J. Baltazar

J. Baltazar
University of Lisbon | UL · Department of Mechanical Engineering

PhD

About

102
Publications
14,735
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
345
Citations
Introduction
João Baltazar, Graduation in Marine Engineering (IST), M.Sc. in Mechanical Engineering (IST) and Ph.D. in Mechanical Engineering (IST), is a researcher and lecturer at IST, the engineering school of the University of Lisbon. João Baltazar teaches or has taught courses such as Fluid Mechanics, Resistance and Propulsion, Offshore Wind Energy, Marine Current & Tidal Energy and Modeling and Control of Ocean Energy Systems. João Baltazar is a researcher of MARETEC – Marine, Environment and Technology Centre. His main areas of research are potential and viscous flow modelling for rotors. His research aims at creating accurate, robust and fast computational tools to be used for the design and analysis of rotors. He has worked on the development of the IST in-house panel code PROPAN.
Additional affiliations
October 2008 - July 2020
University of Lisbon
Position
  • Lecturer
Description
  • Courses: Fluid Mechanics, Modelling and Control of Ocean Energy Systems, Marine Current and Tidal Energy, Offshore Wind Energy, Resistance and Propulsion of Ships.
April 2001 - March 2002
University of Lisbon
Position
  • Lecturer
Description
  • Course: Numerical Methods
September 2000 - present
University of Lisbon
Position
  • Researcher
Description
  • Research activities include the prediction of the aero/hydro-dynamic performance of marine propellers, marine current turbines and wind turbines, using a blade-element momentum model, a lifting line code, a boundary element code and a viscous-flow code.
Education
January 2004 - September 2008
University of Lisbon
Field of study
  • Mechanical Engineering
September 2000 - May 2002
University of Lisbon
Field of study
  • Mechanical Engineering
October 1993 - May 1999
University of Lisbon
Field of study
  • Marine Engineering

Publications

Publications (102)
Conference Paper
Wave energy converters (WECs) are designed to operate near the resonance region, being excited at or close to its natural frequencies. Therefore, they are strongly affected by the interaction with waves, motion and mooring restraints. Floating WECs, such as point absorbers, present small dimensions in relation to the wave length, being typically su...
Article
Full-text available
In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 104 to 107. The k−ω SST turbulence model and the γ−R˜eθt correlation-based transition model are utilised and results compared for a conventional marine propeller. First, the...
Conference Paper
Full-text available
The pitch free decay test response of a floating vertical cylinder will be studied throughout this paper. The present case is based on an experiment (Paredes et al., 2015) and subject of different CFD validation studies (Palm et al.,2015; Rivera-Arreba et al., 2017). Both have found significant discrepancies regarding the damping and natural period...
Article
In this paper a comparison between RANS simulations carried out with the 𝑘 − 𝜔 SST turbulence model and 𝛾−̃R𝑒𝜃𝑡 transition model, and experimental measurements for marine propeller P4119 is made. The experiments were conducted at the David Taylor Model Basin and comprehended three-dimensional velocity components measurements of the blade boundary-l...
Presentation
Full-text available
PROPAN - Potential Flow Code for Foils and Rotors: PROPAN is short for Propeller Panel Method. PROPAN is a panel code for the calculation of steady and unsteady potential flow around foils, open and ducted propellers, and wind and marine current turbines. PROPAN was developed by MARETEC (Marine and Environmental Technology Research Centre) at Insti...
Conference Paper
Full-text available
The aim of the present paper is to present a method for an accurate prediction of the propeller unsteady performance in an artificial wake field using RANSE in a cost-effective way. The propeller performance predictions in this artificial wake field are compared to the predictions in behind the ship. The paper is organised as follows: the major fea...
Conference Paper
The present study describes the planform design of a full-scale turbine using a lifting line theory-based method. A full-scale reference turbine based on Bahaj's experimental model is initially designed and used for comparison, with rotor blades composed of reference sections NACA 63-824, 63-821, 63-818, 63-815 and 63-812, from root to tip. The foi...
Conference Paper
The present study describes a novel design strategy of hydrofoils tailored for marine current turbines. The designation of the newly proposed foil sections is IST-MT1-XX. The hydrofoils are designed with an existing optimization framework, which uses CST for the foil geometry parametrization and a viscous-inviscid panel code to estimate foil hydrod...
Presentation
Full-text available
The aim of the present paper is to present a method for an accurate prediction of the propeller unsteady performance in an artificial wake field using RANSE in a cost-effective way. The propeller performance predictions in this artificial wake field are compared to the predictions in behind the ship. The paper is organised as follows: the major fea...
Presentation
Full-text available
The present study describes the planform design of a full-scale turbine using a lifting line theory-based method. A full-scale reference turbine based on Bahaj's experimental model is initially designed and used for comparison, with rotor blades composed of reference sections NACA 63-824, 63-821, 63-818, 63-815 and 63-812, from root to tip. The foi...
Conference Paper
Full-text available
In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 10^4 to 10^7. The k-\omega SST turbulence model and the \gamma-Re_\theta transition model are utilised and results compared for a conventional marine propeller. First, the se...
Conference Paper
Full-text available
A low-order panel method is used for the performance prediction of a ducted propeller with a blunt trailing-edge. The effect of the Kutta condition for a blunt trailing-edge on the potential flow modelling is investigated. The analysis is carried out for propeller 4902 inside duct 37, for which unsteady pressure measurements on the inner side of th...
Conference Paper
Full-text available
In this paper a comparison between RANSE simulations carried out with the k-\omega SST turbulence model and \gamma-Re_\theta transition model, and experimental measurements for marine propeller P4119 is made. The experiments were conducted at the David Taylor Model Basin and comprehended three-dimensional velocity components measurements of the bla...
Presentation
Full-text available
In this paper a comparison between RANSE simulations carried out with the k-\omega SST turbulence model and \gamma-Re_\theta transition model, and experimental measurements for marine propeller P4119 is made. The experiments were conducted at the David Taylor Model Basin and comprehended three-dimensional velocity components measurements of the bla...
Presentation
Full-text available
In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 10^4 to 10^7. The k-\omega SST turbulence model and the \gamma-Re_\theta transition model are utilised and results compared for a conventional marine propeller. First, the se...
Presentation
Full-text available
A low-order panel method is used for the performance prediction of a ducted propeller with a blunt trailing-edge. The effect of the Kutta condition for a blunt trailing-edge on the potential flow modelling is investigated. The analysis is carried out for propeller 4902 inside duct 37, for which unsteady pressure measurements on the inner side of th...
Article
This article presents an overview of the recent developments at Instituto Superior Técnico and Maritime Research Institute Netherlands in applying computational methods for the hydrodynamic analysis of ducted propellers. The developments focus on the propeller performance prediction in open water conditions using boundary element methods and Reynol...
Article
The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k-\omega SST turbulence model and the \...
Conference Paper
This paper presents an overview of the recent developments at IST and MARIN in applying computational methods for the hydrodynamic analysis of ducted propellers. The developments focus on the propeller performance prediction in open water conditions using Boundary Element Methods and Reynolds-averaged Navier-Stokes solvers. The paper starts with an...
Presentation
Full-text available
This paper presents an overview of the recent developments at IST and MARIN in applying computational methods for the hydrodynamic analysis of ducted propellers. The developments focus on the propeller performance prediction in open water conditions using Boundary Element Methods and Reynolds-averaged Navier-Stokes solvers. The paper starts with an...
Article
Full-text available
In the present work, a comparison between the results obtained by a panel code with a Reynolds-averaged Navier-Stokes (RANS) code is made to obtain a better insight on the viscous effects of the ducted propeller and on the limitations of the inviscid flow model, especially near bollard pull conditions or low advance ratios, which are important in t...
Article
A method to analyze the flow around horizontal axis wind turbines based on the lifting line theory is presented. A non-linear vortex wake alignment scheme is proposed. The wake is discretized in straight line vortices. The velocity induced by the vortex system is computed in multiple sections downstream of the rotor plane. The effect of the radial...
Conference Paper
Full-text available
In the present work, a comparison between the results obtained by a panel code with a RANS code is made to obtain a better insight on the viscous effects of the ducted propeller and on the limitations of the inviscid flow model, especially near bollard pull conditions or low advance ratios , which are important in the design stage. The analysis is...
Conference Paper
Full-text available
The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k−ω SST turbulence model and the γ−Reθ...
Presentation
Full-text available
The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k-\omega SST turbulence model and the \...
Presentation
Full-text available
In the present work, a comparison between the results obtained by a panel code with a RANS code is made to obtain a better insight on the viscous effects of the ducted propeller and on the limitations of the inviscid flow model, especially near bollard pull conditions or low advance ratios, which are important in the design stage. The analysis is c...
Conference Paper
This paper presents Validation exercises of mathematical models for the simulation of flows where transition from laminar to turbulent regime plays an important role on the flow properties. The selected models use the Reynolds-Averaged Navier Stokes equations supplemented by the SST and Wilcox versions of the two-equation k − ω eddy-viscosity model...
Conference Paper
Full-text available
An iteratively coupled solution procedure with a potential-based Boundary Element Method is investigated for the calculation of unsteady sheet cavitation on marine propellers. The solution of the linear system of equations is obtained with an iterative technique which avoids a new matrix inversion at each iteration step in the prediction of the cav...
Conference Paper
Full-text available
An iteratively coupled solution method for the calculation of unsteady sheet cavitation on marine current turbines with a potential-based Boundary Element Method is investigated. The solution of the linear system of equations is obtained with an iterative technique which avoids a new matrix inversion at each iteration step in the prediction of the...
Conference Paper
Full-text available
A hydroelastic analysis of a marine current turbine blade is performed to evaluate its natural frequencies in water. A Finite Element Method (FEM) coupled to a 3-D potential based Boundary Element Method (BEM) is used to perform the eigenmode analysis taking into account the effect of the added mass. A convergence analysis of the FEM and the Fluid-...
Presentation
Full-text available
An iteratively coupled solution method for the calculation of unsteady sheet cavitation on marine current turbines with a potential-based Boundary Element Method is investigated. The solution of the linear system of equations is obtained with an iterative technique which avoids a new matrix inversion at each iteration step in the prediction of the...
Conference Paper
Full-text available
In this paper, viscous flow calculations using a RANS method are presented for two marine propellers in open-water conditions at model-scale. A verification study from a range of geometrically similar grids with different grid densities is made. The results show that the numerical uncertainties for the propeller forces are in the order of 0.4%-2.2%...
Conference Paper
Full-text available
Full-scale propeller performance prediction is mostly based on model-scale experiments that are extrapolated to full-scale values. Computational fluid dynamics (CFD) simulations are able to predict propeller performance at both model and full scale and therefore provide an attractive alternative for predicting scale effects. A prerequisite is of co...
Conference Paper
Full-text available
The present paper discusses several modelling aspects that are important for the performance predictions of a ducted propeller with a low-order panel method. The aspects discussed are the alignment of the blade wake geometry, the influence of the duct boundary layer on the blade wake pitch, the influence of a transpiration velocity through the gap...
Presentation
Full-text available
The present paper discusses several modelling aspects that are important for the performance predictions of a ducted propeller with a low-order panel method. The aspects discussed are the alignment of the blade wake geometry, the influence of the duct boundary layer on the blade wake pitch, the influence of a transpiration velocity through the gap...
Presentation
Full-text available
In this paper, viscous flow calculations using a RANS method are presented for two marine propellers in open-water conditions at model-scale. A verification study from a range of geometrically similar grids with different grid densities is made. The results show that the numerical uncertainties for the propeller forces are in the order of 0.4%-2.2%...
Chapter
Full-text available
In this work, a comparison between results of a panel method and a RANS solver is made for a horizontal axis marine current turbine in uniform inflow conditions. The panel method calculations were made with panel code PROPAN [3]. A vortex pitch wake alignment model is considered for the blade wake. The RANS calculations were carried out with RANS c...
Conference Paper
Full-text available
In this work, a comparison between results of a panel method and a RANS solver is made for a horizontal axis marine current turbine in uniform inflow conditions. The panel method calculations were made with panel code PROPAN (Baltazar, On the modelling of the potential flow about wings and marine propellers using a boundary element method. Ph.D. th...
Presentation
Full-text available
In this paper, a comparison between the results of a panel method and a RANS (Reynolds- Averaged Navier-Stokes) solver is made for a horizontal axis marine current turbine in straight in inflow conditions.
Conference Paper
Full-text available
In this paper, a comparison between results of a panel method and a RANS solver is made for a ducted propeller system in open-water. The panel method calculations were made at IST with the panel code PROPAN. Different wake models are used in the inviscid computations: rigid wake model with prescribed wake geometry and a vortex pitch wake alignment...
Presentation
Full-text available
In this paper, a comparison between results of a panel method and a RANS solver is made for a ducted propeller system in open-water. The panel method calculations were made at IST with the panel code PROPAN. Different wake models are used in the inviscid computations: rigid wake model with prescribed wake geometry and a vortex pitch wake alignment...
Conference Paper
An iteratively coupled solution method for the calculation of partial and super-cavitating flow on propellers with a potential based Boundary Element Method is presented. The solution method explores the fact that only the source strength beneath the cavity changes due to the presence of the cavity. The knowledge of the source strength change is su...
Presentation
Full-text available
An iteratively coupled solution method for the calculation of partial and super-cavitating flow on propellers with a potential based Boundary Element Method is presented. The solution method explores the fact that only the source strength beneath the cavity changes due to the presence of the cavity. The knowledge of the source strength change is su...
Conference Paper
For marine current turbines under certain operation conditions cavitation on the blades may occur. Therefore, it is important from the design stage of such systems to be able to predict the presence and extent of cavitation on the blades. In this paper a boundary element method for the prediction of sheet cavitation of a horizontal axis marine curr...
Presentation
Full-text available
For marine current turbines under certain operation conditions cavitation on the blades may occur. Therefore, it is important from the design stage of such systems to be able to predict the presence and extent of cavitation on the blades. In this paper a boundary element method for the prediction of sheet cavitation of a horizontal axis marine curr...
Conference Paper
Full-text available
This paper presents a study on the aerodynamic performance analysis of the NREL UAE wind turbine in steady axial uniform inflow conditions. Two different models are used in the analysis: a lifting line model and a simple model based on the blade element momentum (BEM) theory. For flow attachment conditions to the turbine blades at high tip speed ra...
Article
Full-text available
This paper discusses several modelling aspects that are important for the performance predictions of a ducted propulsor with a low-order Panel Method. The aspects discussed are the alignment of the wake geometry, the influence of the duct boundary layer on the wake pitch, and the influence of a transpiration velocity through the gap. The analysis i...
Article
A low order potential based panel code is used to analyze the flow around the blades of a horizontal axis marine current turbine. An empirical vortex model is assumed for the turbine wake, which includes the variation of pitch of the helicoidal vortices trailing behind the blades. The analysis is carried out for uniform inflow conditions in steady...
Conference Paper
This paper presents the computational models used by the authors at MARETEC/IST for hydrodynamic design and analysis of horizontal axis marine current turbines. The models combine a lifting line method for the optimization of the turbine blade geometry and an Integral Boundary Element Method (IBEM) for the hydrodynamic analysis. The classical lifti...
Conference Paper
Full-text available
This paper discusses several modelling aspects which are important for the performance predictions of a ducted propulsor with a low-order Panel Method. The aspects discussed are the alignment of the wake geometry, the influence of the duct boundary layer on the wake pitch and the influence of a transpiration velocity through the gap. The analysis i...
Presentation
Full-text available
This paper discusses several modelling aspects which are important for the performance predictions of a ducted propulsor with a low-order Panel Method. The aspects discussed are the alignment of the wake geometry, the influence of the duct boundary layer on the wake pitch and the influence of a transpiration velocity through the gap. The analysis i...
Presentation
Full-text available
This paper presents the computational models used by the authors at MARETEC/IST for hydrodynamic design and analysis of horizontal axis marine current turbines. The models combine a lifting line method for the optimization of the turbine blade geometry and an Integral Boundary Element Method (IBEM) for the hydrodynamic analysis. The classical lifti...
Poster
Full-text available
For the fully analysis of the flow on turbines, a potential flow model may be adequate and cost-effective for use in the design of such systems. The potential flow analysis may be carried out with an Integral Boundary Element Method (IBEM). In this work, a potential based IBEM using a vortex pitch wake alignment model is used. First, numerical res...
Presentation
Full-text available
For the fully analysis of the flow on turbines, a potential flow model may be adequate and cost-effective for use in the design of such systems. The potential flow analysis may be carried out with an Integral Boundary Element Method (IBEM). In this work, a potential based IBEM using a vortex pitch wake alignment model is used. First, numerical resu...
Article
An iteratively coupled solution method for the calculation of the cavitating potential flow on propellers with a potential based Boundary Element Method is investigated. By separately treating the perturbation due to the cavity a reduced system of equations is derived for successive approximations to the cavity source strength. The system is iterat...
Poster
Full-text available
There has been a growing interest in marine current energy conversion systems. One of the most promising systems is based on the use of horizontal axis marine current turbines. The ability to predict the hydrodynamic performance of a marine current turbine in non-uniform inflow conditions and with the occurrence of cavitation is essential for the d...
Presentation
Full-text available
For the fully unsteady analysis of the flow on a marine current turbine with cavitation, a potential flow model may be adequate and cost-effective for use in the design of such systems. The potential flow analysis may be carried out with an Integral Boundary Element Method (IBEM). The IBEM has been applied to a horizontal axis marine current turbin...
Conference Paper
Full-text available
This paper presents the mathematical formulation and the numerical implementation of a Boundary Element Method for the calculation of the steady incompressible potential flow around delta wings with leading-edge vortex sheet separation. A partial wake relaxation model with given wake geometry is used. The configuration studied is a 76 degrees swept...
Presentation
Full-text available
This paper presents the mathematical formulation and the numerical implementation of a Boundary Element Method for the calculation of the steady incompressible potential flow around delta wings with leading-edge vortex sheet separation. A partial wake relaxation model with given wake geometry is used. The configuration studied is a 76 degrees swept...
Presentation
Full-text available
This study addresses some numerical aspects of the implementation of a low-order Boundary Element Method (BEM) for three-dimensional steady potential flow calculations on lifting surfaces with partial cavitation. The method is based on an integral equation for the velocity perturbation potential. The presence of a cavity on the lifting surface is m...
Conference Paper
Full-text available
A low order potential based panel method is used for the analysis of the unsteady flow around marine current turbines. An empirical vortex model independent of the induced velocities is assumed for the turbine wake. The analysis is carried out for a controllable pitch horizontal axis marine current turbine in straight and yawed inflow conditions at...
Conference Paper
Full-text available
This paper focus on the effect of the gap flow modelling in ducted propeller performance predictions with a panel method. Different models for the potential flow in the gap region are investigated: non-zero and zero gap width and a tip leakage model with a vortex sheet shed along the blade tip. A low order panel method for the calculation of steady...
Conference Paper
Full-text available
This study addresses some aspects of the numerical solution with the Boundary Element Method of the three-dimensional potential flow on marine propellers with partial cavitation. An alternative iteratively coupled procedure is proposed to solve the linear system of equations resulting from the formulation of the cavitating flow problem. The alterna...
Presentation
Full-text available
This paper focus on the effect of the gap flow modelling in ducted propeller performance predictions with a panel method. Different models for the potential flow in the gap region are investigated: non-zero and zero gap width and a tip leakage model with a vortex sheet shed along the blade tip. A low order panel method for the calculation of steady...
Presentation
Full-text available
A low order potential based panel method is used for the analysis of the unsteady flow around marine current turbines. An empirical vortex model independent of the induced velocities is assumed for the turbine wake. The analysis is carried out for a controllable pitch horizontal axis marine current turbine in straight and yawed inflow conditions at...
Presentation
Full-text available
This study addresses some aspects of the numerical solution with the Boundary Element Method of the three-dimensional potential flow on marine propellers with partial cavitation. An alternative iteratively coupled procedure is proposed to solve the linear system of equations resulting from the formulation of the cavitating flow problem. The alterna...
Conference Paper
In this paper, we propose the use of parametric coordinates independent of the surface geometry definition as the dependent variables of the surface grid generation process. These parametric coordinates are related to the coordinates of the geometry definition by an intermediate transformation based on piecewise bi-linear interpolations that ensure...
Poster
Full-text available
There has been a growing interest in marine current energy conversion systems. One of the most promising systems receiving considerable attention is based on the use of horizontal axis turbines known as marine current turbines. The ability to predict the hydrodynamic performance of such turbines is of the utmost importance in the design of such sys...
Conference Paper
Full-text available
There has been a growing interest in the utilisation of marine current turbines for electrical power production. The ability to predict the hydrodynamic performance of a marine current turbine is essential for the design and analysis of such systems. Marine current turbines are subject to a non-uniform inflow due to variations on the tidal directio...
Poster
Full-text available
A fully three-dimensional potential flow Boundary Element Method for the analysis of the unsteady flow around marine current turbines is presented. An empirical vortex model independent of the induced velocities is assumed for the turbine wake. The application of the method to the analysis of a controllable pitch horizontal axis marine current turb...
Thesis
Full-text available
A low-order potential-based panel method for the calculation of the incompressible steady potential flow around wings and marine propellers is presented. Three wake models are considered: rigid wake with linear and iterative pressure Kutta condition, partial wake relaxation and full wake relaxation with roll-up. The techniques for the generation of...
Technical Report
Full-text available
This report presents steady and unsteady potential flow analysis with a Boundary Element Method (BEM) for a horizontal axis marine current turbine. An empirical vortex model independent of the induced velocities is assumed for the turbine wake which includes the variation of pitch of the helicoidal vortices trailing behind the blades. The analysis...
Conference Paper
A low order potential based panel code is used to analyse the flow around the blades of a horizontal axis marine current turbine. An empirical vortex model is assumed for the turbine wake which includes the variation of pitch of the helicoidal vor-tices trailing behind the blades. The analysis is carried out for uniform inflow conditions in steady...
Presentation
Full-text available
A low order potential based panel code is used to analyse the flow around the blades of a horizontal axis marine current turbine. An empirical vortex model is assumed for the turbine wake which includes the variation of pitch of the helicoidal vortices trailing behind the blades. The analysis is carried out for uniform inflow conditions in steady f...
Poster
Full-text available
There has been a growing interest in the utilisation of horizontal axis marine current turbines for electrical power production. The ability to predict the hydrodynamic performance is fundamental for the design and analysis of such systems. Marine current turbines are subject to a non-uniform inflow due to variations on the tidal direction and velo...
Technical Report
Full-text available
This report presents a detailed description of the mathematical formulation and the numerical implementation of a panel method for the calculation of the steady incompressible potential flow around ducted propellers. Grid studies were carried out for the duct NSMB 19A, and for the NSMB propeller Ka4-70 inside duct 19A in uniform axisymmetric flow....
Conference Paper
Full-text available
Three-dimensional steady potential flow calculations for ducted propellers with a low order BEM are presented. The numerical results of the duct NSMB 19A are compared with a surface vorticity method, together with wind tunnel measurements. In addition, the sensitivity of the calculation to the position of the stagnation point on the trailing edge i...
Presentation
Full-text available
Three-dimensional steady potential flow calculations for ducted propellers with a low order BEM are presented. The numerical results of the duct NSMB 19A are compared with a surface vorticity method, together with wind tunnel measurements. In addition, the sensitivity of the calculation to the position of the stagnation point on the trailing edge i...