The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Shengping Shen - One of the best experts on this subject based on the ideXlab platform.
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Experimental decoupling of cylindrical flexoelectric Coefficients
Applied Physics Letters, 2018Co-Authors: Shuwen Zhang, Tonghui Wu, Minglong Xu, Shengping ShenAbstract:Flexoelectricity is a property of all dielectric materials in which they polarize in response to deformation gradients such as those produced by pressing, bending, or twisting, and knowledge of flexoelectric Coefficients is essential when considering the applications of flexoelectricity. Here, we describe an experimental approach to the measurement of cylindrical flexoelectric Coefficients of polyvinylidene fluoride. Two specimens are designed to generate and decouple the corresponding strain gradients. Theoretical and finite element analyses are developed and simplified, and specimen designs are then tested to obtain multiple strain-gradient-coupled electric polarization charges. The flexoelectric Coefficients μφzρρ and μφzzρ are then decoupled, using two independent equations together with the experimental data. This work provides an experimental method that can be used to obtain multiple unknown flexoelectric Coefficient Tensor components by imposition of a twisting load, and it reveals the potential for the application of flexoelectricity in irregular structures in complex environments.Flexoelectricity is a property of all dielectric materials in which they polarize in response to deformation gradients such as those produced by pressing, bending, or twisting, and knowledge of flexoelectric Coefficients is essential when considering the applications of flexoelectricity. Here, we describe an experimental approach to the measurement of cylindrical flexoelectric Coefficients of polyvinylidene fluoride. Two specimens are designed to generate and decouple the corresponding strain gradients. Theoretical and finite element analyses are developed and simplified, and specimen designs are then tested to obtain multiple strain-gradient-coupled electric polarization charges. The flexoelectric Coefficients μφzρρ and μφzzρ are then decoupled, using two independent equations together with the experimental data. This work provides an experimental method that can be used to obtain multiple unknown flexoelectric Coefficient Tensor components by imposition of a twisting load, and it reveals the potential f...
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Experimental approach for measuring cylindrical flexoelectric Coefficients
Journal of Applied Physics, 2017Co-Authors: Shuwen Zhang, Tonghui Wu, Minglong Xu, Shengping ShenAbstract:Flexoelectricity is a property of dielectric materials by which applied strain gradients induce electric polarizations within dielectric materials. Experimental research into the Tensor components of the flexoelectric Coefficient is essential. In this work, an experimental approach for measurement of the flexoelectric Coefficient Tensor components in cylindrical coordinates is developed. Two different experimental methods are designed to obtain the two related unknown flexoelectric Coefficient Tensor components. Theoretical and finite element analyses are developed and simplified for each experiment, and the related designs are then tested to obtain the coupled electric polarization charges. The two unknown flexoelectric Coefficient Tensor components of polyvinylidene fluoride are then decoupled. This work provides an experimental method that can be used to obtain multiple unknown flexoelectric Coefficient Tensor components in solid dielectric materials.
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investigation of the 2312 flexoelectric Coefficient component of polyvinylidene fluoride deduction simulation and mensuration
Scientific Reports, 2017Co-Authors: Shuwen Zhang, Hao Shen, Kai Chen, Minglong Xu, Bo Feng, Shengping ShenAbstract:Flexoelectric effects hold promising applications in sensing, actuating, and energy capturing, and thus it is demanded to measure the flexoelectric Coefficient Tensors of dielectric materials accurately. In this work, an approach to measuring the effective flexoelectric Coefficient Tensor component μ 2312 of polymeric materials is developed by imposing a torque load upon a half cylindrical specimen. It is proven that μ 2312 can be calculated by assessing the electric charge on the axial plane and the strain gradient along the radial direction, both induced by the torque. To overcome the difficulty in experimental measurements, the relationship between the strain gradient and torque is deduced theoretically and further verified with finite element analysis. This approach is applied to testing bars machined from bulk polyvinylidene fluoride (PVDF). Potential errors from the piezoelectric effects and the non-uniform strain gradient are discussed to verify the validity of the measurement. The experimental results show good reproducibility and agreement with other measured effective flexoelectric Tensor components of PVDF. This work indicates a potential application of PVDF-based mechanical sensors and provides a method to investigate the effective flexoelectric Coefficient component of polymers.
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Experimental method research on transverse flexoelectric response of poly(vinylidene fluoride)
Japanese Journal of Applied Physics, 2016Co-Authors: Shuwen Zhang, Guoliang Ma, Xu Liang, Minglong Xu, Shengping ShenAbstract:Flexoelectricity describes the strain-gradient-induced electric polarization existing in dielectric materials. The Coefficient that exists between the strain-gradient and the induced electric polarization defines the flexoelectric Coefficient Tensor. It is necessary to analyze different experimental methods to evaluate the procedure of measuring the transverse flexoelectric Coefficient Tensor component. In this work, the transverse flexoelectric Coefficient Tensor component of poly(vinylidene fluoride) (PVDF) is studied using three different experimental methods and the effects of the mentioned methods are evaluated. The results presented in this work are helpful for the design of experiments of different dielectric materials, including ceramics and polymers on flexoelectricity.
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shear flexoelectric Coefficient μ1211 in polyvinylidene fluoride
Journal of Applied Physics, 2015Co-Authors: Shuwen Zhang, Xu Liang, Minglong Xu, Shengping ShenAbstract:Defined as a strain gradient-induced electric polarization, flexoelectricity exists in all dielectric materials. The Coefficient that exists between the strain gradient and the electric polarization defines the flexoelectric Coefficient Tensor. The Tensor components along the longitudinal and transverse directions have been studied widely. However, little progress has been reported on flexoelectric properties in the shear direction to date. In this work, a novel method for measurement of the shear flexoelectric Coefficient μ1211 of polyvinylidene fluoride is presented. An experiment is conducted on a tubular unpolarized specimen, where shear strain gradient is generated along the radial direction by applying torque to the ends of the tube-shaped specimen. Dynamic torque is exerted on specimens with a static bias value and at different frequencies. The generated shear strain gradient is calculated via finite element analysis and the corresponding induced electrical polarization is measured using a charge a...
Wolfgang L. Wendland - One of the best experts on this subject based on the ideXlab platform.
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variational approach for layer potentials of the stokes system with l_ infty symmetrically elliptic Coefficient Tensor and applications to stokes and navier stokes boundary problems
arXiv: Analysis of PDEs, 2020Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:The first aim of this paper is to develop a layer potential theory in $L_2$-based weighted Sobolev spaces on Lipschitz bounded and exterior domains of ${\mathbb R}^n$, $n\geq 3$, for the anisotropic Stokes system with $L_{\infty }$ viscosity Coefficient Tensor satisfying an ellipticity condition for symmetric matrices. To do this, we explore equivalent mixed variational formulations and prove the well-posedness of some transmission problems for the anisotropic Stokes system in Lipschitz domains of ${\mathbb R}^n$, with the given data in $L_2$-based weighted Sobolev spaces. These results are used to define the Newtonian and layer potentials and to obtain their properties. Then we analyze well-posedness of the exterior Dirichlet, Neumann and mixed problems for the Stokes system with $L_{\infty }$ symmetrically elliptic Coefficient Tensor. Solutions of some of these problems are also represented in terms of the anisotropic Stokes Newtonian and layer potentials. Finally, we prove the existence of a weak solution for a transmission problem in complementary Lipschitz domains in ${\mathbb R}^3$ for the anisotropic Navier-Stokes system with general data in $L_2$-based weighted Sobolev spaces. The analysis relies on an existence result for a Dirichlet problem for the anisotropic Navier-Stokes system in a family of bounded domains, and on the Leray-Schauder fixed point theorem.
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Variational approach for layer potentials of the Stokes system with $L_{\infty }$ symmetrically elliptic Coefficient Tensor and applications to Stokes and Navier-Stokes boundary problems
arXiv: Analysis of PDEs, 2020Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:The first aim of this paper is to develop a layer potential theory in $L_2$-based weighted Sobolev spaces on Lipschitz bounded and exterior domains of ${\mathbb R}^n$, $n\geq 3$, for the anisotropic Stokes system with $L_{\infty }$ viscosity Coefficient Tensor satisfying an ellipticity condition for symmetric matrices. To do this, we explore equivalent mixed variational formulations and prove the well-posedness of some transmission problems for the anisotropic Stokes system in Lipschitz domains of ${\mathbb R}^n$, with the given data in $L_2$-based weighted Sobolev spaces. These results are used to define the Newtonian and layer potentials and to obtain their properties. Then we analyze well-posedness of the exterior Dirichlet, Neumann and mixed problems for the Stokes system with $L_{\infty }$ symmetrically elliptic Coefficient Tensor. Solutions of some of these problems are also represented in terms of the anisotropic Stokes Newtonian and layer potentials. Finally, we prove the existence of a weak solution for a transmission problem in complementary Lipschitz domains in ${\mathbb R}^3$ for the anisotropic Navier-Stokes system with general data in $L_2$-based weighted Sobolev spaces. The analysis relies on an existence result for a Dirichlet problem for the anisotropic Navier-Stokes system in a family of bounded domains, and on the Leray-Schauder fixed point theorem.
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Potentials and transmission problems in weighted Sobolev spaces for anisotropic Stokes and Navier-Stokes systems with $L_{\infty}$ strongly elliptic Coefficient Tensor
Complex Variables and Elliptic Equations, 2019Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:We obtain well-posedness results in Lp-based weighted Sobolev spaces for a transmission problem for anisotropic Stokes and Navier–Stokes systems with L∞ strongly elliptic Coefficient Tensor, in com...
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Potentials and transmission problems in weighted Sobolev spaces for anisotropic Stokes and Navier-Stokes systems with $L_{\infty}$ strongly elliptic Coefficient Tensor
arXiv: Analysis of PDEs, 2019Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:We obtain well-posedness results in $L_p$-based weighted Sobolev spaces for a transmission problem for anisotropic Stokes and Navier-Stokes systems with $L_{\infty}$ strongly elliptic Coefficient Tensor, in complementary Lipschitz domains of ${\mathbb R}^n$, $n\ge 3$. The strong ellipticity allows to explore the associated pseudostress setting. First, we use a variational approach that reduces two linear transmission problems for the anisotropic Stokes system to equivalent mixed variational formulations with data in $L_p$-based weighted Sobolev and Besov spaces. We show that such a mixed variational formulation is well-posed in the space ${\mathcal H}^1_{p}({\mathbb R}^n)^n\times L_p({\mathbb R}^n)$, {$n\geq 3$}, for any $p$ in an open interval containing $2$. These results are used to define the Newtonian and layer potential operators for the considered anisotropic Stokes system. Various mapping properties of these operators are also obtained. The potentials are employed to show the well-posedness of some linear transmission problems, which then is combined with a fixed point theorem in order to show the well-posedness of the nonlinear transmission problem for the anisotropic Stokes and Navier-Stokes systems in $L_p$-based weighted Sobolev spaces, whenever the given data are small enough.
Seiichi Miyajima - One of the best experts on this subject based on the ideXlab platform.
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New PFG NMR Spectrometer with a Rotatable Quadrupole Coil for the Measurement of an Anisotropic Self-Diffusion Coefficient Tensor
Journal of magnetic resonance. Series A, 1996Co-Authors: Osamu Oishi, Seiichi MiyajimaAbstract:Abstract A new pulsed-field-gradient spin-echo NMR spectrometer is reported which is specially designed for the measurement of slow and anisotropic self-diffusion by providing an intense and homogeneous field gradient of 12 T m −1 by a quadrupole coil and a high-quality current stabilizer, and also providing a mechanism by which both the sample cell and the quadrupole coil are rotated from the axis of the external field. Diffusion anisotropy is measured by a combination of coil rotation and magic-angle orientation of the sample. The theoretical basis for the method of measuring diffusion anisotropy, instrumentation details, and several sets of test data are given. The experimental results are reported for the rotation pattern of the diffusion Coefficient of a smectic Ad liquid crystal of 4-octyloxy- N -(4-cyanobenzylidene)aniline. The component parallel to the layer normal is shown to be 2.1 times larger than the component within the layer.
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Pulsed-field-gradient stimulated-spin-echo NMR study of anisotropic self-diffusion in smectic Ad liquid crystal CBOOA
Chemical Physics Letters, 1993Co-Authors: Seiichi Miyajima, Andrew F. Mcdowell, R.m. CottsAbstract:Abstract Anisotropic self-diffusion Coefficient Tensor was determined in the smectic Ad (SAd) phase of a polar mesogen CBOOA. The pulsed-field-gradient stimulated-spin-echo NMR technique was applied in combination with angular displacement of a quadrupole coil, to obtain the diffusion Coefficient components both parallel (D|) and perpendicular (D⊥) to the director for the sample oriented at the magic angle from the large magnetic field. It was found that D&.sfnc; >D⊥ (D|/D⊥ = 2.3–3.0), and the activation energies were similar for the two components. Nematic-like diffusion characteristics have been revealed.
Shuwen Zhang - One of the best experts on this subject based on the ideXlab platform.
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Experimental decoupling of cylindrical flexoelectric Coefficients
Applied Physics Letters, 2018Co-Authors: Shuwen Zhang, Tonghui Wu, Minglong Xu, Shengping ShenAbstract:Flexoelectricity is a property of all dielectric materials in which they polarize in response to deformation gradients such as those produced by pressing, bending, or twisting, and knowledge of flexoelectric Coefficients is essential when considering the applications of flexoelectricity. Here, we describe an experimental approach to the measurement of cylindrical flexoelectric Coefficients of polyvinylidene fluoride. Two specimens are designed to generate and decouple the corresponding strain gradients. Theoretical and finite element analyses are developed and simplified, and specimen designs are then tested to obtain multiple strain-gradient-coupled electric polarization charges. The flexoelectric Coefficients μφzρρ and μφzzρ are then decoupled, using two independent equations together with the experimental data. This work provides an experimental method that can be used to obtain multiple unknown flexoelectric Coefficient Tensor components by imposition of a twisting load, and it reveals the potential for the application of flexoelectricity in irregular structures in complex environments.Flexoelectricity is a property of all dielectric materials in which they polarize in response to deformation gradients such as those produced by pressing, bending, or twisting, and knowledge of flexoelectric Coefficients is essential when considering the applications of flexoelectricity. Here, we describe an experimental approach to the measurement of cylindrical flexoelectric Coefficients of polyvinylidene fluoride. Two specimens are designed to generate and decouple the corresponding strain gradients. Theoretical and finite element analyses are developed and simplified, and specimen designs are then tested to obtain multiple strain-gradient-coupled electric polarization charges. The flexoelectric Coefficients μφzρρ and μφzzρ are then decoupled, using two independent equations together with the experimental data. This work provides an experimental method that can be used to obtain multiple unknown flexoelectric Coefficient Tensor components by imposition of a twisting load, and it reveals the potential f...
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Experimental approach for measuring cylindrical flexoelectric Coefficients
Journal of Applied Physics, 2017Co-Authors: Shuwen Zhang, Tonghui Wu, Minglong Xu, Shengping ShenAbstract:Flexoelectricity is a property of dielectric materials by which applied strain gradients induce electric polarizations within dielectric materials. Experimental research into the Tensor components of the flexoelectric Coefficient is essential. In this work, an experimental approach for measurement of the flexoelectric Coefficient Tensor components in cylindrical coordinates is developed. Two different experimental methods are designed to obtain the two related unknown flexoelectric Coefficient Tensor components. Theoretical and finite element analyses are developed and simplified for each experiment, and the related designs are then tested to obtain the coupled electric polarization charges. The two unknown flexoelectric Coefficient Tensor components of polyvinylidene fluoride are then decoupled. This work provides an experimental method that can be used to obtain multiple unknown flexoelectric Coefficient Tensor components in solid dielectric materials.
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investigation of the 2312 flexoelectric Coefficient component of polyvinylidene fluoride deduction simulation and mensuration
Scientific Reports, 2017Co-Authors: Shuwen Zhang, Hao Shen, Kai Chen, Minglong Xu, Bo Feng, Shengping ShenAbstract:Flexoelectric effects hold promising applications in sensing, actuating, and energy capturing, and thus it is demanded to measure the flexoelectric Coefficient Tensors of dielectric materials accurately. In this work, an approach to measuring the effective flexoelectric Coefficient Tensor component μ 2312 of polymeric materials is developed by imposing a torque load upon a half cylindrical specimen. It is proven that μ 2312 can be calculated by assessing the electric charge on the axial plane and the strain gradient along the radial direction, both induced by the torque. To overcome the difficulty in experimental measurements, the relationship between the strain gradient and torque is deduced theoretically and further verified with finite element analysis. This approach is applied to testing bars machined from bulk polyvinylidene fluoride (PVDF). Potential errors from the piezoelectric effects and the non-uniform strain gradient are discussed to verify the validity of the measurement. The experimental results show good reproducibility and agreement with other measured effective flexoelectric Tensor components of PVDF. This work indicates a potential application of PVDF-based mechanical sensors and provides a method to investigate the effective flexoelectric Coefficient component of polymers.
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Experimental method research on transverse flexoelectric response of poly(vinylidene fluoride)
Japanese Journal of Applied Physics, 2016Co-Authors: Shuwen Zhang, Guoliang Ma, Xu Liang, Minglong Xu, Shengping ShenAbstract:Flexoelectricity describes the strain-gradient-induced electric polarization existing in dielectric materials. The Coefficient that exists between the strain-gradient and the induced electric polarization defines the flexoelectric Coefficient Tensor. It is necessary to analyze different experimental methods to evaluate the procedure of measuring the transverse flexoelectric Coefficient Tensor component. In this work, the transverse flexoelectric Coefficient Tensor component of poly(vinylidene fluoride) (PVDF) is studied using three different experimental methods and the effects of the mentioned methods are evaluated. The results presented in this work are helpful for the design of experiments of different dielectric materials, including ceramics and polymers on flexoelectricity.
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shear flexoelectric Coefficient μ1211 in polyvinylidene fluoride
Journal of Applied Physics, 2015Co-Authors: Shuwen Zhang, Xu Liang, Minglong Xu, Shengping ShenAbstract:Defined as a strain gradient-induced electric polarization, flexoelectricity exists in all dielectric materials. The Coefficient that exists between the strain gradient and the electric polarization defines the flexoelectric Coefficient Tensor. The Tensor components along the longitudinal and transverse directions have been studied widely. However, little progress has been reported on flexoelectric properties in the shear direction to date. In this work, a novel method for measurement of the shear flexoelectric Coefficient μ1211 of polyvinylidene fluoride is presented. An experiment is conducted on a tubular unpolarized specimen, where shear strain gradient is generated along the radial direction by applying torque to the ends of the tube-shaped specimen. Dynamic torque is exerted on specimens with a static bias value and at different frequencies. The generated shear strain gradient is calculated via finite element analysis and the corresponding induced electrical polarization is measured using a charge a...
Mirela Kohr - One of the best experts on this subject based on the ideXlab platform.
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variational approach for layer potentials of the stokes system with l_ infty symmetrically elliptic Coefficient Tensor and applications to stokes and navier stokes boundary problems
arXiv: Analysis of PDEs, 2020Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:The first aim of this paper is to develop a layer potential theory in $L_2$-based weighted Sobolev spaces on Lipschitz bounded and exterior domains of ${\mathbb R}^n$, $n\geq 3$, for the anisotropic Stokes system with $L_{\infty }$ viscosity Coefficient Tensor satisfying an ellipticity condition for symmetric matrices. To do this, we explore equivalent mixed variational formulations and prove the well-posedness of some transmission problems for the anisotropic Stokes system in Lipschitz domains of ${\mathbb R}^n$, with the given data in $L_2$-based weighted Sobolev spaces. These results are used to define the Newtonian and layer potentials and to obtain their properties. Then we analyze well-posedness of the exterior Dirichlet, Neumann and mixed problems for the Stokes system with $L_{\infty }$ symmetrically elliptic Coefficient Tensor. Solutions of some of these problems are also represented in terms of the anisotropic Stokes Newtonian and layer potentials. Finally, we prove the existence of a weak solution for a transmission problem in complementary Lipschitz domains in ${\mathbb R}^3$ for the anisotropic Navier-Stokes system with general data in $L_2$-based weighted Sobolev spaces. The analysis relies on an existence result for a Dirichlet problem for the anisotropic Navier-Stokes system in a family of bounded domains, and on the Leray-Schauder fixed point theorem.
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Variational approach for layer potentials of the Stokes system with $L_{\infty }$ symmetrically elliptic Coefficient Tensor and applications to Stokes and Navier-Stokes boundary problems
arXiv: Analysis of PDEs, 2020Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:The first aim of this paper is to develop a layer potential theory in $L_2$-based weighted Sobolev spaces on Lipschitz bounded and exterior domains of ${\mathbb R}^n$, $n\geq 3$, for the anisotropic Stokes system with $L_{\infty }$ viscosity Coefficient Tensor satisfying an ellipticity condition for symmetric matrices. To do this, we explore equivalent mixed variational formulations and prove the well-posedness of some transmission problems for the anisotropic Stokes system in Lipschitz domains of ${\mathbb R}^n$, with the given data in $L_2$-based weighted Sobolev spaces. These results are used to define the Newtonian and layer potentials and to obtain their properties. Then we analyze well-posedness of the exterior Dirichlet, Neumann and mixed problems for the Stokes system with $L_{\infty }$ symmetrically elliptic Coefficient Tensor. Solutions of some of these problems are also represented in terms of the anisotropic Stokes Newtonian and layer potentials. Finally, we prove the existence of a weak solution for a transmission problem in complementary Lipschitz domains in ${\mathbb R}^3$ for the anisotropic Navier-Stokes system with general data in $L_2$-based weighted Sobolev spaces. The analysis relies on an existence result for a Dirichlet problem for the anisotropic Navier-Stokes system in a family of bounded domains, and on the Leray-Schauder fixed point theorem.
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Potentials and transmission problems in weighted Sobolev spaces for anisotropic Stokes and Navier-Stokes systems with $L_{\infty}$ strongly elliptic Coefficient Tensor
Complex Variables and Elliptic Equations, 2019Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:We obtain well-posedness results in Lp-based weighted Sobolev spaces for a transmission problem for anisotropic Stokes and Navier–Stokes systems with L∞ strongly elliptic Coefficient Tensor, in com...
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Potentials and transmission problems in weighted Sobolev spaces for anisotropic Stokes and Navier-Stokes systems with $L_{\infty}$ strongly elliptic Coefficient Tensor
arXiv: Analysis of PDEs, 2019Co-Authors: Mirela Kohr, Sergey E. Mikhailov, Wolfgang L. WendlandAbstract:We obtain well-posedness results in $L_p$-based weighted Sobolev spaces for a transmission problem for anisotropic Stokes and Navier-Stokes systems with $L_{\infty}$ strongly elliptic Coefficient Tensor, in complementary Lipschitz domains of ${\mathbb R}^n$, $n\ge 3$. The strong ellipticity allows to explore the associated pseudostress setting. First, we use a variational approach that reduces two linear transmission problems for the anisotropic Stokes system to equivalent mixed variational formulations with data in $L_p$-based weighted Sobolev and Besov spaces. We show that such a mixed variational formulation is well-posed in the space ${\mathcal H}^1_{p}({\mathbb R}^n)^n\times L_p({\mathbb R}^n)$, {$n\geq 3$}, for any $p$ in an open interval containing $2$. These results are used to define the Newtonian and layer potential operators for the considered anisotropic Stokes system. Various mapping properties of these operators are also obtained. The potentials are employed to show the well-posedness of some linear transmission problems, which then is combined with a fixed point theorem in order to show the well-posedness of the nonlinear transmission problem for the anisotropic Stokes and Navier-Stokes systems in $L_p$-based weighted Sobolev spaces, whenever the given data are small enough.