RT journal article T1 Parallel-in-time adjoint-based optimization – application to unsteady incompressible flows A1 Constanzo, S. A1 Sayadi, T. A1 Fosas de Pando, Miguel Ángel A1 Schmid, P. J. A1 Frey, P. A2 Ingeniería Mecánica y Diseño Industrial K1 Adjoint-based methods K1 Flow control K1 Parallel-in-time algorithm AB Gradient-based optimization algorithms, where gradient information is extracted using adjoint equations, are efficient but can quickly slow down when applied to unsteady and nonlinear flow problems. This is mainly due to the sequential nature of the algorithm, where the primal problem is first integrated forward in time, providing the initial condition for the adjoint problem, which is then integrated backward. In order to address the sequential nature of this optimization procedure parallel-in-time algorithms can be employed. However, the characteristics of the governing equations of interest in this work, and in particular, the divergence-free constraint (incompressibility effect) as well as the nonlinearity and the unsteadiness of the flow, make direct application of existing parallelin-time algorithms less than straightforward. In this work, we introduce a parallel-in-time procedure, applied to the integration of the adjoint problem, which addresses all the existing constraints and allows quick access to local gradients. The performance of the proposed algorithm is assessed for both steady and unsteady actuation; in both cases it readily outperforms the sequential algorithm. PB Elsevier SN 0021-9991 YR 2022 FD 2022-10-06 LK http://hdl.handle.net/10498/32234 UL http://hdl.handle.net/10498/32234 LA eng DS Repositorio Institucional de la Universidad de Cádiz RD 09-may-2026