no termo n~ao linear. Usando a teoria de semigrupos estudamos a existência de soluções para um problema da forma \'d. SUP. dt u(t) - v\'delta\'u(t) + (F(t, \'u IND.t\'). abla)u(t) + abla p = g(t, \'u IND.t\'), em \'OMEGA\' x (0, T), div u(t) = 0 em \'OMEGA\' x (0, T), u(0, x) = \'u POT.0 (x) x PERTENCE a \' OMEGA\', u(t, x) = 0 t > 0, X \'PERTENCE A\' \' PARTIAL\' \'OMEGA\', u(t, x) =\\phi (t, x) t \'PERTENCE A\' (- \'INFINITO\', 0) x \'PERTENCE A\' \'OMEGA\', onde F9t, \'uIND.t) = INT.IND.t SUP. -\' INFINITO\' \' ALFA1(s-t)u(s)ds + u(t-r), g(t, \'u IND.t\') = INT. SUP. t IND. - INFINITO \'BETA\' (s-t)u(s)ds. Similarmente, usando a tecnica de aproximac~oes de Galerkin, estudamos o problema anterior com F(.) e g(.) dadas por f(t; \'u INDS.t\') = u(t-r(t)); e g(t; \'u IND.t\') = G(u(t-\'rô\' (t))), para alguma função G apropriada. Neste caso, também estudamos a estabilidade de soluções estacionarias / In this work we stuy the existence of solutions for a Navier-Stokes typt equations with delay in the external force and in the nonlinear term. Using the semi-group theory we study the existence of solution for a problem in the form \'d. SUP. dt u(t) - v\'delta\'u(t) + (F(t, \'u IND.t\'). abla)u(t) + abla p = g(t, \'u IND.t\'), ijn \'OMEGA\' x (0, T), div u(t) = 0 in \'OMEGA\' x (0, T), u(0, x) = \'u POT.0 (x) x \'IT BELONGS \' OMEGA\', u(t, x) = 0 t > 0, X \'IT BELONGS\' \'PARTIAL\' \'OMEGA\', u(t, x) =\\phi (t, x) t \'IT BELONGS\' (- \'INFINITY\', 0) x \'IT BELONGS\' \'OMEGA\', where F(t, \'u .t) = INT.IND.t SUP. -\' INFINITY\' \' ALFA(s-t)u(s)ds + u(t-r), g(t, \'u IND.t\') = INT. SUP. t IND. - INFINITY \'BETA\' (s-t)u(s)ds. On another hand using the Galerkin appreoximations method we study the same with F(.) e g(.) given by f(t; \'u INDS.t\') = u(t-r(t)); and g(t; \'u IND.t\') = G(u(t-\'rô\' (t))), for some G appropriated. In thiis case, we study also the stability of stanionary solutions

Orientador: Lucas Catão de Freitas Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-19T15:06:30Z (GMT). No. of bitstreams: 1 Alves_BrunoFerreira_M.pdf: 943114 bytes, checksum: 70e3cdb3ee60ae3ed29a79cfeded3f59 (MD5) Previous issue date: 2012 / Resumo: Estudamos as equações de Navier-Stokes (NS) em...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: We study the Navier-Stokes equations (NS) in...Note: The complete abstract is available with the full electronic document / Mestrado / Matematica / Mestre em Matemática

Doctor en Ciencias de la Ingeniería, Mención Modelación Matemática / This thesis is focused on the Navier{Stokes system for incompressible uids with either Dirichlet or nonlinear Navier{slip boundary conditions. For these systems, we exploit some ideas in the context of the control theory and inverse source problems. The thesis is divided in three parts. In the rst part, we deal with the local null controllability for the Navier{Stokes system with nonlinear Navier{slip conditions, where the internal controls have one vanishing component. The novelty of the boundary conditions and the new estimates with respect to the pressure term, has allowed us to extend previous results on controllability for the Navier{ Stokes system. The main ingredients to build our result are the following: a new regularity result for the linearized system around the origin, and a suitable Carleman inequality for the adjoint system associated to the linearized system. Finally, xed point arguments are used in order to conclude the proof. In the second part, we deal with an inverse source problem for the N- dimensional Stokes system from local and missing velocity measurements. More precisely, our main result establishes a reconstruction formula for the source F(x; t) = (t)f(x) from local observations of N ����� 1 components of the velocity. We consider that f(x) is an unknown vectorial function, meanwhile (t) is known. As a consequence, the uniqueness is achieved for f(x) in a suitable Sobolev space. The main tools are the following: connection between null controllability and inverse problems throughout a result on null controllability for the N- dimensional Stokes system with N ����� 1 scalar controls, spectral analysis of the Stokes operator and Volterra integral equations. We also implement this result and present several numerical experiments that show the feasibility of the proposed recovering formula. Finally, the last chapter of the thesis presents a partial result of stability for the Stokes system when we consider a source F(x; t) = R(x; t)g(x), where R(x; t) is a known vectorial function and g(x) is unknown. This result involves the Bukhgeim-Klibanov method for solving inverse problems and some topics in degenerate Sobolev spaces.

Atmospheric mixing is a problem of exceptional importance and difficult to study. The anelastic approximation is the accepted fluid system governing the atmosphere over large vertical scales (about 8 km). The anelastic equations, unlike the Navier-Stokes equations, incorporate a nontrivial spatial divergence constraint on the velocity field. This yields a weakly compressible fluid flow. The basis of this study is to use numerical analysis to explore the effects of weak compressibility in the evolution of fluid governed by the anelastic equations, and the effects of incompressibility governed by the Navier-Stokes equation. The analysis then goes on to investigate the difference between three different initial conditions. Within each initial condition different density profiles are observed while varying parameters are investigated. Numerical results show that comparisons of incompressible Navier-Stokes equations to the anelastic fluid flow equations do not produce similar results. The weakly compressible flow creates a mixing barrier, stopping vertical fluid exchange. The perturbed middle region / US Navy (USN) author

這篇論文將對三維不可壓納維 - 斯托克斯方程的軸對稱解的正則性理論作綜述。 / 在第一章會先重溫一些經典的正則性結果，例如用於 Leray-Hopf 弱解上的Serrin類條件和用於適當弱解上的Caffarelli-Kohn-Nirenberg 類理論。 / 第二章會處理假設為無漩的軸對稱解，由 Uchovskii 和Ladyzhenskaya 提出的整體正則解的唯一存在的結果將包含在其中。 / 從第三章起，解的漩將不再被假設為零，在這熱門的研究領域中，一些值得注意的結果會包含在論文之中。 / In this thesis, a survey on the regularity theory for axisymmetric solutions to the 3D incompressible Navier-Stokes equations is conducted. / In chapter 1, some classical results such as the Serrin-type criteria on the Leray-Hopf weak solutions and the Ca arelli-Kohn-Nirenberg partial regularity theory on the suitable weak solutions to the equations are reviewed. / Chapter 2 deals with the axisymmetric solutions of the equations assuming the unknown velocity has no swirl. The existence result on the unique regular global-in-time solution by Uchovskii and Ladyzhenskaya is included. / In chapter 3, the swirl component of the unknown velocity is no longer assumed to be zero and some remarkable results on this hot research area are presented and discussed in the thesis. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Lau, Tsz Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 49-51). / Abstracts also in Chinese. / Chapter 1 --- Classical Results on the 3D Incompressible Navier-Stokes Equations --- p.3 / Chapter 1.1 --- Introduction --- p.3 / Chapter 1.1.1 --- Backgrounds of the Equations --- p.3 / Chapter 1.1.2 --- A Boundary Value Problem on Pressure --- p.4 / Chapter 1.1.3 --- The Helmholtz-Leray Decomposition --- p.5 / Chapter 1.1.4 --- The Energy Equality --- p.6 / Chapter 1.1.5 --- The Leray-Hopf Weak Solution --- p.8 / Chapter 1.1.6 --- Foreword to the Regularity Problem --- p.9 / Chapter 1.2 --- Serrin's Regularity Result --- p.10 / Chapter 1.2.1 --- The Vorticity Form --- p.11 / Chapter 1.2.2 --- Regularity of the Vorticity --- p.12 / Chapter 1.2.3 --- The Biot-Savart Law and Parabolic Regularity --- p.13 / Chapter 1.2.4 --- Later Developments --- p.14 / Chapter 1.3 --- CKN Partial Regularity Theory --- p.14 / Chapter 1.3.1 --- Backgrounds and the Main Result --- p.14 / Chapter 1.3.2 --- A Local Conditions for Regularity of u --- p.16 / Chapter 1.3.3 --- The Blow-up Estimate --- p.19 / Chapter 1.3.4 --- Estimating the Singular Set --- p.22 / Chapter 1.3.5 --- Later Developments --- p.23 / Chapter 2 --- On Axially Symmetric Flows Without Swirl --- p.25 / Chapter 2.1 --- Introduction and the Main Result --- p.25 / Chapter 2.2 --- A Local-in-time Existence Result --- p.26 / Chapter 2.3 --- A Priori Estimate --- p.27 / Chapter 2.4 --- Proving the Global Existence Result --- p.31 / Chapter 3 --- On Axially Symmetric Flows with Non-zero Swirl --- p.32 / Chapter 3.1 --- Serrin's Type Regularity Conditions --- p.32 / Chapter 3.1.1 --- Backgrounds and the Main Result --- p.32 / Chapter 3.1.2 --- A Brief Discussion on the Proof --- p.33 / Chapter 3.1.3 --- Later Developments --- p.36 / Chapter 3.2 --- Lower Bound on the Blow-up Rate --- p.37 / Chapter 3.2.1 --- Backgrounds and the Main Result --- p.37 / Chapter 3.2.2 --- Construction of Suitable Weak Solutions --- p.38 / Chapter 3.2.3 --- Idea of the Proof --- p.40 / Chapter 3.2.4 --- Later Developments --- p.42 / Chapter 3.3 --- An Alternative Proof on Slow Blow-up --- p.43 / Chapter 3.3.1 --- Backgrounds and the Main Result --- p.43 / Chapter 3.3.2 --- Liouville Type Theorems --- p.44 / Chapter 3.3.3 --- The Re-scaling Procedure --- p.46 / Chapter 3.3.4 --- Later Developments --- p.47

本文研究了不可壓Navier-Stokes 方程和其他相關係統的解的正則性，包括适当弱解和Leray-Hopf 弱解。 / 首先，我們考慮了不可壓穩態Navier-Stokes 方程和磁流体方程的適當弱解的部分正則性，包括內部和邊界情況。與五維情況不同，最關鍵的爆破方法在這種情況下不適用，我們用了靴帶法。但是對於邊界情況，在壓力的迭代中出現了困難項。為了克服它們，我們充分利用了改進的局部能量不等式並且找到了一個新的迭代量。這在本文定理的證明中起到了關鍵的作用。此外，這給我們提供了一種處理適當弱解的邊界正則性的新方法。 / 接著，我們得到了一些不依賴於磁場的四維磁流體方程的內部正則性準則。考慮到四維是臨界情況，我們仍然採用靴帶法。為了保證解的正則性準則不依賴於磁場，我們要做更精細的估計。 / 再次，对于三維轴对称磁流体方程，我們讨论了兩种LerayHopf弱解的正則性准則。利用标准的能量方法和爆破准則，我們得到了一些充分条件。这些条件保证了解的光滑性。 / 最後，對於帶有部分粘性的三維軸對稱磁流體方程，我們得到了Leray-Hopf 弱解的整體正則性。在部分粘性缺失的情況下，相關方向失了光滑性效應。在這種情況下，我們充分利用了磁流體的方程的特殊結構去彌補這個困難。 / In this thesis, we study the regularity of solutions to the incompressible Navier- Stokes equations and other related systems, including both suitable weak solutions and Leray-Hopf weak solutions. / Firstly, we consider the partial regualrity of suitable weak solutions to the 6D steady-state Navier-Stokes and MHD equations, including both interior and boundary case. Be different from the five dimensional case, the key blow-up arguments don't hold in this case, we use the bootstrap arguments instead. However, for the boundary case, hard terms appear in the interation of pressure. To overcome them, we make full use of the revised local energy inequality and find a new iteration quantity which plays a crucial role in the proof. Moreover, this provides a new method to deal with the boundary regularity of suitable weak solutions. / Secondly, we obtain some interior regularity criterias for the four dimensional MHD equations indepedent of magnetic field. Considering that four dimension is the critical case, we still use the bootstrap arguments. To guarantee that the criterias is independent of magnetic, we should do more subtle estimates. / Thirdly, we discuss two kinds of regularity criterias of Leray-Hopf weak solutions to 3D axisymmetric MHD equations. By use of standard energy method and blow-up arguments, we derive some sufficient conditions which guarantee the smoothness of solutions. / Finally, we get the global regualrity of Leray-Hopf weak solutions of 3D axisymmetric MHD equations with partial viscosities. In the absence of partial viscosities, there is no smoothing effect on that directions. Under this circumstance, we take full advantage of the special structure of MHD equations to make up this shortcoming. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Liu, Jitao. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 132-142). / Abstracts also in Chinese. / Introduction --- p.4 / Chapter 1 --- Interior and Boundary Regularity Criterias for 6D Steady-State incompressible Navier-Stokes and MHD equations --- p.17 / Chapter 1.1 --- Introduction --- p.18 / Chapter 1.2 --- Notations --- p.18 / Chapter 1.3 --- Interior Regualrity --- p.20 / Chapter 1.3.1 --- Main results --- p.20 / Chapter 1.3.2 --- Proof of Theorem 2.1.2 --- p.23 / Chapter 1.3.3 --- Proof of Theorem 2.1.3 --- p.27 / Chapter 1.3.4 --- Proof of Theorem 2.5.4 --- p.29 / Chapter 1.4 --- Boundary Regularity --- p.36 / Chapter 1.4.1 --- Main Results --- p.36 / Chapter 1.4.2 --- Some technical lemmas --- p.39 / Chapter 1.4.3 --- Proof of Theorem 1.4.2 --- p.42 / Chapter 1.4.4 --- Proof of Proposition 1.4.8 --- p.45 / Chapter 2 --- Interior Regularity Criterias for the incompressible MHD Equations in four diemnsion --- p.54 / Chapter 2.1 --- Introduction --- p.55 / Chapter 2.2 --- Notations and some technical lemmas --- p.57 / Chapter 2.3 --- Proof of Theorem 2.1.2: Estimates of the velocity --- p.60 / Chapter 2.4 --- Proof of Theorem 2.1.3: Estimates of the gradient of the velocity --- p.65 / Chapter 2.5 --- Proof of Proposition 2.1.4: "-regularity --- p.67 / Chapter 3 --- Regularity Criterias of the 3D axisymmetric MHD Equations --- p.73 / Chapter 3.1 --- Introduction --- p.74 / Chapter 3.2 --- Preliminaries --- p.76 / Chapter 3.2.1 --- Notations --- p.76 / Chapter 3.2.2 --- Some useful estimates --- p.77 / Chapter 3.3 --- Proof of Theorem 3.1.1 --- p.82 / Chapter 3.4 --- Proof of Theorem 3.1.2 and 3.1.3 --- p.86 / Chapter 3.4.1 --- Proof of Theorem 3.1.2 --- p.86 / Chapter 3.4.2 --- Proof of Theorem 3.1.3 --- p.91 / Chapter 3.5 --- Proof of Theorem 3.1.4 --- p.94 / Chapter 4 --- Global regularity for the 3D axisymmetric MHD Equations with horizontal dissipation and vertical magnetic dicusion --- p.103 / Chapter 4.1 --- Introduction --- p.104 / Chapter 4.2 --- Notations and some technical lemmas --- p.104 / Chapter 4.2.1 --- Notations --- p.105 / Chapter 4.2.2 --- Some estimates about axisymmetric structure --- p.106 / Chapter 4.2.3 --- Some estimates about partial viscosities --- p.109 / Chapter 4.3 --- A Priori Estimates --- p.110 / Chapter 4.3.1 --- L² and H¹ Estimates --- p.110 / Chapter 4.3.2 --- H² Estimates --- p.117 / Chapter 4.4 --- Proof of Theorem 4.1.1 --- p.126 / Chapter 5 --- Discussions on the Future Research --- p.130 / Chapter 5.1 --- Incompressible Navier-Stokes equations --- p.130 / Chapter 5.2 --- Incompressible MHD equations --- p.131 / Bibliography --- p.131

Li Jing. / "June 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 66-71). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Zhou Yong. / "July 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 105-112). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Finally, we prove a blow up criterion for the full compressible Navier-Stokes equations just in terms of the gradient of the velocity. / In this thesis, the author study the blowup of solutions for strong and classical solutions to the compressible Navier-Stokes equations. In the first part, we prove a blow up criterion for strong solutions to the compressible Navier-Stokes equations, similar to the Beal-Kato-Majda criterion for the ideal incompressible flows. / The same criterion for classical solutions to the compressible Navier-Stokes equations is established in the second part of this thesis. In addition, initial vacuum is allowed in both cases. / Huang, Xiangdi. / Adviser: Zhouping Xin. / Source: Dissertation Abstracts International, Volume: 73-09(E), Section: B. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 90-96). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.