On a multiwavelet spectral element method for integral equation of a generalized Cauchy problem

In this paper we deal with construction and analysis of a multiwavelet spectral element scheme for a generalized Cauchy type problem with Caputo fractional derivative. Numerical schemes for this type of problems, often suffer from the draw-back of spurious oscillations. A common remedy is to render the problem to an equivalent integral equation. For the generalized Cauchy type problem, a corresponding integral equation is of nonlinear Volterra type. In this paper we investigate wellposedness and convergence of a stabilizing multiwavelet scheme for a, one-dimensional case (in [a,\ua0b] or [0,\ua01]), of this problem. Based on multiwavelets, we construct an approximation procedure for the fractional integral operator that yields a linear system of equations with sparse coefficient matrix. In this setting, choosing an appropriate threshold, the number of non-zero coefficients in the system is substantially reduced. A severe obstacle in the convergence analysis is the lack of continuous derivatives in the vicinity of the inflow/ starting boundary point. We overcome this issue through separating a J (mesh)-dependent, small, neighborhood of a (or origin) from the interval, where we only take L2-norm. The estimate in this part relies on Chebyshev polynomials, viz. As reported by Richardson(Chebyshev interpolation for functions with endpoint singularities via exponential and double-exponential transforms, Oxford University, UK, 2012) and decreases, almost, exponentially by raising J. At the remaining part of the domain the solution is sufficiently regular to derive the desired optimal error bound. We construct such a modified scheme and analyze its wellposedness, efficiency and accuracy. The robustness of the proposed scheme is confirmed implementing numerical examples

High-Accuracy Multiscale Simulation of Three-Dimensional Squeezing Carbon Nanotube-Based Flow inside a Rotating Stretching Channel

Enhancing the heat transfer rate using nanofluids is of great interest to engineers and scientists. This research aims to study the heat and mass transfer analysis of three-dimensional squeezing carbon nanotube- (CNT-) based nanofluid flow inside a rotating stretching channel. The upper wall of the channel is assumed to have a reciprocating movement, and the lower wall is assumed to be stationary and permeable. Also, radiative effects are taken into account using the Taylor series approximation. The momentum and energy equations are transformed into a coupled system of nonlinear ordinary differential equations utilizing similarity solutions. A new multiscale and accurate method was developed to solve the achieved nonlinear systems of equations. Water is chosen as the base fluid; single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs) are added to it, and then two types of nanofluids were created. The effect of different variables such as the concentration of nanotubes, nanotube’s type, suction parameter, rotation parameter, squeezing number, Eckert number, and radiation parameter on the velocity and temperature profiles is investigated. Our results reveal that the temperature profile is an increasing function of the squeezing number, suction, rotation, and radiation parameters when the upper wall moves towards the lower one