Juan M. GimenezInternational Center for Numerical Methods in Engineering | CIMNE · Structural Mechanics
Juan M. Gimenez
Doctor of Engineering
About
67
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Introduction
I have shown groundbreaking research through developing many numerical approaches such as particle methods and Lagrangian formulations for multi-phase and turbulent flows. I have a strong background in technologies like high-performance computing, machine learning and multi-scale modelling. Recent developments have been applied to studying atmospheric boundary layers in urban environments.
Additional affiliations
July 2017 - present
April 2016 - April 2018
January 2011 - April 2018
Publications
Publications (67)
Efficiently simulating turbulent fluid flow within a boundary layer is one of the major challenges in fluid mechanics. While skin friction may have a limited impact on drag at high Reynolds numbers, it plays a crucial role in determining the location of fluid separation points. Shifts in these separation points can dramatically alter drag and lift,...
A multiscale data-driven (MSDD) methodology is proposed for simulating the thermomechanical behavior of granular materials subjected to thermal expansion.
The macroscale is handled using a continuous model based on the Finite Volume Method (FVM), while the microscale response is captured at Representative Volume Elements (RVEs) with the Discrete El...
Database of dimensionless components of the effective thermal conductivity (Kxx and Kyy) and Cauchy stress (Sxx and Syy) tensors, as well as porosity and fabric increments, for a given porosity, fabric and thermal strain, generated from the homogenization of DEM solutions in several Representative Volume Elements (RVEs).
A simulação Airflow Network (AFN)/Building Energy Simulations (BES) é muito usada para incluir os efeitos da ventilação natural em análises de conforto térmico e eficiência energética. Para isso os coeficientes de pressão (Cp) são um dado de entrada importante; embora esta informação possa ser obtida através de Simulações fluidodinâmicas (CFD), est...
Wind turbines (WTs) face a high risk of failure due to environmental factors like erosion, particularly in high-precipitation areas and offshore scenarios. In this paper we introduce a novel computational tool for the fast prediction of rain erosion damage on WT blades that is useful in operation and maintenance decision making tasks. The approach...
Balconies have the potential to promote airflow and regulate solar heat gain, which can reduce energy usage for cooling in buildings. However, designing these elements can be challenging due to complex trade-offs for natural ventilation and energy performance, highlighting the need for advanced simulation tools to guide balcony design decisions. Th...
This work presents a data-driven continuum–discrete multiscale methodology to simulate heat transfer through granular materials. The two scales are hierarchically coupled, where the effective thermal conductivity tensor required by the continuous method at the macroscale is obtained from offline microscale analyses. A set of granular media samples...
Database of the dimensionless components of the effective thermal conductivity tensor (Kxx, Kyy, and Kxy) for a given porosity and fabric, generated from the homogenization of DEM solutions in several Representative Volume Elements (RVEs).
Recognizing the urgent need for mitigating global warming, natural ventilation presents a potential strategy to reduce cooling energy demands, enhance thermal comfort, and contribute to indoor air quality. H-shaped buildings are prevalent worldwide, and they constitute the majority of the social housing construction in Brazil. Research suggests tha...
We present a family of fast explicit time integration schemes of first, second and third order accuracy for parabolic problems in mechanics solved via standard numerical methods that have considerable higher computational efficiency versus existing explicit methods of the same order. The derivation of the new explicit schemes is inspired on the fin...
Powder coating is a finishing process used in various industries where electrostatically charged particles are sprayed onto metal surfaces.
High-fidelity simulation is becoming increasingly popular to optimize this technique. However, the current standard approaches based on modeling the individual particles require substantial computational effort...
This work presents a continuum-discrete hierarchical multiscale methodology based on data-driven computations of the microscale response to simulate heat conduction in static granular materials. The effective thermal conductivity tensors of the continuous method at the macroscale is obtained from a database of microscale results. The microscale dat...
An overview of the Pseudo-Direct Numerical Simulation (P-DNS) method is presented. This is a multi-scale method aiming at numerically solving the unknown fields at two different scales, namely coarse and fine. The P-DNS method is built around four key ideas. The first one is that of numerically solving both scales, which facilitates obtaining solut...
The goal of this research is to improve and validate a Reynolds Averaged Navier-Stokes (RANS) turbulence model to perform accurate Computational Fluid Dynamics (CFD) simulations of the urban wind flow. The k-ω SST model is selected for calibration since its blended formulation holds remarkable optimization potential and has increased relevancy in r...
Despite the well-known potential of Computational Fluid Dynamics (CFD) to enhance the prediction of Building Performance Simulation (BPS) models, several barriers prevent BPS simulators from actively using CFD. A recognized obstacle is the proficiency required to get a high-quality computational mesh to study the atmospheric boundary layer (ABL) fl...
The multiscale method called Pseudo-Direct Numerical Simulation (P-DNS) is presented as a Reduced Order Model (ROM) aiming to solve problems obtaining similar accuracy to a solution with many degrees of freedom (DOF). The theoretical basis of P-DNS is other than any standard ROM. However, from a methodological point of view, P-DNS shares the idea o...
It is well known that the inherent three‐dimensional and unsteady nature of turbulent flows is a stumbling block for all approaches aimed at resolving their spatial and temporal variability. The Pseudo‐Direct Numerical Simulation (P‐DNS) method for turbulent flows, proposed by the authors in a previous publication, focused on resolving the spatial...
The methodology previously proposed by the authors to solve particle-laden turbulent flows through a multiscale approach is extended by introducing a continuous function for the dispersed phase concentration. The proposed continuous model is especially useful for studying the motion of particle streams in which gravitational and inertial effects ca...
A deterministic pathogen transmission model based on high-fidelity physics has been developed. The model combines computational fluid dynamics and computational crowd dynamics in order to be able to provide accurate tracing of viral matter that is exhaled, transmitted and inhaled via aerosols. The examples shown indicate that even with modest compu...
A deterministic pathogen transmission model based on high-fidelity physics has been developed. The model combines computational fluid dynamics and computational crowd dynamics in order to be able to provide accurate tracing of viral matter that is exhaled, transmitted and inhaled via aerosols. The examples shown indicate that even with modest compu...
Natural ventilation (NV) is a key passive strategy to design energy-efficient buildings and improve indoor air quality. Therefore, accurate modeling of the NV effects is a basic requirement to include this technique during the building design process. However, there is an important lack of wind pressure coefficients (C p ) data, essential input par...
We present an overview of the Pseudo-Direct Numerical Simulation (P-DNS in short) method for the solution of multi-scale phenomena. The method can be seen as an adaptation of the variational multi-scale (VMS) method, where the fine solution is solved numerically instead of analytically. Also, from the point of view of homogenization methods it can...
A multiscale approach for the detailed simulation of water droplets dispersed in a turbulent airflow is presented. The multiscale procedure combines a novel representative volume element (RVE) with the Pseudo Direct Numerical Simulation (P-DNS) method. The solution at the coarse-scale relies on a synthetic model, constructed using precomputed offli...
Accepting as a premise that the solution of a Direct Numerical Simulation (DNS) is a reliable result, Pseudo-DNS (P-DNS) is a multi-scale method where both the coarse and the fine scales are solved numerically[1]. The most expensive part of the computations, the solution of the fine-scale, is performed offline where its results, stress tensors at e...
El objetivo de este trabajo es presentar una nueva herramienta basada en la nube para simular la ventilación natural en edificios. En particular, en este documento se desarrolla una herramienta automática de simulación de dinámica de fluidos computacional (CFD) para predecir los coeficientes de presión promedio en la superficie (Cp) para, luego, ut...
Being associated with natural ventilation, the pressure distribution on surfaces is relevant for energy consumption, thermal comfort, and air quality in buildings. The aim of this work is to present a simulation-based optimization methodology to recalibrate the closure coefficients of Reynolds-averaged Navier-Stokes (RANS) turbulence models in orde...
In this work, a new model for the analysis of incompressible fluid flows with massive instabilities at different scales is presented. It relies on resolving all the instabilities at all scales without any additional model, i.e., following the direct numerical simulation style. Nevertheless, the computation is carried out at two levels or scales, te...
This paper describes how the global stability of a circular cylinder is affected when submerged in a two-phase gravitational flow. The flow behavior is governed by both the Reynolds and the Froude number, while the depth of the cylinder has been varied to create different scenarios for the stability analysis. The baseflow obtained by the numerical...
This work presents a novel proposal of a second-order accurate (in time and space) particle-based method for solving transport equations including incompressible flows problems within a mixed Lagrangian-Eulerian formulation. This methodology consists of a symmetrical operator splitting, the use of high-order operators to transfer data between the p...
Natural ventilation (NV) is a relevant passive strategy for the design of buildings in seek of energy savings and the improvement of the indoor air quality and the thermal comfort. The main aim of this work is to present a comprehensive NV modeling study of a non-rectangular floor-plan dwelling. Given the arbitrary shape of the building, recourse i...
This Artificial Neural Network (ANN) model gives the surface-average pressure coefficient (Cp) for all the surfaces of gable-roofed low-rise buildings with rectangular floor-plan.
This Artificial Neural Network (ANN) model gives the surface-average pressure coefficient (Cp) for all the surfaces of flat-roofed low-rise buildings with rectangular floor-plan.
This Artificial Neural Network (ANN) model gives the surface-average pressure coefficient (Cp) for all the surfaces of hip-roofed low-rise buildings with rectangular floor-plan.
Numerical simulation of piston–cylinder problems such as internal combustion engines suffers from two difficulties related to discretization: the non-matching interfaces between cylinder and ports and the large deformation of the cylinder region. In this context, this paper presents a parallelized computational strategy, based on the Finite Volume...
In a previous paper the authors present an elemental enriched space to be used in a finite element framework (EFEM) capable to reproduce kinks and jumps in an unknown function using a fixed mesh in which the jumps and kinks do not coincide with the inter-element boundaries. In this previous publication, only scalar transport problems where solved (...
Knowing the pressure coefficient on building surfaces is important for the evaluation of wind loads and natural ventilation. The main objective of this paper is to present and to validate a computational modeling approach to accurately predict the mean wind pressure coefficient on the surfaces of flat-, gable- and hip-roofed rectangular buildings....
The latest version of the Particle Finite Element Method (PFEM-2) [1] is a numerical method based on the Lagrangian formulation of the equations which presents advantages in terms of robustness and efficiency over classical Eulerian methodologies especially when convection plays an important role [2]. Previous publications demonstrated its ability...
The main goal of this paper is to validate experimentally the principal conclusions previuosly published in [?]. Two manufactured test cases were considered with their respective analytic solutions. First, an scalar transport equation is taken written in such a way that several parameters are included to stress the limits where the Eulerian and the...
This work presents a new and efficient strategy to handle non-conformal interfaces with the aim of assuring the conservation of fluxes in Finite Volume problems. A conservative interpolation is developed for general transport equations. Due to the arbitrary connectivity between the interfaces, the interpolations require flux-based weights defining...
This work presents a new strategy to handle non-conformal interfaces with the aim of assuring the conservation of fluxes in Finite Volume problems. A conservative interpolation is developed for general transport equations. Due to the arbitrary connectivity between the interfaces, the interpolations require flux-based weights defining a complex nume...
The curvature calculation in the context of the Volume of Fluid method is a crucial step in order to accurately solve multiphase problems with dominant surface-tension forces. Most of techniques fail in obtaining mesh convergence, even increasing the parasitical currents due to wrong calculated curvatures. This work presents the application of the...
La medida integral del rendimiento de un vehículo de competición es el tiempo de vuelta. Con el fin de minimizar el mismo, se debe realizar una elección correcta de los elementos aerodinámicos, dinámicos y parámetros de configuración del automóvil, los cuales dependen fuertemente del dibujo del circuito. En este contexto, la optimización de las dif...
The main goal of this paper is to validate experimentally the principal conclusions previously published in [17]. Two manufactured test cases were considered with their respective analytic solutions. First, a scalar transport equation is considered written in such a way that several parameters are included to stress the limiting situation where the...
The latest generation of the particle finite element method (PFEM-2) is a numerical method based on the Lagrangian formulation of the equations, which presents advantages in terms of robustness and efficiency over classical Eulerian methodologies when certain kind of flows are simulated, especially those where convection plays an important role. Th...
This paper presents a finite element that incorporate weak, strong and both weak plus strong discontinuities with linear interpolations of the unknown jumps for the modeling of internal interfaces. The new enriched space is built by subdividing each triangular or tetrahedral element in several standard linear sub-elements. The new degrees of freedo...
In previous works [S. R. Idelsohn, J. Marti, P. Becker, E. O nate, Analysis of multifluid flows with large time steps using the particle
Trends in Computational Mechanics that may have Future.
The analysis, comprehension and study of incompressible flows is a field of great interest in industry and academia. Several categorizations can be found in order to organize and simplify the modeling, being the most important the distinction about the number of fluid-phases involved in the scenario. The development and analysis of numerical method...
In this paper, a new generation of the particle method known as Particle Finite Element Method (PFEM-2) [13], which combines convective particle movement and a fixed mesh resolution, is applied to a 2D flow past a circular cylinder intersecting or close to a free surface at Reynolds 180 [4]. To accomplish this task, different improved versions of d...
In this paper, a new generation of the particle method known as Particle Finite Element Method (PFEM), which combines convective particle movement and a fixed mesh resolution, is applied to free surface flows. This interesting variant, previously described in the literature as PFEM-2, is able to use larger time steps when compared to other similar...
The latest version of the Particle-Finite Element Method (PFEM), which incorporates the novel explicit integration strategy named eXplicit Integration of Velocity and Acceleration following Streamlines (X-IVAS), has proven to be fast and accurate to solve homogeneous flows, mainly thanks to the possibility of using large time-steps. In this work th...
The latest version of the Particle-Finite Element Method (PFEM), which incorporates the novel explicit integration strategy named eXplicit Integration of Velocity and Acceleration following Streamlines (X-IVAS), has proven to be fast and accurate to solve homogeneous flows, mainly thanks to the possibility of using large time-steps. In this work th...
In this work a new generation of the particle method known as Particle Finite Element Method (PFEM), which combines convective particle movement and fixed mesh resolution, is applied to free surface flows. This methodology, named PFEM-2, presents basically two novel steps: first, the possibility of using larger time steps compared to other similar...
This paper presents a state of the art in the Particle Finite Element Method, normally called PFEM, its emphasis in the new ideas oriented to extend its application not only to solve fluid structure interaction and multifluid problems, also bring new opportunities to shorten the gap between engineering design times and computational simulation time...
This paper presents a high performance implementation for the particle-mesh based method called particle finite element method two (PFEM-2). It consists of a material derivative based formulation of the equations with a hybrid spatial discretization which uses an Eulerian mesh and Lagrangian particles. The main aim of PFEM-2 is to solve transport e...
Purpose ‐ The purpose of this paper is to highlight the possibilities of a novel Lagrangian formulation in dealing with the solution of the incompressible Navier-Stokes equations with very large time steps. Design/methodology/approach ‐ The design of the paper is based on introducing the origin of this novel numerical method, originally inspired on...
![Figure 3: Description of the test. h = 5[m], R = 0.5[m]](profile/Juan-Gimenez-2/publication/292962067/figure/fig3/AS:667841640534017@1536237263031/Description-of-the-test-h-5m-R-05m_Q320.jpg)
The implementation of a Lagrangian particle transport model in non-homogeneous turbulent flow is presented. The model proposes one-way interaction between the continuous and the discrete phases where the behavior of the continuous one is previously solved with other CFD software. Particle dynamics include four forces terms: buoyancy, inertial, drag...
Particle Finite Element Method-Second generation (PFEM-2) is a method characterized by using both particles and mesh to solve physics equations. In some previous papers the mathematical and numerical basis of the method with also some results were presented showing a good accuracy and high performance for solving scalar-transport and momentum-trans...
Over the last twenty years, computer simulation of incompressible fluid flow has been based on the Eulerian formulation of the fluid mechanics equations on continuous domains. However, it is still difficult to analyze problems in which the shape of the free surfaces or internal interfaces changes continuously or in fluid-structure interactions wher...
OpenFOAM (R) libraries are a great contribution to CFD community and a powerful way to create solvers and other tools. Nevertheless in this creative process a deep knowledge is needed concerning with classes structure, for value storage in geometric fields and also for matrices resulting from equation systems, becoming a hard task for debugging. To...
Particle Finite Element Method-Second Generation (PFEM-2) is a numerical method written in a Lagrangian formulation that uses both particles and a mesh to solve the physics equations in an uncoupled way. The method uses fractional-steps with explicit and implicit calculations as needed. The difference with the original form, is that in this second...
