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We discuss two aspects of turbulent Rayleigh-B\'{e}nard convection (RBC) on the basis of high-resolution direct numerical simulations in a unique setting; a closed cylindrical cell of aspect ratio of one. First, we present a comprehensive…

Fluid Dynamics · Physics 2017-11-29 Janet D. Scheel , Jörg Schumacher

We propose a new way to implement Dirichlet boundary conditions for complex shapes using data from a single node only, in the context of the lattice Boltzmann method. The resulting novel method exhibits second-order convergence for the…

Computational Physics · Physics 2021-05-26 Francesco Marson , Yann Thorimbert , Jonas Latt , Bastien Chopard

Semilinear parabolic systems with bi-linear nonlinearities cover a lot of applications and their optimal control leads to relatively simple optimality conditions. An example is the incompressible Navier-Stokes system for homogeneous fluids,…

Analysis of PDEs · Mathematics 2021-08-31 Tomáš Roubíček

In optimal control, extending the class of admissible controls is a common strategy to guarantee the existence of optimal solutions. However, such extensions may introduce a gap between the infimum of the original problem and the minimum of…

Optimization and Control · Mathematics 2026-03-09 Monica Motta , Michele Palladino , Franco Rampazzo

In the context of the multi-dimensional infinite horizon optimal consumption-investment problem with proportional transaction costs, we provide the first order expansion in small transact costs. Similar to the one-dimensional derivation in…

Analysis of PDEs · Mathematics 2013-01-23 Dylan Possamaï , H. Mete Soner , Nizar Touzi

We formulate a weakly-nonlinear exit condition for open ends of acoustic waveguides without mean flow; to our knowledge this is the first time an acoustic open end has been analysed outside the linear regime. The resulting admittance…

Fluid Dynamics · Physics 2025-12-05 Freddie Jensen , Harry Turnbull , Edward James Brambley

We consider the two-dimensional Rayeigh-B\'enard convection problem between Navier-slip fixed-temperature boundary conditions and present a new upper bound for the Nusselt number. The result, based on a localization principle for the…

Analysis of PDEs · Mathematics 2024-10-29 Fabian Bleitner , Camilla Nobili

In this paper we consider the vanishing viscosity limit of solutions to the initial boundary value problem for compressible viscoelastic equations in the half space. When the initial deformation gradient does not degenerate and there is no…

Analysis of PDEs · Mathematics 2023-07-18 Xumin Gu , Dehua Wang , Feng Xie

The complicated dynamics of the contact line of a moving droplet on a solid substrate often hamper the efficient modeling of microfluidic systems. In particular, the selection of the effective boundary conditions, specifying the contact…

We consider a new framework where a continuous, though bounded, random variable has unobserved bounds that vary over time. In the context of univariate time series, we look at the bounds as parameters of the distribution of the bounded…

Machine Learning · Statistics 2023-06-26 Amandine Pierrot , Pierre Pinson

We address the mechanism of drag reduction by polymers in turbulent wall bounded flows. On the basis of the equations of fluid mechanics we present a quantitative derivation of the "maximum drag reduction (MDR) asymptote" which is the…

Chaotic Dynamics · Physics 2007-05-23 Victor S. L'vov , Anna Pomyalov , Itamar Procaccia , Vasil Tiberkevich

We investigate a two-parameter hyperbolic relaxation approximation to the incompressible Navier-Stokes equations, incorporating a first-order relaxation and the artificial compressibility method. With vanishingly small perturbations of…

Analysis of PDEs · Mathematics 2026-01-28 Qian Huang , Christian Rohde , Ruixi Zhang

Continual learning aims to avoid catastrophic forgetting and effectively leverage learned experiences to master new knowledge. Existing gradient projection approaches impose hard constraints on the optimization space for new tasks to…

Machine Learning · Computer Science 2023-01-31 Zeyuan Yang , Zonghan Yang , Peng Li , Yang Liu

This work proposes an adaptive structure-preserving model order reduction method for finite-dimensional parametrized Hamiltonian systems modeling non-dissipative phenomena. To overcome the slowly decaying Kolmogorov width typical of…

Numerical Analysis · Mathematics 2022-02-02 Jan S. Hesthaven , Cecilia Pagliantini , Nicolò Ripamonti

We deal with the barotropic compressible Navier-Stokes equations subject to large external potential forces with slip boundary condition in a 3D simply connected bounded domain, whose smooth boundary has a finite number of 2D connected…

Analysis of PDEs · Mathematics 2021-02-26 Guocai Cai , Bin Huang , Xiaoding Shi

Local perturbations of an infinitely long rod go away to infinity. On the contrary, in the case of a finite length of the rod, the perturbations reach its boundary and are reflected from it. The boundary conditions constructed here for the…

Numerical Analysis · Mathematics 2020-07-15 Vladimir A. Gordin , Aleksandr A. Shemendyuk

When the nonconvex problem is complicated by stochasticity, the sample complexity of stochastic first-order methods may depend linearly on the problem dimension, which is undesirable for large-scale problems. To alleviate this linear…

Optimization and Control · Mathematics 2025-09-30 Yue Xie , Jiawen Bi , Hongcheng Liu

Identifying the relevant variables for a classification model with correct confidence levels is a central but difficult task in high-dimension. Despite the core role of sparse logistic regression in statistics and machine learning, it still…

Machine Learning · Statistics 2022-05-31 Binh T. Nguyen , Bertrand Thirion , Sylvain Arlot

The choice of the boundary conditions in mechanical problems has to reflect the interaction of the considered material with the surface, despite the assumption of the no-slip condition is preferred to avoid boundary terms in the analysis…

Analysis of PDEs · Mathematics 2020-09-22 Anna Abbatiello , Miroslav Bulíček , Erika Maringová

In this paper, we present a high-order expansion for elliptic equations in high-contrast media. The background conductivity is taken to be one and we assume the medium contains high (or low) conductivity inclusions. We derive an asymptotic…

Analysis of PDEs · Mathematics 2014-01-28 Victor M. Calo , Yalchin Efendiev , Juan Galvis